# Copyright 2023 Meta AI and The HuggingFace Inc. team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""PyTorch Musicgen model."""

import copy
import inspect
import math
import random
from collections.abc import Callable
from dataclasses import dataclass
from typing import TYPE_CHECKING, Any, Optional

import torch
import torch.nn as nn
from torch.nn import CrossEntropyLoss

from ... import initialization as init
from ...activations import ACT2FN
from ...cache_utils import Cache, DynamicCache, EncoderDecoderCache
from ...generation import (
    ClassifierFreeGuidanceLogitsProcessor,
    GenerationConfig,
    GenerationMixin,
    GenerationMode,
    LogitsProcessorList,
    StoppingCriteriaList,
)
from ...masking_utils import create_bidirectional_mask, create_causal_mask
from ...modeling_flash_attention_utils import (
    FlashAttentionKwargs,
)
from ...modeling_layers import GradientCheckpointingLayer
from ...modeling_outputs import (
    BaseModelOutput,
    BaseModelOutputWithPastAndCrossAttentions,
    CausalLMOutputWithCrossAttentions,
    ModelOutput,
    Seq2SeqLMOutput,
)
from ...modeling_utils import ALL_ATTENTION_FUNCTIONS, PreTrainedModel
from ...processing_utils import Unpack
from ...utils import TransformersKwargs, auto_docstring, logging
from ..auto.configuration_auto import AutoConfig
from ..auto.modeling_auto import AutoModel
from .configuration_musicgen import MusicgenConfig, MusicgenDecoderConfig


if TYPE_CHECKING:
    from ...generation.streamers import BaseStreamer

logger = logging.get_logger(__name__)


@dataclass
@auto_docstring
class MusicgenUnconditionalInput(ModelOutput):
    r"""
    encoder_outputs (`tuple[torch.FloatTensor]` of length 1, with tensor shape `(batch_size, sequence_length, hidden_size)`):
        Sequence of hidden-states at the output of the last layer of the text encoder model.
    attention_mask (`torch.LongTensor`)  of shape `(batch_size, sequence_length)`, *optional*):
        Encoder attention mask to avoid performing attention on padding token indices. Mask values selected in `[0,
        1]`: 1 for tokens that are **not masked**, 0 for tokens that are **masked**.
    guidance_scale (`float`, *optional*):
        Guidance scale for classifier free guidance, setting the balance between the conditional logits (predicted
        from the prompts) and the unconditional logits (predicted without prompts).
    """

    encoder_outputs: tuple[torch.FloatTensor] | None = None
    attention_mask: torch.LongTensor | None = None
    guidance_scale: float | None = None


def shift_tokens_right(input_ids: torch.Tensor, pad_token_id: int, decoder_start_token_id: int):
    """
    Shift input ids one token to the right.
    """
    # transpose to get (bsz, num_codebooks, seq_len)
    input_ids = input_ids.transpose(1, 2)
    shifted_input_ids = input_ids.new_zeros(input_ids.shape)
    shifted_input_ids[..., 1:] = input_ids[..., :-1].clone()
    if decoder_start_token_id is None:
        raise ValueError("Make sure to set the decoder_start_token_id attribute of the model's configuration.")
    shifted_input_ids[..., 0] = decoder_start_token_id

    if pad_token_id is None:
        raise ValueError("Make sure to set the pad_token_id attribute of the model's configuration.")
    # replace possible -100 values in labels by `pad_token_id`
    shifted_input_ids.masked_fill_(shifted_input_ids == -100, pad_token_id)

    return shifted_input_ids


class MusicgenSinusoidalPositionalEmbedding(nn.Module):
    """This module produces sinusoidal positional embeddings of any length."""

    def __init__(self, num_positions: int, embedding_dim: int):
        super().__init__()
        self.embedding_dim = embedding_dim
        self.num_positions = num_positions
        self.make_weights(num_positions, embedding_dim)

    def make_weights(self, num_embeddings: int, embedding_dim: int):
        emb_weights = self.get_embedding(num_embeddings, embedding_dim)
        if hasattr(self, "weights"):
            # in forward put the weights on the correct dtype and device of the param
            emb_weights = emb_weights.to(dtype=self.weights.dtype, device=self.weights.device)

        self.register_buffer("weights", emb_weights, persistent=False)

    @staticmethod
    def get_embedding(num_embeddings: int, embedding_dim: int):
        """
        Build sinusoidal embeddings. This matches the implementation in tensor2tensor, but differs slightly from the
        description in Section 3.5 of "Attention Is All You Need".
        """
        half_dim = embedding_dim // 2
        emb = math.log(10000) / (half_dim - 1)
        emb = torch.exp(torch.arange(half_dim, dtype=torch.int64).float() * -emb)
        emb = torch.arange(num_embeddings, dtype=torch.int64).float().unsqueeze(1) * emb.unsqueeze(0)
        emb = torch.cat([torch.cos(emb), torch.sin(emb)], dim=1).view(num_embeddings, -1)
        if embedding_dim % 2 == 1:
            # zero pad
            emb = torch.cat([emb, torch.zeros(num_embeddings, 1)], dim=1)
        return emb.to(torch.get_default_dtype())

    @torch.no_grad()
    def forward(self, input_ids: torch.Tensor, past_key_values_length: int = 0):
        bsz, codebooks, seq_len = input_ids.size()
        # Create the position ids from the input token ids.
        position_ids = (torch.arange(seq_len) + past_key_values_length).to(input_ids.device)
        # expand embeddings if needed
        if seq_len > self.weights.size(0):
            self.make_weights(seq_len, self.embedding_dim)
        return self.weights.index_select(0, position_ids.view(-1)).detach()


# Copied from transformers.models.bert.modeling_bert.eager_attention_forward
def eager_attention_forward(
    module: nn.Module,
    query: torch.Tensor,
    key: torch.Tensor,
    value: torch.Tensor,
    attention_mask: torch.Tensor | None,
    scaling: float | None = None,
    dropout: float = 0.0,
    **kwargs: Unpack[TransformersKwargs],
):
    if scaling is None:
        scaling = query.size(-1) ** -0.5

    # Take the dot product between "query" and "key" to get the raw attention scores.
    attn_weights = torch.matmul(query, key.transpose(2, 3)) * scaling

    if attention_mask is not None:
        attn_weights = attn_weights + attention_mask

    attn_weights = nn.functional.softmax(attn_weights, dim=-1)
    attn_weights = nn.functional.dropout(attn_weights, p=dropout, training=module.training)

    attn_output = torch.matmul(attn_weights, value)
    attn_output = attn_output.transpose(1, 2).contiguous()

    return attn_output, attn_weights


class MusicgenAttention(nn.Module):
    """Multi-headed attention from 'Attention Is All You Need' paper"""

    def __init__(
        self,
        embed_dim: int,
        num_heads: int,
        dropout: float | None = 0.0,
        is_decoder: bool | None = False,
        bias: bool | None = True,
        is_causal: bool | None = False,
        config: MusicgenConfig | None = None,
        layer_idx: int | None = None,
    ):
        super().__init__()
        self.embed_dim = embed_dim
        self.num_heads = num_heads
        self.dropout = dropout
        self.head_dim = embed_dim // num_heads
        self.config = config

        if (self.head_dim * num_heads) != self.embed_dim:
            raise ValueError(
                f"embed_dim must be divisible by num_heads (got `embed_dim`: {self.embed_dim}"
                f" and `num_heads`: {num_heads})."
            )
        self.scaling = self.head_dim**-0.5
        self.is_decoder = is_decoder
        self.is_causal = is_causal
        self.layer_idx = layer_idx

        self.k_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
        self.v_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
        self.q_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
        self.out_proj = nn.Linear(embed_dim, embed_dim, bias=bias)

    def forward(
        self,
        hidden_states: torch.Tensor,
        key_value_states: torch.Tensor | None = None,
        past_key_values: Cache | None = None,
        attention_mask: torch.Tensor | None = None,
        output_attentions: bool | None = False,
        cache_position: torch.Tensor | None = None,
        # TODO: we need a refactor so that the different attention modules can get their specific kwargs
        # ATM, we have mixed things encoder, decoder, and encoder-decoder attn
        **kwargs: Unpack[FlashAttentionKwargs],
    ) -> tuple[torch.Tensor, torch.Tensor | None, tuple[torch.Tensor] | None]:
        """Input shape: Batch x Time x Channel"""

        # if key_value_states are provided this layer is used as a cross-attention layer
        # for the decoder
        is_cross_attention = key_value_states is not None

        # determine input shapes
        bsz, tgt_len = hidden_states.shape[:-1]
        src_len = key_value_states.shape[1] if is_cross_attention else tgt_len

        q_input_shape = (bsz, tgt_len, -1, self.head_dim)
        kv_input_shape = (bsz, src_len, -1, self.head_dim)

        # get query proj
        query_states = self.q_proj(hidden_states).view(*q_input_shape).transpose(1, 2)

        is_updated = False
        if past_key_values is not None:
            if isinstance(past_key_values, EncoderDecoderCache):
                is_updated = past_key_values.is_updated.get(self.layer_idx)
                if is_cross_attention:
                    # after the first generated id, we can subsequently re-use all key/value_layer from cache
                    curr_past_key_values = past_key_values.cross_attention_cache
                else:
                    curr_past_key_values = past_key_values.self_attention_cache
            else:
                curr_past_key_values = past_key_values

        current_states = key_value_states if is_cross_attention else hidden_states
        if is_cross_attention and past_key_values is not None and is_updated:
            # reuse k,v, cross_attentions
            key_states = curr_past_key_values.layers[self.layer_idx].keys
            value_states = curr_past_key_values.layers[self.layer_idx].values
        else:
            key_states = self.k_proj(current_states).view(*kv_input_shape).transpose(1, 2)
            value_states = self.v_proj(current_states).view(*kv_input_shape).transpose(1, 2)

            if past_key_values is not None:
                # save all key/value_states to cache to be re-used for fast auto-regressive generation
                cache_position = cache_position if not is_cross_attention else None
                key_states, value_states = curr_past_key_values.update(
                    key_states, value_states, self.layer_idx, {"cache_position": cache_position}
                )
                # set flag that curr layer for cross-attn is already updated so we can re-use in subsequent calls
                if is_cross_attention and isinstance(past_key_values, EncoderDecoderCache):
                    past_key_values.is_updated[self.layer_idx] = True

        attention_interface: Callable = ALL_ATTENTION_FUNCTIONS.get_interface(
            self.config._attn_implementation, eager_attention_forward
        )

        attn_output, attn_weights = attention_interface(
            self,
            query_states,
            key_states,
            value_states,
            attention_mask,
            dropout=0.0 if not self.training else self.dropout,
            scaling=self.scaling,
            output_attentions=output_attentions,
            **kwargs,
        )

        attn_output = attn_output.reshape(bsz, tgt_len, -1).contiguous()
        attn_output = self.out_proj(attn_output)

        return attn_output, attn_weights


class MusicgenDecoderLayer(GradientCheckpointingLayer):
    def __init__(self, config: MusicgenDecoderConfig, layer_idx=None):
        super().__init__()
        self.embed_dim = config.hidden_size

        self.self_attn = MusicgenAttention(
            embed_dim=self.embed_dim,
            num_heads=config.num_attention_heads,
            dropout=config.attention_dropout,
            is_decoder=True,
            bias=False,
            is_causal=True,
            config=config,
            layer_idx=layer_idx,
        )
        self.dropout = config.dropout
        self.activation_fn = ACT2FN[config.activation_function]
        self.activation_dropout = config.activation_dropout

        self.self_attn_layer_norm = nn.LayerNorm(self.embed_dim)
        self.encoder_attn = MusicgenAttention(
            self.embed_dim,
            config.num_attention_heads,
            dropout=config.attention_dropout,
            is_decoder=True,
            bias=False,
            config=config,
            layer_idx=layer_idx,
        )
        self.encoder_attn_layer_norm = nn.LayerNorm(self.embed_dim)
        self.fc1 = nn.Linear(self.embed_dim, config.ffn_dim, bias=False)
        self.fc2 = nn.Linear(config.ffn_dim, self.embed_dim, bias=False)
        self.final_layer_norm = nn.LayerNorm(self.embed_dim)

    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.Tensor | None = None,
        encoder_attention_mask: torch.Tensor | None = None,
        past_key_values: Cache | None = None,
        output_attentions: bool | None = False,
        use_cache: bool | None = True,
        cache_position: torch.Tensor | None = None,
    ) -> torch.Tensor:
        """
        Args:
            hidden_states (`torch.FloatTensor`): input to the layer of shape `(batch, seq_len, embed_dim)`
            attention_mask (`torch.FloatTensor`): attention mask of size
                `(batch, 1, tgt_len, src_len)` where padding elements are indicated by very large negative values.
            encoder_hidden_states (`torch.FloatTensor`):
                cross attention input to the layer of shape `(batch, seq_len, embed_dim)`
            encoder_attention_mask (`torch.FloatTensor`): encoder attention mask of size
                `(batch, 1, tgt_len, src_len)` where padding elements are indicated by very large negative values.
            past_key_values (`Cache`): cached past key and value projection states
            output_attentions (`bool`, *optional*):
                Whether or not to return the attentions tensors of all attention layers. See `attentions` under
                returned tensors for more detail.
        """
        residual = hidden_states
        hidden_states = self.self_attn_layer_norm(hidden_states)

        # Self Attention
        hidden_states, self_attn_weights = self.self_attn(
            hidden_states=hidden_states,
            past_key_values=past_key_values,
            attention_mask=attention_mask,
            output_attentions=output_attentions,
            cache_position=cache_position,
        )
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
        hidden_states = residual + hidden_states

        # Cross-Attention Block
        cross_attn_weights = None
        if encoder_hidden_states is not None:
            residual = hidden_states
            hidden_states = self.encoder_attn_layer_norm(hidden_states)

            hidden_states, cross_attn_weights = self.encoder_attn(
                hidden_states=hidden_states,
                key_value_states=encoder_hidden_states,
                attention_mask=encoder_attention_mask,
                past_key_values=past_key_values,
                output_attentions=output_attentions,
                cache_position=cache_position,
            )
            hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
            hidden_states = residual + hidden_states

        # Fully Connected
        residual = hidden_states
        hidden_states = self.final_layer_norm(hidden_states)
        hidden_states = self.activation_fn(self.fc1(hidden_states))
        hidden_states = nn.functional.dropout(hidden_states, p=self.activation_dropout, training=self.training)
        hidden_states = self.fc2(hidden_states)
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
        hidden_states = residual + hidden_states

        outputs = (hidden_states,)

        if output_attentions:
            outputs += (self_attn_weights, cross_attn_weights)
        return outputs


@auto_docstring
class MusicgenPreTrainedModel(PreTrainedModel):
    config: MusicgenDecoderConfig
    base_model_prefix = "model"
    supports_gradient_checkpointing = True
    _no_split_modules = ["MusicgenDecoderLayer", "MusicgenAttention"]
    _supports_flash_attn = True
    _supports_sdpa = True
    _supports_flex_attn = True

    @torch.no_grad()
    def _init_weights(self, module):
        std = self.config.initializer_factor
        if isinstance(module, nn.Linear):
            init.normal_(module.weight, mean=0.0, std=std)
            if module.bias is not None:
                init.zeros_(module.bias)
        elif isinstance(module, nn.LayerNorm):
            init.ones_(module.weight)
            init.zeros_(module.bias)
        elif isinstance(module, nn.Embedding):
            init.normal_(module.weight, mean=0.0, std=std)
            # Here we need the check explicitly, as we slice the weight in the `zeros_` call, so it looses the flag
            if module.padding_idx is not None and not getattr(module.weight, "_is_hf_initialized", False):
                init.zeros_(module.weight[module.padding_idx])
        elif isinstance(module, MusicgenSinusoidalPositionalEmbedding):
            emb_weights = module.get_embedding(module.num_positions, module.embedding_dim)
            init.copy_(module.weights, emb_weights)


class MusicgenDecoder(MusicgenPreTrainedModel):
    """
    Transformer decoder consisting of *config.num_hidden_layers* layers. Each layer is a [`MusicgenDecoderLayer`]
    """

    def __init__(self, config: MusicgenDecoderConfig):
        super().__init__(config)
        self.dropout = config.dropout
        self.layerdrop = config.layerdrop
        self.max_target_positions = config.max_position_embeddings
        self.d_model = config.hidden_size
        self.num_codebooks = config.num_codebooks
        self.embed_scale = math.sqrt(config.hidden_size) if config.scale_embedding else 1.0

        embed_dim = config.vocab_size + 1
        self.embed_tokens = nn.ModuleList(
            [nn.Embedding(embed_dim, config.hidden_size) for _ in range(config.num_codebooks)]
        )

        self.embed_positions = MusicgenSinusoidalPositionalEmbedding(
            config.max_position_embeddings,
            config.hidden_size,
        )

        self.layers = nn.ModuleList(
            [MusicgenDecoderLayer(config, layer_idx=i) for i in range(config.num_hidden_layers)]
        )
        self.layer_norm = nn.LayerNorm(config.hidden_size)
        self.attn_implementation = config._attn_implementation

        self.gradient_checkpointing = False
        # Initialize weights and apply final processing
        self.post_init()

    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.FloatTensor | None = None,
        encoder_attention_mask: torch.LongTensor | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        use_cache: bool | None = None,
        output_attentions: bool | None = None,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        cache_position: torch.Tensor | None = None,
        **kwargs,
    ) -> tuple | BaseModelOutputWithPastAndCrossAttentions:
        r"""
        input_ids (`torch.LongTensor` of shape `(batch_size * num_codebooks, sequence_length)`):
            Indices of input sequence tokens in the vocabulary, corresponding to the sequence of audio codes.

            Indices can be obtained by encoding an audio prompt with an audio encoder model to predict audio codes,
            such as with the [`EncodecModel`]. See [`EncodecModel.encode`] for details.

            [What are input IDs?](../glossary#input-ids)

            <Tip warning={true}>

            The `input_ids` will automatically be converted from shape `(batch_size * num_codebooks,
            target_sequence_length)` to `(batch_size, num_codebooks, target_sequence_length)` in the forward pass. If
            you obtain audio codes from an audio encoding model, such as [`EncodecModel`], ensure that the number of
            frames is equal to 1, and that you reshape the audio codes from `(frames, batch_size, num_codebooks,
            target_sequence_length)` to `(batch_size * num_codebooks, target_sequence_length)` prior to passing them as
            `input_ids`.

            </Tip>
        encoder_hidden_states (`torch.FloatTensor` of shape `(batch_size, encoder_sequence_length, hidden_size)`, *optional*):
            Sequence of hidden-states at the output of the last layer of the encoder. Used in the cross-attention of
            the decoder.
        encoder_attention_mask (`torch.LongTensor` of shape `(batch_size, encoder_sequence_length)`, *optional*):
            Mask to avoid performing cross-attention on padding tokens indices of encoder input_ids. Mask values
            selected in `[0, 1]`:

            - 1 for tokens that are **not masked**,
            - 0 for tokens that are **masked**.

            [What are attention masks?](../glossary#attention-mask)
        """
        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        use_cache = use_cache if use_cache is not None else self.config.use_cache
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        # retrieve input_ids and inputs_embeds
        if input_ids is not None and inputs_embeds is not None:
            raise ValueError("You cannot specify both decoder_input_ids and decoder_inputs_embeds at the same time")
        elif input_ids is not None:
            # (bsz * codebooks, seq_len) -> (bsz, codebooks, seq_len)
            input = input_ids.reshape(-1, self.num_codebooks, input_ids.shape[-1])
            bsz, num_codebooks, seq_len = input.shape
        elif inputs_embeds is not None:
            input = inputs_embeds[:, :, -1:]
        else:
            raise ValueError("You have to specify either decoder_input_ids or decoder_inputs_embeds")

        if self.gradient_checkpointing and self.training:
            if use_cache:
                logger.warning_once(
                    "`use_cache=True` is incompatible with gradient checkpointing`. Setting `use_cache=False`..."
                )
                use_cache = False

        if use_cache and past_key_values is None:
            past_key_values = EncoderDecoderCache(DynamicCache(config=self.config), DynamicCache(config=self.config))

        past_key_values_length = past_key_values.get_seq_length() if past_key_values is not None else 0

        if inputs_embeds is None:
            inputs_embeds = sum(self.embed_tokens[codebook](input[:, codebook]) for codebook in range(num_codebooks))

        if cache_position is None:
            past_seen_tokens = past_key_values.get_seq_length() if past_key_values is not None else 0
            cache_position: torch.Tensor = (
                torch.arange(inputs_embeds.shape[1], device=inputs_embeds.device) + past_seen_tokens
            )

        attention_mask = create_causal_mask(
            config=self.config,
            inputs_embeds=inputs_embeds,
            attention_mask=attention_mask,
            cache_position=cache_position,
            past_key_values=past_key_values,
        )
        encoder_attention_mask = create_bidirectional_mask(
            config=self.config,
            inputs_embeds=inputs_embeds,
            attention_mask=encoder_attention_mask,
            encoder_hidden_states=encoder_hidden_states,
        )

        # embed positions
        positions = self.embed_positions(input, past_key_values_length)
        hidden_states = inputs_embeds + positions.to(inputs_embeds.device)
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)

        # decoder layers
        all_hidden_states = () if output_hidden_states else None
        all_self_attns = () if output_attentions else None
        all_cross_attentions = () if (output_attentions and encoder_hidden_states is not None) else None

        for idx, decoder_layer in enumerate(self.layers):
            # add LayerDrop (see https://huggingface.co/papers/1909.11556 for description)
            if output_hidden_states:
                all_hidden_states += (hidden_states,)
            dropout_probability = random.uniform(0, 1)
            if self.training and (dropout_probability < self.layerdrop):
                continue

            layer_outputs = decoder_layer(
                hidden_states,
                attention_mask,
                encoder_hidden_states,  # as a positional argument for gradient checkpointing
                encoder_attention_mask=encoder_attention_mask,
                past_key_values=past_key_values,
                output_attentions=output_attentions,
                use_cache=use_cache,
                cache_position=cache_position,
            )
            hidden_states = layer_outputs[0]
            if output_attentions:
                all_self_attns += (layer_outputs[1],)

                if encoder_hidden_states is not None:
                    all_cross_attentions += (layer_outputs[2],)

        hidden_states = self.layer_norm(hidden_states)

        # add hidden states from the last decoder layer
        if output_hidden_states:
            all_hidden_states += (hidden_states,)

        if not return_dict:
            return tuple(
                v
                for v in [hidden_states, past_key_values, all_hidden_states, all_self_attns, all_cross_attentions]
                if v is not None
            )
        return BaseModelOutputWithPastAndCrossAttentions(
            last_hidden_state=hidden_states,
            past_key_values=past_key_values,
            hidden_states=all_hidden_states,
            attentions=all_self_attns,
            cross_attentions=all_cross_attentions,
        )


@auto_docstring
class MusicgenModel(MusicgenPreTrainedModel):
    def __init__(self, config: MusicgenDecoderConfig):
        super().__init__(config)
        self.decoder = MusicgenDecoder(config)
        # Initialize weights and apply final processing
        self.post_init()

    def get_input_embeddings(self):
        return self.decoder.embed_tokens

    def set_input_embeddings(self, value):
        self.decoder.embed_tokens = value

    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.FloatTensor | None = None,
        encoder_attention_mask: torch.LongTensor | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        use_cache: bool | None = None,
        output_attentions: bool | None = None,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        cache_position: torch.Tensor | None = None,
        **kwargs,
    ) -> tuple | BaseModelOutputWithPastAndCrossAttentions:
        r"""
        input_ids (`torch.LongTensor` of shape `(batch_size * num_codebooks, sequence_length)`):
            Indices of input sequence tokens in the vocabulary, corresponding to the sequence of audio codes.

            Indices can be obtained by encoding an audio prompt with an audio encoder model to predict audio codes,
            such as with the [`EncodecModel`]. See [`EncodecModel.encode`] for details.

            [What are input IDs?](../glossary#input-ids)

            <Tip warning={true}>

            The `input_ids` will automatically be converted from shape `(batch_size * num_codebooks,
            target_sequence_length)` to `(batch_size, num_codebooks, target_sequence_length)` in the forward pass. If
            you obtain audio codes from an audio encoding model, such as [`EncodecModel`], ensure that the number of
            frames is equal to 1, and that you reshape the audio codes from `(frames, batch_size, num_codebooks,
            target_sequence_length)` to `(batch_size * num_codebooks, target_sequence_length)` prior to passing them as
            `input_ids`.

            </Tip>
        encoder_hidden_states (`torch.FloatTensor` of shape `(batch_size, encoder_sequence_length, hidden_size)`, *optional*):
            Sequence of hidden-states at the output of the last layer of the encoder. Used in the cross-attention of
            the decoder.
        encoder_attention_mask (`torch.LongTensor` of shape `(batch_size, encoder_sequence_length)`, *optional*):
            Mask to avoid performing cross-attention on padding tokens indices of encoder input_ids. Mask values
            selected in `[0, 1]`:

            - 1 for tokens that are **not masked**,
            - 0 for tokens that are **masked**.

            [What are attention masks?](../glossary#attention-mask)
        """
        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        use_cache = use_cache if use_cache is not None else self.config.use_cache
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        # decoder outputs consists of (dec_features, past_key_values, dec_hidden, dec_attn)
        decoder_outputs = self.decoder(
            input_ids=input_ids,
            attention_mask=attention_mask,
            encoder_attention_mask=encoder_attention_mask,
            encoder_hidden_states=encoder_hidden_states,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
            cache_position=cache_position,
        )

        if not return_dict:
            return decoder_outputs

        return BaseModelOutputWithPastAndCrossAttentions(
            last_hidden_state=decoder_outputs.last_hidden_state,
            past_key_values=decoder_outputs.past_key_values,
            hidden_states=decoder_outputs.hidden_states,
            attentions=decoder_outputs.attentions,
            cross_attentions=decoder_outputs.cross_attentions,
        )


@auto_docstring(
    custom_intro="""
    The MusicGen decoder model with a language modelling head on top.
    """
)
class MusicgenForCausalLM(MusicgenPreTrainedModel, GenerationMixin):
    output_modalities = ("audio",)

    def __init__(self, config: MusicgenDecoderConfig):
        super().__init__(config)

        self.model = MusicgenModel(config)

        self.num_codebooks = config.num_codebooks
        self.lm_heads = nn.ModuleList(
            [nn.Linear(config.hidden_size, config.vocab_size, bias=False) for _ in range(config.num_codebooks)]
        )

        # Initialize weights and apply final processing
        self.post_init()

    def get_input_embeddings(self):
        return self.model.decoder.embed_tokens

    def set_input_embeddings(self, value):
        self.model.decoder.embed_tokens = value

    def get_output_embeddings(self):
        return self.lm_heads

    def set_output_embeddings(self, new_embeddings):
        self.lm_heads = new_embeddings

    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.FloatTensor | None = None,
        encoder_attention_mask: torch.LongTensor | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        labels: torch.LongTensor | None = None,
        use_cache: bool | None = None,
        output_attentions: bool | None = None,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        cache_position: torch.Tensor | None = None,
        **kwargs,
    ) -> tuple | CausalLMOutputWithCrossAttentions:
        r"""
        input_ids (`torch.LongTensor` of shape `(batch_size * num_codebooks, sequence_length)`):
            Indices of input sequence tokens in the vocabulary, corresponding to the sequence of audio codes.

            Indices can be obtained by encoding an audio prompt with an audio encoder model to predict audio codes,
            such as with the [`EncodecModel`]. See [`EncodecModel.encode`] for details.

            [What are input IDs?](../glossary#input-ids)

            <Tip warning={true}>

            The `input_ids` will automatically be converted from shape `(batch_size * num_codebooks,
            target_sequence_length)` to `(batch_size, num_codebooks, target_sequence_length)` in the forward pass. If
            you obtain audio codes from an audio encoding model, such as [`EncodecModel`], ensure that the number of
            frames is equal to 1, and that you reshape the audio codes from `(frames, batch_size, num_codebooks,
            target_sequence_length)` to `(batch_size * num_codebooks, target_sequence_length)` prior to passing them as
            `input_ids`.

            </Tip>
        encoder_hidden_states (`torch.FloatTensor` of shape `(batch_size, encoder_sequence_length, hidden_size)`, *optional*):
            Sequence of hidden-states at the output of the last layer of the encoder. Used in the cross-attention of
            the decoder.
        encoder_attention_mask (`torch.LongTensor` of shape `(batch_size, encoder_sequence_length)`, *optional*):
            Mask to avoid performing cross-attention on padding tokens indices of encoder input_ids. Mask values
            selected in `[0, 1]`:

            - 1 for tokens that are **not masked**,
            - 0 for tokens that are **masked**.

            [What are attention masks?](../glossary#attention-mask)
        labels (`torch.LongTensor` of shape `(batch_size, sequence_length, num_codebooks)`, *optional*):
            Labels for language modeling. Note that the labels **are shifted** inside the model, i.e. you can set
            `labels = input_ids` Indices are selected in `[-100, 0, ..., config.vocab_size]` All labels set to `-100`
            are ignored (masked), the loss is only computed for labels in `[0, ..., config.vocab_size]`
        """

        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        if (labels is not None) and (input_ids is None and inputs_embeds is None):
            input_ids = shift_tokens_right(labels, self.config.pad_token_id, self.config.bos_token_id)

        outputs = self.model(
            input_ids,
            attention_mask=attention_mask,
            encoder_hidden_states=encoder_hidden_states,
            encoder_attention_mask=encoder_attention_mask,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
            cache_position=cache_position,
        )

        hidden_states = outputs[0]

        lm_logits = torch.stack([head(hidden_states) for head in self.lm_heads], dim=1)

        loss = None
        if labels is not None:
            # since encoder hidden states have been concatenated to the decoder hidden states,
            # we take the last timestamps corresponding to labels
            logits = lm_logits[:, :, -labels.shape[1] :]

            loss_fct = CrossEntropyLoss()
            loss = torch.zeros([], device=self.device)

            # per codebook cross-entropy
            # -100 labels are ignored
            labels = labels.masked_fill(labels == self.config.pad_token_id, -100)

            # per codebook cross-entropy
            # ref: https://github.com/facebookresearch/audiocraft/blob/69fea8b290ad1b4b40d28f92d1dfc0ab01dbab85/audiocraft/solvers/musicgen.py#L242-L243
            for codebook in range(self.config.num_codebooks):
                codebook_logits = logits[:, codebook].contiguous().view(-1, logits.shape[-1])
                codebook_labels = labels[..., codebook].contiguous().view(-1)
                loss += loss_fct(codebook_logits, codebook_labels)

            loss = loss / self.config.num_codebooks

        # (bsz, num_codebooks, seq_len, vocab_size) -> (bsz * num_codebooks, seq_len, vocab_size)
        lm_logits = lm_logits.reshape(-1, *lm_logits.shape[2:])

        if not return_dict:
            output = (lm_logits,) + outputs[1:]
            return ((loss,) + output) if loss is not None else output

        return CausalLMOutputWithCrossAttentions(
            loss=loss,
            logits=lm_logits,
            past_key_values=outputs.past_key_values,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
            cross_attentions=outputs.cross_attentions,
        )

    def prepare_inputs_for_generation(
        self,
        input_ids,
        attention_mask=None,
        encoder_hidden_states=None,
        encoder_attention_mask=None,
        past_key_values=None,
        use_cache=True,
        delay_pattern_mask=None,
        guidance_scale=None,
        **kwargs,
    ):
        # Overwritten -- MusicGen has custom processing
        if delay_pattern_mask is None:
            input_ids, delay_pattern_mask = self.build_delay_pattern_mask(
                input_ids,
                pad_token_id=self.generation_config.pad_token_id,
                max_length=self.generation_config.max_length,
            )

        # apply the delay pattern mask
        input_ids = self.apply_delay_pattern_mask(input_ids, delay_pattern_mask)

        if guidance_scale is not None and guidance_scale > 1:
            # for classifier free guidance we need to replicate the decoder args across the batch dim (we'll split these
            # before sampling)
            input_ids = input_ids.repeat((2, 1))
            if attention_mask is not None:
                attention_mask = attention_mask.repeat((2, 1))

        if past_key_values is not None:
            input_ids = input_ids[:, -1:]

        return {
            "input_ids": input_ids,
            "attention_mask": attention_mask,
            "encoder_hidden_states": encoder_hidden_states,
            "encoder_attention_mask": encoder_attention_mask,
            "past_key_values": past_key_values,
            "use_cache": use_cache,
        }

    def build_delay_pattern_mask(self, input_ids: torch.LongTensor, pad_token_id: int, max_length: int | None = None):
        """Build a delayed pattern mask to the input_ids. Each codebook is offset by the previous codebook by
        one, giving a delayed pattern mask at the start of sequence and end of sequence. Take the example where there
        are 4 codebooks and a max sequence length of 8, we have the delayed pattern mask of shape `(codebooks,
        seq_len)`:
        - [P, -1, -1, -1, -1, P, P, P]
        - [P, P, -1, -1, -1, -1, P, P]
        - [P, P, P, -1, -1, -1, -1, P]
        - [P, P, P, P, -1, -1, -1, -1]
        where P is the special padding token id and -1 indicates that the token is valid for prediction. If we include
        a prompt (decoder input ids), the -1 positions indicate where new tokens should be predicted. Otherwise, the
        mask is set to the value in the prompt:
        - [P, a, b, -1, -1, P, P, P]
        - [P, P, c, d, -1, -1, P, P]
        - [P, P, P, e, f, -1, -1, P]
        - [P, P, P, P, g, h, -1, -1]
        where a-h indicate the input prompt (decoder input ids) that are offset by 1. Now, we only override the -1
        tokens in our prediction.
        """
        # (bsz * num_codebooks, seq_len) -> (bsz, num_codebooks, seq_len)
        input_ids = input_ids.reshape(-1, self.num_codebooks, input_ids.shape[-1])
        bsz, num_codebooks, seq_len = input_ids.shape

        max_length = max_length if max_length is not None else self.generation_config.max_length
        input_ids_shifted = (
            torch.ones((bsz, num_codebooks, max_length), dtype=torch.long, device=input_ids.device) * -1
        )

        channel_codebooks = num_codebooks // 2 if self.config.audio_channels == 2 else num_codebooks
        # we only apply the mask if we have a large enough seq len - otherwise we return as is
        if max_length < 2 * channel_codebooks - 1:
            return input_ids.reshape(bsz * num_codebooks, -1), input_ids_shifted.reshape(bsz * num_codebooks, -1)

        # fill the shifted ids with the prompt entries, offset by the codebook idx
        for codebook in range(channel_codebooks):
            if self.config.audio_channels == 1:
                # mono channel - loop over the codebooks one-by-one
                input_ids_shifted[:, codebook, codebook : seq_len + codebook] = input_ids[:, codebook]
            else:
                # left/right channels are interleaved in the generated codebooks, so handle one then the other
                input_ids_shifted[:, 2 * codebook, codebook : seq_len + codebook] = input_ids[:, 2 * codebook]
                input_ids_shifted[:, 2 * codebook + 1, codebook : seq_len + codebook] = input_ids[:, 2 * codebook + 1]

        # construct a pattern mask that indicates the positions of padding tokens for each codebook
        # first fill the upper triangular part (the EOS padding)
        delay_pattern = torch.triu(
            torch.ones((channel_codebooks, max_length), dtype=torch.bool), diagonal=max_length - channel_codebooks + 1
        )
        # then fill the lower triangular part (the BOS padding)
        delay_pattern = delay_pattern + torch.tril(torch.ones((channel_codebooks, max_length), dtype=torch.bool))

        if self.config.audio_channels == 2:
            # for left/right channel we need to duplicate every row of the pattern mask in an interleaved fashion
            delay_pattern = delay_pattern.repeat_interleave(2, dim=0)

        mask = ~delay_pattern.to(input_ids.device)
        input_ids = mask * input_ids_shifted + ~mask * pad_token_id

        # find the first position to start generating - this is the first place we have the -1 token
        # and will always be in the first codebook (since it has no codebook offset)
        first_codebook_ids = input_ids[:, 0, :]
        start_ids = (first_codebook_ids == -1).nonzero()[:, 1]
        if len(start_ids) > 0:
            first_start_id = min(start_ids)
        else:
            # we have no tokens that need to be filled - return entire matrix of input ids
            first_start_id = seq_len

        # (bsz * num_codebooks, seq_len) -> (bsz, num_codebooks, seq_len)
        pattern_mask = input_ids.reshape(bsz * num_codebooks, -1)
        input_ids = input_ids[..., :first_start_id].reshape(bsz * num_codebooks, -1)
        return input_ids, pattern_mask

    @staticmethod
    def apply_delay_pattern_mask(input_ids, decoder_pad_token_mask):
        """Apply a delay pattern mask to the decoder input ids, only preserving predictions where
        the mask is set to -1, and otherwise setting to the value detailed in the mask."""
        seq_len = input_ids.shape[-1]
        decoder_pad_token_mask = decoder_pad_token_mask[..., :seq_len]
        input_ids = torch.where(decoder_pad_token_mask == -1, input_ids, decoder_pad_token_mask)
        return input_ids

    @torch.no_grad()
    def generate(
        self,
        inputs: torch.Tensor | None = None,
        generation_config: GenerationConfig | None = None,
        logits_processor: LogitsProcessorList | None = None,
        stopping_criteria: StoppingCriteriaList | None = None,
        synced_gpus: bool | None = None,
        streamer: Optional["BaseStreamer"] = None,
        **kwargs,
    ):
        """

        Generates sequences of token ids for models with a language modeling head.

        <Tip warning={true}>

        Most generation-controlling parameters are set in `generation_config` which, if not passed, will be set to the
        model's default generation configuration. You can override any `generation_config` by passing the corresponding
        parameters to generate(), e.g. `.generate(inputs, num_beams=4, do_sample=True)`.

        For an overview of generation strategies and code examples, check out the [following
        guide](./generation_strategies).

        </Tip>

        Parameters:
            inputs (`torch.Tensor` of varying shape depending on the modality, *optional*):
                The sequence used as a prompt for the generation or as model inputs to the encoder. If `None` the
                method initializes it with `bos_token_id` and a batch size of 1. For decoder-only models `inputs`
                should be in the format `input_ids`. For encoder-decoder models *inputs* can represent any of
                `input_ids`, `input_values`, `input_features`, or `pixel_values`.
            generation_config (`~generation.GenerationConfig`, *optional*):
                The generation configuration to be used as base parametrization for the generation call. `**kwargs`
                passed to generate matching the attributes of `generation_config` will override them. If
                `generation_config` is not provided, the default will be used, which had the following loading
                priority: 1) from the `generation_config.json` model file, if it exists; 2) from the model
                configuration. Please note that unspecified parameters will inherit [`~generation.GenerationConfig`]'s
                default values, whose documentation should be checked to parameterize generation.
            logits_processor (`LogitsProcessorList`, *optional*):
                Custom logits processors that complement the default logits processors built from arguments and
                generation config. If a logit processor is passed that is already created with the arguments or a
                generation config an error is thrown. This feature is intended for advanced users.
            stopping_criteria (`StoppingCriteriaList`, *optional*):
                Custom stopping criteria that complement the default stopping criteria built from arguments and a
                generation config. If a stopping criteria is passed that is already created with the arguments or a
                generation config an error is thrown. This feature is intended for advanced users.
            synced_gpus (`bool`, *optional*, defaults to `False`):
                Whether to continue running the while loop until max_length (needed to avoid deadlocking with
                `FullyShardedDataParallel` and DeepSpeed ZeRO Stage 3).
            streamer (`BaseStreamer`, *optional*):
                Streamer object that will be used to stream the generated sequences. Generated tokens are passed
                through `streamer.put(token_ids)` and the streamer is responsible for any further processing.
            kwargs (`dict[str, Any]`, *optional*):
                Ad hoc parametrization of `generate_config` and/or additional model-specific kwargs that will be
                forwarded to the `forward` function of the model. If the model is an encoder-decoder model, encoder
                specific kwargs should not be prefixed and decoder specific kwargs should be prefixed with *decoder_*.

        Return:
            [`~utils.ModelOutput`] or `torch.LongTensor`: A [`~utils.ModelOutput`] (if `return_dict_in_generate=True`
            or when `config.return_dict_in_generate=True`) or a `torch.FloatTensor`.

                If the model is *not* an encoder-decoder model (`model.config.is_encoder_decoder=False`), the possible
                [`~utils.ModelOutput`] types are:

                    - [`~generation.GenerateDecoderOnlyOutput`],
                    - [`~generation.GenerateBeamDecoderOnlyOutput`]

                If the model is an encoder-decoder model (`model.config.is_encoder_decoder=True`), the possible
                [`~utils.ModelOutput`] types are:

                    - [`~generation.GenerateEncoderDecoderOutput`],
                    - [`~generation.GenerateBeamEncoderDecoderOutput`]
        """
        # 1. Handle `generation_config` and kwargs that might update it, and validate the resulting objects
        if generation_config is None:
            generation_config = self.generation_config

        generation_config = copy.deepcopy(generation_config)
        model_kwargs = generation_config.update(**kwargs)  # All unused kwargs must be model kwargs
        generation_config.validate()
        self._validate_model_kwargs(model_kwargs.copy())

        # 2. Set generation parameters if not already defined
        logits_processor = logits_processor if logits_processor is not None else LogitsProcessorList()
        stopping_criteria = stopping_criteria if stopping_criteria is not None else StoppingCriteriaList()

        requires_attention_mask = "encoder_outputs" not in model_kwargs
        kwargs_has_attention_mask = model_kwargs.get("attention_mask", None) is not None

        # 3. Define model inputs`
        input_ids, model_input_name, model_kwargs = self._prepare_model_inputs(
            inputs, generation_config.bos_token_id, model_kwargs
        )
        batch_size = input_ids.shape[0] // self.num_codebooks
        self._prepare_special_tokens(generation_config, kwargs_has_attention_mask, device=input_ids.device)

        # 4. Define other model kwargs
        model_kwargs["use_cache"] = generation_config.use_cache
        model_kwargs["guidance_scale"] = generation_config.guidance_scale

        if model_kwargs.get("attention_mask", None) is None and requires_attention_mask:
            model_kwargs["attention_mask"] = self._prepare_attention_mask_for_generation(
                input_ids, generation_config, model_kwargs
            )

        # 5. Prepare `max_length` depending on other stopping criteria.
        input_ids_length = input_ids.shape[-1]
        has_default_max_length = kwargs.get("max_length") is None and generation_config.max_length is not None
        has_default_min_length = kwargs.get("min_length") is None and generation_config.min_length is not None
        generation_config = self._prepare_generated_length(
            generation_config=generation_config,
            has_default_max_length=has_default_max_length,
            has_default_min_length=has_default_min_length,
            model_input_name=model_input_name,
            inputs_tensor=input_ids,
            input_ids_length=input_ids_length,
        )

        self._validate_generated_length(generation_config, input_ids_length, has_default_max_length)

        # 6. Prepare the cache.
        # - `model_kwargs` may be updated in place with a cache as defined by the parameters in `generation_config`.
        # - different models have a different cache name expected by the model (default = "past_key_values")
        # - `max_length`, prepared above, is used to determine the maximum cache length
        max_cache_length = generation_config.max_length - 1
        if (
            input_ids_length.shape[1] != input_ids_length
            and model_input_name == "inputs_embeds"
            and not self.config.is_encoder_decoder
        ):
            max_cache_length += input_ids_length.shape[1]
        self._prepare_cache_for_generation(
            generation_config,
            model_kwargs,
            generation_mode=None,
            batch_size=batch_size,
            max_cache_length=max_cache_length,
        )

        # 7. Prepare `input_ids` which will be used for auto-regressive generation
        # Build the delay pattern mask for offsetting each codebook prediction by 1 (this behaviour is specific to MusicGen)
        input_ids, delay_pattern_mask = self.build_delay_pattern_mask(
            input_ids,
            pad_token_id=generation_config._decoder_start_token_tensor,
            max_length=generation_config.max_length,
        )

        if streamer is not None:
            streamer.put(input_ids.cpu())

        # stash the delay mask so that we don't have to recompute it in each forward pass
        model_kwargs["delay_pattern_mask"] = delay_pattern_mask

        # 8. determine generation mode
        generation_mode = generation_config.get_generation_mode()

        # 9. prepare batched CFG externally (to enable coexistence with the unbatched CFG)
        if generation_config.guidance_scale is not None and generation_config.guidance_scale > 1:
            logits_processor.append(ClassifierFreeGuidanceLogitsProcessor(generation_config.guidance_scale))
            generation_config.guidance_scale = None

        # 10. prepare distribution pre_processing samplers
        logits_processor = self._get_logits_processor(
            generation_config=generation_config,
            input_ids_seq_length=input_ids_length,
            encoder_input_ids=input_ids,
            prefix_allowed_tokens_fn=None,
            logits_processor=logits_processor,
            device=input_ids.device,
        )

        # 10. prepare stopping criteria
        stopping_criteria = self._get_stopping_criteria(
            generation_config=generation_config, stopping_criteria=stopping_criteria
        )

        if generation_mode in (GenerationMode.SAMPLE, GenerationMode.GREEDY_SEARCH):
            # expand input_ids with `num_return_sequences` additional sequences per batch
            input_ids, model_kwargs = self._expand_inputs_for_generation(
                input_ids=input_ids,
                expand_size=generation_config.num_return_sequences,
                **model_kwargs,
            )

            # 11. run sample
            outputs = self._sample(
                input_ids,
                logits_processor=logits_processor,
                stopping_criteria=stopping_criteria,
                generation_config=generation_config,
                synced_gpus=synced_gpus,
                streamer=streamer,
                **model_kwargs,
            )

        else:
            raise ValueError(
                "Got incompatible mode for generation, should be one of greedy or sampling. "
                "Ensure that beam search is de-activated by setting `num_beams=1`."
            )

        if generation_config.return_dict_in_generate:
            output_ids = outputs.sequences
        else:
            output_ids = outputs

        # apply the pattern mask to the final ids
        output_ids = self.apply_delay_pattern_mask(output_ids, model_kwargs["delay_pattern_mask"])

        # revert the pattern delay mask by filtering the pad token id
        output_ids = output_ids[output_ids != generation_config._pad_token_tensor].reshape(
            batch_size, self.num_codebooks, -1
        )

        if generation_config.return_dict_in_generate:
            outputs.sequences = output_ids
            return outputs
        else:
            return output_ids


@auto_docstring(
    custom_intro="""
    The composite MusicGen model with a text encoder, audio encoder and Musicgen decoder,
    """
)
class MusicgenForConditionalGeneration(MusicgenPreTrainedModel, GenerationMixin):
    config: MusicgenConfig
    output_modalities = ("audio",)
    base_model_prefix = "encoder_decoder"
    main_input_name = "input_ids"
    supports_gradient_checkpointing = True

    def __init__(
        self,
        config: MusicgenConfig | None = None,
        text_encoder: PreTrainedModel | None = None,
        audio_encoder: PreTrainedModel | None = None,
        decoder: MusicgenForCausalLM | None = None,
    ):
        r"""
        text_encoder (`PreTrainedModel`, *optional*):
            The text encoder model that encodes text into hidden states for conditioning.
        audio_encoder (`PreTrainedModel`, *optional*):
            The audio encoder model that encodes audio into hidden states for conditioning.
        decoder (`MusicgenForCausalLM`, *optional*):
            The decoder model that generates audio tokens based on conditioning signals.
        """
        if config is None and (text_encoder is None or audio_encoder is None or decoder is None):
            raise ValueError(
                "Either a configuration has to be provided, or all three of text encoder, audio encoder and MusicGen decoder."
            )
        if config is None:
            config = MusicgenConfig(
                text_encoder=text_encoder.config, audio_encoder=audio_encoder.config, decoder=decoder.config
            )
        else:
            if not isinstance(config, self.config_class):
                raise ValueError(f"Config: {config} has to be of type {self.config_class}")

        if config.decoder.cross_attention_hidden_size is not None:
            if config.decoder.cross_attention_hidden_size != config.text_encoder.hidden_size:
                raise ValueError(
                    "If `cross_attention_hidden_size` is specified in the MusicGen decoder's configuration, it has to be equal"
                    f" to the text encoder's `hidden_size`. Got {config.decoder.cross_attention_hidden_size} for"
                    f" `config.decoder.cross_attention_hidden_size` and {config.text_encoder.hidden_size} for"
                    " `config.text_encoder.hidden_size`."
                )

        # initialize with config
        super().__init__(config)

        if text_encoder is None:
            from ..auto.modeling_auto import AutoModelForTextEncoding

            text_encoder = AutoModelForTextEncoding.from_config(config.text_encoder)

        if audio_encoder is None:
            from ..auto.modeling_auto import AutoModel

            audio_encoder = AutoModel.from_config(config.audio_encoder)

        if decoder is None:
            decoder = MusicgenForCausalLM._from_config(config.decoder)

        self.text_encoder = text_encoder
        self.audio_encoder = audio_encoder
        self.decoder = decoder

        if self.text_encoder.config.to_dict() != self.config.text_encoder.to_dict():
            logger.warning(
                f"Config of the text_encoder: {self.text_encoder.__class__} is overwritten by shared text_encoder config:"
                f" {self.config.text_encoder}"
            )
        if self.audio_encoder.config.to_dict() != self.config.audio_encoder.to_dict():
            logger.warning(
                f"Config of the audio_encoder: {self.audio_encoder.__class__} is overwritten by shared audio_encoder config:"
                f" {self.config.audio_encoder}"
            )
        if self.decoder.config.to_dict() != self.config.decoder.to_dict():
            logger.warning(
                f"Config of the decoder: {self.decoder.__class__} is overwritten by shared decoder config:"
                f" {self.config.decoder}"
            )

        # make sure that the individual model's config refers to the shared config
        # so that the updates to the config will be synced
        self.config.text_encoder._attn_implementation = self.text_encoder.config._attn_implementation
        self.config.audio_encoder._attn_implementation = self.audio_encoder.config._attn_implementation
        self.config.decoder._attn_implementation = self.decoder.config._attn_implementation
        self.text_encoder.config = self.config.text_encoder
        self.audio_encoder.config = self.config.audio_encoder
        self.decoder.config = self.config.decoder

        # text encoder outputs might need to be projected to different dimension for decoder
        if (
            self.text_encoder.config.hidden_size != self.decoder.config.hidden_size
            and self.decoder.config.cross_attention_hidden_size is None
        ):
            self.enc_to_dec_proj = nn.Linear(self.text_encoder.config.hidden_size, self.decoder.config.hidden_size)

        if self.text_encoder.get_output_embeddings() is not None:
            raise ValueError(
                f"The encoder {self.text_encoder} should not have a LM Head. Please use a model without and LM Head"
            )

        decoder_signature = set(inspect.signature(self.decoder.forward).parameters.keys())
        if "encoder_hidden_states" not in decoder_signature:
            raise ValueError(
                "The selected decoder is not prepared for the encoder hidden states to be passed. Please see the "
                "following discussion on GitHub: https://github.com/huggingface/transformers/issues/23350"
            )

        # tie text encoder, decoder weights if config set accordingly
        self.post_init()

    def get_input_embeddings(self):
        return self.text_encoder.get_input_embeddings()

    def get_output_embeddings(self):
        return self.decoder.get_output_embeddings()

    def set_output_embeddings(self, new_embeddings):
        return self.decoder.set_output_embeddings(new_embeddings)

    @classmethod
    def from_sub_models_pretrained(
        cls,
        text_encoder_pretrained_model_name_or_path: str | None = None,
        audio_encoder_pretrained_model_name_or_path: str | None = None,
        decoder_pretrained_model_name_or_path: str | None = None,
        *model_args,
        **kwargs,
    ) -> PreTrainedModel:
        r"""
        Instantiate a text encoder, an audio encoder, and a MusicGen decoder from one, two or three base classes of the
        library from pretrained model checkpoints.


        The model is set in evaluation mode by default using `model.eval()` (Dropout modules are deactivated). To train
        the model, you need to first set it back in training mode with `model.train()`.

        Params:
            text_encoder_pretrained_model_name_or_path (`str`, *optional*):
                Information necessary to initiate the text encoder. Can be either:

                    - A string, the *model id* of a pretrained model hosted inside a model repo on huggingface.co.
                    - A path to a *directory* containing model weights saved using
                      [`~PreTrainedModel.save_pretrained`], e.g., `./my_model_directory/`.

            audio_encoder_pretrained_model_name_or_path (`str`, *optional*):
                Information necessary to initiate the audio encoder. Can be either:

                    - A string, the *model id* of a pretrained model hosted inside a model repo on huggingface.co.
                    - A path to a *directory* containing model weights saved using
                      [`~PreTrainedModel.save_pretrained`], e.g., `./my_model_directory/`.

            decoder_pretrained_model_name_or_path (`str`, *optional*, defaults to `None`):
                Information necessary to initiate the decoder. Can be either:

                    - A string, the *model id* of a pretrained model hosted inside a model repo on huggingface.co.
                    - A path to a *directory* containing model weights saved using
                      [`~PreTrainedModel.save_pretrained`], e.g., `./my_model_directory/`.

            model_args (remaining positional arguments, *optional*):
                All remaining positional arguments will be passed to the underlying model's `__init__` method.

            kwargs (remaining dictionary of keyword arguments, *optional*):
                Can be used to update the configuration object (after it being loaded) and initiate the model (e.g.,
                `output_attentions=True`).

                - To update the text encoder configuration, use the prefix *text_encoder_* for each configuration
                  parameter.
                - To update the audio encoder configuration, use the prefix *audio_encoder_* for each configuration
                  parameter.
                - To update the decoder configuration, use the prefix *decoder_* for each configuration parameter.
                - To update the parent model configuration, do not use a prefix for each configuration parameter.

                Behaves differently depending on whether a `config` is provided or automatically loaded.

        Example:

        ```python
        >>> from transformers import MusicgenForConditionalGeneration

        >>> # initialize a musicgen model from a t5 text encoder, encodec audio encoder, and musicgen decoder
        >>> model = MusicgenForConditionalGeneration.from_sub_models_pretrained(
        ...     text_encoder_pretrained_model_name_or_path="google-t5/t5-base",
        ...     audio_encoder_pretrained_model_name_or_path="facebook/encodec_24khz",
        ...     decoder_pretrained_model_name_or_path="facebook/musicgen-small",
        ... )
        >>> # saving model after fine-tuning
        >>> model.save_pretrained("./musicgen-ft")
        >>> # load fine-tuned model
        >>> model = MusicgenForConditionalGeneration.from_pretrained("./musicgen-ft")
        ```"""

        kwargs_text_encoder = {
            argument[len("text_encoder_") :]: value
            for argument, value in kwargs.items()
            if argument.startswith("text_encoder_")
        }

        kwargs_audio_encoder = {
            argument[len("audio_encoder_") :]: value
            for argument, value in kwargs.items()
            if argument.startswith("audio_encoder_")
        }

        kwargs_decoder = {
            argument[len("decoder_") :]: value for argument, value in kwargs.items() if argument.startswith("decoder_")
        }

        # remove text encoder, audio encoder and decoder kwargs from kwargs
        for key in kwargs_text_encoder:
            del kwargs["text_encoder_" + key]
        for key in kwargs_audio_encoder:
            del kwargs["audio_encoder_" + key]
        for key in kwargs_decoder:
            del kwargs["decoder_" + key]

        # Load and initialize the encoder and decoder
        # The distinction between encoder and decoder at the model level is made
        # by the value of the flag `is_decoder` that we need to set correctly.
        text_encoder = kwargs_text_encoder.pop("model", None)
        if text_encoder is None:
            if text_encoder_pretrained_model_name_or_path is None:
                raise ValueError(
                    "If `text_encoder_model` is not defined as an argument, a `text_encoder_pretrained_model_name_or_path` has "
                    "to be defined."
                )

            if "config" not in kwargs_text_encoder:
                encoder_config, kwargs_text_encoder = AutoConfig.from_pretrained(
                    text_encoder_pretrained_model_name_or_path, **kwargs_text_encoder, return_unused_kwargs=True
                )

                if encoder_config.is_decoder is True or encoder_config.add_cross_attention is True:
                    logger.info(
                        f"Initializing {text_encoder_pretrained_model_name_or_path} as a text_encoder model "
                        "from a decoder model. Cross-attention and causal mask are disabled."
                    )
                    encoder_config.is_decoder = False
                    encoder_config.add_cross_attention = False

                kwargs_text_encoder["config"] = encoder_config

            text_encoder = AutoModel.from_pretrained(
                text_encoder_pretrained_model_name_or_path, *model_args, **kwargs_text_encoder
            )

        audio_encoder = kwargs_audio_encoder.pop("model", None)
        if audio_encoder is None:
            if audio_encoder_pretrained_model_name_or_path is None:
                raise ValueError(
                    "If `audio_encoder_model` is not defined as an argument, an `audio_encoder_pretrained_model_name_or_path` has "
                    "to be defined."
                )

            if "config" not in kwargs_audio_encoder:
                encoder_config, kwargs_audio_encoder = AutoConfig.from_pretrained(
                    audio_encoder_pretrained_model_name_or_path, **kwargs_audio_encoder, return_unused_kwargs=True
                )

                if encoder_config.is_decoder is True or encoder_config.add_cross_attention is True:
                    logger.info(
                        f"Initializing {audio_encoder_pretrained_model_name_or_path} as an audio_encoder model "
                        "from a decoder model. Cross-attention and causal mask are disabled."
                    )
                    encoder_config.is_decoder = False
                    encoder_config.add_cross_attention = False

                kwargs_audio_encoder["config"] = encoder_config

            audio_encoder = AutoModel.from_pretrained(
                audio_encoder_pretrained_model_name_or_path, *model_args, **kwargs_audio_encoder
            )

        decoder = kwargs_decoder.pop("model", None)
        if decoder is None:
            if decoder_pretrained_model_name_or_path is None:
                raise ValueError(
                    "If `decoder_model` is not defined as an argument, a `decoder_pretrained_model_name_or_path` has "
                    "to be defined."
                )

            if "config" not in kwargs_decoder:
                decoder_config, kwargs_decoder = AutoConfig.from_pretrained(
                    decoder_pretrained_model_name_or_path, **kwargs_decoder, return_unused_kwargs=True
                )

                if isinstance(decoder_config, MusicgenConfig):
                    decoder_config = decoder_config.decoder

                if decoder_config.is_decoder is False or decoder_config.add_cross_attention is False:
                    logger.info(
                        f"Initializing {decoder_pretrained_model_name_or_path} as a decoder model. Cross attention"
                        f" layers are added to {decoder_pretrained_model_name_or_path} and randomly initialized if"
                        f" {decoder_pretrained_model_name_or_path}'s architecture allows for cross attention layers."
                    )
                    decoder_config.is_decoder = True
                    decoder_config.add_cross_attention = True

                kwargs_decoder["config"] = decoder_config

            if kwargs_decoder["config"].is_decoder is False or kwargs_decoder["config"].add_cross_attention is False:
                logger.warning(
                    f"Decoder model {decoder_pretrained_model_name_or_path} is not initialized as a decoder. "
                    f"In order to initialize {decoder_pretrained_model_name_or_path} as a decoder, "
                    "make sure that the attributes `is_decoder` and `add_cross_attention` of `decoder_config` "
                    "passed to `.from_sub_models_pretrained(...)` are set to `True` or do not pass a "
                    "`decoder_config` to `.from_sub_models_pretrained(...)`"
                )

            decoder = MusicgenForCausalLM.from_pretrained(decoder_pretrained_model_name_or_path, **kwargs_decoder)

        # instantiate config with corresponding kwargs
        config = MusicgenConfig(
            text_encoder=text_encoder.config, audio_encoder=audio_encoder.config, decoder=decoder.config, **kwargs
        )
        return cls(text_encoder=text_encoder, audio_encoder=audio_encoder, decoder=decoder, config=config)

    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.BoolTensor | None = None,
        input_values: torch.FloatTensor | None = None,
        padding_mask: torch.BoolTensor | None = None,
        decoder_input_ids: torch.LongTensor | None = None,
        decoder_attention_mask: torch.BoolTensor | None = None,
        encoder_outputs: tuple[torch.FloatTensor] | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        decoder_inputs_embeds: torch.FloatTensor | None = None,
        labels: torch.LongTensor | None = None,
        use_cache: bool | None = None,
        output_attentions: bool | None = None,
        output_hidden_states: bool | None = None,
        return_dict: bool | None = None,
        **kwargs,
    ) -> tuple | Seq2SeqLMOutput:
        r"""
        padding_mask (`torch.BoolTensor` of shape `(batch_size, sequence_length)`, *optional*):
            Mask to avoid performing attention on padding token indices. Mask values selected in `[0, 1]`:

            - 1 for tokens that are **not masked**,
            - 0 for tokens that are **masked**.

            [What are attention masks?](../glossary#attention-mask)
        decoder_input_ids (`torch.LongTensor` of shape `(batch_size * num_codebooks, target_sequence_length)`, *optional*):
            Indices of decoder input sequence tokens in the vocabulary, corresponding to the sequence of audio codes.

            Indices can be obtained by encoding an audio prompt with an audio encoder model to predict audio codes,
            such as with the [`EncodecModel`]. See [`EncodecModel.encode`] for details.

            [What are decoder input IDs?](../glossary#decoder-input-ids)

            <Tip warning={true}>

            The `decoder_input_ids` will automatically be converted from shape `(batch_size * num_codebooks,
            target_sequence_length)` to `(batch_size, num_codebooks, target_sequence_length)` in the forward pass. If
            you obtain audio codes from an audio encoding model, such as [`EncodecModel`], ensure that the number of
            frames is equal to 1, and that you reshape the audio codes from `(frames, batch_size, num_codebooks,
            target_sequence_length)` to `(batch_size * num_codebooks, target_sequence_length)` prior to passing them as
            `decoder_input_ids`.

            </Tip>
        decoder_attention_mask (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Default behavior: generate a tensor that ignores pad tokens in `decoder_input_ids`. Causal mask will also
            be used by default.
        labels (`torch.LongTensor` of shape `(batch_size, sequence_length, num_codebooks)`, *optional*):
            Labels for language modeling. Note that the labels **are shifted** inside the model, i.e. you can set
            `labels = input_ids` Indices are selected in `[-100, 0, ..., config.vocab_size]` All labels set to `-100`
            are ignored (masked), the loss is only computed for labels in `[0, ..., config.vocab_size]`

        Examples:
        ```python
        >>> from transformers import AutoProcessor, MusicgenForConditionalGeneration
        >>> import torch

        >>> processor = AutoProcessor.from_pretrained("facebook/musicgen-small")
        >>> model = MusicgenForConditionalGeneration.from_pretrained("facebook/musicgen-small")

        >>> inputs = processor(
        ...     text=["80s pop track with bassy drums and synth", "90s rock song with loud guitars and heavy drums"],
        ...     padding=True,
        ...     return_tensors="pt",
        ... )

        >>> pad_token_id = model.generation_config.pad_token_id
        >>> decoder_input_ids = (
        ...     torch.ones((inputs.input_ids.shape[0] * model.decoder.num_codebooks, 1), dtype=torch.long)
        ...     * pad_token_id
        ... )

        >>> logits = model(**inputs, decoder_input_ids=decoder_input_ids).logits
        >>> logits.shape  # (bsz * num_codebooks, tgt_len, vocab_size)
        torch.Size([8, 1, 2048])
        ```"""
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        kwargs_text_encoder = {
            argument[len("text_encoder_")]: value
            for argument, value in kwargs.items()
            if argument.startswith("text_encoder_")
        }

        kwargs_audio_encoder = {
            argument[len("audio_encoder_")]: value
            for argument, value in kwargs.items()
            if argument.startswith("audio_encoder_")
        }

        kwargs_decoder = {
            argument[len("decoder_") :]: value for argument, value in kwargs.items() if argument.startswith("decoder_")
        }

        if encoder_outputs is None:
            encoder_outputs = self.text_encoder(
                input_ids=input_ids,
                attention_mask=attention_mask,
                inputs_embeds=inputs_embeds,
                output_attentions=output_attentions,
                output_hidden_states=output_hidden_states,
                return_dict=return_dict,
                **kwargs_text_encoder,
            )
        elif isinstance(encoder_outputs, tuple):
            encoder_outputs = BaseModelOutput(*encoder_outputs)

        encoder_hidden_states = encoder_outputs[0]

        # optionally project encoder_hidden_states
        if (
            self.text_encoder.config.hidden_size != self.decoder.config.hidden_size
            and self.decoder.config.cross_attention_hidden_size is None
        ):
            encoder_hidden_states = self.enc_to_dec_proj(encoder_hidden_states)

        if attention_mask is not None:
            encoder_hidden_states = encoder_hidden_states * attention_mask[..., None]

        if (labels is not None) and (decoder_input_ids is None and decoder_inputs_embeds is None):
            decoder_input_ids = shift_tokens_right(
                labels, self.config.decoder.pad_token_id, self.config.decoder.decoder_start_token_id
            )

        elif decoder_input_ids is None and decoder_inputs_embeds is None:
            audio_encoder_outputs = self.audio_encoder(
                input_values=input_values,
                padding_mask=padding_mask,
                **kwargs_audio_encoder,
            )
            audio_codes = audio_encoder_outputs.audio_codes
            frames, bsz, codebooks, seq_len = audio_codes.shape
            if frames != 1:
                raise ValueError(
                    f"Expected 1 frame in the audio code outputs, got {frames} frames. Ensure chunking is "
                    "disabled by setting `chunk_length=None` in the audio encoder."
                )

            if self.config.decoder.audio_channels == 2 and audio_codes.shape[2] == self.decoder.num_codebooks // 2:
                # mono input through encodec that we convert to stereo
                audio_codes = audio_codes.repeat_interleave(2, dim=2)

            decoder_input_ids = audio_codes[0, ...].reshape(bsz * self.decoder.num_codebooks, seq_len)

        # Decode
        decoder_outputs = self.decoder(
            input_ids=decoder_input_ids,
            attention_mask=decoder_attention_mask,
            encoder_hidden_states=encoder_hidden_states,
            encoder_attention_mask=attention_mask,
            inputs_embeds=decoder_inputs_embeds,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            use_cache=use_cache,
            past_key_values=past_key_values,
            return_dict=return_dict,
            labels=labels,
            **kwargs_decoder,
        )

        if not return_dict:
            return decoder_outputs + encoder_outputs

        return Seq2SeqLMOutput(
            loss=decoder_outputs.loss,
            logits=decoder_outputs.logits,
            past_key_values=decoder_outputs.past_key_values,
            decoder_hidden_states=decoder_outputs.hidden_states,
            decoder_attentions=decoder_outputs.attentions,
            cross_attentions=decoder_outputs.cross_attentions,
            encoder_last_hidden_state=encoder_outputs.last_hidden_state,
            encoder_hidden_states=encoder_outputs.hidden_states,
            encoder_attentions=encoder_outputs.attentions,
        )

    def prepare_inputs_for_generation(
        self,
        decoder_input_ids,
        past_key_values=None,
        attention_mask=None,
        decoder_attention_mask=None,
        use_cache=None,
        encoder_outputs=None,
        decoder_delay_pattern_mask=None,
        guidance_scale=None,
        cache_position=None,
        **kwargs,
    ):
        # Overwritten -- MusicGen has custom processing
        if decoder_delay_pattern_mask is None:
            decoder_input_ids, decoder_delay_pattern_mask = self.decoder.build_delay_pattern_mask(
                decoder_input_ids,
                self.generation_config.pad_token_id,
                max_length=self.generation_config.max_length,
            )

        # apply the delay pattern mask
        decoder_input_ids = self.decoder.apply_delay_pattern_mask(decoder_input_ids, decoder_delay_pattern_mask)

        if guidance_scale is not None and guidance_scale > 1:
            # for classifier free guidance we need to replicate the decoder args across the batch dim (we'll split these
            # before sampling)
            decoder_input_ids = decoder_input_ids.repeat((2, 1))
            if decoder_attention_mask is not None:
                decoder_attention_mask = decoder_attention_mask.repeat((2, 1))

        if past_key_values is not None:
            if cache_position[-1] >= decoder_input_ids.shape[1]:
                decoder_input_ids = decoder_input_ids[:, -cache_position.shape[0] :]
            elif (
                decoder_input_ids.shape[1] != cache_position.shape[0]
            ):  # Default case (the "else", a no op, is Exception 2)
                decoder_input_ids = decoder_input_ids[:, cache_position]
            else:
                # Default to old behavior: keep only final ID
                decoder_input_ids = decoder_input_ids[:, -1:]

        return {
            "input_ids": None,  # encoder_outputs is defined. input_ids not needed
            "encoder_outputs": encoder_outputs,
            "past_key_values": past_key_values,
            "decoder_input_ids": decoder_input_ids,
            "attention_mask": attention_mask,
            "decoder_attention_mask": decoder_attention_mask,
            "use_cache": use_cache,
        }

    def _prepare_decoder_input_ids_for_generation(
        self,
        batch_size: int,
        model_input_name: str,
        model_kwargs: dict[str, torch.Tensor],
        decoder_start_token_id: int | None = None,
        bos_token_id: int | None = None,
        device: torch.device | None = None,
    ) -> tuple[torch.LongTensor, dict[str, torch.Tensor]]:
        """Prepares `decoder_input_ids` for generation with encoder-decoder models"""

        # 1. Check whether the user has defined `decoder_input_ids` manually. To facilitate in terms of input naming,
        # we also allow the user to pass it under `input_ids`, if the encoder does not use it as the main input.
        if model_kwargs is not None and "decoder_input_ids" in model_kwargs:
            decoder_input_ids = model_kwargs.pop("decoder_input_ids")
        elif "input_ids" in model_kwargs and model_input_name != "input_ids":
            decoder_input_ids = model_kwargs.pop("input_ids")
        else:
            decoder_input_ids = None

        # 2. Encoder-decoder models expect the `decoder_input_ids` to start with a special token. Let's ensure that.
        decoder_start_token_id = self._get_decoder_start_token_id(decoder_start_token_id, bos_token_id)
        if device is None:
            device = self.device
        decoder_input_ids_start = (
            torch.ones((batch_size * self.decoder.num_codebooks, 1), dtype=torch.long, device=device)
            * decoder_start_token_id
        )

        # no user input -> use decoder_start_token_id as decoder_input_ids
        if decoder_input_ids is None:
            decoder_input_ids = decoder_input_ids_start

        # user input but doesn't start with decoder_start_token_id -> prepend decoder_start_token_id (and adjust
        # decoder_attention_mask if provided)
        elif (decoder_input_ids[..., 0] != decoder_start_token_id).all().item():
            decoder_input_ids = torch.cat([decoder_input_ids_start, decoder_input_ids], dim=-1)
            if "decoder_attention_mask" in model_kwargs:
                decoder_attention_mask = model_kwargs["decoder_attention_mask"]
                decoder_attention_mask = torch.cat(
                    (torch.ones_like(decoder_attention_mask)[:, :1], decoder_attention_mask),
                    dim=-1,
                )
                model_kwargs["decoder_attention_mask"] = decoder_attention_mask

        return decoder_input_ids, model_kwargs

    def _prepare_text_encoder_kwargs_for_generation(
        self,
        inputs_tensor: torch.Tensor,
        model_kwargs,
        model_input_name: str | None,
        generation_config: GenerationConfig,
    ) -> dict[str, Any]:
        # 1. get text encoder
        encoder = self.get_encoder()
        # Compatibility with Accelerate big model inference: we need the encoder to outputs stuff on the same device
        # as the inputs.
        if hasattr(encoder, "_hf_hook"):
            encoder._hf_hook.io_same_device = True

        # 2. Prepare encoder args and encoder kwargs from model kwargs.
        irrelevant_prefix = ["decoder_", "cross_attn", "use_cache"]
        encoder_kwargs = {
            argument: value
            for argument, value in model_kwargs.items()
            if not any(argument.startswith(p) for p in irrelevant_prefix)
        }
        encoder_signature = set(inspect.signature(encoder.forward).parameters)
        encoder_accepts_wildcard = "kwargs" in encoder_signature or "model_kwargs" in encoder_signature
        if not encoder_accepts_wildcard:
            encoder_kwargs = {
                argument: value for argument, value in encoder_kwargs.items() if argument in encoder_signature
            }
        encoder_kwargs["output_attentions"] = generation_config.output_attentions
        encoder_kwargs["output_hidden_states"] = generation_config.output_hidden_states
        guidance_scale = generation_config.guidance_scale

        # 3. make sure that encoder returns `ModelOutput`
        model_input_name = model_input_name if model_input_name is not None else self.text_encoder.main_input_name
        encoder_kwargs["return_dict"] = True
        encoder_kwargs[model_input_name] = inputs_tensor
        last_hidden_state = encoder(**encoder_kwargs).last_hidden_state

        # for classifier free guidance we need to add a 'null' input to our encoder hidden states
        if guidance_scale is not None and guidance_scale > 1:
            last_hidden_state = torch.concatenate([last_hidden_state, torch.zeros_like(last_hidden_state)], dim=0)
            if "attention_mask" in model_kwargs:
                model_kwargs["attention_mask"] = torch.concatenate(
                    [model_kwargs["attention_mask"], torch.zeros_like(model_kwargs["attention_mask"])], dim=0
                )

        model_kwargs["encoder_outputs"] = BaseModelOutput(last_hidden_state=last_hidden_state)

        return model_kwargs

    def _prepare_audio_encoder_kwargs_for_generation(
        self, input_values, model_kwargs, model_input_name: str | None = None
    ):
        # 1. get audio encoder
        encoder = self.get_encoder(modality="audio")
        # Compatibility with Accelerate big model inference: we need the encoder to outputs stuff on the same device
        # as the inputs.
        if hasattr(encoder, "_hf_hook"):
            encoder._hf_hook.io_same_device = True

        # 2. Prepare encoder args and encoder kwargs from model kwargs.
        irrelevant_prefix = ["decoder_", "cross_attn", "use_cache"]
        encoder_kwargs = {
            argument: value
            for argument, value in model_kwargs.items()
            if not any(argument.startswith(p) for p in irrelevant_prefix)
        }
        encoder_signature = set(inspect.signature(encoder.forward).parameters)
        encoder_accepts_wildcard = "kwargs" in encoder_signature or "model_kwargs" in encoder_signature
        if not encoder_accepts_wildcard:
            encoder_kwargs = {
                argument: value for argument, value in encoder_kwargs.items() if argument in encoder_signature
            }

        # 3. make sure that encoder returns `ModelOutput`
        model_input_name = model_input_name if model_input_name is not None else self.audio_encoder.main_input_name
        encoder_kwargs["return_dict"] = True

        if self.decoder.config.audio_channels == 1:
            encoder_kwargs[model_input_name] = input_values
            audio_encoder_outputs = encoder.encode(**encoder_kwargs)
            audio_codes = audio_encoder_outputs.audio_codes
            audio_scales = audio_encoder_outputs.audio_scales

            frames, bsz, codebooks, seq_len = audio_codes.shape

        else:
            if input_values.shape[1] != 2:
                raise ValueError(
                    f"Expected stereo audio (2-channels) but example has {input_values.shape[1]} channel."
                )

            encoder_kwargs[model_input_name] = input_values[:, :1, :]
            audio_encoder_outputs_left = encoder.encode(**encoder_kwargs)
            audio_codes_left = audio_encoder_outputs_left.audio_codes
            audio_scales_left = audio_encoder_outputs_left.audio_scales

            encoder_kwargs[model_input_name] = input_values[:, 1:, :]
            audio_encoder_outputs_right = encoder.encode(**encoder_kwargs)
            audio_codes_right = audio_encoder_outputs_right.audio_codes
            audio_scales_right = audio_encoder_outputs_right.audio_scales

            frames, bsz, codebooks, seq_len = audio_codes_left.shape
            # copy alternating left/right channel codes into stereo codebook
            audio_codes = audio_codes_left.new_ones((frames, bsz, 2 * codebooks, seq_len))

            audio_codes[:, :, ::2, :] = audio_codes_left
            audio_codes[:, :, 1::2, :] = audio_codes_right

            if audio_scales_left != [None] or audio_scales_right != [None]:
                audio_scales = torch.stack([audio_scales_left, audio_scales_right], dim=1)
            else:
                audio_scales = [None] * bsz

        if frames != 1:
            raise ValueError(
                f"Expected 1 frame in the audio code outputs, got {frames} frames. Ensure chunking is "
                "disabled by setting `chunk_length=None` in the audio encoder."
            )

        decoder_input_ids = audio_codes[0, ...].reshape(bsz * self.decoder.num_codebooks, seq_len)

        model_kwargs["decoder_input_ids"] = decoder_input_ids
        model_kwargs["audio_scales"] = audio_scales
        return model_kwargs

    def prepare_decoder_input_ids_from_labels(self, labels: torch.Tensor):
        return shift_tokens_right(labels, self.config.decoder.pad_token_id, self.config.decoder.bos_token_id)

    def resize_token_embeddings(self, *args, **kwargs):
        raise NotImplementedError(
            "Resizing the embedding layers via the EncoderDecoderModel directly is not supported. Please use the"
            " respective methods of the wrapped objects (model.encoder.resize_token_embeddings(...) or"
            " model.decoder.resize_token_embeddings(...))"
        )

    def freeze_audio_encoder(self):
        """
        Freeze the audio encoder weights.
        """
        for param in self.audio_encoder.parameters():
            param.requires_grad = False
        self.audio_encoder._requires_grad = False

    def freeze_text_encoder(self):
        """
        Freeze the text encoder weights.
        """
        for param in self.text_encoder.parameters():
            param.requires_grad = False
        self.text_encoder._requires_grad = False

    def _maybe_initialize_input_ids_for_generation(
        self,
        inputs: torch.Tensor | None = None,
        bos_token_id: int | None = None,
        model_kwargs: dict[str, torch.Tensor] | None = None,
    ) -> torch.LongTensor:
        """Initializes input ids for generation, if necessary."""
        if inputs is not None:
            return inputs

        encoder_outputs = model_kwargs.get("encoder_outputs")
        if encoder_outputs is not None:
            # make dummy input_ids with value -100, as a sanity check ensuring that they won't be used for encoding
            shape = encoder_outputs[0].size()[:-1]
            return torch.ones(shape, dtype=torch.long, device=self.device) * -100

        if bos_token_id is None:
            raise ValueError("`bos_token_id` has to be defined when no `input_ids` are provided.")

        # If there is some tensor in `model_kwargs`, we can infer the batch size from it. This is helpful with
        # soft-prompting or in multimodal implementations built on top of decoder-only language models.
        batch_size = 1
        for value in model_kwargs.values():
            if isinstance(value, torch.Tensor):
                batch_size = value.shape[0]
                break
        return torch.ones((batch_size, 1), dtype=torch.long, device=self.device) * bos_token_id

    def _get_decoder_start_token_id(
        self, decoder_start_token_id: int | list[int] | None = None, bos_token_id: int | None = None
    ) -> int:
        decoder_start_token_id = (
            decoder_start_token_id
            if decoder_start_token_id is not None
            else self.generation_config.decoder_start_token_id
        )
        bos_token_id = bos_token_id if bos_token_id is not None else self.generation_config.bos_token_id

        if decoder_start_token_id is not None:
            return decoder_start_token_id
        elif bos_token_id is not None:
            return bos_token_id
        raise ValueError(
            "`decoder_start_token_id` or `bos_token_id` has to be defined for encoder-decoder generation."
        )

    @torch.no_grad()
    def generate(
        self,
        inputs: torch.Tensor | None = None,
        generation_config: GenerationConfig | None = None,
        logits_processor: LogitsProcessorList | None = None,
        stopping_criteria: StoppingCriteriaList | None = None,
        synced_gpus: bool | None = None,
        streamer: Optional["BaseStreamer"] = None,
        **kwargs,
    ):
        """

        Generates sequences of token ids for models with a language modeling head.

        <Tip warning={true}>

        Most generation-controlling parameters are set in `generation_config` which, if not passed, will be set to the
        model's default generation configuration. You can override any `generation_config` by passing the corresponding
        parameters to generate(), e.g. `.generate(inputs, num_beams=4, do_sample=True)`.

        For an overview of generation strategies and code examples, check out the [following
        guide](./generation_strategies).

        </Tip>

        Parameters:
            inputs (`torch.Tensor` of varying shape depending on the modality, *optional*):
                The sequence used as a prompt for the generation or as model inputs to the encoder. If `None` the
                method initializes it with `bos_token_id` and a batch size of 1. For decoder-only models `inputs`
                should be in the format `input_ids`. For encoder-decoder models *inputs* can represent any of
                `input_ids`, `input_values`, `input_features`, or `pixel_values`.
            generation_config (`~generation.GenerationConfig`, *optional*):
                The generation configuration to be used as base parametrization for the generation call. `**kwargs`
                passed to generate matching the attributes of `generation_config` will override them. If
                `generation_config` is not provided, the default will be used, which had the following loading
                priority: 1) from the `generation_config.json` model file, if it exists; 2) from the model
                configuration. Please note that unspecified parameters will inherit [`~generation.GenerationConfig`]'s
                default values, whose documentation should be checked to parameterize generation.
            logits_processor (`LogitsProcessorList`, *optional*):
                Custom logits processors that complement the default logits processors built from arguments and
                generation config. If a logit processor is passed that is already created with the arguments or a
                generation config an error is thrown. This feature is intended for advanced users.
            stopping_criteria (`StoppingCriteriaList`, *optional*):
                Custom stopping criteria that complement the default stopping criteria built from arguments and a
                generation config. If a stopping criteria is passed that is already created with the arguments or a
                generation config an error is thrown. This feature is intended for advanced users.
            synced_gpus (`bool`, *optional*, defaults to `False`):
                Whether to continue running the while loop until max_length (needed to avoid deadlocking with
                `FullyShardedDataParallel` and DeepSpeed ZeRO Stage 3).
            streamer (`BaseStreamer`, *optional*):
                Streamer object that will be used to stream the generated sequences. Generated tokens are passed
                through `streamer.put(token_ids)` and the streamer is responsible for any further processing.
            kwargs (`dict[str, Any]`, *optional*):
                Ad hoc parametrization of `generate_config` and/or additional model-specific kwargs that will be
                forwarded to the `forward` function of the model. If the model is an encoder-decoder model, encoder
                specific kwargs should not be prefixed and decoder specific kwargs should be prefixed with *decoder_*.

        Return:
            [`~utils.ModelOutput`] or `torch.LongTensor`: A [`~utils.ModelOutput`] (if `return_dict_in_generate=True`
            or when `config.return_dict_in_generate=True`) or a `torch.FloatTensor`.

                If the model is *not* an encoder-decoder model (`model.config.is_encoder_decoder=False`), the possible
                [`~utils.ModelOutput`] types are:

                    - [`~generation.GenerateDecoderOnlyOutput`],
                    - [`~generation.GenerateBeamDecoderOnlyOutput`]

                If the model is an encoder-decoder model (`model.config.is_encoder_decoder=True`), the possible
                [`~utils.ModelOutput`] types are:

                    - [`~generation.GenerateEncoderDecoderOutput`],
                    - [`~generation.GenerateBeamEncoderDecoderOutput`]
        """
        # 1. Handle `generation_config` and kwargs that might update it, and validate the resulting objects
        generation_mode_kwargs = self._extract_generation_mode_kwargs(None, kwargs, False, None, None)
        generation_config, model_kwargs = self._prepare_generation_config(generation_config, **kwargs)
        generation_mode = generation_config.get_generation_mode()
        if generation_mode not in [GenerationMode.SAMPLE, GenerationMode.GREEDY_SEARCH]:
            raise ValueError(
                "Got incompatible mode for generation, should be one of greedy or sampling. "
                "Ensure that beam search is de-activated by setting `num_beams=1`."
            )

        self._validate_model_kwargs(model_kwargs.copy())
        self._validate_generation_mode(generation_mode, generation_config, generation_mode_kwargs)

        if model_kwargs.get("encoder_outputs") is not None and type(model_kwargs["encoder_outputs"]) is tuple:
            # wrap the unconditional outputs as a BaseModelOutput for compatibility with the rest of generate
            model_kwargs["encoder_outputs"] = BaseModelOutput(last_hidden_state=model_kwargs["encoder_outputs"][0])

        # 2. Set generation parameters if not already defined
        logits_processor = logits_processor if logits_processor is not None else LogitsProcessorList()
        stopping_criteria = stopping_criteria if stopping_criteria is not None else StoppingCriteriaList()

        requires_attention_mask = "encoder_outputs" not in model_kwargs
        kwargs_has_attention_mask = model_kwargs.get("attention_mask", None) is not None

        # 3. Define model inputs
        inputs_tensor, model_input_name, model_kwargs = self._prepare_model_inputs(
            inputs, generation_config.bos_token_id, model_kwargs
        )
        batch_size = inputs_tensor.shape[0]
        self._prepare_special_tokens(generation_config, kwargs_has_attention_mask, device=inputs_tensor.device)

        # 4. Define other model kwargs
        model_kwargs["use_cache"] = generation_config.use_cache
        model_kwargs["guidance_scale"] = generation_config.guidance_scale

        if model_kwargs.get("attention_mask", None) is None and requires_attention_mask:
            model_kwargs["attention_mask"] = self._prepare_attention_mask_for_generation(
                inputs_tensor, generation_config, model_kwargs
            )

        if "encoder_outputs" not in model_kwargs:
            # encoder_outputs are created and added to `model_kwargs`
            model_kwargs = self._prepare_text_encoder_kwargs_for_generation(
                inputs_tensor, model_kwargs, model_input_name, generation_config
            )

        if "decoder_input_ids" not in model_kwargs and "input_values" in model_kwargs:
            model_kwargs = self._prepare_audio_encoder_kwargs_for_generation(
                model_kwargs["input_values"],
                model_kwargs,
            )

        # 5. Prepare `input_ids` which will be used for auto-regressive generation
        input_ids, model_kwargs = self._prepare_decoder_input_ids_for_generation(
            batch_size=batch_size,
            model_input_name=model_input_name,
            model_kwargs=model_kwargs,
            decoder_start_token_id=generation_config._decoder_start_token_tensor,
            bos_token_id=generation_config._bos_token_tensor,
            device=inputs_tensor.device,
        )

        # 6. Prepare `max_length` depending on other stopping criteria.
        input_ids_length = input_ids.shape[-1]
        has_default_max_length = kwargs.get("max_length") is None and generation_config.max_length is not None
        has_default_min_length = kwargs.get("min_length") is None and generation_config.min_length is not None
        generation_config = self._prepare_generated_length(
            generation_config=generation_config,
            has_default_max_length=has_default_max_length,
            has_default_min_length=has_default_min_length,
            model_input_name=model_input_name,
            inputs_tensor=inputs_tensor,
            input_ids_length=input_ids_length,
        )

        # build the delay pattern mask for offsetting each codebook prediction by 1 (this behaviour is specific to MusicGen)
        input_ids, decoder_delay_pattern_mask = self.decoder.build_delay_pattern_mask(
            input_ids,
            pad_token_id=generation_config._decoder_start_token_tensor,
            max_length=generation_config.max_length,
        )
        # stash the delay mask so that we don't have to recompute in each forward pass
        model_kwargs["decoder_delay_pattern_mask"] = decoder_delay_pattern_mask

        # input_ids are ready to be placed on the streamer (if used)
        if streamer is not None:
            streamer.put(input_ids.cpu())

        # 7. determine generation mode
        generation_mode = generation_config.get_generation_mode()

        # 8. prepare batched CFG externally (to enable coexistence with the unbatched CFG)
        if generation_config.guidance_scale is not None and generation_config.guidance_scale > 1:
            logits_processor.append(ClassifierFreeGuidanceLogitsProcessor(generation_config.guidance_scale))
            generation_config.guidance_scale = None

        # 9. prepare distribution pre_processing samplers
        logits_processor = self._get_logits_processor(
            generation_config=generation_config,
            input_ids_seq_length=input_ids_length,
            encoder_input_ids=inputs_tensor,
            prefix_allowed_tokens_fn=None,
            logits_processor=logits_processor,
            device=input_ids.device,
        )

        # 10. prepare stopping criteria
        stopping_criteria = self._get_stopping_criteria(
            generation_config=generation_config, stopping_criteria=stopping_criteria
        )

        # expand input_ids with `num_return_sequences` additional sequences per batch
        input_ids, model_kwargs = self._expand_inputs_for_generation(
            input_ids=input_ids,
            expand_size=generation_config.num_return_sequences,
            is_encoder_decoder=self.config.is_encoder_decoder,
            **model_kwargs,
        )

        # 10b. prepare prefill outputs
        generation_mode_kwargs["prefill_outputs"] = self._prefill(input_ids, generation_config, model_kwargs)

        # 11. run sample
        outputs = self._sample(
            input_ids,
            logits_processor=logits_processor,
            stopping_criteria=stopping_criteria,
            generation_config=generation_config,
            **generation_mode_kwargs,
            **model_kwargs,
        )

        if generation_config.return_dict_in_generate:
            output_ids = outputs.sequences
        else:
            output_ids = outputs

        # apply the pattern mask to the final ids
        output_ids = self.decoder.apply_delay_pattern_mask(output_ids, model_kwargs["decoder_delay_pattern_mask"])

        # revert the pattern delay mask by filtering the pad token id
        output_ids = output_ids[output_ids != generation_config._pad_token_tensor].reshape(
            batch_size, self.decoder.num_codebooks, -1
        )

        # append the frame dimension back to the audio codes
        output_ids = output_ids[None, ...]

        audio_scales = model_kwargs.get("audio_scales")
        if audio_scales is None:
            audio_scales = [None] * batch_size

        if self.decoder.config.audio_channels == 1:
            output_values = self.audio_encoder.decode(
                output_ids,
                audio_scales=audio_scales,
            ).audio_values
        else:
            codec_outputs_left = self.audio_encoder.decode(output_ids[:, :, ::2, :], audio_scales=audio_scales)
            output_values_left = codec_outputs_left.audio_values

            codec_outputs_right = self.audio_encoder.decode(output_ids[:, :, 1::2, :], audio_scales=audio_scales)
            output_values_right = codec_outputs_right.audio_values

            output_values = torch.cat([output_values_left, output_values_right], dim=1)

        if generation_config.return_dict_in_generate:
            outputs.sequences = output_values
            return outputs
        else:
            return output_values

    def get_unconditional_inputs(self, num_samples=1):
        """
        Helper function to get null inputs for unconditional generation, enabling the model to be used without the
        feature extractor or tokenizer.

        Args:
            num_samples (int, *optional*):
                Number of audio samples to unconditionally generate.
            max_new_tokens (int, *optional*):
                Number of tokens to generate for each sample. More tokens means longer audio samples, at the expense of
                longer inference (since more audio tokens need to be generated per sample).

        Example:
        ```python
        >>> from transformers import MusicgenForConditionalGeneration

        >>> model = MusicgenForConditionalGeneration.from_pretrained("facebook/musicgen-small")

        >>> # get the unconditional (or 'null') inputs for the model
        >>> unconditional_inputs = model.get_unconditional_inputs(num_samples=1)
        >>> audio_samples = model.generate(**unconditional_inputs, max_new_tokens=256)
        ```"""
        last_hidden_state = torch.zeros(
            (num_samples, 1, self.config.text_encoder.hidden_size), device=self.device, dtype=self.dtype
        )

        attention_mask = torch.zeros((num_samples, 1), device=self.device, dtype=torch.long)

        return MusicgenUnconditionalInput(
            encoder_outputs=(last_hidden_state,),
            attention_mask=attention_mask,
            guidance_scale=1.0,
        )


__all__ = ["MusicgenForConditionalGeneration", "MusicgenForCausalLM", "MusicgenModel", "MusicgenPreTrainedModel"]
