/*

 * Copyright (c) 2002, 2013, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package build.tools.generatecharacter;

import java.text.*;

import java.util.*;

public class Utility {

    static byte peekByte(String s, int index) {

        char c = s.charAt(index/2);

        return ((index&1)==0)?(byte)(c>>8):(byte)c;

    }

    static short peekShort(String s, int index) {

        return (short)s.charAt(index);

    }

    static int peekInt(String s, int index) {

        index *= 2;

        return (((int)s.charAt(index)) << 16) | s.charAt(index+1);

    }

    static void poke(String s, int index, byte value) {

        int mask = 0xFF00;

        int ivalue = value;

        if ((index&1)==0) {

            ivalue <<= 8;

            mask = 0x00FF;

        }

        index /= 2;

        if (index == s.length()) {

            s = s + (char)ivalue;

        }

        else if (index == 0) {

            s = (char)(ivalue|(s.charAt(0)&mask)) + s.substring(1);

        }

        else {

            s = s.substring(0, index) + (char)(ivalue|(s.charAt(index)&mask))

                + s.substring(index+1);

        }

    }

    static void poke(String s, int index, short value) {

        if (index == s.length()) {

            s = s + (char)value;

        }

        else if (index == 0) {

            s = (char)value + s.substring(1);

        }

        else {

            s = s.substring(0, index) + (char)value + s.substring(index+1);

        }

    }

    static void poke(String s, int index, int value) {

        index *= 2;

        char hi = (char)(value >> 16);

        if (index == s.length()) {

            s = s + hi + (char)value;

        }

        else if (index == 0) {

            s = hi + (char)value + s.substring(2);

        }

        else {

            s = s.substring(0, index) + hi + (char)value + s.substring(index+2);

        }

    }

    /**

     * The ESCAPE character is used during run-length encoding.  It signals

     * a run of identical chars.

     */

    static final char ESCAPE = '\uA5A5';

    /**

     * The ESCAPE_BYTE character is used during run-length encoding.  It signals

     * a run of identical bytes.

     */

    static final byte ESCAPE_BYTE = (byte)0xA5;

    /**

     * Construct a string representing a short array.  Use run-length encoding.

     * A character represents itself, unless it is the ESCAPE character.  Then

     * the following notations are possible:

     *   ESCAPE ESCAPE   ESCAPE literal

     *   ESCAPE n c      n instances of character c

     * Since an encoded run occupies 3 characters, we only encode runs of 4 or

     * more characters.  Thus we have n > 0 and n != ESCAPE and n <= 0xFFFF.

     * If we encounter a run where n == ESCAPE, we represent this as:

     *   c ESCAPE n-1 c

     * The ESCAPE value is chosen so as not to collide with commonly

     * seen values.

     */

    static final String arrayToRLEString(short[] a) {

        StringBuffer buffer = new StringBuffer();

        // for (int i=0; i<a.length; ++i) buffer.append((char) a[i]);

        buffer.append((char) (a.length >> 16));

        buffer.append((char) a.length);

        short runValue = a[0];

        int runLength = 1;

        for (int i=1; i<a.length; ++i) {

            short s = a[i];

            if (s == runValue && runLength < 0xFFFF) ++runLength;

            else {

                encodeRun(buffer, runValue, runLength);

                runValue = s;

                runLength = 1;

            }

        }

        encodeRun(buffer, runValue, runLength);

        return buffer.toString();

    }

    /**

     * Construct a string representing a byte array.  Use run-length encoding.

     * Two bytes are packed into a single char, with a single extra zero byte at

     * the end if needed.  A byte represents itself, unless it is the

     * ESCAPE_BYTE.  Then the following notations are possible:

     *   ESCAPE_BYTE ESCAPE_BYTE   ESCAPE_BYTE literal

     *   ESCAPE_BYTE n b           n instances of byte b

     * Since an encoded run occupies 3 bytes, we only encode runs of 4 or

     * more bytes.  Thus we have n > 0 and n != ESCAPE_BYTE and n <= 0xFF.

     * If we encounter a run where n == ESCAPE_BYTE, we represent this as:

     *   b ESCAPE_BYTE n-1 b

     * The ESCAPE_BYTE value is chosen so as not to collide with commonly

     * seen values.

     */

    static final String arrayToRLEString(byte[] a) {

        StringBuffer buffer = new StringBuffer();

        buffer.append((char) (a.length >> 16));

        buffer.append((char) a.length);

        byte runValue = a[0];

        int runLength = 1;

        byte[] state = new byte[2];

        for (int i=1; i<a.length; ++i) {

            byte b = a[i];

            if (b == runValue && runLength < 0xFF) ++runLength;

            else {

                encodeRun(buffer, runValue, runLength, state);

                runValue = b;

                runLength = 1;

            }

        }

        encodeRun(buffer, runValue, runLength, state);

        // We must save the final byte, if there is one, by padding

        // an extra zero.

        if (state[0] != 0) appendEncodedByte(buffer, (byte)0, state);

        return buffer.toString();

    }

    /**

     * Encode a run, possibly a degenerate run (of < 4 values).

     * @param length The length of the run; must be > 0 && <= 0xFFFF.

     */

    private static final void encodeRun(StringBuffer buffer, short value, int length) {

        if (length < 4) {

            for (int j=0; j<length; ++j) {

                if (value == (int) ESCAPE) buffer.append(ESCAPE);

                buffer.append((char) value);

            }

        }

        else {

            if (length == (int) ESCAPE) {

                if (value == (int) ESCAPE) buffer.append(ESCAPE);

                buffer.append((char) value);

                --length;

            }

            buffer.append(ESCAPE);

            buffer.append((char) length);

            buffer.append((char) value); // Don't need to escape this value

        }

    }

    /**

     * Encode a run, possibly a degenerate run (of < 4 values).

     * @param length The length of the run; must be > 0 && <= 0xFF.

     */

    private static final void encodeRun(StringBuffer buffer, byte value, int length,

                                        byte[] state) {

        if (length < 4) {

            for (int j=0; j<length; ++j) {

                if (value == ESCAPE_BYTE) appendEncodedByte(buffer, ESCAPE_BYTE, state);

                appendEncodedByte(buffer, value, state);

            }

        }

        else {

            if (length == ESCAPE_BYTE) {

                if (value == ESCAPE_BYTE) appendEncodedByte(buffer, ESCAPE_BYTE, state);

                appendEncodedByte(buffer, value, state);

                --length;

            }

            appendEncodedByte(buffer, ESCAPE_BYTE, state);

            appendEncodedByte(buffer, (byte)length, state);

            appendEncodedByte(buffer, value, state); // Don't need to escape this value

        }

    }

    /**

     * Append a byte to the given StringBuffer, packing two bytes into each

     * character.  The state parameter maintains intermediary data between

     * calls.

     * @param state A two-element array, with state[0] == 0 if this is the

     * first byte of a pair, or state[0] != 0 if this is the second byte

     * of a pair, in which case state[1] is the first byte.

     */

    private static final void appendEncodedByte(StringBuffer buffer, byte value,

                                                byte[] state) {

        if (state[0] != 0) {

            char c = (char) ((state[1] << 8) | (((int) value) & 0xFF));

            buffer.append(c);

            state[0] = 0;

        }

        else {

            state[0] = 1;

            state[1] = value;

        }

    }

    /**

     * Construct an array of shorts from a run-length encoded string.

     */

    static final short[] RLEStringToShortArray(String s) {

        int length = (((int) s.charAt(0)) << 16) | ((int) s.charAt(1));

        short[] array = new short[length];

        int ai = 0;

        for (int i=2; i<s.length(); ++i) {

            char c = s.charAt(i);

            if (c == ESCAPE) {

                c = s.charAt(++i);

                if (c == ESCAPE) array[ai++] = (short) c;

                else {

                    int runLength = (int) c;

                    short runValue = (short) s.charAt(++i);

                    for (int j=0; j<runLength; ++j) array[ai++] = runValue;

                }

            }

            else {

                array[ai++] = (short) c;

            }

        }

        if (ai != length)

            throw new InternalError("Bad run-length encoded short array");

        return array;

    }

    /**

     * Construct an array of bytes from a run-length encoded string.

     */

    static final byte[] RLEStringToByteArray(String s) {

        int length = (((int) s.charAt(0)) << 16) | ((int) s.charAt(1));

        byte[] array = new byte[length];

        boolean nextChar = true;

        char c = 0;

        int node = 0;

        int runLength = 0;

        int i = 2;

        for (int ai=0; ai<length; ) {

            // This part of the loop places the next byte into the local

            // variable 'b' each time through the loop.  It keeps the

            // current character in 'c' and uses the boolean 'nextChar'

            // to see if we've taken both bytes out of 'c' yet.

            byte b;

            if (nextChar) {

                c = s.charAt(i++);

                b = (byte) (c >> 8);

                nextChar = false;

            }

            else {

                b = (byte) (c & 0xFF);

                nextChar = true;

            }

            // This part of the loop is a tiny state machine which handles

            // the parsing of the run-length encoding.  This would be simpler

            // if we could look ahead, but we can't, so we use 'node' to

            // move between three nodes in the state machine.

            switch (node) {

            case 0:

                // Normal idle node

                if (b == ESCAPE_BYTE) {

                    node = 1;

                }

                else {

                    array[ai++] = b;

                }

                break;

            case 1:

                // We have seen one ESCAPE_BYTE; we expect either a second

                // one, or a run length and value.

                if (b == ESCAPE_BYTE) {

                    array[ai++] = ESCAPE_BYTE;

                    node = 0;

                }

                else {

                    runLength = b;

                    // Interpret signed byte as unsigned

                    if (runLength < 0) runLength += 0x100;

                    node = 2;

                }

                break;

            case 2:

                // We have seen an ESCAPE_BYTE and length byte.  We interpret

                // the next byte as the value to be repeated.

                for (int j=0; j<runLength; ++j) array[ai++] = b;

                node = 0;

                break;

            }

        }

        if (node != 0)

            throw new InternalError("Bad run-length encoded byte array");

        if (i != s.length())

            throw new InternalError("Excess data in RLE byte array string");

        return array;

    }

    /**

     * Format a String for representation in a source file.  This includes

     * breaking it into lines escaping characters using octal notation

     * when necessary (control characters and double quotes).

     */

    static final String formatForSource(String s) {

        return formatForSource(s, "        ");

    }

    /**

     * Format a String for representation in a source file.  This includes

     * breaking it into lines escaping characters using octal notation

     * when necessary (control characters and double quotes).

     */

    static final String formatForSource(String s, String indent) {

        StringBuffer buffer = new StringBuffer();

        for (int i=0; i<s.length();) {

            if (i > 0) buffer.append("+\n");

            int limit = buffer.length() + 78; // Leave 2 for trailing <"+>

            buffer.append(indent + '"');

            while (i<s.length() && buffer.length()<limit) {

                char c = s.charAt(i++);

                /* This works too but it's kind of unnecessary; might as

                   well keep things simple.

                if (c == '\\' || c == '"') {

                    // Escape backslash and double-quote.  Don't need to

                    // escape single-quote.

                    buffer.append("\\" + c);

                }

                else if (c >= '\u0020' && c <= '\u007E') {

                    // Printable ASCII ranges from ' ' to '~'

                    buffer.append(c);

                }

                else

                */

                if (c <= '\377') {

                    // Represent control characters

                    // using octal notation; otherwise the string we form

                    // won't compile, since Unicode escape sequences are

                    // processed before tokenization.

                    buffer.append('\\');

                    buffer.append(HEX_DIGIT[(c & 0700) >> 6]); // HEX_DIGIT works for octal

                    buffer.append(HEX_DIGIT[(c & 0070) >> 3]);

                    buffer.append(HEX_DIGIT[(c & 0007)]);

                }

                else {

                    // Handle the rest with Unicode

                    buffer.append("\\u");

                    buffer.append(HEX_DIGIT[(c & 0xF000) >> 12]);

                    buffer.append(HEX_DIGIT[(c & 0x0F00) >> 8]);

                    buffer.append(HEX_DIGIT[(c & 0x00F0) >> 4]);

                    buffer.append(HEX_DIGIT[(c & 0x000F)]);

                }

            }

            buffer.append('"');

        }

        return buffer.toString();

    }

    static final char[] HEX_DIGIT = {'0','1','2','3','4','5','6','7',

                                     '8','9','A','B','C','D','E','F'};

}