/*
 * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */
package javax.swing;

import java.text.Collator;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * An implementation of <code>RowSorter</code> that provides sorting and
 * filtering around a grid-based data model.
 * Beyond creating and installing a <code>RowSorter</code>, you very rarely
 * need to interact with one directly.  Refer to
 * {@link javax.swing.table.TableRowSorter TableRowSorter} for a concrete
 * implementation of <code>RowSorter</code> for <code>JTable</code>.
 * <p>
 * Sorting is done based on the current <code>SortKey</code>s, in order.
 * If two objects are equal (the <code>Comparator</code> for the
 * column returns 0) the next <code>SortKey</code> is used.  If no
 * <code>SortKey</code>s remain or the order is <code>UNSORTED</code>, then
 * the order of the rows in the model is used.
 * <p>
 * Sorting of each column is done by way of a <code>Comparator</code>
 * that you can specify using the <code>setComparator</code> method.
 * If a <code>Comparator</code> has not been specified, the
 * <code>Comparator</code> returned by
 * <code>Collator.getInstance()</code> is used on the results of
 * calling <code>toString</code> on the underlying objects.  The
 * <code>Comparator</code> is never passed <code>null</code>.  A
 * <code>null</code> value is treated as occurring before a
 * non-<code>null</code> value, and two <code>null</code> values are
 * considered equal.
 * <p>
 * If you specify a <code>Comparator</code> that casts its argument to
 * a type other than that provided by the model, a
 * <code>ClassCastException</code> will be thrown when the data is sorted.
 * <p>
 * In addition to sorting, <code>DefaultRowSorter</code> provides the
 * ability to filter rows.  Filtering is done by way of a
 * <code>RowFilter</code> that is specified using the
 * <code>setRowFilter</code> method.  If no filter has been specified all
 * rows are included.
 * <p>
 * By default, rows are in unsorted order (the same as the model) and
 * every column is sortable. The default <code>Comparator</code>s are
 * documented in the subclasses (for example, {@link
 * javax.swing.table.TableRowSorter TableRowSorter}).
 * <p>
 * If the underlying model structure changes (the
 * <code>modelStructureChanged</code> method is invoked) the following
 * are reset to their default values: <code>Comparator</code>s by
 * column, current sort order, and whether each column is sortable. To
 * find the default <code>Comparator</code>s, see the concrete
 * implementation (for example, {@link
 * javax.swing.table.TableRowSorter TableRowSorter}).  The default
 * sort order is unsorted (the same as the model), and columns are
 * sortable by default.
 * <p>
 * <code>DefaultRowSorter</code> is an abstract class.  Concrete
 * subclasses must provide access to the underlying data by invoking
 * {@code setModelWrapper}. The {@code setModelWrapper} method
 * <b>must</b> be invoked soon after the constructor is
 * called, ideally from within the subclass's constructor.
 * Undefined behavior will result if you use a {@code
 * DefaultRowSorter} without specifying a {@code ModelWrapper}.
 * <p>
 * <code>DefaultRowSorter</code> has two formal type parameters.  The
 * first type parameter corresponds to the class of the model, for example
 * <code>DefaultTableModel</code>.  The second type parameter
 * corresponds to the class of the identifier passed to the
 * <code>RowFilter</code>.  Refer to <code>TableRowSorter</code> and
 * <code>RowFilter</code> for more details on the type parameters.
 *
 * @param <M> the type of the model
 * @param <I> the type of the identifier passed to the <code>RowFilter</code>
 * @see javax.swing.table.TableRowSorter
 * @see javax.swing.table.DefaultTableModel
 * @see java.text.Collator
 * @since 1.6
 */
public abstract class DefaultRowSorter<M, I> extends RowSorter<M> {
    /**
     * Whether or not we resort on TableModelEvent.UPDATEs.
     */
    private boolean sortsOnUpdates;

    /**
     * View (JTable) -> model.
     */
    private Row[] viewToModel;

    /**
     * model -> view (JTable)
     */
    private int[] modelToView;

    /**
     * Comparators specified by column.
     */
    private Comparator<?>[] comparators;

    /**
     * Whether or not the specified column is sortable, by column.
     */
    private boolean[] isSortable;

    /**
     * Cached SortKeys for the current sort.
     */
    private SortKey[] cachedSortKeys;

    /**
     * Cached comparators for the current sort
     */
    private Comparator<?>[] sortComparators;

    /**
     * Developer supplied Filter.
     */
    private RowFilter<? super M,? super I> filter;

    /**
     * Value passed to the filter.  The same instance is passed to the
     * filter for different rows.
     */
    private FilterEntry filterEntry;

    /**
     * The sort keys.
     */
    private List<SortKey> sortKeys;

    /**
     * Whether or not to use getStringValueAt.  This is indexed by column.
     */
    private boolean[] useToString;

    /**
     * Indicates the contents are sorted.  This is used if
     * getSortsOnUpdates is false and an update event is received.
     */
    private boolean sorted;

    /**
     * Maximum number of sort keys.
     */
    private int maxSortKeys;

    /**
     * Provides access to the data we're sorting/filtering.
     */
    private ModelWrapper<M,I> modelWrapper;

    /**
     * Size of the model. This is used to enforce error checking within
     * the table changed notification methods (such as rowsInserted).
     */
    private int modelRowCount;

    // Whether to print warning about JDK-8160087
    private static boolean warning8160087 = true;

    /**
     * Creates an empty <code>DefaultRowSorter</code>.
     */
    public DefaultRowSorter() {
        sortKeys = Collections.emptyList();
        maxSortKeys = 3;
    }

    /**
     * Sets the model wrapper providing the data that is being sorted and
     * filtered.
     *
     * @param modelWrapper the model wrapper responsible for providing the
     *         data that gets sorted and filtered
     * @throws IllegalArgumentException if {@code modelWrapper} is
     *         {@code null}
     */
    protected final void setModelWrapper(ModelWrapper<M,I> modelWrapper) {
        if (modelWrapper == null) {
            throw new IllegalArgumentException(
                "modelWrapper most be non-null");
        }
        ModelWrapper<M,I> last = this.modelWrapper;
        this.modelWrapper = modelWrapper;
        if (last != null) {
            modelStructureChanged();
        } else {
            // If last is null, we're in the constructor. If we're in
            // the constructor we don't want to call to overridable methods.
            modelRowCount = getModelWrapper().getRowCount();
        }
    }

    /**
     * Returns the model wrapper providing the data that is being sorted and
     * filtered.
     *
     * @return the model wrapper responsible for providing the data that
     *         gets sorted and filtered
     */
    protected final ModelWrapper<M,I> getModelWrapper() {
        return modelWrapper;
    }

    /**
     * Returns the underlying model.
     *
     * @return the underlying model
     */
    public final M getModel() {
        return getModelWrapper().getModel();
    }

    /**
     * Sets whether or not the specified column is sortable.  The specified
     * value is only checked when <code>toggleSortOrder</code> is invoked.
     * It is still possible to sort on a column that has been marked as
     * unsortable by directly setting the sort keys.  The default is
     * true.
     *
     * @param column the column to enable or disable sorting on, in terms
     *        of the underlying model
     * @param sortable whether or not the specified column is sortable
     * @throws IndexOutOfBoundsException if <code>column</code> is outside
     *         the range of the model
     * @see #toggleSortOrder
     * @see #setSortKeys
     */
    public void setSortable(int column, boolean sortable) {
        checkColumn(column);
        if (isSortable == null) {
            isSortable = new boolean[getModelWrapper().getColumnCount()];
            for (int i = isSortable.length - 1; i >= 0; i--) {
                isSortable[i] = true;
            }
        }
        isSortable[column] = sortable;
    }

    /**
     * Returns true if the specified column is sortable; otherwise, false.
     *
     * @param column the column to check sorting for, in terms of the
     *        underlying model
     * @return true if the column is sortable
     * @throws IndexOutOfBoundsException if column is outside
     *         the range of the underlying model
     */
    public boolean isSortable(int column) {
        checkColumn(column);
        return (isSortable == null) ? true : isSortable[column];
    }

    /**
     * Sets the sort keys. This creates a copy of the supplied
     * {@code List}; subsequent changes to the supplied
     * {@code List} do not effect this {@code DefaultRowSorter}.
     * If the sort keys have changed this triggers a sort.
     *
     * @param sortKeys the new <code>SortKeys</code>; <code>null</code>
     *        is a shorthand for specifying an empty list,
     *        indicating that the view should be unsorted
     * @throws IllegalArgumentException if any of the values in
     *         <code>sortKeys</code> are null or have a column index outside
     *         the range of the model
     */
    public void setSortKeys(List<? extends SortKey> sortKeys) {
        List<SortKey> old = this.sortKeys;
        if (sortKeys != null && sortKeys.size() > 0) {
            int max = getModelWrapper().getColumnCount();
            for (SortKey key : sortKeys) {
                if (key == null || key.getColumn() < 0 ||
                        key.getColumn() >= max) {
                    throw new IllegalArgumentException("Invalid SortKey");
                }
            }
            this.sortKeys = Collections.unmodifiableList(
                    new ArrayList<SortKey>(sortKeys));
        }
        else {
            this.sortKeys = Collections.emptyList();
        }
        if (!this.sortKeys.equals(old)) {
            fireSortOrderChanged();
            if (viewToModel == null) {
                // Currently unsorted, use sort so that internal fields
                // are correctly set.
                sort();
            } else {
                sortExistingData();
            }
        }
    }

    /**
     * Returns the current sort keys.  This returns an unmodifiable
     * {@code non-null List}. If you need to change the sort keys,
     * make a copy of the returned {@code List}, mutate the copy
     * and invoke {@code setSortKeys} with the new list.
     *
     * @return the current sort order
     */
    public List<? extends SortKey> getSortKeys() {
        return sortKeys;
    }

    /**
     * Sets the maximum number of sort keys.  The number of sort keys
     * determines how equal values are resolved when sorting.  For
     * example, assume a table row sorter is created and
     * <code>setMaxSortKeys(2)</code> is invoked on it. The user
     * clicks the header for column 1, causing the table rows to be
     * sorted based on the items in column 1.  Next, the user clicks
     * the header for column 2, causing the table to be sorted based
     * on the items in column 2; if any items in column 2 are equal,
     * then those particular rows are ordered based on the items in
     * column 1. In this case, we say that the rows are primarily
     * sorted on column 2, and secondarily on column 1.  If the user
     * then clicks the header for column 3, then the items are
     * primarily sorted on column 3 and secondarily sorted on column
     * 2.  Because the maximum number of sort keys has been set to 2
     * with <code>setMaxSortKeys</code>, column 1 no longer has an
     * effect on the order.
     * <p>
     * The maximum number of sort keys is enforced by
     * <code>toggleSortOrder</code>.  You can specify more sort
     * keys by invoking <code>setSortKeys</code> directly and they will
     * all be honored.  However if <code>toggleSortOrder</code> is subsequently
     * invoked the maximum number of sort keys will be enforced.
     * The default value is 3.
     *
     * @param max the maximum number of sort keys
     * @throws IllegalArgumentException if <code>max</code> &lt; 1
     */
    public void setMaxSortKeys(int max) {
        if (max < 1) {
            throw new IllegalArgumentException("Invalid max");
        }
        maxSortKeys = max;
    }

    /**
     * Returns the maximum number of sort keys.
     *
     * @return the maximum number of sort keys
     */
    public int getMaxSortKeys() {
        return maxSortKeys;
    }

    /**
     * If true, specifies that a sort should happen when the underlying
     * model is updated (<code>rowsUpdated</code> is invoked).  For
     * example, if this is true and the user edits an entry the
     * location of that item in the view may change.  The default is
     * false.
     *
     * @param sortsOnUpdates whether or not to sort on update events
     */
    public void setSortsOnUpdates(boolean sortsOnUpdates) {
        this.sortsOnUpdates = sortsOnUpdates;
    }

    /**
     * Returns true if  a sort should happen when the underlying
     * model is updated; otherwise, returns false.
     *
     * @return whether or not to sort when the model is updated
     */
    public boolean getSortsOnUpdates() {
        return sortsOnUpdates;
    }

    /**
     * Sets the filter that determines which rows, if any, should be
     * hidden from the view.  The filter is applied before sorting.  A value
     * of <code>null</code> indicates all values from the model should be
     * included.
     * <p>
     * <code>RowFilter</code>'s <code>include</code> method is passed an
     * <code>Entry</code> that wraps the underlying model.  The number
     * of columns in the <code>Entry</code> corresponds to the
     * number of columns in the <code>ModelWrapper</code>.  The identifier
     * comes from the <code>ModelWrapper</code> as well.
     * <p>
     * This method triggers a sort.
     *
     * @param filter the filter used to determine what entries should be
     *        included
     */
    public void setRowFilter(RowFilter<? super M,? super I> filter) {
        this.filter = filter;
        sort();
    }

    /**
     * Returns the filter that determines which rows, if any, should
     * be hidden from view.
     *
     * @return the filter
     */
    public RowFilter<? super M,? super I> getRowFilter() {
        return filter;
    }

    /**
     * Reverses the sort order from ascending to descending (or
     * descending to ascending) if the specified column is already the
     * primary sorted column; otherwise, makes the specified column
     * the primary sorted column, with an ascending sort order.  If
     * the specified column is not sortable, this method has no
     * effect.
     *
     * @param column index of the column to make the primary sorted column,
     *        in terms of the underlying model
     * @throws IndexOutOfBoundsException {@inheritDoc}
     * @see #setSortable(int,boolean)
     * @see #setMaxSortKeys(int)
     */
    public void toggleSortOrder(int column) {
        checkColumn(column);
        if (isSortable(column)) {
            List<SortKey> keys = new ArrayList<SortKey>(getSortKeys());
            SortKey sortKey;
            int sortIndex;
            for (sortIndex = keys.size() - 1; sortIndex >= 0; sortIndex--) {
                if (keys.get(sortIndex).getColumn() == column) {
                    break;
                }
            }
            if (sortIndex == -1) {
                // Key doesn't exist
                sortKey = new SortKey(column, SortOrder.ASCENDING);
                keys.add(0, sortKey);
            }
            else if (sortIndex == 0) {
                // It's the primary sorting key, toggle it
                keys.set(0, toggle(keys.get(0)));
            }
            else {
                // It's not the first, but was sorted on, remove old
                // entry, insert as first with ascending.
                keys.remove(sortIndex);
                keys.add(0, new SortKey(column, SortOrder.ASCENDING));
            }
            if (keys.size() > getMaxSortKeys()) {
                keys = keys.subList(0, getMaxSortKeys());
            }
            setSortKeys(keys);
        }
    }

    private SortKey toggle(SortKey key) {
        if (key.getSortOrder() == SortOrder.ASCENDING) {
            return new SortKey(key.getColumn(), SortOrder.DESCENDING);
        }
        return new SortKey(key.getColumn(), SortOrder.ASCENDING);
    }

    /**
     * {@inheritDoc}
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public int convertRowIndexToView(int index) {
        if (modelToView == null) {
            return convertUnsortedUnfiltered(index);
        }
        return modelToView[index];
    }

    /**
     * {@inheritDoc}
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public int convertRowIndexToModel(int index) {
        if (viewToModel == null) {
            return convertUnsortedUnfiltered(index);
        }
        return viewToModel[index].modelIndex;
    }

    private int convertUnsortedUnfiltered(int index) {
        if (index < 0 || index >= modelRowCount) {
            if(index >= modelRowCount &&
                                      index < getModelWrapper().getRowCount()) {
                // 8160087
                if(warning8160087) {
                    warning8160087 = false;
                    System.err.println("WARNING: row index is bigger than " +
                            "sorter's row count. Most likely this is a wrong " +
                            "sorter usage.");
                }
            } else {
                throw new IndexOutOfBoundsException("Invalid index");
            }
        }
        return index;
    }


    private boolean isUnsorted() {
        List<? extends SortKey> keys = getSortKeys();
        int keySize = keys.size();
        return (keySize == 0 || keys.get(0).getSortOrder() ==
                SortOrder.UNSORTED);
    }

    /**
     * Sorts the existing filtered data.  This should only be used if
     * the filter hasn't changed.
     */
    private void sortExistingData() {
        int[] lastViewToModel = getViewToModelAsInts(viewToModel);

        updateUseToString();
        cacheSortKeys(getSortKeys());

        if (isUnsorted()) {
            if (getRowFilter() == null) {
                viewToModel = null;
                modelToView = null;
            } else {
                int included = 0;
                for (int i = 0; i < modelToView.length; i++) {
                    if (modelToView[i] != -1) {
                        viewToModel[included].modelIndex = i;
                        modelToView[i] = included++;
                    }
                }
            }
        } else {
            // sort the data
            Arrays.sort(viewToModel);

            // Update the modelToView array
            setModelToViewFromViewToModel(false);
        }
        fireRowSorterChanged(lastViewToModel);
    }

    /**
     * Sorts and filters the rows in the view based on the sort keys
     * of the columns currently being sorted and the filter, if any,
     * associated with this sorter.  An empty <code>sortKeys</code> list
     * indicates that the view should unsorted, the same as the model.
     *
     * @see #setRowFilter
     * @see #setSortKeys
     */
    public void sort() {
        sorted = true;
        int[] lastViewToModel = getViewToModelAsInts(viewToModel);
        updateUseToString();
        if (isUnsorted()) {
            // Unsorted
            cachedSortKeys = new SortKey[0];
            if (getRowFilter() == null) {
                // No filter & unsorted
                if (viewToModel != null) {
                    // sorted -> unsorted
                    viewToModel = null;
                    modelToView = null;
                }
                else {
                    // unsorted -> unsorted
                    // No need to do anything.
                    return;
                }
            }
            else {
                // There is filter, reset mappings
                initializeFilteredMapping();
            }
        }
        else {
            cacheSortKeys(getSortKeys());

            if (getRowFilter() != null) {
                initializeFilteredMapping();
            }
            else {
                createModelToView(getModelWrapper().getRowCount());
                createViewToModel(getModelWrapper().getRowCount());
            }

            // sort them
            Arrays.sort(viewToModel);

            // Update the modelToView array
            setModelToViewFromViewToModel(false);
        }
        fireRowSorterChanged(lastViewToModel);
    }

    /**
     * Updates the useToString mapping before a sort.
     */
    private void updateUseToString() {
        int i = getModelWrapper().getColumnCount();
        if (useToString == null || useToString.length != i) {
            useToString = new boolean[i];
        }
        for (--i; i >= 0; i--) {
            useToString[i] = useToString(i);
        }
    }

    /**
     * Resets the viewToModel and modelToView mappings based on
     * the current Filter.
     */
    private void initializeFilteredMapping() {
        int rowCount = getModelWrapper().getRowCount();
        int i, j;
        int excludedCount = 0;

        // Update model -> view
        createModelToView(rowCount);
        for (i = 0; i < rowCount; i++) {
            if (include(i)) {
                modelToView[i] = i - excludedCount;
            }
            else {
                modelToView[i] = -1;
                excludedCount++;
            }
        }

        // Update view -> model
        createViewToModel(rowCount - excludedCount);
        for (i = 0, j = 0; i < rowCount; i++) {
            if (modelToView[i] != -1) {
                viewToModel[j++].modelIndex = i;
            }
        }
    }

    /**
     * Makes sure the modelToView array is of size rowCount.
     */
    private void createModelToView(int rowCount) {
        if (modelToView == null || modelToView.length != rowCount) {
            modelToView = new int[rowCount];
        }
    }

    /**
     * Resets the viewToModel array to be of size rowCount.
     */
    private void createViewToModel(int rowCount) {
        int recreateFrom = 0;
        if (viewToModel != null) {
            recreateFrom = Math.min(rowCount, viewToModel.length);
            if (viewToModel.length != rowCount) {
                Row[] oldViewToModel = viewToModel;
                viewToModel = new Row[rowCount];
                System.arraycopy(oldViewToModel, 0, viewToModel,
                                 0, recreateFrom);
            }
        }
        else {
            viewToModel = new Row[rowCount];
        }
        int i;
        for (i = 0; i < recreateFrom; i++) {
            viewToModel[i].modelIndex = i;
        }
        for (i = recreateFrom; i < rowCount; i++) {
            viewToModel[i] = new Row(this, i);
        }
    }

    /**
     * Caches the sort keys before a sort.
     */
    private void cacheSortKeys(List<? extends SortKey> keys) {
        int keySize = keys.size();
        sortComparators = new Comparator<?>[keySize];
        for (int i = 0; i < keySize; i++) {
            sortComparators[i] = getComparator0(keys.get(i).getColumn());
        }
        cachedSortKeys = keys.toArray(new SortKey[keySize]);
    }

    /**
     * Returns whether or not to convert the value to a string before
     * doing comparisons when sorting.  If true
     * <code>ModelWrapper.getStringValueAt</code> will be used, otherwise
     * <code>ModelWrapper.getValueAt</code> will be used.  It is up to
     * subclasses, such as <code>TableRowSorter</code>, to honor this value
     * in their <code>ModelWrapper</code> implementation.
     *
     * @param column the index of the column to test, in terms of the
     *        underlying model
     * @return true if values are to be converted to strings before doing
     *              comparisons when sorting
     * @throws IndexOutOfBoundsException if <code>column</code> is not valid
     */
    protected boolean useToString(int column) {
        return (getComparator(column) == null);
    }

    /**
     * Refreshes the modelToView mapping from that of viewToModel.
     * If <code>unsetFirst</code> is true, all indices in modelToView are
     * first set to -1.
     */
    private void setModelToViewFromViewToModel(boolean unsetFirst) {
        int i;
        if (unsetFirst) {
            for (i = modelToView.length - 1; i >= 0; i--) {
                modelToView[i] = -1;
            }
        }
        for (i = viewToModel.length - 1; i >= 0; i--) {
            modelToView[viewToModel[i].modelIndex] = i;
        }
    }

    private int[] getViewToModelAsInts(Row[] viewToModel) {
        if (viewToModel != null) {
            int[] viewToModelI = new int[viewToModel.length];
            for (int i = viewToModel.length - 1; i >= 0; i--) {
                viewToModelI[i] = viewToModel[i].modelIndex;
            }
            return viewToModelI;
        }
        return new int[0];
    }

    /**
     * Sets the <code>Comparator</code> to use when sorting the specified
     * column.  This does not trigger a sort.  If you want to sort after
     * setting the comparator you need to explicitly invoke <code>sort</code>.
     *
     * @param column the index of the column the <code>Comparator</code> is
     *        to be used for, in terms of the underlying model
     * @param comparator the <code>Comparator</code> to use
     * @throws IndexOutOfBoundsException if <code>column</code> is outside
     *         the range of the underlying model
     */
    public void setComparator(int column, Comparator<?> comparator) {
        checkColumn(column);
        if (comparators == null) {
            comparators = new Comparator<?>[getModelWrapper().getColumnCount()];
        }
        comparators[column] = comparator;
    }

    /**
     * Returns the <code>Comparator</code> for the specified
     * column.  This will return <code>null</code> if a <code>Comparator</code>
     * has not been specified for the column.
     *
     * @param column the column to fetch the <code>Comparator</code> for, in
     *        terms of the underlying model
     * @return the <code>Comparator</code> for the specified column
     * @throws IndexOutOfBoundsException if column is outside
     *         the range of the underlying model
     */
    public Comparator<?> getComparator(int column) {
        checkColumn(column);
        if (comparators != null) {
            return comparators[column];
        }
        return null;
    }

    // Returns the Comparator to use during sorting.  Where as
    // getComparator() may return null, this will never return null.
    private Comparator<?> getComparator0(int column) {
        Comparator<?> comparator = getComparator(column);
        if (comparator != null) {
            return comparator;
        }
        // This should be ok as useToString(column) should have returned
        // true in this case.
        return Collator.getInstance();
    }

    private RowFilter.Entry<M,I> getFilterEntry(int modelIndex) {
        if (filterEntry == null) {
            filterEntry = new FilterEntry();
        }
        filterEntry.modelIndex = modelIndex;
        return filterEntry;
    }

    /**
     * {@inheritDoc}
     */
    public int getViewRowCount() {
        if (viewToModel != null) {
            // When filtering this may differ from getModelWrapper().getRowCount()
            return viewToModel.length;
        }
        return Math.max(getModelWrapper().getRowCount(), modelRowCount);
    }

    /**
     * {@inheritDoc}
     */
    public int getModelRowCount() {
        return getModelWrapper().getRowCount();
    }

    private void allChanged() {
        modelToView = null;
        viewToModel = null;
        comparators = null;
        isSortable = null;
        if (isUnsorted()) {
            // Keys are already empty, to force a resort we have to
            // call sort
            sort();
        } else {
            setSortKeys(null);
        }
    }

    /**
     * {@inheritDoc}
     */
    public void modelStructureChanged() {
        allChanged();
        modelRowCount = getModelWrapper().getRowCount();
    }

    /**
     * {@inheritDoc}
     */
    public void allRowsChanged() {
        modelRowCount = getModelWrapper().getRowCount();
        sort();
    }

    /**
     * {@inheritDoc}
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public void rowsInserted(int firstRow, int endRow) {
        checkAgainstModel(firstRow, endRow);
        int newModelRowCount = getModelWrapper().getRowCount();
        if (endRow >= newModelRowCount) {
            throw new IndexOutOfBoundsException("Invalid range");
        }
        modelRowCount = newModelRowCount;
        if (shouldOptimizeChange(firstRow, endRow)) {
            rowsInserted0(firstRow, endRow);
        }
    }

    /**
     * {@inheritDoc}
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public void rowsDeleted(int firstRow, int endRow) {
        checkAgainstModel(firstRow, endRow);
        if (firstRow >= modelRowCount || endRow >= modelRowCount) {
            throw new IndexOutOfBoundsException("Invalid range");
        }
        modelRowCount = getModelWrapper().getRowCount();
        if (shouldOptimizeChange(firstRow, endRow)) {
            rowsDeleted0(firstRow, endRow);
        }
    }

    /**
     * {@inheritDoc}
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public void rowsUpdated(int firstRow, int endRow) {
        checkAgainstModel(firstRow, endRow);
        if (firstRow >= modelRowCount || endRow >= modelRowCount) {
            throw new IndexOutOfBoundsException("Invalid range");
        }
        if (getSortsOnUpdates()) {
            if (shouldOptimizeChange(firstRow, endRow)) {
                rowsUpdated0(firstRow, endRow);
            }
        }
        else {
            sorted = false;
        }
    }

    /**
     * {@inheritDoc}
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public void rowsUpdated(int firstRow, int endRow, int column) {
        checkColumn(column);
        rowsUpdated(firstRow, endRow);
    }

    private void checkAgainstModel(int firstRow, int endRow) {
        if (firstRow > endRow || firstRow < 0 || endRow < 0 ||
                firstRow > modelRowCount) {
            throw new IndexOutOfBoundsException("Invalid range");
        }
    }

    /**
     * Returns true if the specified row should be included.
     */
    private boolean include(int row) {
        RowFilter<? super M, ? super I> filter = getRowFilter();
        if (filter != null) {
            return filter.include(getFilterEntry(row));
        }
        // null filter, always include the row.
        return true;
    }

    @SuppressWarnings("unchecked")
    private int compare(int model1, int model2) {
        int column;
        SortOrder sortOrder;
        Object v1, v2;
        int result;

        for (int counter = 0; counter < cachedSortKeys.length; counter++) {
            column = cachedSortKeys[counter].getColumn();
            sortOrder = cachedSortKeys[counter].getSortOrder();
            if (sortOrder == SortOrder.UNSORTED) {
                result = model1 - model2;
            } else {
                // v1 != null && v2 != null
                if (useToString[column]) {
                    v1 = getModelWrapper().getStringValueAt(model1, column);
                    v2 = getModelWrapper().getStringValueAt(model2, column);
                } else {
                    v1 = getModelWrapper().getValueAt(model1, column);
                    v2 = getModelWrapper().getValueAt(model2, column);
                }
                // Treat nulls as < then non-null
                if (v1 == null) {
                    if (v2 == null) {
                        result = 0;
                    } else {
                        result = -1;
                    }
                } else if (v2 == null) {
                    result = 1;
                } else {
                    Comparator<Object> c =
                        (Comparator<Object>)sortComparators[counter];
                    result = c.compare(v1, v2);
                }
                if (sortOrder == SortOrder.DESCENDING) {
                    result *= -1;
                }
            }
            if (result != 0) {
                return result;
            }
        }
        // If we get here, they're equal. Fallback to model order.
        return model1 - model2;
    }

    /**
     * Whether not we are filtering/sorting.
     */
    private boolean isTransformed() {
        return (viewToModel != null);
    }

    /**
     * Insets new set of entries.
     *
     * @param toAdd the Rows to add, sorted
     * @param current the array to insert the items into
     */
    private void insertInOrder(List<Row> toAdd, Row[] current) {
        int last = 0;
        int index;
        int max = toAdd.size();
        for (int i = 0; i < max; i++) {
            index = Arrays.binarySearch(current, toAdd.get(i));
            if (index < 0) {
                index = -1 - index;
            }
            System.arraycopy(current, last,
                             viewToModel, last + i, index - last);
            viewToModel[index + i] = toAdd.get(i);
            last = index;
        }
        System.arraycopy(current, last, viewToModel, last + max,
                         current.length - last);
    }

    /**
     * Returns true if we should try and optimize the processing of the
     * <code>TableModelEvent</code>.  If this returns false, assume the
     * event was dealt with and no further processing needs to happen.
     */
    private boolean shouldOptimizeChange(int firstRow, int lastRow) {
        if (!isTransformed()) {
            // Not transformed, nothing to do.
            return false;
        }
        if (!sorted || viewToModel.length == 0 ||
                (lastRow - firstRow) > viewToModel.length / 10) {
            // We either weren't sorted, or too much changed, sort it all or
            // this is the first row added and we have to update different caches
            sort();
            return false;
        }
        return true;
    }

    private void rowsInserted0(int firstRow, int lastRow) {
        int[] oldViewToModel = getViewToModelAsInts(viewToModel);
        int i;
        int delta = (lastRow - firstRow) + 1;
        List<Row> added = new ArrayList<Row>(delta);

        // Build the list of Rows to add into added
        for (i = firstRow; i <= lastRow; i++) {
            if (include(i)) {
                added.add(new Row(this, i));
            }
        }

        // Adjust the model index of rows after the effected region
        int viewIndex;
        for (i = modelToView.length - 1; i >= firstRow; i--) {
            viewIndex = modelToView[i];
            if (viewIndex != -1) {
                viewToModel[viewIndex].modelIndex += delta;
            }
        }

        // Insert newly added rows into viewToModel
        if (added.size() > 0) {
            Collections.sort(added);
            Row[] lastViewToModel = viewToModel;
            viewToModel = new Row[viewToModel.length + added.size()];
            insertInOrder(added, lastViewToModel);
        }

        // Update modelToView
        createModelToView(getModelWrapper().getRowCount());
        setModelToViewFromViewToModel(true);

        // Notify of change
        fireRowSorterChanged(oldViewToModel);
    }

    private void rowsDeleted0(int firstRow, int lastRow) {
        int[] oldViewToModel = getViewToModelAsInts(viewToModel);
        int removedFromView = 0;
        int i;
        int viewIndex;

        // Figure out how many visible rows are going to be effected.
        for (i = firstRow; i <= lastRow; i++) {
            viewIndex = modelToView[i];
            if (viewIndex != -1) {
                removedFromView++;
                viewToModel[viewIndex] = null;
            }
        }

        // Update the model index of rows after the effected region
        int delta = lastRow - firstRow + 1;
        for (i = modelToView.length - 1; i > lastRow; i--) {
            viewIndex = modelToView[i];
            if (viewIndex != -1) {
                viewToModel[viewIndex].modelIndex -= delta;
            }
        }

        // Then patch up the viewToModel array
        if (removedFromView > 0) {
            Row[] newViewToModel = new Row[viewToModel.length -
                                           removedFromView];
            int newIndex = 0;
            int last = 0;
            for (i = 0; i < viewToModel.length; i++) {
                if (viewToModel[i] == null) {
                    System.arraycopy(viewToModel, last,
                                     newViewToModel, newIndex, i - last);
                    newIndex += (i - last);
                    last = i + 1;
                }
            }
            System.arraycopy(viewToModel, last,
                    newViewToModel, newIndex, viewToModel.length - last);
            viewToModel = newViewToModel;
        }

        // Update the modelToView mapping
        createModelToView(getModelWrapper().getRowCount());
        setModelToViewFromViewToModel(true);

        // And notify of change
        fireRowSorterChanged(oldViewToModel);
    }

    private void rowsUpdated0(int firstRow, int lastRow) {
        int[] oldViewToModel = getViewToModelAsInts(viewToModel);
        int i, j;
        int delta = lastRow - firstRow + 1;
        int modelIndex;
        int last;
        int index;

        if (getRowFilter() == null) {
            // Sorting only:

            // Remove the effected rows
            Row[] updated = new Row[delta];
            for (j = 0, i = firstRow; i <= lastRow; i++, j++) {
                updated[j] = viewToModel[modelToView[i]];
            }

            // Sort the update rows
            Arrays.sort(updated);

            // Build the intermediary array: the array of
            // viewToModel without the effected rows.
            Row[] intermediary = new Row[viewToModel.length - delta];
            for (i = 0, j = 0; i < viewToModel.length; i++) {
                modelIndex = viewToModel[i].modelIndex;
                if (modelIndex < firstRow || modelIndex > lastRow) {
                    intermediary[j++] = viewToModel[i];
                }
            }

            // Build the new viewToModel
            insertInOrder(Arrays.asList(updated), intermediary);

            // Update modelToView
            setModelToViewFromViewToModel(false);
        }
        else {
            // Sorting & filtering.

            // Remove the effected rows, adding them to updated and setting
            // modelToView to -2 for any rows that were not filtered out
            List<Row> updated = new ArrayList<Row>(delta);
            int newlyVisible = 0;
            int newlyHidden = 0;
            int effected = 0;
            for (i = firstRow; i <= lastRow; i++) {
                if (modelToView[i] == -1) {
                    // This row was filtered out
                    if (include(i)) {
                        // No longer filtered
                        updated.add(new Row(this, i));
                        newlyVisible++;
                    }
                }
                else {
                    // This row was visible, make sure it should still be
                    // visible.
                    if (!include(i)) {
                        newlyHidden++;
                    }
                    else {
                        updated.add(viewToModel[modelToView[i]]);
                    }
                    modelToView[i] = -2;
                    effected++;
                }
            }

            // Sort the updated rows
            Collections.sort(updated);

            // Build the intermediary array: the array of
            // viewToModel without the updated rows.
            Row[] intermediary = new Row[viewToModel.length - effected];
            for (i = 0, j = 0; i < viewToModel.length; i++) {
                modelIndex = viewToModel[i].modelIndex;
                if (modelToView[modelIndex] != -2) {
                    intermediary[j++] = viewToModel[i];
                }
            }

            // Recreate viewToModel, if necessary
            if (newlyVisible != newlyHidden) {
                viewToModel = new Row[viewToModel.length + newlyVisible -
                                      newlyHidden];
            }

            // Rebuild the new viewToModel array
            insertInOrder(updated, intermediary);

            // Update modelToView
            setModelToViewFromViewToModel(true);
        }
        // And finally fire a sort event.
        fireRowSorterChanged(oldViewToModel);
    }

    private void checkColumn(int column) {
        if (column < 0 || column >= getModelWrapper().getColumnCount()) {
            throw new IndexOutOfBoundsException(
                    "column beyond range of TableModel");
        }
    }


    /**
     * <code>DefaultRowSorter.ModelWrapper</code> is responsible for providing
     * the data that gets sorted by <code>DefaultRowSorter</code>.  You
     * normally do not interact directly with <code>ModelWrapper</code>.
     * Subclasses of <code>DefaultRowSorter</code> provide an
     * implementation of <code>ModelWrapper</code> wrapping another model.
     * For example,
     * <code>TableRowSorter</code> provides a <code>ModelWrapper</code> that
     * wraps a <code>TableModel</code>.
     * <p>
     * <code>ModelWrapper</code> makes a distinction between values as
     * <code>Object</code>s and <code>String</code>s.  This allows
     * implementations to provide a custom string
     * converter to be used instead of invoking <code>toString</code> on the
     * object.
     *
     * @param <M> the type of the underlying model
     * @param <I> the identifier supplied to the filter
     * @since 1.6
     * @see RowFilter
     * @see RowFilter.Entry
     */
    protected abstract static class ModelWrapper<M,I> {
        /**
         * Creates a new <code>ModelWrapper</code>.
         */
        protected ModelWrapper() {
        }

        /**
         * Returns the underlying model that this <code>Model</code> is
         * wrapping.
         *
         * @return the underlying model
         */
        public abstract M getModel();

        /**
         * Returns the number of columns in the model.
         *
         * @return the number of columns in the model
         */
        public abstract int getColumnCount();

        /**
         * Returns the number of rows in the model.
         *
         * @return the number of rows in the model
         */
        public abstract int getRowCount();

        /**
         * Returns the value at the specified index.
         *
         * @param row the row index
         * @param column the column index
         * @return the value at the specified index
         * @throws IndexOutOfBoundsException if the indices are outside
         *         the range of the model
         */
        public abstract Object getValueAt(int row, int column);

        /**
         * Returns the value as a <code>String</code> at the specified
         * index.  This implementation uses <code>toString</code> on
         * the result from <code>getValueAt</code> (making sure
         * to return an empty string for null values).  Subclasses that
         * override this method should never return null.
         *
         * @param row the row index
         * @param column the column index
         * @return the value at the specified index as a <code>String</code>
         * @throws IndexOutOfBoundsException if the indices are outside
         *         the range of the model
         */
        public String getStringValueAt(int row, int column) {
            Object o = getValueAt(row, column);
            if (o == null) {
                return "";
            }
            String string = o.toString();
            if (string == null) {
                return "";
            }
            return string;
        }

        /**
         * Returns the identifier for the specified row.  The return value
         * of this is used as the identifier for the
         * <code>RowFilter.Entry</code> that is passed to the
         * <code>RowFilter</code>.
         *
         * @param row the row to return the identifier for, in terms of
         *            the underlying model
         * @return the identifier
         * @see RowFilter.Entry#getIdentifier
         */
        public abstract I getIdentifier(int row);
    }


    /**
     * RowFilter.Entry implementation that delegates to the ModelWrapper.
     * getFilterEntry(int) creates the single instance of this that is
     * passed to the Filter.  Only call getFilterEntry(int) to get
     * the instance.
     */
    private class FilterEntry extends RowFilter.Entry<M,I> {
        /**
         * The index into the model, set in getFilterEntry
         */
        int modelIndex;

        public M getModel() {
            return getModelWrapper().getModel();
        }

        public int getValueCount() {
            return getModelWrapper().getColumnCount();
        }

        public Object getValue(int index) {
            return getModelWrapper().getValueAt(modelIndex, index);
        }

        public String getStringValue(int index) {
            return getModelWrapper().getStringValueAt(modelIndex, index);
        }

        public I getIdentifier() {
            return getModelWrapper().getIdentifier(modelIndex);
        }
    }


    /**
     * Row is used to handle the actual sorting by way of Comparable.  It
     * will use the sortKeys to do the actual comparison.
     */
    // NOTE: this class is static so that it can be placed in an array
    private static class Row implements Comparable<Row> {
        private DefaultRowSorter<?, ?> sorter;
        int modelIndex;

        public Row(DefaultRowSorter<?, ?> sorter, int index) {
            this.sorter = sorter;
            modelIndex = index;
        }

        public int compareTo(Row o) {
            return sorter.compare(modelIndex, o.modelIndex);
        }
    }
}
