/*

 * Copyright (c) 2014, 2018, 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 jdk.internal.net.http.hpack;

import java.io.IOException;

import java.nio.ByteBuffer;

import static java.lang.String.format;

/**

 * Huffman coding table.

 *

 * <p> Instances of this class are safe for use by multiple threads.

 *

 * @since 9

 */

public final class NaiveHuffman {

    // TODO: check if reset is done in both reader and writer

    static final class Reader implements Huffman.Reader {

        private Node curr; // position in the trie

        private int len;   // length of the path from the root to 'curr'

        private int p;     // byte probe

        {

            reset();

        }

        @Override

        public void read(ByteBuffer source,

                         Appendable destination,

                         boolean isLast) throws IOException {

            read(source, destination, true, isLast);

        }

        // Takes 'isLast' rather than returns whether the reading is done or

        // not, for more informative exceptions.

        void read(ByteBuffer source,

                  Appendable destination,

                  boolean reportEOS, /* reportEOS is exposed for tests */

                  boolean isLast) throws IOException {

            Node c = curr;

            int l = len;

            /*

               Since ByteBuffer is itself stateful, its position is

               remembered here NOT as a part of Reader's state,

               but to set it back in the case of a failure

             */

            int pos = source.position();

            while (source.hasRemaining()) {

                int d = source.get();

                for (; p != 0; p >>= 1) {

                    c = c.getChild(p & d);

                    l++;

                    if (c.isLeaf()) {

                        if (reportEOS && c.isEOSPath) {

                            throw new IOException("Encountered EOS");

                        }

                        char ch;

                        try {

                            ch = c.getChar();

                        } catch (IllegalStateException e) {

                            source.position(pos); // do we need this?

                            throw new IOException(e);

                        }

                        try {

                            destination.append(ch);

                        } catch (IOException e) {

                            source.position(pos); // do we need this?

                            throw e;

                        }

                        c = INSTANCE.root;

                        l = 0;

                    }

                    curr = c;

                    len = l;

                }

                resetProbe();

                pos++;

            }

            if (!isLast) {

                return; // it's too early to jump to any conclusions, let's wait

            }

            if (c.isLeaf()) {

                return; // it's perfectly ok, no extra padding bits

            }

            if (c.isEOSPath && len <= 7) {

                return; // it's ok, some extra padding bits

            }

            if (c.isEOSPath) {

                throw new IOException(

                        "Padding is too long (len=" + len + ") " +

                                "or unexpected end of data");

            }

            throw new IOException(

                    "Not a EOS prefix padding or unexpected end of data");

        }

        @Override

        public void reset() {

            curr = INSTANCE.root;

            len = 0;

            resetProbe();

        }

        private void resetProbe() {

            p = 0x80;

        }

    }

    static final class Writer implements Huffman.Writer {

        private int pos;       // position in 'source'

        private int avail = 8; // number of least significant bits available in 'curr'

        private int curr;      // next byte to put to the destination

        private int rem;       // number of least significant bits in 'code' yet to be processed

        private int code;      // current code being written

        private CharSequence source;

        private int end;

        @Override

        public Writer from(CharSequence input, int start, int end) {

            if (start < 0 || end < 0 || end > input.length() || start > end) {

                throw new IndexOutOfBoundsException(

                        String.format("input.length()=%s, start=%s, end=%s",

                                      input.length(), start, end));

            }

            pos = start;

            this.end = end;

            this.source = input;

            return this;

        }

        @Override

        public boolean write(ByteBuffer destination) {

            for (; pos < end; pos++) {

                if (rem == 0) {

                    Code desc = INSTANCE.codeOf(source.charAt(pos));

                    rem = desc.length;

                    code = desc.code;

                }

                while (rem > 0) {

                    if (rem < avail) {

                        curr |= (code << (avail - rem));

                        avail -= rem;

                        rem = 0;

                    } else {

                        int c = (curr | (code >>> (rem - avail)));

                        if (destination.hasRemaining()) {

                            destination.put((byte) c);

                        } else {

                            return false;

                        }

                        curr = c;

                        code <<= (32 - rem + avail);  // throw written bits off the cliff (is this Sparta?)

                        code >>>= (32 - rem + avail); // return to the position

                        rem -= avail;

                        curr = 0;

                        avail = 8;

                    }

                }

            }

            if (avail < 8) { // have to pad

                if (destination.hasRemaining()) {

                    destination.put((byte) (curr | (INSTANCE.EOS.code >>> (INSTANCE.EOS.length - avail))));

                    avail = 8;

                } else {

                    return false;

                }

            }

            return true;

        }

        @Override

        public Writer reset() {

            source = null;

            end = -1;

            pos = -1;

            avail = 8;

            curr = 0;

            code = 0;

            return this;

        }

        @Override

        public int lengthOf(CharSequence value, int start, int end) {

            return INSTANCE.lengthOf(value, start, end);

        }

    }

    /**

     * Shared instance.

     */

    public static final NaiveHuffman INSTANCE = new NaiveHuffman();

    private final Code EOS = new Code(0x3fffffff, 30);

    private final Code[] codes = new Code[257];

    private final Node root = new Node() {

        @Override

        public String toString() { return "root"; }

    };

    // TODO: consider builder and immutable trie

    private NaiveHuffman() {

        // @formatter:off

        addChar(0,   0x1ff8,     13);

        addChar(1,   0x7fffd8,   23);

        addChar(2,   0xfffffe2,  28);

        addChar(3,   0xfffffe3,  28);

        addChar(4,   0xfffffe4,  28);

        addChar(5,   0xfffffe5,  28);

        addChar(6,   0xfffffe6,  28);

        addChar(7,   0xfffffe7,  28);

        addChar(8,   0xfffffe8,  28);

        addChar(9,   0xffffea,   24);

        addChar(10,  0x3ffffffc, 30);

        addChar(11,  0xfffffe9,  28);

        addChar(12,  0xfffffea,  28);

        addChar(13,  0x3ffffffd, 30);

        addChar(14,  0xfffffeb,  28);

        addChar(15,  0xfffffec,  28);

        addChar(16,  0xfffffed,  28);

        addChar(17,  0xfffffee,  28);

        addChar(18,  0xfffffef,  28);

        addChar(19,  0xffffff0,  28);

        addChar(20,  0xffffff1,  28);

        addChar(21,  0xffffff2,  28);

        addChar(22,  0x3ffffffe, 30);

        addChar(23,  0xffffff3,  28);

        addChar(24,  0xffffff4,  28);

        addChar(25,  0xffffff5,  28);

        addChar(26,  0xffffff6,  28);

        addChar(27,  0xffffff7,  28);

        addChar(28,  0xffffff8,  28);

        addChar(29,  0xffffff9,  28);

        addChar(30,  0xffffffa,  28);

        addChar(31,  0xffffffb,  28);

        addChar(32,  0x14,        6);

        addChar(33,  0x3f8,      10);

        addChar(34,  0x3f9,      10);

        addChar(35,  0xffa,      12);

        addChar(36,  0x1ff9,     13);

        addChar(37,  0x15,        6);

        addChar(38,  0xf8,        8);

        addChar(39,  0x7fa,      11);

        addChar(40,  0x3fa,      10);

        addChar(41,  0x3fb,      10);

        addChar(42,  0xf9,        8);

        addChar(43,  0x7fb,      11);

        addChar(44,  0xfa,        8);

        addChar(45,  0x16,        6);

        addChar(46,  0x17,        6);

        addChar(47,  0x18,        6);

        addChar(48,  0x0,         5);

        addChar(49,  0x1,         5);

        addChar(50,  0x2,         5);

        addChar(51,  0x19,        6);

        addChar(52,  0x1a,        6);

        addChar(53,  0x1b,        6);

        addChar(54,  0x1c,        6);

        addChar(55,  0x1d,        6);

        addChar(56,  0x1e,        6);

        addChar(57,  0x1f,        6);

        addChar(58,  0x5c,        7);

        addChar(59,  0xfb,        8);

        addChar(60,  0x7ffc,     15);

        addChar(61,  0x20,        6);

        addChar(62,  0xffb,      12);

        addChar(63,  0x3fc,      10);

        addChar(64,  0x1ffa,     13);

        addChar(65,  0x21,        6);

        addChar(66,  0x5d,        7);

        addChar(67,  0x5e,        7);

        addChar(68,  0x5f,        7);

        addChar(69,  0x60,        7);

        addChar(70,  0x61,        7);

        addChar(71,  0x62,        7);

        addChar(72,  0x63,        7);

        addChar(73,  0x64,        7);

        addChar(74,  0x65,        7);

        addChar(75,  0x66,        7);

        addChar(76,  0x67,        7);

        addChar(77,  0x68,        7);

        addChar(78,  0x69,        7);

        addChar(79,  0x6a,        7);

        addChar(80,  0x6b,        7);

        addChar(81,  0x6c,        7);

        addChar(82,  0x6d,        7);

        addChar(83,  0x6e,        7);

        addChar(84,  0x6f,        7);

        addChar(85,  0x70,        7);

        addChar(86,  0x71,        7);

        addChar(87,  0x72,        7);

        addChar(88,  0xfc,        8);

        addChar(89,  0x73,        7);

        addChar(90,  0xfd,        8);

        addChar(91,  0x1ffb,     13);

        addChar(92,  0x7fff0,    19);

        addChar(93,  0x1ffc,     13);

        addChar(94,  0x3ffc,     14);

        addChar(95,  0x22,        6);

        addChar(96,  0x7ffd,     15);

        addChar(97,  0x3,         5);

        addChar(98,  0x23,        6);

        addChar(99,  0x4,         5);

        addChar(100, 0x24,        6);

        addChar(101, 0x5,         5);

        addChar(102, 0x25,        6);

        addChar(103, 0x26,        6);

        addChar(104, 0x27,        6);

        addChar(105, 0x6,         5);

        addChar(106, 0x74,        7);

        addChar(107, 0x75,        7);

        addChar(108, 0x28,        6);

        addChar(109, 0x29,        6);

        addChar(110, 0x2a,        6);

        addChar(111, 0x7,         5);

        addChar(112, 0x2b,        6);

        addChar(113, 0x76,        7);

        addChar(114, 0x2c,        6);

        addChar(115, 0x8,         5);

        addChar(116, 0x9,         5);

        addChar(117, 0x2d,        6);

        addChar(118, 0x77,        7);

        addChar(119, 0x78,        7);

        addChar(120, 0x79,        7);

        addChar(121, 0x7a,        7);

        addChar(122, 0x7b,        7);

        addChar(123, 0x7ffe,     15);

        addChar(124, 0x7fc,      11);

        addChar(125, 0x3ffd,     14);

        addChar(126, 0x1ffd,     13);

        addChar(127, 0xffffffc,  28);

        addChar(128, 0xfffe6,    20);

        addChar(129, 0x3fffd2,   22);

        addChar(130, 0xfffe7,    20);

        addChar(131, 0xfffe8,    20);

        addChar(132, 0x3fffd3,   22);

        addChar(133, 0x3fffd4,   22);

        addChar(134, 0x3fffd5,   22);

        addChar(135, 0x7fffd9,   23);

        addChar(136, 0x3fffd6,   22);

        addChar(137, 0x7fffda,   23);

        addChar(138, 0x7fffdb,   23);

        addChar(139, 0x7fffdc,   23);

        addChar(140, 0x7fffdd,   23);

        addChar(141, 0x7fffde,   23);

        addChar(142, 0xffffeb,   24);

        addChar(143, 0x7fffdf,   23);

        addChar(144, 0xffffec,   24);

        addChar(145, 0xffffed,   24);

        addChar(146, 0x3fffd7,   22);

        addChar(147, 0x7fffe0,   23);

        addChar(148, 0xffffee,   24);

        addChar(149, 0x7fffe1,   23);

        addChar(150, 0x7fffe2,   23);

        addChar(151, 0x7fffe3,   23);

        addChar(152, 0x7fffe4,   23);

        addChar(153, 0x1fffdc,   21);

        addChar(154, 0x3fffd8,   22);

        addChar(155, 0x7fffe5,   23);

        addChar(156, 0x3fffd9,   22);

        addChar(157, 0x7fffe6,   23);

        addChar(158, 0x7fffe7,   23);

        addChar(159, 0xffffef,   24);

        addChar(160, 0x3fffda,   22);

        addChar(161, 0x1fffdd,   21);

        addChar(162, 0xfffe9,    20);

        addChar(163, 0x3fffdb,   22);

        addChar(164, 0x3fffdc,   22);

        addChar(165, 0x7fffe8,   23);

        addChar(166, 0x7fffe9,   23);

        addChar(167, 0x1fffde,   21);

        addChar(168, 0x7fffea,   23);

        addChar(169, 0x3fffdd,   22);

        addChar(170, 0x3fffde,   22);

        addChar(171, 0xfffff0,   24);

        addChar(172, 0x1fffdf,   21);

        addChar(173, 0x3fffdf,   22);

        addChar(174, 0x7fffeb,   23);

        addChar(175, 0x7fffec,   23);

        addChar(176, 0x1fffe0,   21);

        addChar(177, 0x1fffe1,   21);

        addChar(178, 0x3fffe0,   22);

        addChar(179, 0x1fffe2,   21);

        addChar(180, 0x7fffed,   23);

        addChar(181, 0x3fffe1,   22);

        addChar(182, 0x7fffee,   23);

        addChar(183, 0x7fffef,   23);

        addChar(184, 0xfffea,    20);

        addChar(185, 0x3fffe2,   22);

        addChar(186, 0x3fffe3,   22);

        addChar(187, 0x3fffe4,   22);

        addChar(188, 0x7ffff0,   23);

        addChar(189, 0x3fffe5,   22);

        addChar(190, 0x3fffe6,   22);

        addChar(191, 0x7ffff1,   23);

        addChar(192, 0x3ffffe0,  26);

        addChar(193, 0x3ffffe1,  26);

        addChar(194, 0xfffeb,    20);

        addChar(195, 0x7fff1,    19);

        addChar(196, 0x3fffe7,   22);

        addChar(197, 0x7ffff2,   23);

        addChar(198, 0x3fffe8,   22);

        addChar(199, 0x1ffffec,  25);

        addChar(200, 0x3ffffe2,  26);

        addChar(201, 0x3ffffe3,  26);

        addChar(202, 0x3ffffe4,  26);

        addChar(203, 0x7ffffde,  27);

        addChar(204, 0x7ffffdf,  27);

        addChar(205, 0x3ffffe5,  26);

        addChar(206, 0xfffff1,   24);

        addChar(207, 0x1ffffed,  25);

        addChar(208, 0x7fff2,    19);

        addChar(209, 0x1fffe3,   21);

        addChar(210, 0x3ffffe6,  26);

        addChar(211, 0x7ffffe0,  27);

        addChar(212, 0x7ffffe1,  27);

        addChar(213, 0x3ffffe7,  26);

        addChar(214, 0x7ffffe2,  27);

        addChar(215, 0xfffff2,   24);

        addChar(216, 0x1fffe4,   21);

        addChar(217, 0x1fffe5,   21);

        addChar(218, 0x3ffffe8,  26);

        addChar(219, 0x3ffffe9,  26);

        addChar(220, 0xffffffd,  28);

        addChar(221, 0x7ffffe3,  27);

        addChar(222, 0x7ffffe4,  27);

        addChar(223, 0x7ffffe5,  27);

        addChar(224, 0xfffec,    20);

        addChar(225, 0xfffff3,   24);

        addChar(226, 0xfffed,    20);

        addChar(227, 0x1fffe6,   21);

        addChar(228, 0x3fffe9,   22);

        addChar(229, 0x1fffe7,   21);

        addChar(230, 0x1fffe8,   21);

        addChar(231, 0x7ffff3,   23);

        addChar(232, 0x3fffea,   22);

        addChar(233, 0x3fffeb,   22);

        addChar(234, 0x1ffffee,  25);

        addChar(235, 0x1ffffef,  25);

        addChar(236, 0xfffff4,   24);

        addChar(237, 0xfffff5,   24);

        addChar(238, 0x3ffffea,  26);

        addChar(239, 0x7ffff4,   23);

        addChar(240, 0x3ffffeb,  26);

        addChar(241, 0x7ffffe6,  27);

        addChar(242, 0x3ffffec,  26);

        addChar(243, 0x3ffffed,  26);

        addChar(244, 0x7ffffe7,  27);

        addChar(245, 0x7ffffe8,  27);

        addChar(246, 0x7ffffe9,  27);

        addChar(247, 0x7ffffea,  27);

        addChar(248, 0x7ffffeb,  27);

        addChar(249, 0xffffffe,  28);

        addChar(250, 0x7ffffec,  27);

        addChar(251, 0x7ffffed,  27);

        addChar(252, 0x7ffffee,  27);

        addChar(253, 0x7ffffef,  27);

        addChar(254, 0x7fffff0,  27);

        addChar(255, 0x3ffffee,  26);

        addEOS (256, EOS.code,   EOS.length);

        // @formatter:on

    }

    /**

     * Calculates the number of bytes required to represent the given {@code

     * CharSequence} with the Huffman coding.

     *

     * @param value

     *         characters

     *

     * @return number of bytes

     *

     * @throws NullPointerException

     *         if the value is null

     */

    public int lengthOf(CharSequence value) {

        return lengthOf(value, 0, value.length());

    }

    /**

     * Calculates the number of bytes required to represent a subsequence of the

     * given {@code CharSequence} with the Huffman coding.

     *

     * @param value

     *         characters

     * @param start

     *         the start index, inclusive

     * @param end

     *         the end index, exclusive

     *

     * @return number of bytes

     *

     * @throws NullPointerException

     *         if the value is null

     * @throws IndexOutOfBoundsException

     *         if any invocation of {@code value.charAt(i)}, where

     *         {@code start <= i < end} would throw an IndexOutOfBoundsException

     */