/*

 * Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "libavutil/mem.h"

#include "mlz.h"

av_cold int ff_mlz_init_dict(void *context, MLZ *mlz)

{

    mlz->dict = av_mallocz(TABLE_SIZE * sizeof(*mlz->dict));

    if (!mlz->dict)

        return AVERROR(ENOMEM);

    mlz->flush_code            = FLUSH_CODE;

    mlz->current_dic_index_max = DIC_INDEX_INIT;

    mlz->dic_code_bit          = CODE_BIT_INIT;

    mlz->bump_code             = (DIC_INDEX_INIT - 1);

    mlz->next_code             = FIRST_CODE;

    mlz->freeze_flag           = 0;

    mlz->context               = context;

    return 0;

}

av_cold void ff_mlz_flush_dict(MLZ *mlz) {

    MLZDict *dict = mlz->dict;

    int i;

    for ( i = 0; i < TABLE_SIZE; i++ ) {

        dict[i].string_code = CODE_UNSET;

        dict[i].parent_code = CODE_UNSET;

        dict[i].match_len = 0;

    }

    mlz->current_dic_index_max = DIC_INDEX_INIT;

    mlz->dic_code_bit          = CODE_BIT_INIT;  // DicCodeBitInit;

    mlz->bump_code             = mlz->current_dic_index_max - 1;

    mlz->next_code             = FIRST_CODE;

    mlz->freeze_flag           = 0;

}

static void set_new_entry_dict(MLZDict* dict, int string_code, int parent_code, int char_code) {

    dict[string_code].parent_code = parent_code;

    dict[string_code].string_code = string_code;

    dict[string_code].char_code   = char_code;

    if (parent_code < FIRST_CODE) {

        dict[string_code].match_len = 2;

    } else {

        dict[string_code].match_len = (dict[parent_code].match_len) + 1;

    }

}

static int decode_string(MLZ* mlz, unsigned char *buff, int string_code, int *first_char_code, unsigned long bufsize) {

    MLZDict* dict = mlz->dict;

    unsigned long count, offset;

    int current_code, parent_code, tmp_code;

    count            = 0;

    current_code     = string_code;

    *first_char_code = CODE_UNSET;

    while (count < bufsize) {

        switch (current_code) {

        case CODE_UNSET:

            return count;

            break;

        default:

            if (current_code < FIRST_CODE) {

                *first_char_code = current_code;

                buff[0] = current_code;

                count++;

                return count;

            } else {

                offset  = dict[current_code].match_len - 1;

                tmp_code = dict[current_code].char_code;

                if (offset >= bufsize) {

                    av_log(mlz->context, AV_LOG_ERROR, "MLZ offset error.\n");

                    return count;

                }

                buff[offset] = tmp_code;

                count++;

            }

            current_code = dict[current_code].parent_code;

            if ((current_code < 0) || (current_code > (DIC_INDEX_MAX - 1))) {

                av_log(mlz->context, AV_LOG_ERROR, "MLZ dic index error.\n");

                return count;

            }

            if (current_code > FIRST_CODE) {

                parent_code = dict[current_code].parent_code;

                offset = (dict[current_code].match_len) - 1;

                if (parent_code < 0 || parent_code > DIC_INDEX_MAX-1) {

                    av_log(mlz->context, AV_LOG_ERROR, "MLZ dic index error.\n");

                    return count;

                }

                if (( offset > (DIC_INDEX_MAX - 1))) {

                    av_log(mlz->context, AV_LOG_ERROR, "MLZ dic offset error.\n");

                    return count;

                }

            }

            break;

        }

    }

    return count;

}

static int input_code(GetBitContext* gb, int len) {

    int tmp_code = 0;

    int i;

    for (i = 0; i < len; ++i) {

        tmp_code |= get_bits1(gb) << i;

    }

    return tmp_code;

}

int ff_mlz_decompression(MLZ* mlz, GetBitContext* gb, int size, unsigned char *buff) {

    MLZDict *dict = mlz->dict;

    unsigned long output_chars;

    int string_code, last_string_code, char_code;

    string_code = 0;

    char_code   = -1;

    last_string_code = -1;

    output_chars = 0;

    while (output_chars < size) {

        string_code = input_code(gb, mlz->dic_code_bit);

        switch (string_code) {

            case FLUSH_CODE:

            case MAX_CODE:

                ff_mlz_flush_dict(mlz);

                char_code = -1;

                last_string_code = -1;

                break;

            case FREEZE_CODE:

                mlz->freeze_flag = 1;

                break;

            default:

                if (string_code > mlz->current_dic_index_max) {

                    av_log(mlz->context, AV_LOG_ERROR, "String code %d exceeds maximum value of %d.\n", string_code, mlz->current_dic_index_max);

                    return output_chars;

                }

                if (string_code == (int) mlz->bump_code) {

                    ++mlz->dic_code_bit;

                    mlz->current_dic_index_max *= 2;

                    mlz->bump_code = mlz->current_dic_index_max - 1;

                } else {

                    if (string_code >= mlz->next_code) {

                        int ret = decode_string(mlz, &buff[output_chars], last_string_code, &char_code, size - output_chars);

                        if (ret < 0 || ret > size - output_chars) {

                            av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n");

                            return output_chars;

                        }

                        output_chars += ret;

                        ret = decode_string(mlz, &buff[output_chars], char_code, &char_code, size - output_chars);

                        if (ret < 0 || ret > size - output_chars) {

                            av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n");

                            return output_chars;

                        }

                        output_chars += ret;

                        set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);

                        if (mlz->next_code >= TABLE_SIZE - 1) {

                            av_log(mlz->context, AV_LOG_ERROR, "Too many MLZ codes\n");

                            return output_chars;

                        }

                        mlz->next_code++;

                    } else {

                        int ret = decode_string(mlz, &buff[output_chars], string_code, &char_code, size - output_chars);

                        if (ret < 0 || ret > size - output_chars) {

                            av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n");

                            return output_chars;

                        }

                        output_chars += ret;

                        if (output_chars <= size && !mlz->freeze_flag) {

                            if (last_string_code != -1) {

                                set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);

                                if (mlz->next_code >= TABLE_SIZE - 1) {

                                    av_log(mlz->context, AV_LOG_ERROR, "Too many MLZ codes\n");

                                    return output_chars;

                                }

                                mlz->next_code++;

                            }

                        } else {

                            break;

                        }

                    }

                    last_string_code = string_code;

                }

                break;

        }

    }

    return output_chars;

}