/*
 * Copyright 2005-2006 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.codemodel.internal.util;

import java.nio.CharBuffer;
import java.nio.charset.CoderResult;


/**
 * Utility class for dealing with surrogates.
 *
 * @author Mark Reinhold
 * @version 1.11, 03/01/23
 */

class Surrogate {

    private Surrogate() { }

    // UTF-16 surrogate-character ranges
    //
    public static final char MIN_HIGH = '\uD800';
    public static final char MAX_HIGH = '\uDBFF';
    public static final char MIN_LOW  = '\uDC00';
    public static final char MAX_LOW  = '\uDFFF';
    public static final char MIN = MIN_HIGH;
    public static final char MAX = MAX_LOW;

    // Range of UCS-4 values that need surrogates in UTF-16
    //
    public static final int UCS4_MIN = 0x10000;
    public static final int UCS4_MAX = (1 << 20) + UCS4_MIN - 1;

    /**
     * Tells whether or not the given UTF-16 value is a high surrogate.
     */
    public static boolean isHigh(int c) {
        return (MIN_HIGH <= c) && (c <= MAX_HIGH);
    }

    /**
     * Tells whether or not the given UTF-16 value is a low surrogate.
     */
    public static boolean isLow(int c) {
        return (MIN_LOW <= c) && (c <= MAX_LOW);
    }

    /**
     * Tells whether or not the given UTF-16 value is a surrogate character,
     */
    public static boolean is(int c) {
        return (MIN <= c) && (c <= MAX);
    }

    /**
     * Tells whether or not the given UCS-4 character must be represented as a
     * surrogate pair in UTF-16.
     */
    public static boolean neededFor(int uc) {
        return (uc >= UCS4_MIN) && (uc <= UCS4_MAX);
    }

    /**
     * Returns the high UTF-16 surrogate for the given UCS-4 character.
     */
    public static char high(int uc) {
        return (char)(0xd800 | (((uc - UCS4_MIN) >> 10) & 0x3ff));
    }

    /**
     * Returns the low UTF-16 surrogate for the given UCS-4 character.
     */
    public static char low(int uc) {
        return (char)(0xdc00 | ((uc - UCS4_MIN) & 0x3ff));
    }

    /**
     * Converts the given surrogate pair into a 32-bit UCS-4 character.
     */
    public static int toUCS4(char c, char d) {
        return (((c & 0x3ff) << 10) | (d & 0x3ff)) + 0x10000;
    }

    /**
     * Surrogate parsing support.  Charset implementations may use instances of
     * this class to handle the details of parsing UTF-16 surrogate pairs.
     */
    public static class Parser {

        public Parser() { }

        private int character;          // UCS-4
        private CoderResult error = CoderResult.UNDERFLOW;
        private boolean isPair;

        /**
         * Returns the UCS-4 character previously parsed.
         */
        public int character() {
            return character;
        }

        /**
         * Tells whether or not the previously-parsed UCS-4 character was
         * originally represented by a surrogate pair.
         */
        public boolean isPair() {
            return isPair;
        }

        /**
         * Returns the number of UTF-16 characters consumed by the previous
         * parse.
         */
        public int increment() {
            return isPair ? 2 : 1;
        }

        /**
         * If the previous parse operation detected an error, return the object
         * describing that error.
         */
        public CoderResult error() {
            return error;
        }

        /**
         * Returns an unmappable-input result object, with the appropriate
         * input length, for the previously-parsed character.
         */
        public CoderResult unmappableResult() {
            return CoderResult.unmappableForLength(isPair ? 2 : 1);
        }

        /**
         * Parses a UCS-4 character from the given source buffer, handling
         * surrogates.
         *
         * @param  c    The first character
         * @param  in   The source buffer, from which one more character
         *              will be consumed if c is a high surrogate
         *
         * @return   Either a parsed UCS-4 character, in which case the isPair()
         *           and increment() methods will return meaningful values, or
         *           -1, in which case error() will return a descriptive result
         *           object
         */
        public int parse(char c, CharBuffer in) {
            if (isHigh(c)) {
                if (!in.hasRemaining()) {
                    error = CoderResult.UNDERFLOW;
                    return -1;
                }
                char d = in.get();
                if (isLow(d)) {
                    character = toUCS4(c, d);
                    isPair = true;
                    error = null;
                    return character;
                }
                error = CoderResult.malformedForLength(1);
                return -1;
            }
            if (isLow(c)) {
                error = CoderResult.malformedForLength(1);
                return -1;
            }
            character = c;
            isPair = false;
            error = null;
            return character;
        }

        /**
         * Parses a UCS-4 character from the given source buffer, handling
         * surrogates.
         *
         * @param  c    The first character
         * @param  ia   The input array, from which one more character
         *              will be consumed if c is a high surrogate
         * @param  ip   The input index
         * @param  il   The input limit
         *
         * @return   Either a parsed UCS-4 character, in which case the isPair()
         *           and increment() methods will return meaningful values, or
         *           -1, in which case error() will return a descriptive result
         *           object
         */
        public int parse(char c, char[] ia, int ip, int il) {
            if (isHigh(c)) {
                if (il - ip < 2) {
                    error = CoderResult.UNDERFLOW;
                    return -1;
                }
                char d = ia[ip + 1];
                if (isLow(d)) {
                    character = toUCS4(c, d);
                    isPair = true;
                    error = null;
                    return character;
                }
                error = CoderResult.malformedForLength(1);
                return -1;
            }
            if (isLow(c)) {
                error = CoderResult.malformedForLength(1);
                return -1;
            }
            character = c;
            isPair = false;
            error = null;
            return character;
        }

    }

    /**
     * Surrogate generation support.  Charset implementations may use instances
     * of this class to handle the details of generating UTF-16 surrogate
     * pairs.
     */
    public static class Generator {

        public Generator() { }

        private CoderResult error = CoderResult.OVERFLOW;

        /**
         * If the previous generation operation detected an error, return the
         * object describing that error.
         */
        public CoderResult error() {
            return error;
        }

        /**
         * Generates one or two UTF-16 characters to represent the given UCS-4
         * character.
         *
         * @param  uc   The UCS-4 character
         * @param  len  The number of input bytes from which the UCS-4 value
         *              was constructed (used when creating result objects)
         * @param  dst  The destination buffer, to which one or two UTF-16
         *              characters will be written
         *
         * @return   Either a positive count of the number of UTF-16 characters
         *           written to the destination buffer, or -1, in which case
         *           error() will return a descriptive result object
         */
        public int generate(int uc, int len, CharBuffer dst) {
            if (uc <= 0xffff) {
                if (is(uc)) {
                    error = CoderResult.malformedForLength(len);
                    return -1;
                }
                if (dst.remaining() < 1) {
                    error = CoderResult.OVERFLOW;
                    return -1;
                }
                dst.put((char)uc);
                error = null;
                return 1;
            }
            if (uc < UCS4_MIN) {
                error = CoderResult.malformedForLength(len);
                return -1;
            }
            if (uc <= UCS4_MAX) {
                if (dst.remaining() < 2) {
                    error = CoderResult.OVERFLOW;
                    return -1;
                }
                dst.put(high(uc));
                dst.put(low(uc));
                error = null;
                return 2;
            }
            error = CoderResult.unmappableForLength(len);
            return -1;
        }

        /**
         * Generates one or two UTF-16 characters to represent the given UCS-4
         * character.
         *
         * @param  uc   The UCS-4 character
         * @param  len  The number of input bytes from which the UCS-4 value
         *              was constructed (used when creating result objects)
         * @param  da   The destination array, to which one or two UTF-16
         *              characters will be written
         * @param  dp   The destination position
         * @param  dl   The destination limit
         *
         * @return   Either a positive count of the number of UTF-16 characters
         *           written to the destination buffer, or -1, in which case
         *           error() will return a descriptive result object
         */
        public int generate(int uc, int len, char[] da, int dp, int dl) {
            if (uc <= 0xffff) {
                if (is(uc)) {
                    error = CoderResult.malformedForLength(len);
                    return -1;
                }
                if (dl - dp < 1) {
                    error = CoderResult.OVERFLOW;
                    return -1;
                }
                da[dp] = (char)uc;
                error = null;
                return 1;
            }
            if (uc < UCS4_MIN) {
                error = CoderResult.malformedForLength(len);
                return -1;
            }
            if (uc <= UCS4_MAX) {
                if (dl - dp < 2) {
                    error = CoderResult.OVERFLOW;
                    return -1;
                }
                da[dp] = high(uc);
                da[dp + 1] = low(uc);
                error = null;
                return 2;
            }
            error = CoderResult.unmappableForLength(len);
            return -1;
        }

    }

}
