/*
 * @(#)XmlChars.java    1.1 00/08/05
 * 
 * Copyright (c) 1998 Sun Microsystems, Inc. All Rights Reserved.
 */

package com.sun.msv.scanner.dtd;


/**
 * Methods in this class are used to determine whether characters may
 * appear in certain roles in XML documents.  Such methods are used
 * both to parse and to create such documents.
 *
 * @version 1.1, 00/08/05
 * @author David Brownell
 */
public class XmlChars
{
    // can't construct instances
    private XmlChars () { }

    /**
     * Returns true if the argument, a UCS-4 character code, is valid in
     * XML documents.  Unicode characters fit into the low sixteen
     * bits of a UCS-4 character, and pairs of Unicode <em>surrogate
     * characters</em> can be combined to encode UCS-4 characters in
     * documents containing only Unicode.  (The <code>char</code> datatype
     * in the Java Programming Language represents Unicode characters,
     * including unpaired surrogates.)
     *
     * <P> In XML, UCS-4 characters can also be encoded by the use of
     * <em>character references</em> such as <b>&amp;#x12345678;</b>, which
     * happens to refer to a character that is disallowed in XML documents.
     * UCS-4 characters allowed in XML documents can be expressed with
     * one or two Unicode characters.
     *
     * @param ucs4char The 32-bit UCS-4 character being tested.
     */
    static public boolean isChar (int ucs4char)
    {
    // [2] Char ::= #x0009 | #x000A | #x000D
    //            | [#x0020-#xD7FF]
    //    ... surrogates excluded!
    //            | [#xE000-#xFFFD]
    //             | [#x10000-#x10ffff]
    return ((ucs4char >= 0x0020 && ucs4char <= 0xD7FF)
        || ucs4char == 0x000A || ucs4char == 0x0009
        || ucs4char == 0x000D
        || (ucs4char >= 0xE000 && ucs4char <= 0xFFFD)
        || (ucs4char >= 0x10000 && ucs4char <= 0x10ffff));
    }

    /**
     * Returns true if the character is allowed to be a non-initial
     * character in names according to the XML recommendation.
     * @see #isNCNameChar(char)
     * @see #isLetter(char)
     */
    public static boolean isNameChar (char c)
    {
    // [4] NameChar ::= Letter | Digit | '.' | '_' | ':'
    //            | CombiningChar | Extender

    if (isLetter2 (c))
        return true;
    else if (c == '>')
        return false;
    else if (c == '.' || c == '-' || c == '_' || c == ':'
        || isExtender (c))
        return true;
    else
        return false;
    }

    /**
     * Returns true if the character is allowed to be a non-initial
     * character in unscoped names according to the rules of the XML
     * Namespaces proposed recommendation.  Except for precluding
     * the colon (used to separate names from their scopes) these
     * characters are just as allowed by the XML recommendation.
     * @see #isNameChar(char)
     * @see #isLetter(char)
     */
    public static boolean isNCNameChar (char c)
    {
    // [NC 5] NCNameChar ::= Letter | Digit | '.' | '_' 
    //            | CombiningChar | Extender
    return c != ':' && isNameChar (c);
    }

    /**
     * Returns true if the character is allowed where XML supports
     * whitespace characters, false otherwise.
     */
    public static boolean isSpace (char c)
    {
    return c == ' ' || c == '\t' || c == '\n' || c == '\r';
    }


    /*
     * NOTE:  java.lang.Character.getType() values are:
     *
     * UNASSIGNED                    = 0,
     *
     * UPPERCASE_LETTER            = 1,    // Lu
     * LOWERCASE_LETTER            = 2,    // Ll
     * TITLECASE_LETTER            = 3,    // Lt
     * MODIFIER_LETTER             = 4,    // Lm
     * OTHER_LETTER                = 5,    // Lo
     * NON_SPACING_MARK            = 6,    // Mn
     * ENCLOSING_MARK              = 7,    // Me
     * COMBINING_SPACING_MARK      = 8,    // Mc
     * DECIMAL_DIGIT_NUMBER        = 9,    // Nd
     * LETTER_NUMBER               = 10,   // Nl
     * OTHER_NUMBER                = 11,   // No
     * SPACE_SEPARATOR             = 12,   // Zs
     * LINE_SEPARATOR              = 13,   // Zl
     * PARAGRAPH_SEPARATOR         = 14,   // Zp
     * CONTROL                     = 15,   // Cc
     * FORMAT                      = 16,   // Cf
     *                         // 17 reserved for proposed Ci category
     * PRIVATE_USE                 = 18,   // Co
     * SURROGATE                   = 19,   // Cs
     * DASH_PUNCTUATION            = 20,   // Pd
     * START_PUNCTUATION           = 21,   // Ps
     * END_PUNCTUATION             = 22,   // Pe
     * CONNECTOR_PUNCTUATION       = 23,   // Pc
     * OTHER_PUNCTUATION           = 24,   // Po
     * MATH_SYMBOL                 = 25,   // Sm
     * CURRENCY_SYMBOL             = 26,   // Sc
     * MODIFIER_SYMBOL             = 27,   // Sk
     * OTHER_SYMBOL                = 28;   // So
     */

    /**
     * Returns true if the character is an XML "letter".  XML Names must
     * start with Letters or a few other characters, but other characters
     * in names must only satisfy the <em>isNameChar</em> predicate.
     *
     * @see #isNameChar(char)
     * @see #isNCNameChar(char)
     */
    public static boolean isLetter (char c)
    {
    // [84] Letter ::= BaseChar | Ideographic
    // [85] BaseChar ::= ... too much to repeat
    // [86] Ideographic ::= ... too much to repeat

    //
    // Optimize the typical case.
    //
    if (c >= 'a' && c <= 'z')
        return true;
    if (c == '/')
        return false;
    if (c >= 'A' && c <= 'Z')
        return true;

    //
    // Since the tables are too ridiculous to use in code,
    // we're using the footnotes here to drive this test.
    //
    switch (Character.getType (c)) {
        // app. B footnote says these are 'name start'
        // chars' ...
      case Character.LOWERCASE_LETTER:        // Ll
      case Character.UPPERCASE_LETTER:        // Lu
      case Character.OTHER_LETTER:            // Lo
      case Character.TITLECASE_LETTER:        // Lt
      case Character.LETTER_NUMBER:            // Nl

        // OK, here we just have some exceptions to check...
        return !isCompatibilityChar (c)
            // per "5.14 of Unicode", rule out some combiners
        && !(c >= 0x20dd && c <= 0x20e0);

      default:
        // check for some exceptions:  these are "alphabetic"
        return ((c >= 0x02bb && c <=  0x02c1)
            || c == 0x0559 || c == 0x06e5 || c == 0x06e6);
    }
    }

    //
    // XML 1.0 discourages "compatibility" characters in names; these
    // were defined to permit passing through some information stored in
    // older non-Unicode character sets.  These always have alternative
    // representations in Unicode, e.g. using combining chars.
    //
    private static boolean isCompatibilityChar (char c)
    {
    // the numerous comparisions here seem unavoidable,
    // but the switch can reduce the number which must
    // actually be executed.

    switch ((c >> 8) & 0x0ff) {
      case 0x00:
        // ISO Latin/1 has a few compatibility characters
        return c == 0x00aa || c == 0x00b5 || c == 0x00ba;

      case 0x01:
        // as do Latin Extended A and (parts of) B
        return (c >= 0x0132 && c <= 0x0133)
        || (c >= 0x013f && c <= 0x0140)
        || c == 0x0149
        || c == 0x017f
        || (c >= 0x01c4 && c <= 0x01cc)
        || (c >= 0x01f1 && c <= 0x01f3) ;

      case 0x02:
           // some spacing modifiers
        return (c >= 0x02b0 && c <= 0x02b8)
        || (c >= 0x02e0 && c <= 0x02e4);
      
      case 0x03:
        return c == 0x037a;            // Greek

      case 0x05:
        return c == 0x0587;            // Armenian

      case 0x0e:
        return c >= 0x0edc && c <= 0x0edd;    // Laotian

      case 0x11:
        // big chunks of Hangul Jamo are all "compatibility"
        return c == 0x1101
        || c == 0x1104
        || c == 0x1108
        || c == 0x110a
        || c == 0x110d
        || (c >= 0x1113 && c <= 0x113b)
        || c == 0x113d
        || c == 0x113f
        || (c >= 0x1141 && c <= 0x114b)
        || c == 0x114d
        || c == 0x114f
        || (c >= 0x1151 && c <= 0x1153)
        || (c >= 0x1156 && c <= 0x1158)
        || c == 0x1162
        || c == 0x1164
        || c == 0x1166
        || c == 0x1168
        || (c >= 0x116a && c <= 0x116c)
        || (c >= 0x116f && c <= 0x1171)
        || c == 0x1174
        || (c >= 0x1176 && c <= 0x119d)
        || (c >= 0x119f && c <= 0x11a2)
        || (c >= 0x11a9 && c <= 0x11aa)
        || (c >= 0x11ac && c <= 0x11ad)
        || (c >= 0x11b0 && c <= 0x11b6)
        || c == 0x11b9
        || c == 0x11bb
        || (c >= 0x11c3 && c <= 0x11ea)
        || (c >= 0x11ec && c <= 0x11ef)
        || (c >= 0x11f1 && c <= 0x11f8)
        ;

      case 0x20:
        return c == 0x207f;            // superscript

      case 0x21:
        return
        // various letterlike symbols
           c == 0x2102
        || c == 0x2107
        || (c >= 0x210a && c <= 0x2113)
        || c == 0x2115
        || (c >= 0x2118 && c <= 0x211d)
        || c == 0x2124
        || c == 0x2128
        || (c >= 0x212c && c <= 0x212d)
        || (c >= 0x212f && c <= 0x2138)

            // most Roman numerals (less 1K, 5K, 10K)
        || (c >= 0x2160 && c <= 0x217f)
        ;

      case 0x30:
        // some Hiragana
        return c >= 0x309b && c <= 0x309c;

      case 0x31:
        // all Hangul Compatibility Jamo
        return c >= 0x3131 && c <= 0x318e;

      case 0xf9:
      case 0xfa:
      case 0xfb:
      case 0xfc:
      case 0xfd:
      case 0xfe:
      case 0xff:
        // the whole "compatibility" area is for that purpose!
        return true;
    
      default:
        // most of Unicode isn't flagged as being for compatibility
        return false;
    }
    }

    // guts of isNameChar/isNCNameChar
    private static boolean isLetter2 (char c)
    {
    // [84] Letter ::= BaseChar | Ideographic
    // [85] BaseChar ::= ... too much to repeat
    // [86] Ideographic ::= ... too much to repeat
    // [87] CombiningChar ::= ... too much to repeat

    //
    // Optimize the typical case.
    //
    if (c >= 'a' && c <= 'z')
        return true;
    if (c == '>')
        return false;
    if (c >= 'A' && c <= 'Z')
        return true;

    //
    // Since the tables are too ridiculous to use in code,
    // we're using the footnotes here to drive this test.
    //
    switch (Character.getType (c)) {
        // app. B footnote says these are 'name start'
        // chars' ...
      case Character.LOWERCASE_LETTER:        // Ll
      case Character.UPPERCASE_LETTER:        // Lu
      case Character.OTHER_LETTER:            // Lo
      case Character.TITLECASE_LETTER:        // Lt
      case Character.LETTER_NUMBER:            // Nl
        // ... and these are name characters 'other
        // than name start characters'
      case Character.COMBINING_SPACING_MARK:    // Mc
      case Character.ENCLOSING_MARK:        // Me
      case Character.NON_SPACING_MARK:        // Mn
      case Character.MODIFIER_LETTER:        // Lm
      case Character.DECIMAL_DIGIT_NUMBER:        // Nd

        // OK, here we just have some exceptions to check...
        return !isCompatibilityChar (c)
            // per "5.14 of Unicode", rule out some combiners
        && !(c >= 0x20dd && c <= 0x20e0);

      default:
        // added a character ...
        return c == 0x0387;
    }
    }

    private static boolean isDigit (char c)
    {
    // [88] Digit ::= ... 

    //
    // java.lang.Character.isDigit is correct from the XML point
    // of view except that it allows "fullwidth" digits.
    //
    return Character.isDigit (c)
        && ! ( (c >= 0xff10) && (c <= 0xff19));
    }

    private static boolean isExtender (char c)
    {
    // [89] Extender ::= ... 
    return c == 0x00b7 || c == 0x02d0 || c == 0x02d1 || c == 0x0387
        || c == 0x0640 || c == 0x0e46 || c == 0x0ec6
        || c == 0x3005 || (c >= 0x3031 && c <= 0x3035)
        || (c >= 0x309d && c <= 0x309e)
        || (c >= 0x30fc && c <= 0x30fe)
        ;
    }
}
