#include "png_fix.h"

namespace png_fix
{
    bool str_match_ascii(char *in, const char *signature, int size)
    {
        bool match = true;
        for (int i = 0; i < size; i++)
            if (in[i] != signature[i])
                match = false;
        return match;
    }

    bool str_match_bin(uint8_t *in, std::vector<uint8_t> signature)
    {
        bool match = true;
        for (unsigned int i = 0; i < signature.size(); i++)
            if (in[i] != signature[i])
                match = false;
        return match;
    }

    uint32_t pack32_bits(uint8_t *t)
    {
        return t[0] << 24 | t[1] << 16 | t[2] << 8 | t[3];
    }

    static uint32_t crc_table[256] =
        {
            0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
            0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
            0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
            0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
            0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
            0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
            0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
            0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
            0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
            0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
            0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
            0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
            0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
            0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
            0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
            0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
            0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
            0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
            0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
            0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
            0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
            0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
            0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
            0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
            0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
            0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
            0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
            0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
            0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
            0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
            0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
            0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
            0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
            0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
            0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
            0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
            0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
            0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
            0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
            0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
            0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
            0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
            0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
            0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
            0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
            0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
            0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
            0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
            0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
            0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
            0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
            0x2d02ef8d};

    uint32_t compute_crc(uint8_t *buf, int len)
    {
        uint32_t c = 0xFFFFFFFF; // Initial value
        for (int i = 0; i < len; ++i)
            c = crc_table[(c & 0xFF) ^ buf[i]] ^ (c >> 8);
        return c ^ 0xFFFFFFFF;
    }

    bool check_chunk(uint8_t *chunk, int length)
    {
        if (length > 2147483647)
        {
            //  printf("Invalid length!\n");
            return false;
        }

        if (pack32_bits(&chunk[8 + length]) !=
                compute_crc(&chunk[4], 4 + length) &&
            length > 0)
        {
            //   printf("Invalid CRC!\n");
            return false;
        }

        return true;
    }

    bool repair_png(std::vector<uint8_t> in, std::vector<uint8_t> &out)
    {
        if (!str_match_bin(&in[0], {0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A}))
        {
            //   printf("Not a PNG!\n");
            return true; // Not a PNG
        }

        bool has_ihdr = false;
        bool has_iend = false;

        out.insert(out.end(), &in[0], &in[8]);

        bool bad_idat = false;
        bool has_idat = false;

        // Find block using headers
        for (unsigned int i = 8; i < in.size(); i++)
        {
            uint32_t length = pack32_bits(&in[i + 0]);
            char *chunk_type = (char *)&in[i + 4];

            if (length + 4 > in.size() - i)
                continue;

            if (str_match_ascii(chunk_type, "IHDR", 4))
            {
                if (check_chunk(&in[i], length))
                {
                    //  printf("Found IHDR!\n");
                    has_ihdr = true;
                    out.insert(out.end(), &in[i], &in[i + 4 + 4 + length + 4]);
                }
            }

            if (str_match_ascii(chunk_type, "tEXt", 4))
            {
                if (check_chunk(&in[i], length))
                {
                    // printf("Found tEXt!\n");
                    out.insert(out.end(), &in[i], &in[i + 4 + 4 + length + 4]);
                }
            }

            if (str_match_ascii(chunk_type, "IDAT", 4))
            {
                if (check_chunk(&in[i], length) && !bad_idat)
                {
                    // printf("Found IDAT!\n");
                    has_idat = true;
                    out.insert(out.end(), &in[i], &in[i + 4 + 4 + length + 4]);
                }
                else
                {
                    bad_idat = true;
                }
            }

            if (str_match_ascii(chunk_type, "IEND", 4))
            {
                if (check_chunk(&in[i], length))
                {
                    //  printf("Found IEND!\n");
                    has_iend = true;
                    out.insert(out.end(), &in[i], &in[i + 4 + 4 + length + 4]);
                }
            }
        }

        return !(has_ihdr && has_idat && has_iend);
    }
}