/*
*******************************************************************************
*   Copyright (C) 2001, International Business Machines
*   Corporation and others.  All Rights Reserved.
*******************************************************************************
*/

package com.ibm.icu.text;

import com.ibm.icu.lang.*;

/**
 * Shape Arabic text on a character basis.
 *
 * <p>ArabicShaping performs basic operations for "shaping" Arabic text. It is most
 * useful for use with legacy data formats and legacy display technology
 * (simple terminals). All operations are performed on Unicode characters.</p>
 *
 * <p>Text-based shaping means that some character code points in the text are
 * replaced by others depending on the context. It transforms one kind of text
 * into another. In comparison, modern displays for Arabic text select
 * appropriate, context-dependent font glyphs for each text element, which means
 * that they transform text into a glyph vector.</p>
 *
 * <p>Text transformations are necessary when modern display technology is not
 * available or when text needs to be transformed to or from legacy formats that
 * use "shaped" characters. Since the Arabic script is cursive, connecting
 * adjacent letters to each other, computers select images for each letter based
 * on the surrounding letters. This usually results in four images per Arabic
 * letter: initial, middle, final, and isolated forms. In Unicode, on the other
 * hand, letters are normally stored abstract, and a display system is expected
 * to select the necessary glyphs. (This makes searching and other text
 * processing easier because the same letter has only one code.) It is possible
 * to mimic this with text transformations because there are characters in
 * Unicode that are rendered as letters with a specific shape
 * (or cursive connectivity). They were included for interoperability with
 * legacy systems and codepages, and for unsophisticated display systems.</p>
 *
 * <p>A second kind of text transformations is supported for Arabic digits:
 * For compatibility with legacy codepages that only include European digits,
 * it is possible to replace one set of digits by another, changing the
 * character code points. These operations can be performed for either
 * Arabic-Indic Digits (U+0660...U+0669) or Eastern (Extended) Arabic-Indic
 * digits (U+06f0...U+06f9).</p>
 *
 * <p>Some replacements may result in more or fewer characters (code points).
 * By default, this means that the destination buffer may receive text with a
 * length different from the source length. Some legacy systems rely on the
 * length of the text to be constant. They expect extra spaces to be added
 * or consumed either next to the affected character or at the end of the
 * text.</p>
 * @stable ICU 2.0
 */
public final class ArabicShaping {
    private final int options;
    private boolean isLogical; // convenience

    /**
     * Convert a range of text in the source array, putting the result 
     * into a range of text in the destination array, and return the number
     * of characters written.
     *
     * @param source An array containing the input text
     * @param sourceStart The start of the range of text to convert
     * @param sourceLength The length of the range of text to convert
     * @param dest The destination array that will receive the result.
     *   It may be <code>NULL</code> only if  <code>destSize</code> is 0.  
     * @param destStart The start of the range of the destination buffer to use.
     * @param destSize The size (capacity) of the destination buffer.
     *   If <code>destSize</code> is 0, then no output is produced,
     *   but the necessary buffer size is returned ("preflighting").  This
     *   does not validate the text against the options, for example, 
     *   if letters are being unshaped, and spaces are being consumed
     *   following lamalef, this will not detect a lamalef without a 
     *   corresponding space.  An error will be thrown when the actual
     *   conversion is attempted.
     * @return The number of chars written to the destination buffer.
     *   If an error occurs, then no output was written, or it may be
     *   incomplete.
     * @throws ArabicShapingException if the text cannot be converted according to the options.
     * @stable ICU 2.0
     */
    public int shape(char[] source, int sourceStart, int sourceLength,
                     char[] dest, int destStart, int destSize) throws ArabicShapingException {
        if (source == null) {
            throw new IllegalArgumentException("source can not be null");
        }
        if (sourceStart < 0 || sourceLength < 0 || sourceStart + sourceLength > source.length) {
            throw new IllegalArgumentException("bad source start (" + sourceStart +
                                               ") or length (" + sourceLength +
                                               ") for buffer of length " + source.length);
        }
        if (dest == null && destSize != 0) {
            throw new IllegalArgumentException("null dest requires destSize == 0");
        }
        if ((destSize != 0) &&
            (destStart < 0 || destSize < 0 || destStart + destSize > dest.length)) {
            throw new IllegalArgumentException("bad dest start (" + destStart + 
                                               ") or size (" + destSize + 
                                               ") for buffer of length " + dest.length);
        }

        return internalShape(source, sourceStart, sourceLength, dest, destStart, destSize);
    }

    /**
     * Convert a range of text in place.  This may only be used if the Length option
     * does not grow or shrink the text.
     *
     * @param source An array containing the input text
     * @param start The start of the range of text to convert
     * @param length The length of the range of text to convert
     * @throws ArabicShapingException if the text cannot be converted according to the options.
     * @stable ICU 2.0
     */
    public void shape(char[] source, int start, int length) throws ArabicShapingException {
        if ((options & LENGTH_MASK) == LENGTH_GROW_SHRINK) {
            throw new ArabicShapingException("Cannot shape in place with length option grow/shrink.");
        }
        shape(source, start, length, source, start, length);
    }

    /**
     * Convert a string, returning the new string.
     *
     * @param source The string to convert.
     * @return The converted string.
     * @throws ArabicShapingException if the string cannot be converted according to the options.
     * @stable ICU 2.0
     */
    public String shape(String text) throws ArabicShapingException {
        char[] src = text.toCharArray();
        char[] dest = src;
        if (((options & LENGTH_MASK) == LENGTH_GROW_SHRINK) &&
            ((options & LETTERS_MASK) == LETTERS_UNSHAPE)) {

            dest = new char[src.length * 2]; // max
        }
        int len = shape(src, 0, src.length, dest, 0, dest.length);

        return new String(dest, 0, len);
    }

    /**
     * Construct ArabicShaping using the options flags.
     * The flags are as follows:<br>
     * 'LENGTH' flags control whether the text can change size, and if not,
     * how to maintain the size of the text when LamAlef ligatures are 
     * formed or broken.<br>
     * 'TEXT_DIRECTION' flags control whether the text is read and written
     * in visual order or in logical order.<br>
     * 'LETTERS_SHAPE' flags control whether conversion is to or from
     * presentation forms.<br>
     * 'DIGITS' flags control whether digits are shaped, and whether from
     * European to Arabic-Indic or vice-versa.<br>
     * 'DIGIT_TYPE' flags control whether standard or extended Arabic-Indic
     * digits are used when performing digit conversion.
     * @stable ICU 2.0
     */
    public ArabicShaping(int options) {
        this.options = options;
        if ((options & DIGITS_MASK) > 0x80) {
            throw new IllegalArgumentException("bad DIGITS options");
        }
        isLogical = (options & TEXT_DIRECTION_MASK) == TEXT_DIRECTION_LOGICAL;
    }

    /**
     * Memory option: allow the result to have a different length than the source.
     * @stable ICU 2.0
     */
    public static final int LENGTH_GROW_SHRINK = 0;

    /**
     * Memory option: the result must have the same length as the source.
     * If more room is necessary, then try to consume spaces next to modified characters.
     * @stable ICU 2.0
     */
    public static final int LENGTH_FIXED_SPACES_NEAR = 1;

    /**
     * Memory option: the result must have the same length as the source.
     * If more room is necessary, then try to consume spaces at the end of the text.
     * @stable ICU 2.0
     */
    public static final int LENGTH_FIXED_SPACES_AT_END = 2;

    /**
     * Memory option: the result must have the same length as the source.
     * If more room is necessary, then try to consume spaces at the beginning of the text.
     * @stable ICU 2.0
     */
    public static final int LENGTH_FIXED_SPACES_AT_BEGINNING = 3;

    /** 
     * Bit mask for memory options. 
     * @stable ICU 2.0
     */
    public static final int LENGTH_MASK = 3;


    /** 
     * Direction indicator: the source is in logical (keyboard) order. 
     * @stable ICU 2.0
     */
    public static final int TEXT_DIRECTION_LOGICAL = 0;

    /** 
     * Direction indicator: the source is in visual (display) order, that is,
     * the leftmost displayed character is stored first.
     * @stable ICU 2.0
     */
    public static final int TEXT_DIRECTION_VISUAL_LTR = 4;

    /** 
     * Bit mask for direction indicators. 
     * @stable ICU 2.0
     */
    public static final int TEXT_DIRECTION_MASK = 4;


    /**
     * Letter shaping option: do not perform letter shaping. 
     * @stable ICU 2.0
     */
    public static final int LETTERS_NOOP = 0;

    /** 
     * Letter shaping option: replace normative letter characters in the U+0600 (Arabic) block,
     * by shaped ones in the U+FE70 (Presentation Forms B) block. Performs Lam-Alef ligature
     * substitution.
     * @stable ICU 2.0
     */
    public static final int LETTERS_SHAPE = 8;

    /** 
     * Letter shaping option: replace shaped letter characters in the U+FE70 (Presentation Forms B) block
     * by normative ones in the U+0600 (Arabic) block.  Converts Lam-Alef ligatures to pairs of Lam and
     * Alef characters, consuming spaces if required.
     * @stable ICU 2.0
     */
    public static final int LETTERS_UNSHAPE = 0x10;

    /**
     * Letter shaping option: replace normative letter characters in the U+0600 (Arabic) block,
     * except for the TASHKEEL characters at U+064B...U+0652, by shaped ones in the U+Fe70
     * (Presentation Forms B) block.  The TASHKEEL characters will always be converted to
     * the isolated forms rather than to their correct shape.
     * @stable ICU 2.0
     */
    public static final int LETTERS_SHAPE_TASHKEEL_ISOLATED = 0x18;

    /** 
     * Bit mask for letter shaping options. 
     * @stable ICU 2.0
     */
    public static final int LETTERS_MASK = 0x18;


    /** 
     * Digit shaping option: do not perform digit shaping. 
     * @stable ICU 2.0
     */
    public static final int DIGITS_NOOP = 0;

    /**
     * Digit shaping option: Replace European digits (U+0030...U+0039) by Arabic-Indic digits.
     * @stable ICU 2.0
     */
    public static final int DIGITS_EN2AN = 0x20;

    /**
     * Digit shaping option: Replace Arabic-Indic digits by European digits (U+0030...U+0039).
     * @stable ICU 2.0
     */
    public static final int DIGITS_AN2EN = 0x40;

    /**
     * Digit shaping option:
     * Replace European digits (U+0030...U+0039) by Arabic-Indic digits
     * if the most recent strongly directional character
     * is an Arabic letter (its Bidi direction value is RIGHT_TO_LEFT_ARABIC). 
     * The initial state at the start of the text is assumed to be not an Arabic,
     * letter, so European digits at the start of the text will not change.
     * Compare to DIGITS_ALEN2AN_INIT_AL.
     * @stable ICU 2.0
     */
    public static final int DIGITS_EN2AN_INIT_LR = 0x60;

    /**
     * Digit shaping option:
     * Replace European digits (U+0030...U+0039) by Arabic-Indic digits
     * if the most recent strongly directional character
     * is an Arabic letter (its Bidi direction value is RIGHT_TO_LEFT_ARABIC). 
     * The initial state at the start of the text is assumed to be an Arabic,
     * letter, so European digits at the start of the text will change.
     * Compare to DIGITS_ALEN2AN_INT_LR.
     * @stable ICU 2.0
     */
    public static final int DIGITS_EN2AN_INIT_AL = 0x80;

    /** Not a valid option value. */
    private static final int DIGITS_RESERVED = 0xa0;

    /** 
     * Bit mask for digit shaping options. 
     * @stable ICU 2.0
     */
    public static final int DIGITS_MASK = 0xe0;

    /** 
     * Digit type option: Use Arabic-Indic digits (U+0660...U+0669). 
     * @stable ICU 2.0
     */
    public static final int DIGIT_TYPE_AN = 0;

    /** 
     * Digit type option: Use Eastern (Extended) Arabic-Indic digits (U+06f0...U+06f9). 
     * @stable ICU 2.0
     */
    public static final int DIGIT_TYPE_AN_EXTENDED = 0x100;

    /** 
     * Bit mask for digit type options. 
     * @stable ICU 2.0
     */
    public static final int DIGIT_TYPE_MASK = 0x0100; // 0x3f00?

    /**
     * @stable ICU 2.0
     */
    public boolean equals(Object rhs) {
        return rhs != null && 
            rhs.getClass() == ArabicShaping.class && 
            options == ((ArabicShaping)rhs).options;
    }

    /**
     * @stable ICU 2.0
     */
     ///CLOVER:OFF
    public int hashCode() {
        return options;
    }

    /**
     * @stable ICU 2.0
     */
    public String toString() {
        StringBuffer buf = new StringBuffer(super.toString());
        buf.append('[');
        switch (options & LENGTH_MASK) {
        case LENGTH_GROW_SHRINK: buf.append("grow/shrink"); break;
        case LENGTH_FIXED_SPACES_NEAR: buf.append("spaces near"); break;
        case LENGTH_FIXED_SPACES_AT_END: buf.append("spaces at end"); break;
        case LENGTH_FIXED_SPACES_AT_BEGINNING: buf.append("spaces at beginning"); break;
        }
        switch (options & TEXT_DIRECTION_MASK) {
        case TEXT_DIRECTION_LOGICAL: buf.append(", logical"); break;
        case TEXT_DIRECTION_VISUAL_LTR: buf.append(", visual"); break;
        }
        switch (options & LETTERS_MASK) {
        case LETTERS_NOOP: buf.append(", no letter shaping"); break;
        case LETTERS_SHAPE: buf.append(", shape letters"); break;
        case LETTERS_SHAPE_TASHKEEL_ISOLATED: buf.append(", shape letters tashkeel isolated"); break;
        case LETTERS_UNSHAPE: buf.append(", unshape letters"); break;
        }
        switch (options & DIGITS_MASK) {
        case DIGITS_NOOP: buf.append(", no digit shaping"); break;
        case DIGITS_EN2AN: buf.append(", shape digits to AN"); break;
        case DIGITS_AN2EN: buf.append(", shape digits to EN"); break;
        case DIGITS_EN2AN_INIT_LR: buf.append(", shape digits to AN contextually: default EN"); break;
        case DIGITS_EN2AN_INIT_AL: buf.append(", shape digits to AN contextually: default AL"); break;
        }
        switch (options & DIGIT_TYPE_MASK) {
        case DIGIT_TYPE_AN: buf.append(", standard Arabic-Indic digits"); break;
        case DIGIT_TYPE_AN_EXTENDED: buf.append(", extended Arabic-Indic digits"); break;
        }
        buf.append("]");

        return buf.toString();
    }
    ///CLOVER:ON

    //
    // ported api
    //

    private static final int IRRELEVANT = 4;
    private static final int LAMTYPE = 16;
    private static final int ALEFTYPE = 32;

    private static final int LINKR = 1;
    private static final int LINKL = 2;
    private static final int LINK_MASK = 3;

    private static final int irrelevantPos[] = { 
        0x0, 0x2, 0x4, 0x6, 0x8, 0xA, 0xC, 0xE 
    };

    private static final char convertLamAlef[] =  {
        '\u0622', // FEF5 
        '\u0622', // FEF6
        '\u0623', // FEF7
        '\u0623', // FEF8
        '\u0625', // FEF9
        '\u0625', // FEFA
        '\u0627', // FEFB
        '\u0627'  // FEFC 
    };

    private static final char convertNormalizedLamAlef[] = {
        '\u0622', // 065C
        '\u0623', // 065D
        '\u0625', // 065E
        '\u0627', // 065F
    };

    private static final int[] araLink = {
        1           + 32 + 256 * 0x11,  /*0x0622*/
        1           + 32 + 256 * 0x13,  /*0x0623*/
        1                + 256 * 0x15,  /*0x0624*/
        1           + 32 + 256 * 0x17,  /*0x0625*/
        1 + 2            + 256 * 0x19,  /*0x0626*/
        1           + 32 + 256 * 0x1D,  /*0x0627*/
        1 + 2            + 256 * 0x1F,  /*0x0628*/
        1                + 256 * 0x23,  /*0x0629*/
        1 + 2            + 256 * 0x25,  /*0x062A*/
        1 + 2            + 256 * 0x29,  /*0x062B*/
        1 + 2            + 256 * 0x2D,  /*0x062C*/
        1 + 2            + 256 * 0x31,  /*0x062D*/
        1 + 2            + 256 * 0x35,  /*0x062E*/
        1                + 256 * 0x39,  /*0x062F*/
        1                + 256 * 0x3B,  /*0x0630*/
        1                + 256 * 0x3D,  /*0x0631*/
        1                + 256 * 0x3F,  /*0x0632*/
        1 + 2            + 256 * 0x41,  /*0x0633*/
        1 + 2            + 256 * 0x45,  /*0x0634*/
        1 + 2            + 256 * 0x49,  /*0x0635*/
        1 + 2            + 256 * 0x4D,  /*0x0636*/
        1 + 2            + 256 * 0x51,  /*0x0637*/
        1 + 2            + 256 * 0x55,  /*0x0638*/
        1 + 2            + 256 * 0x59,  /*0x0639*/
        1 + 2            + 256 * 0x5D,  /*0x063A*/
        0, 0, 0, 0, 0,                  /*0x063B-0x063F*/
        1 + 2,                          /*0x0640*/
        1 + 2            + 256 * 0x61,  /*0x0641*/
        1 + 2            + 256 * 0x65,  /*0x0642*/
        1 + 2            + 256 * 0x69,  /*0x0643*/
        1 + 2       + 16 + 256 * 0x6D,  /*0x0644*/
        1 + 2            + 256 * 0x71,  /*0x0645*/
        1 + 2            + 256 * 0x75,  /*0x0646*/
        1 + 2            + 256 * 0x79,  /*0x0647*/
        1                + 256 * 0x7D,  /*0x0648*/
        1                + 256 * 0x7F,  /*0x0649*/
        1 + 2            + 256 * 0x81,  /*0x064A*/
        4, 4, 4, 4,                     /*0x064B-0x064E*/
        4, 4, 4, 4,                     /*0x064F-0x0652*/
        4, 4, 4, 0, 0,                  /*0x0653-0x0657*/
        0, 0, 0, 0,                     /*0x0658-0x065B*/
        1                + 256 * 0x85,  /*0x065C*/
        1                + 256 * 0x87,  /*0x065D*/
        1                + 256 * 0x89,  /*0x065E*/
        1                + 256 * 0x8B,  /*0x065F*/
        0, 0, 0, 0, 0,                  /*0x0660-0x0664*/
        0, 0, 0, 0, 0,                  /*0x0665-0x0669*/
        0, 0, 0, 0, 0, 0,               /*0x066A-0x066F*/
        4,                              /*0x0670*/
        0,                              /*0x0671*/
        1           + 32,               /*0x0672*/
        1           + 32,               /*0x0673*/
        0,                              /*0x0674*/
        1           + 32,               /*0x0675*/
        1, 1,                           /*0x0676-0x0677*/
        1+2, 1+2, 1+2, 1+2, 1+2, 1+2,   /*0x0678-0x067D*/
        1+2, 1+2, 1+2, 1+2, 1+2, 1+2,   /*0x067E-0x0683*/
        1+2, 1+2, 1+2, 1+2,             /*0x0684-0x0687*/
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1,   /*0x0688-0x0691*/
        1, 1, 1, 1, 1, 1, 1, 1,         /*0x0692-0x0699*/
        1+2, 1+2, 1+2, 1+2, 1+2, 1+2,   /*0x069A-0x06A3*/
        1+2, 1+2, 1+2, 1+2,             /*0x069A-0x06A3*/
        1+2, 1+2, 1+2, 1+2, 1+2, 1+2,   /*0x06A4-0x06AD*/
        1+2, 1+2, 1+2, 1+2,             /*0x06A4-0x06AD*/
        1+2, 1+2, 1+2, 1+2, 1+2, 1+2,   /*0x06AE-0x06B7*/
        1+2, 1+2, 1+2, 1+2,             /*0x06AE-0x06B7*/
        1+2, 1+2, 1+2, 1+2, 1+2, 1+2,   /*0x06B8-0x06BF*/
        1+2, 1+2,                       /*0x06B8-0x06BF*/
        1,                              /*0x06C0*/
        1+2,                            /*0x06C1*/
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1,   /*0x06C2-0x06CB*/
        1+2,                            /*0x06CC*/
        1,                              /*0x06CD*/
        1+2, 1+2, 1+2, 1+2,             /*0x06CE-0x06D1*/
        1, 1                            /*0x06D2-0x06D3*/
    };

    private static final int[] presLink = {
        1 + 2,                        /*0xFE70*/
        1 + 2,                        /*0xFE71*/
        1 + 2, 0, 1+ 2, 0, 1+ 2,      /*0xFE72-0xFE76*/
        1 + 2,                        /*0xFE77*/
        1+ 2, 1 + 2, 1+2, 1 + 2,      /*0xFE78-0xFE81*/
        1+ 2, 1 + 2, 1+2, 1 + 2,      /*0xFE82-0xFE85*/
        0, 0 + 32, 1 + 32, 0 + 32,    /*0xFE86-0xFE89*/
        1 + 32, 0, 1,  0 + 32,        /*0xFE8A-0xFE8D*/
        1 + 32, 0, 2,  1 + 2,         /*0xFE8E-0xFE91*/
        1, 0 + 32, 1 + 32, 0,         /*0xFE92-0xFE95*/
        2, 1 + 2, 1, 0,               /*0xFE96-0xFE99*/
        1, 0, 2, 1 + 2,               /*0xFE9A-0xFE9D*/
        1, 0, 2, 1 + 2,               /*0xFE9E-0xFEA1*/
        1, 0, 2, 1 + 2,               /*0xFEA2-0xFEA5*/
        1, 0, 2, 1 + 2,               /*0xFEA6-0xFEA9*/
        1, 0, 2, 1 + 2,               /*0xFEAA-0xFEAD*/
        1, 0, 1, 0,                   /*0xFEAE-0xFEB1*/
        1, 0, 1, 0,                   /*0xFEB2-0xFEB5*/
        1, 0, 2, 1+2,                 /*0xFEB6-0xFEB9*/
        1, 0, 2, 1+2,                 /*0xFEBA-0xFEBD*/
        1, 0, 2, 1+2,                 /*0xFEBE-0xFEC1*/
        1, 0, 2, 1+2,                 /*0xFEC2-0xFEC5*/
        1, 0, 2, 1+2,                 /*0xFEC6-0xFEC9*/
        1, 0, 2, 1+2,                 /*0xFECA-0xFECD*/
        1, 0, 2, 1+2,                 /*0xFECE-0xFED1*/
        1, 0, 2, 1+2,                 /*0xFED2-0xFED5*/
        1, 0, 2, 1+2,                 /*0xFED6-0xFED9*/
        1, 0, 2, 1+2,                 /*0xFEDA-0xFEDD*/
        1, 0, 2, 1+2,                 /*0xFEDE-0xFEE1*/
        1, 0 + 16, 2 + 16, 1 + 2 +16, /*0xFEE2-0xFEE5*/
        1 + 16, 0, 2, 1+2,            /*0xFEE6-0xFEE9*/
        1, 0, 2, 1+2,                 /*0xFEEA-0xFEED*/
        1, 0, 2, 1+2,                 /*0xFEEE-0xFEF1*/
        1, 0, 1, 0,                   /*0xFEF2-0xFEF5*/
        1, 0, 2, 1+2,                 /*0xFEF6-0xFEF9*/
        1, 0, 1, 0,                   /*0xFEFA-0xFEFD*/
        1, 0, 1, 0,
        1
    };

    private static int[] convertFEto06 = {
        /***********0******1******2******3******4******5******6******7******8******9******A******B******C******D******E******F***/
        /*FE7*/   0x64B, 0x64B, 0x64C, 0x64C, 0x64D, 0x64D, 0x64E, 0x64E, 0x64F, 0x64F, 0x650, 0x650, 0x651, 0x651, 0x652, 0x652,
        /*FE8*/   0x621, 0x622, 0x622, 0x623, 0x623, 0x624, 0x624, 0x625, 0x625, 0x626, 0x626, 0x626, 0x626, 0x627, 0x627, 0x628,
        /*FE9*/   0x628, 0x628, 0x628, 0x629, 0x629, 0x62A, 0x62A, 0x62A, 0x62A, 0x62B, 0x62B, 0x62B, 0x62B, 0x62C, 0x62C, 0x62C,
        /*FEA*/   0x62C, 0x62D, 0x62D, 0x62D, 0x62D, 0x62E, 0x62E, 0x62E, 0x62E, 0x62F, 0x62F, 0x630, 0x630, 0x631, 0x631, 0x632,
        /*FEB*/   0x632, 0x633, 0x633, 0x633, 0x633, 0x634, 0x634, 0x634, 0x634, 0x635, 0x635, 0x635, 0x635, 0x636, 0x636, 0x636,
        /*FEC*/   0x636, 0x637, 0x637, 0x637, 0x637, 0x638, 0x638, 0x638, 0x638, 0x639, 0x639, 0x639, 0x639, 0x63A, 0x63A, 0x63A,
        /*FED*/   0x63A, 0x641, 0x641, 0x641, 0x641, 0x642, 0x642, 0x642, 0x642, 0x643, 0x643, 0x643, 0x643, 0x644, 0x644, 0x644,
        /*FEE*/   0x644, 0x645, 0x645, 0x645, 0x645, 0x646, 0x646, 0x646, 0x646, 0x647, 0x647, 0x647, 0x647, 0x648, 0x648, 0x649,
        /*FEF*/   0x649, 0x64A, 0x64A, 0x64A, 0x64A, 0x65C, 0x65C, 0x65D, 0x65D, 0x65E, 0x65E, 0x65F, 0x65F
    };

    private static final int shapeTable[][][] = {
        { {0,0,0,0}, {0,0,0,0}, {0,1,0,3}, {0,1,0,1} },
        { {0,0,2,2}, {0,0,1,2}, {0,1,1,2}, {0,1,1,3} },
        { {0,0,0,0}, {0,0,0,0}, {0,1,0,3}, {0,1,0,3} },
        { {0,0,1,2}, {0,0,1,2}, {0,1,1,2}, {0,1,1,3} }
    };

    /*
     * This function shapes European digits to Arabic-Indic digits
     * in-place, writing over the input characters.  Data is in visual
     * order.
     */
    private void shapeToArabicDigitsWithContext(char[] dest,
                                                int start,
                                                int length,
                                                char digitBase,
                                                boolean lastStrongWasAL) {

        digitBase -= '0'; // move common adjustment out of loop

        for(int i = start + length; --i >= start;) {
            char ch = dest[i];
            switch (UCharacter.getDirection(ch)) {
            case UCharacterDirection.LEFT_TO_RIGHT:
            case UCharacterDirection.RIGHT_TO_LEFT:
                lastStrongWasAL = false;
                break;
            case UCharacterDirection.RIGHT_TO_LEFT_ARABIC:
                lastStrongWasAL = true;
                break;
            case UCharacterDirection.EUROPEAN_NUMBER:
                if (lastStrongWasAL && ch <= '\u0039') {
                    dest[i] = (char)(ch + digitBase);
                }
                break;
            default:
                break;
            }
        }
    }

    /*
     * Name    : invertBuffer
     * Function: This function inverts the buffer, it's used
     *           in case the user specifies the buffer to be
     *           TEXT_DIRECTION_LOGICAL
     */
    private static void invertBuffer(char[] buffer,
                                     int start,
                                     int length) {

        for(int i = start, j = start + length - 1; i < j; i++, --j) {
            char temp = buffer[i];
            buffer[i] = buffer[j];
            buffer[j] = temp;
        }
    }

    /*
     * Name    : changeLamAlef
     * Function: Converts the Alef characters into an equivalent
     *           LamAlef location in the 0x06xx Range, this is an
     *           intermediate stage in the operation of the program
     *           later it'll be converted into the 0xFExx LamAlefs 
     *           in the shaping function.
     */
    private static char changeLamAlef(char ch) {
        switch(ch) {
        case '\u0622': return '\u065C';
        case '\u0623': return '\u065D';
        case '\u0625': return '\u065E';
        case '\u0627': return '\u065F';
        default:  return '\u0000'; // not a lamalef
        }
    }

    /*
     * Name    : specialChar
     * Function: Special Arabic characters need special handling in the shapeUnicode
     *           function, this function returns 1 or 2 for these special characters
     */
    private static int specialChar(char ch) {
        if ((ch > '\u0621' && ch < '\u0626') || 
            (ch == '\u0627') ||
            (ch > '\u062E' && ch < '\u0633') ||
            (ch > '\u0647' && ch < '\u064A') ||
            (ch == '\u0629')) {
            return 1;
        } else if (ch >= '\u064B' && ch<= '\u0652') {
            return 2;
        } else if (ch >= 0x0653 && ch <= 0x0655 || 
                   ch == 0x0670 ||
                   ch >= 0xFE70 && ch <= 0xFE7F) {
            return 3;
        } else {
            return 0;
        }
    }
    
    /*
     * Name    : getLink
     * Function: Resolves the link between the characters as 
     *           Arabic characters have four forms :
     *           Isolated, Initial, Middle and Final Form
     */
    private static int getLink(char ch) {
        if (ch >= '\u0622' && ch <= '\u06D3') {
            return araLink[ch - '\u0622'];
        } else if (ch == '\u200D') {
            return 3;
        } else if (ch >= '\u206D' && ch <= '\u206F') {
            return 4;
        } else if (ch >= '\uFE70' && ch <= '\uFEFC') {
            return presLink[ch - '\uFE70'];
        } else {
            return 0;
        }
    }

    /*
     * Name    : countSpaces
     * Function: Counts the number of spaces
     *           at each end of the logical buffer
     */
    private static int countSpacesLeft(char[] dest, 
                                       int start,
                                       int count) {
        for (int i = start, e = start + count; i < e; ++i) {
            if (dest[i] != '\u0020') {
                return i - start;
            }
        }
        return count;
    }

    private static int countSpacesRight(char[] dest,
                                        int start,
                                        int count) {

        for (int i = start + count; --i >= start;) {
            if (dest[i] != '\u0020') {
                return start + count - 1 - i;
            }
        }
        return count;
    }

    /*
     * Name    : isTashkeelChar
     * Function: Returns 1 for Tashkeel characters else return 0
     */
    private static boolean isTashkeelChar(char ch) {
        return ch >='\u064B' && ch <= '\u0652';
    }

    /*
     * Name    : isAlefChar
     * Function: Returns 1 for Alef characters else return 0
     */
    private static boolean isAlefChar(char ch) {
        return ch == '\u0622' || ch == '\u0623' || ch == '\u0625' || ch == '\u0627';
    }

    /*
     * Name    : isLamAlefChar
     * Function: Returns 1 for LamAlef characters else return 0
     */
    private static boolean isLamAlefChar(char ch) {
        return ch >= '\uFEF5' && ch <= '\uFEFC';
    }

    private static boolean isNormalizedLamAlefChar(char ch) {
        return ch >= '\u065C' && ch <= '\u065F';
    }

    /*
     * Name    : calculateSize
     * Function: This function calculates the destSize to be used in preflighting
     *           when the destSize is equal to 0
     */
    private int calculateSize(char[] source,
                              int sourceStart,
                              int sourceLength) {
	
        int destSize = sourceLength;

        switch (options & LETTERS_MASK) {
        case LETTERS_SHAPE:
        case LETTERS_SHAPE_TASHKEEL_ISOLATED:
            if (isLogical) {
                for (int i = sourceStart, e = sourceStart + sourceLength - 1; i < e; ++i) {
                    if (source[i] == '\u0644' && isAlefChar(source[i+1])) {
                        --destSize;
                    }
                }
            } else { // visual
                for(int i = sourceStart + 1, e = sourceStart + sourceLength; i < e; ++i) {
                    if (source[i] == '\u0644' && isAlefChar(source[i-1])) {
                        --destSize;
                    }
                }
            }
            break;

        case LETTERS_UNSHAPE:
            for(int i = sourceStart, e = sourceStart + sourceLength; i < e; ++i) {
                if (isLamAlefChar(source[i])) {
                    destSize++;
                }
            }
            break;

        default:
            break;
        }

        return destSize;
    }

    /*
     * Name    : removeLamAlefSpaces
     * Function: The shapeUnicode function converts Lam + Alef into LamAlef + space,
     *           this function removes the spaces behind the LamAlefs according to
     *           the options the user specifies, the spaces are removed to the end
     *           of the buffer, or shrink the buffer and remove spaces for good
     *           or leave the buffer as it is LamAlef + space.
     */
    private int removeLamAlefSpaces(char[] dest, 
                                    int start,
                                    int length) {
	
        int lenOptions = options & LENGTH_MASK;
        if (!isLogical) {
            switch (lenOptions) {
            case LENGTH_FIXED_SPACES_AT_BEGINNING: lenOptions = LENGTH_FIXED_SPACES_AT_END; break;
            case LENGTH_FIXED_SPACES_AT_END: lenOptions = LENGTH_FIXED_SPACES_AT_BEGINNING; break;
            default: break;
            }
        }

        if (lenOptions == LENGTH_FIXED_SPACES_NEAR) {
            for (int i = start, e = i + length; i < e; ++i) {
                if (dest[i] == '\uffff') {
                    dest[i] = '\u0020';
                }
            }
        } else {
            final int e = start + length;
            int w = e;
            int r = e;
            while (--r >= start) {
                char ch = dest[r];
                if (ch != '\uffff') {
                    --w;
                    if (w != r) {
                        dest[w] = ch;
                    }
                }
            }

            if (lenOptions == LENGTH_FIXED_SPACES_AT_END) {
                while (w > start) {
                    dest[--w] = '\u0020';
                }
            } else {
                if (w > start) {
                    // shift, assume small buffer size so don't use arraycopy
                    r = w;
                    w = start;
                    while (r < e) {
                        dest[w++] = dest[r++];
                    }
                } else {
                    w = e;
                }
                if (lenOptions == LENGTH_GROW_SHRINK) {
                    length = w - start;
                } else { // spaces at beginning
                    while (w < e) {
                        dest[w++] = '\u0020';
                    }
                }
            }
        }
        return length;
    }

    /*
     * Name    : expandLamAlef
     * Function: LamAlef needs special handling as the LamAlef is
     *           one character while expanding it will give two
     *           characters Lam + Alef, so we need to expand the LamAlef
     *           in near or far spaces according to the options the user
     *           specifies or increase the buffer size.
     *           Dest has enough room for the expansion if we are growing.
     *           lamalef are normalized to the 'special characters'
     */
    private int expandLamAlef(char[] dest,
                              int start,
                              int length,
                              int lacount) throws ArabicShapingException {

        int lenOptions = options & LENGTH_MASK;
        if (!isLogical) {
            switch (lenOptions) {
            case LENGTH_FIXED_SPACES_AT_BEGINNING: lenOptions = LENGTH_FIXED_SPACES_AT_END; break;
            case LENGTH_FIXED_SPACES_AT_END: lenOptions = LENGTH_FIXED_SPACES_AT_BEGINNING; break;
            default: break;
            }
        }

        switch (lenOptions) {
        case LENGTH_GROW_SHRINK: 
            {
                for (int r = start + length, w = r + lacount; --r >= start;) {
                    char ch = dest[r];
                    if (isNormalizedLamAlefChar(ch)) {
                        dest[--w] = '\u0644';
                        dest[--w] = convertNormalizedLamAlef[ch - '\u065C'];
                    } else {
                        dest[--w] = ch;
                    }
                }
            }
            length += lacount;
            break;

        case LENGTH_FIXED_SPACES_NEAR: 
            {
                if (isNormalizedLamAlefChar(dest[start])) {
                    throw new ArabicShapingException("no space for lamalef");
                }
                for (int i = start + length; --i > start;) { // don't check start, already checked
                    char ch = dest[i];
                    if (isNormalizedLamAlefChar(ch)) {
                        if (dest[i-1] == '\u0020') {
                            dest[i] = '\u0644';
                            dest[--i] = convertNormalizedLamAlef[ch - '\u065C'];
                        } else {
                            throw new ArabicShapingException("no space for lamalef");
                        }
                    }
                }
            }
            break;

        case LENGTH_FIXED_SPACES_AT_END: 
            {
                if (lacount > countSpacesLeft(dest, start, length)) {
                    throw new ArabicShapingException("no space for lamalef");
                }
                for (int r = start + lacount, w = start, e = start + length; r < e; ++r) {
                    char ch = dest[r];
                    if (isNormalizedLamAlefChar(ch)) {
                        dest[w++] = convertNormalizedLamAlef[ch - '\u065C'];
                        dest[w++] = '\u0644';
                    } else {
                        dest[w++] = ch;
                    }
                }
            }
            break;
                
        case LENGTH_FIXED_SPACES_AT_BEGINNING: 
            {
                if (lacount > countSpacesRight(dest, start, length)) {
                    throw new ArabicShapingException("no space for lamalef");
                }
                for (int r = start + length - lacount, w = start + length; --r >= start;) {
                    char ch = dest[r];
                    if (isNormalizedLamAlefChar(ch)) {
                        dest[--w] = '\u0644';
                        dest[--w] = convertNormalizedLamAlef[ch - '\u065C'];
                    } else {
                        dest[--w] = ch;
                    }
                }
            }
            break;
        }

        return length;
    }

    /* Convert the input buffer from FExx Range into 06xx Range
     * to put all characters into the 06xx range
     * even the lamalef is converted to the special region in
     * the 06xx range.  Return the number of lamalef chars found.
     */
    private int normalize(char[] dest, int start, int length) {
        int lacount = 0;
        for (int i = start, e = i + length; i < e; ++i) {
            char ch = dest[i];
            if (ch >= '\uFE70' && ch <= '\uFEFC') {
                if (isLamAlefChar(ch)) {
                    ++lacount;
                }
                dest[i] = (char)convertFEto06[ch - '\uFE70'];
            }
        }
        return lacount;
    }

    /*
     * Name    : shapeUnicode
     * Function: Converts an Arabic Unicode buffer in 06xx Range into a shaped
     *           arabic Unicode buffer in FExx Range
     */
    private int shapeUnicode(char[] dest, 
                             int start,
                             int length,
                             int destSize,
                             int tashkeelFlag) {


        normalize(dest, start, length);

        // resolve the link between the characters.
        // Arabic characters have four forms: Isolated, Initial, Medial and Final.
        // Tashkeel characters have two, isolated or medial, and sometimes only isolated.
        // tashkeelFlag == 0: shape normally, 1: shape isolated, 2: don't shape

        boolean lamalef_found = false;
        int i = start + length - 1;
        int currLink = getLink(dest[i]);
        int nextLink = 0;
        int prevLink = 0;
        int lastLink = 0;
        int prevPos = i;
        int lastPos = i;
        int nx = -2;
        int nw = 0;

        while (i >= 0) {
            // If high byte of currLink > 0 then there might be more than one shape
            if ((currLink & '\uFF00') > 0 || isTashkeelChar(dest[i])) {
                nw = i - 1;
                nx = -2;
                while (nx < 0) { // we need to know about next char
                    if (nw == -1) {
                        nextLink = 0;
                        nx = Integer.MAX_VALUE;
                    } else {
                        nextLink = getLink(dest[nw]);
                        if ((nextLink & IRRELEVANT) == 0) {
                            nx = nw;
                        } else {
                            --nw;
                        }
                    }
                }

                if (((currLink & ALEFTYPE) > 0) && ((lastLink & LAMTYPE) > 0)) {
                    lamalef_found = true; 
                    char wLamalef = changeLamAlef(dest[i]); // get from 0x065C-0x065f
                    if (wLamalef != '\u0000') {
                        // replace alef by marker, it will be removed later
                        dest[i] = '\uffff';
                        dest[lastPos] = wLamalef;
                        i = lastPos;
                    }

                    lastLink = prevLink;
                    currLink = getLink(wLamalef); // requires '\u0000', unfortunately
                }

                // get the proper shape according to link ability of neighbors
                // and of character; depends on the order of the shapes
                // (isolated, initial, middle, final) in the compatibility area

                int flag = specialChar(dest[i]);

                int shape = shapeTable[nextLink & LINK_MASK]
                    [lastLink & LINK_MASK]
                    [currLink & LINK_MASK];

                if (flag == 1) {
                    shape &= 0x1;
                } else if (flag == 2) {
                    if (tashkeelFlag == 0 &&
                        ((lastLink & LINKL) != 0) && 
                        ((nextLink & LINKR) != 0) && 
                        dest[i] != '\u064C' && 
                        dest[i] != '\u064D' &&
                        !((nextLink & ALEFTYPE) == ALEFTYPE && 
                          (lastLink & LAMTYPE) == LAMTYPE)) {
		
                        shape = 1;
                    } else {
                        shape = 0;
                    }
                }

                if (flag == 2) {
                    if (tashkeelFlag < 2) {
                        dest[i] = (char)('\uFE70' + irrelevantPos[dest[i] - '\u064B'] + shape);
                    } // else leave tashkeel alone                    
                } else {
                    dest[i] = (char)('\uFE70' + (currLink >> 8) + shape);
                }
            }

            // move one notch forward
            if ((currLink & IRRELEVANT) == 0) {
                prevLink = lastLink;
                lastLink = currLink;
                prevPos = lastPos;
                lastPos = i;
            }

            --i;
            if (i == nx) {
                currLink = nextLink;
                nx = -2;
            } else if (i != -1) {
                currLink = getLink(dest[i]);
            }
        }

        // If we found a lam/alef pair in the buffer 
        // call removeLamAlefSpaces to remove the spaces that were added

        if (lamalef_found) {
            destSize = removeLamAlefSpaces(dest, start, length);
        } else {
            destSize = length;
        }
        
        return destSize;
    }

    /*
     * Name    : deShapeUnicode
     * Function: Converts an Arabic Unicode buffer in FExx Range into unshaped
     *           arabic Unicode buffer in 06xx Range
     */
    private int deShapeUnicode(char[] dest, 
                               int start,
                               int length,
                               int destSize) throws ArabicShapingException {

        int lamalef_count = normalize(dest, start, length);

        // If there was a lamalef in the buffer call expandLamAlef
        if (lamalef_count != 0) {
            // need to adjust dest to fit expanded buffer... !!!
            destSize = expandLamAlef(dest, start, length, lamalef_count);
        } else {
            destSize = length;
        }

        return destSize;
    }

    private int internalShape(char[] source, 
                              int sourceStart,
                              int sourceLength,
                              char[] dest,
                              int destStart,
                              int destSize) throws ArabicShapingException {

        if (sourceLength == 0) {
            return 0;
        }

        if (destSize == 0) {
            if (((options & LETTERS_MASK) != LETTERS_NOOP) &&
                ((options & LENGTH_MASK) == LENGTH_GROW_SHRINK)) {
	
                return calculateSize(source, sourceStart, sourceLength);
            } else {
                return sourceLength; // by definition
            }
        }

        // always use temp buffer
        char[] temp = new char[sourceLength * 2]; // all lamalefs requiring expansion
        System.arraycopy(source, sourceStart, temp, 0, sourceLength);

        if (isLogical) {
            invertBuffer(temp, 0, sourceLength);
        }

        int outputSize = sourceLength;

        switch (options & LETTERS_MASK) {
        case LETTERS_SHAPE_TASHKEEL_ISOLATED:
            outputSize = shapeUnicode(temp, 0, sourceLength, destSize, 1);
            break;

        case LETTERS_SHAPE:
            outputSize = shapeUnicode(temp, 0, sourceLength, destSize, 0);
            break;

        case LETTERS_UNSHAPE:
            outputSize = deShapeUnicode(temp, 0, sourceLength, destSize);
            break; 

        default:
            break;
        }
                
        if (outputSize > destSize) {
            throw new ArabicShapingException("not enough room for result data");
        }

        if ((options & DIGITS_MASK) != DIGITS_NOOP) {
            char digitBase = '\u0030'; // European digits
            switch (options & DIGIT_TYPE_MASK) {
            case DIGIT_TYPE_AN:
                digitBase = '\u0660';  // Arabic-Indic digits
                break;

            case DIGIT_TYPE_AN_EXTENDED:
                digitBase = '\u06f0';  // Eastern Arabic-Indic digits (Persian and Urdu)
                break;

            default:
                break;
            }

            switch (options & DIGITS_MASK) {
            case DIGITS_EN2AN:
                {
                    int digitDelta = digitBase - '\u0030';
                    for (int i = 0; i < outputSize; ++i) {
                        char ch = temp[i];
                        if (ch <= '\u0039' && ch >= '\u0030') {
                            temp[i] += digitDelta;
                        }
                    }
                }
                break;

            case DIGITS_AN2EN:
                {
                    char digitTop = (char)(digitBase + 9);
                    int digitDelta = '\u0030' - digitBase;
                    for (int i = 0; i < outputSize; ++i) {
                        char ch = temp[i];
                        if (ch <= digitTop && ch >= digitBase) {
                            temp[i] += digitDelta;
                        }
                    }
                }
                break;

            case DIGITS_EN2AN_INIT_LR:
                shapeToArabicDigitsWithContext(temp, 0, outputSize, digitBase, false);
                break;

            case DIGITS_EN2AN_INIT_AL:
                shapeToArabicDigitsWithContext(temp, 0, outputSize, digitBase, true);
                break;

            default:
                break;
            }
        }

        if (isLogical) {
            invertBuffer(temp, 0, outputSize);
        }
      
        System.arraycopy(temp, 0, dest, destStart, outputSize);
      
        return outputSize;
    }
}