#include "gif.h"
#include <cstdio>  // Para fprintf, stderr
#include <cstdlib> // Para exit, malloc, calloc, free, realloc
#include <vector>  // Para vector

void Gif::uncompress(int code_length, const uint8_t *input, int input_length, uint8_t *out)
{
    int i, bit;
    int code, prev = -1;
    std::vector<DictionaryEntry> dictionary;
    int dictionary_ind;
    unsigned int mask = 0x01;
    int reset_code_length;
    int clear_code;
    int stop_code;
    int match_len;

    clear_code = 1 << (code_length);
    stop_code = clear_code + 1;
    reset_code_length = code_length;

    dictionary.resize(1 << (code_length + 1));

    for (dictionary_ind = 0; dictionary_ind < (1 << code_length); dictionary_ind++)
    {
        dictionary[dictionary_ind].byte = dictionary_ind;
        dictionary[dictionary_ind].prev = -1;
        dictionary[dictionary_ind].len = 1;
    }

    dictionary_ind += 2;

    while (input_length)
    {
        code = 0x0;
        for (i = 0; i < (code_length + 1); i++)
        {
            bit = (*input & mask) ? 1 : 0;
            mask <<= 1;

            if (mask == 0x100)
            {
                mask = 0x01;
                input++;
                input_length--;
            }

            code = code | (bit << i);
        }

        if (code == clear_code)
        {
            code_length = reset_code_length;
            dictionary.resize(1 << (code_length + 1));

            for (dictionary_ind = 0; dictionary_ind < (1 << code_length); dictionary_ind++)
            {
                dictionary[dictionary_ind].byte = dictionary_ind;
                dictionary[dictionary_ind].prev = -1;
                dictionary[dictionary_ind].len = 1;
            }
            dictionary_ind += 2;
            prev = -1;
            continue;
        }
        else if (code == stop_code)
        {
            break;
        }

        if ((prev > -1) && (code_length < 12))
        {
            if (code > dictionary_ind)
            {
                fprintf(stderr, "code = %.02x, but dictionary_ind = %.02x\n", code, dictionary_ind);
                exit(0);
            }

            if (code == dictionary_ind)
            {
                int ptr = prev;
                while (dictionary[ptr].prev != -1)
                {
                    ptr = dictionary[ptr].prev;
                }
                dictionary[dictionary_ind].byte = dictionary[ptr].byte;
            }
            else
            {
                int ptr = code;
                while (dictionary[ptr].prev != -1)
                {
                    ptr = dictionary[ptr].prev;
                }
                dictionary[dictionary_ind].byte = dictionary[ptr].byte;
            }

            dictionary[dictionary_ind].prev = prev;
            dictionary[dictionary_ind].len = dictionary[prev].len + 1;
            dictionary_ind++;

            if ((dictionary_ind == (1 << (code_length + 1))) && (code_length < 11))
            {
                code_length++;
                dictionary.resize(1 << (code_length + 1));
            }
        }

        prev = code;

        match_len = dictionary[code].len;
        while (code != -1)
        {
            out[dictionary[code].len - 1] = dictionary[code].byte;
            if (dictionary[code].prev == code)
            {
                fprintf(stderr, "Internal error; self-reference.");
                exit(0);
            }
            code = dictionary[code].prev;
        }

        out += match_len;
    }
}

int Gif::read_sub_blocks(uint8_t *buffer, uint8_t **data)
{
    int data_length = 0;
    int index = 0;
    uint8_t block_size;

    *data = nullptr;

    while (true)
    {
        READ(&block_size, 1);

        if (block_size == 0)
        {
            break;
        }

        data_length += block_size;
        *data = (uint8_t *)realloc(*data, data_length);

        READ(*data + index, block_size);
        index += block_size;
    }

    return data_length;
}

uint8_t *Gif::process_image_descriptor(uint8_t *buffer, RGB *gct, int gct_size, int resolution_bits)
{
    ImageDescriptor image_descriptor;
    int compressed_data_length;
    uint8_t *compressed_data = nullptr;
    uint8_t lzw_code_size;
    int uncompressed_data_length = 0;
    uint8_t *uncompressed_data = nullptr;

    READ(&image_descriptor, 9);
    READ(&lzw_code_size, 1);

    compressed_data_length = read_sub_blocks(buffer, &compressed_data);
    uncompressed_data_length = image_descriptor.image_width * image_descriptor.image_height;
    uncompressed_data = (uint8_t *)malloc(uncompressed_data_length);

    uncompress(lzw_code_size, compressed_data, compressed_data_length, uncompressed_data);

    if (compressed_data)
    {
        free(compressed_data);
    }

    return uncompressed_data;
}

uint32_t *Gif::LoadPalette(uint8_t *buffer)
{
    uint8_t header[7];
    ScreenDescriptor screen_descriptor;
    int global_color_table_size = 0;
    uint32_t *global_color_table = nullptr;

    READ(header, 6);
    READ(&screen_descriptor, 7);

    global_color_table = (uint32_t *)calloc(1, 1024);

    if (screen_descriptor.fields & 0x80)
    {
        global_color_table_size = 1 << (((screen_descriptor.fields & 0x07) + 1));

        for (int i = 0; i < global_color_table_size; ++i)
        {
            global_color_table[i] = (buffer[0] << 16) + (buffer[1] << 8) + buffer[2];
            buffer += 3;
        }
    }
    return global_color_table;
}

uint8_t *Gif::process_gif_stream(uint8_t *buffer, uint16_t *w, uint16_t *h)
{
    uint8_t header[7];
    ScreenDescriptor screen_descriptor;
    int color_resolution_bits;
    int global_color_table_size = 0;
    RGB *global_color_table = nullptr;
    uint8_t block_type = 0x0;

    READ(header, 6);
    header[6] = 0x0;

    READ(&screen_descriptor, 7);
    *w = screen_descriptor.width;
    *h = screen_descriptor.height;

    color_resolution_bits = ((screen_descriptor.fields & 0x70) >> 4) + 1;

    if (screen_descriptor.fields & 0x80)
    {
        global_color_table_size = 1 << (((screen_descriptor.fields & 0x07) + 1));
        global_color_table = (RGB *)malloc(3 * global_color_table_size);
        READ(global_color_table, 3 * global_color_table_size);
    }

    while (block_type != TRAILER)
    {
        READ(&block_type, 1);

        uint8_t size;
        switch (block_type)
        {
        case IMAGE_DESCRIPTOR:
            return process_image_descriptor(buffer, global_color_table, global_color_table_size, color_resolution_bits);
        case EXTENSION_INTRODUCER:
            buffer++;
            size = *(buffer++);
            buffer += size;
            do
            {
                size = *(buffer++);
                buffer += size;
            } while (size != 0);
            break;
        case TRAILER:
            break;
        default:
            fprintf(stderr, "Bailing on unrecognized block type %.02x\n", block_type);
            return nullptr;
        }
    }
    return nullptr;
}

uint8_t *Gif::LoadGif(uint8_t *buffer, uint16_t *w, uint16_t *h)
{
    return process_gif_stream(buffer, w, h);
}