#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

typedef struct Header
{
    unsigned char tag[3];
    unsigned char v1;
    unsigned char v2;
    unsigned char flags;
    unsigned char size[4];
} mp3Header;

unsigned char *formatFrameData(int size, unsigned char *data)
{
    unsigned char *result;
    result = (unsigned char*)malloc(sizeof(unsigned char) * ((size-3)/2 + 1));
    int pos = 0;
    //pass 3 bytes and every NUL symbol
    for (int i = 3; i < size; i+=2)
    {
        *(result + pos) = *(data + i);
        pos++;
    }
    *(result + pos) = '\0';
    return result;
}

void printID3v2FrameInfo(unsigned char fid[5], int size, unsigned char *data)
{
        printf("\n[%s]:\t%s\n", fid, formatFrameData(size, data));
}

typedef struct FrameHeader
{
    unsigned char tag[4];
    unsigned char size[4];
    unsigned char flags[2];
} id3v2Frame;

unsigned char frames[77][5] = {
    "AENC",
    "APIC",
    "COMM",
    "COMR",
    "ENCR",
    "EQUA",
    "ETCO",
    "GEOB",
    "GRID",
    "IPLS",
    "LINK",
    "MCDI",
    "MLLT",
    "OWNE",
    "PRIV",
    "PCNT",
    "POPM",
    "POSS",
    "RBUF",
    "RVAD",
    "RVRB",
    "SYLT",
    "SYTC",
    "TALB",
    "TBPM",
    "TCMP",
    "TCOM",
    "TCON",
    "TCOP",
    "TDAT",
    "TDLY",
    "TENC",
    "TEXT",
    "TFLT",
    "TIME",
    "TIT1",
    "TIT2",
    "TIT3",
    "TKEY",
    "TLAN",
    "TLEN",
    "TMED",
    "TOAL",
    "TOFN",
    "TOLY",
    "TOPE",
    "TORY",
    "TOWN",
    "TPE1",
    "TPE2",
    "TPE3",
    "TPE4",
    "TPOS",
    "TPUB",
    "TRCK",
    "TRDA",
    "TRSN",
    "TRSO",
    "TSIZ",
    "TSO2",
    "TSOC",
    "TSRC",
    "TSSE",
    "TYER",
    "TXXX",
    "UFID",
    "USER",
    "USLT",
    "WCOM",
    "WCOP",
    "WOAF",
    "WOAR",
    "WOAS",
    "WORS",
    "WPAY",
    "WPUB",
    "WXXX"
};


int getHeaderSize(unsigned char size[4])
{
    int c = 0;
    int res = 0;

    for (int i = 3; i >= 0; i--)
    {
        for (int j = 0; j < 7; j++)
        {
            res += (size[i] % 2) * pow(2, c);
            c++;
            size[i] /= 2;
        }
    }

    return res;
}

int getFrameSize(unsigned char size[4])
{
    int res = 0;
    int c = 0;

    for (int i = 3; i >= 0; i--)
    {
        while (size[i])
        {
            res += (size[i] % 2) * pow(2, c);
            c++;
            size[i] /= 2;
        }
    }
    return res;
}

int checkFrame(char *frame)
{

    int found = 0;

    for (int i = 0; i < 77; i++)
    {
        if (strcmp(frame, frames[i]) == 0)
        {
            found = 1;
            break;
        }
    }

    return found;
}

void getFrames(FILE *f, unsigned char *frame)
{
    id3v2Frame newFrame;
    unsigned char *frameData;
    int success = 0;
    fread(&newFrame, 1, 10, f);
    int frameSize = getFrameSize(newFrame.size);
    while (checkFrame(newFrame.tag))
    {
        frameData = (unsigned char*)malloc(sizeof(unsigned char) * frameSize);
        fread(frameData, frameSize, 1, f);
        if (*frame == '\0' || strcmp(frame, newFrame.tag) == 0)
        {
            printID3v2FrameInfo(newFrame.tag, frameSize, frameData);
            success = 1;
        }
        fread(&newFrame, 1, 10, f);
        frameSize = getFrameSize(newFrame.size);
    }
    if (success == 0)
        printf("[ERROR] There's no such frame (%s).", frame);
}

unsigned char *formHeaderSize(int size)
{
    unsigned char *cur;
    cur = (unsigned char*)malloc(sizeof(unsigned char) * 4);
    for (int i = 0; i < 4; i++)
        cur[i] = 0;
    unsigned char sz[32];
    int c = 0;
    for (int i = 0; i < 32; i++)
        sz[i] = '0';
    while (size)
    {
        sz[31 - c] = '0' + size % 2;
        c++;
        size /= 2;
    }
    for (int k = 3; k >= 0; k--)
    {
        c = 0;
        for (int i = (k == 3 ? (k + 1) * 8 - 1 : (k + 1) * 8); i > k * 8; i--)
        {
            cur[k] += (sz[i] - '0') * pow(2, c);
            c++;
        }
    }
    return cur;
}

unsigned char *updFrameData(unsigned char *in, int size)
{
    unsigned char *out;
    out = (unsigned char*)malloc(sizeof(unsigned char) * (size * 2 + 3));
    *(out + 0) = 1;
    *(out + 1) = 255;
    *(out + 2) = 254;
    int pos = 3;
    for (int i = 0; i < size; i++)
    {
        *(out + pos) = *(in + i);
        pos++;
        *(out + pos) = 0;
        pos++;
    }

    return out;
}

unsigned char *formFrameSize(int size)
{
    unsigned char *out;
    out = (unsigned char*)malloc(sizeof(unsigned char)*4);

    for (int i = 0; i < 4; i++)
        *(out + i) = 0;
    int c = 0;
    int k = 3;
    while(size)
    {
        *(out + k) += (size % 2) * pow(2, c);
        c++;
        size /= 2;
        if (c == 8)
        {
            c = 0;
            k--;
        }
    }
    return out;
}

void rewriteID3v2(FILE *f, unsigned char *frame, unsigned char *value, unsigned char *filename, long headersize, long filesize)
{
    unsigned char **framesIDs;
    int *framesSizes;
    unsigned char **framesData;

    int sizeofNewHeader = 0;

    id3v2Frame newFrame;
    int c = 0;
    int ex = 0;
    fread(&newFrame, 1, 10, f);
    int frameSize = getFrameSize(newFrame.size);

    framesData = (unsigned char**)malloc(sizeof(unsigned char*) * 77);
    framesIDs = (unsigned char**)malloc(sizeof(unsigned char*) * 77);
    framesSizes = (int*)malloc(sizeof(int) * 77);

    while (checkFrame(newFrame.tag))
    {
        sizeofNewHeader += 10;
        if (strcmp(frame, newFrame.tag) == 0)
        {
            *(framesIDs + c) = (unsigned char*)malloc(sizeof(unsigned char) * 5);
            strcpy(*(framesIDs + c), newFrame.tag);
            *(framesSizes + c) = strlen(value) * 2 + 3;
            sizeofNewHeader += strlen(value) * 2 + 3;
            *(framesData + c) = (unsigned char*)malloc(sizeof(unsigned char) * (strlen(value)*2 + 3));
            unsigned char *formattedValue = updFrameData(value, strlen(value) * 2 + 3);
            for(int i = 0; i < strlen(value) * 2 + 3; i++)
                *(*(framesData + c) + i) = *(formattedValue + i);
            fseek(f, frameSize, SEEK_CUR);
            ex = 1;
        }
        else
        {
            *(framesIDs + c) = (unsigned char*)malloc(sizeof(unsigned char) * 5);
            strcpy(*(framesIDs + c), newFrame.tag);
            *(framesSizes + c) = frameSize;
            sizeofNewHeader += frameSize;
            *(framesData + c) = (unsigned char*)malloc(sizeof(unsigned char) * frameSize);
            fread(*(framesData + c), frameSize, 1, f);
        }

        fread(&newFrame, 1, 10, f);
        //printf("%s\n", newFrame.tag);
        frameSize = getFrameSize(newFrame.size);
        c++;
    }
    if (ex == 0)
    {
        *(framesIDs + c) = (unsigned char*)malloc(sizeof(unsigned char) * 5);
        strcpy(*(framesIDs + c), frame);
        *(framesSizes + c) = strlen(value) * 2 + 3;
        sizeofNewHeader += strlen(value) * 2 + 3 + 10;
        *(framesData + c) = (unsigned char*)malloc(sizeof(unsigned char) * (strlen(value)*2 + 3));
        unsigned char *formattedValue = updFrameData(value, strlen(value) * 2 + 3);
        for(int i = 0; i < strlen(value) * 2 + 3; i++)
            *(*(framesData + c) + i) = *(formattedValue + i);
    }

    unsigned char *new_file;

    new_file = (unsigned char*)malloc(sizeof(unsigned char) * (strlen(filename) + 5));
    char *fn = strtok(filename, ".");
    sprintf (new_file, "%s_new.mp3", fn);

    FILE *o = fopen(new_file, "wb");

    fwrite("ID3", 1, 3, o);
    unsigned char t[1] = {3};
    fwrite(t, 1, 1, o);
    t[0] = 0;
    fwrite(t, 1, 1, o);
    fwrite(t, 1, 1, o);
    fwrite(formHeaderSize(sizeofNewHeader), 1, 4, o);

    for (int i = 0; i <= (ex == 0 ? c : c - 1) ; i++)
    {
        fwrite(*(framesIDs + i), 1, 4, o);
        fwrite(formFrameSize(*(framesSizes + i)), 1, 4, o);
        fwrite(t, 1, 1, o);
        fwrite(t, 1, 1, o);
        fwrite(*(framesData + i), 1, *(framesSizes + i), o);
    }

    char *mp3;
    mp3 = (unsigned char*)malloc(sizeof(unsigned char) * filesize);

    fseek(f, headersize, SEEK_SET);

    fread(mp3, 1, filesize, f);

    fwrite(mp3, 1, filesize, o);

    fclose(o);
}

int main(int argc, unsigned char **argv)
{
    unsigned char *val;
    unsigned char *filename;
    unsigned char *getFrame;
    unsigned char *setFrame;
    unsigned char *setFrameVal;
    int show = 0;
    int get = 0;
    int set = 0;
    for (int i = 1; i < argc; i++)
    {
        val = strtok(*(argv + i), "=");
        if (strcmp(val, "--filepath") == 0)
        {
            val = strtok(NULL, "=");
            filename = val;
        }
        else if (strcmp(val, "--get") == 0)
        {
            val = strtok(NULL, "=");
            getFrame = val;
            get = 1;
        }
        else if (strcmp(val, "--set") == 0)
        {
            val = strtok(NULL, "=");
            setFrame = val;
            set = 1;
        }
        else if (strcmp(val, "--value") == 0)
        {
            val = strtok(NULL, "=");
            setFrameVal = val;
        }
        else if (strcmp(val, "--show") == 0)
        {
            show = 1;
        }
    }

    FILE *f = fopen(filename, "rw");

    mp3Header header;

    fread(&header, 1, 10, f);

    if (show == 1)
    {
        getFrames(f, "");
        fclose(f);
        return 0;
    }

    if (get == 1)
    {
        getFrames(f, getFrame);
        fclose(f);
        return 0;
    }

    if (set == 1)
    {
        fseek(f, 0, SEEK_END);
        long f_size = ftell(f);
        fseek(f, 0, SEEK_SET);
        fread(&header, 1, 10, f);
        int hz = getHeaderSize(header.size);
        rewriteID3v2(f, setFrame, setFrameVal, filename, hz + 10, f_size - hz - 10);
        fclose(f);
        return 0;
    }

    return (0);
}