#include <stdio.h>
#include <stdlib.h>
#include "locale.h"
#include "malloc.h"
#include <string.h>
#include <math.h>

/*
file structure:
    ID3v2/file identifier   "ID3"
    ID3v2 version           $03 00
    ID3v2 flags             %abc00000
    ID3v2 size              4 * %0xxxxxxx

    Frame ID       $xx xx xx xx (four characters)
    Size           $xx xx xx xx
    Flags          $xx xx

    <Frame contents>

    etc...
 */

int buffToIntegerForFrame(unsigned char *bytes) //char to integer size
{
    return
            bytes[0] * pow(2, 24) +   //2^21
            bytes[1] * pow(2, 16) +     //2^14
            bytes[2] * pow(2, 8) +       //2^7
            bytes[3];
}

int buffToInteger(unsigned char *bytes) {
    return
            bytes[0] * 0x200000 +   //2^21
            bytes[1] * 0x4000 +     //2^14
            bytes[2] * 0x80 +       //2^7
            bytes[3];
}

void integerToBuff(int number, unsigned char *result) {
    result[0] = (unsigned char) ((number & 0xfe00000) >> 21); //0100000
    result[1] = (unsigned char) ((number & 0x1fc000) >> 14);  //0010010
    result[2] = (unsigned char) ((number & 0x3f80) >> 7); //0000001
    result[3] = (unsigned char) (number & 0x7f); //0000100
}

void integerToBuffForFrame(int number, unsigned char *result) {
    result[0] = (unsigned char) ((number & 0xff000000) >> 24); //0100000
    result[1] = (unsigned char) ((number & 0xff0000) >> 16);  //0010010
    result[2] = (unsigned char) ((number & 0xff00) >> 8); //0000001
    result[3] = (unsigned char) (number & 0xff); //0000100
}

struct tagHeader {
    unsigned char name[3]; //ID3
    unsigned char version[2]; //2 bytes ex. 3 0
    unsigned char flags; //1 byte
    unsigned int framesCount;
    unsigned int size; //4 bytes for tagHeader`s size
};
struct oframe {
    unsigned char name[4];//4 bytes FRAME NAME ex. TIT2, TALB and etc.
    unsigned char flags[2]; //2 bytes
    unsigned int size; //4 FRAME`S size
    unsigned char enc; //1 encoding
    unsigned char *content; //container
};

void readBytes(unsigned char *res, unsigned int size, FILE *file) {
    for (int i = 0; i < size; i++) {
        res[i] = getc(file);
    }
}

void writeBytes(unsigned char *res, unsigned int size, FILE *file) {
    for (int i = 0; i < size; i++) {
        putc(res[i], file);
    }
}

struct tagHeader readTagHeader(FILE *file) //function
{
    struct tagHeader tag;
    unsigned char flags[1]; // flags
    unsigned char sizeb[4]; // tag size in bytes
    readBytes(tag.name, 3, file);
    readBytes(tag.version, 2, file);
    readBytes(flags, 1, file);
    readBytes(sizeb, 4, file);
    tag.flags = flags[0];
    tag.size = buffToInteger(sizeb);
    return tag;
}

void writeTagHeader(FILE *file, struct tagHeader tag) //function
{
    unsigned char flags[1]; // flags
    unsigned char sizeb[4]; // tag size in bytes
    writeBytes(tag.name, 3, file);
    writeBytes(tag.version, 2, file);
    flags[0] = tag.flags;
    writeBytes(flags, 1, file);
    integerToBuff(tag.size, sizeb);
    writeBytes(sizeb, 4, file);
}

void writeFrame(FILE *file, struct oframe frame) //function
{
    unsigned char sizeb[4]; // tag size in bytes
    unsigned char enc[1]; // tag size in bytes
    writeBytes(frame.name, 4, file);
    integerToBuffForFrame(frame.size, sizeb);
    writeBytes(sizeb, 4, file);
    writeBytes(frame.flags, 2, file);
    enc[0] = frame.enc;
    writeBytes(enc, 1, file);
    writeBytes(frame.content, frame.size - 1, file);
}

int checkName(char *name) {
    for (int i = 0; i < strlen(name); i++) {
        if ((name[i] < 60 | name[i] > 90) & (name[i] > 57 | name[i] < 48)) {
            return 0;
        }
    }
    return 1;
}

struct oframe readoframe(FILE *file, int readedBytes) {
    struct oframe frame;
    unsigned char sizeb[4]; // tag size in bytes
    readBytes(frame.name, 4, file);
    readBytes(sizeb, 4, file);
    frame.size = buffToIntegerForFrame(sizeb);
    if (frame.size + 10 > readedBytes | frame.size == 0 | frame.size > 134 * pow(10, 5) | checkName(frame.name) == 0) {
        fseek(file, frame.size + 2, SEEK_CUR);
        frame.size = 0;
        return frame;
    }
    frame.content = malloc(frame.size);
    readBytes(frame.flags, 2, file);
    unsigned char enc[1];
    readBytes(enc, 1, file);
    frame.enc = enc[0];
    readBytes(frame.content, frame.size - 1, file);
    return frame;
}

void set(char *filepath, char *framename, char *value) {
    FILE *fp = fopen(filepath, "rb");
    struct tagHeader tag = readTagHeader(fp);
    int old_size = tag.size;
    tag.framesCount = 0;
    //END OF TAG HEADER
    int diff = 0;
    int bytesReaded = 10;
    struct oframe frames[tag.size / 11 + 1];
    int i = 0;
    while (tag.size > bytesReaded) {
        frames[tag.framesCount] = readoframe(fp, tag.size - bytesReaded);
        if (frames[tag.framesCount].size == 0) {
            break;
        }
        bytesReaded += 10 + frames[tag.framesCount].size;
        tag.framesCount += 1;
    }
    //END OF READING METADATA FROM FILE
    //BEGIN OF WRITING NEW FILE
    remove("temp.mp3");
    FILE *outf = fopen("temp.mp3", "wb");
    writeTagHeader(outf, tag);
    for (int i = 0; i < tag.framesCount; i++) {
        if (strcmp(frames[i].name, framename) == 0) {
            diff = strlen(value) - strlen(frames[i].content);
            tag.size += diff;
            strcpy(frames[i].content, value);
            frames[i].size = strlen(value) + 1;
        }
        writeFrame(outf, frames[i]);
        /*printf("%s %d ", frames[i].name, frames[i].size);
        for (int j = 0; j < frames[i].size; j++) {
            printf("%c", frames[i].content[j]);
        }
        printf("\n");*/
    }
    int pos;
    pos = ftell(outf);
    int countzeros = 10 + tag.size - ((int) pos);
    unsigned char zeros[countzeros];
    for (int i = 0; i < countzeros; i++) {
        zeros[i] = 0;
    }
    writeBytes(zeros, countzeros, outf);
    char tmp;
    fseek(fp, old_size + 10, SEEK_SET);
    fseek(outf, tag.size + 10, SEEK_SET);
    tmp = fgetc(fp);
    while (!feof(fp)){
        fputc(tmp, outf);
        tmp = fgetc(fp);
    }
    fclose(outf);
    fclose(fp);
}

void get(char *filepath, char *framename) {
    FILE *fp = fopen(filepath, "rb");
    struct tagHeader tag = readTagHeader(fp);
    //END OF TAG HEADER

    int bytesReaded = 10;
    struct oframe frames[tag.size / 11 + 1];
    int i = 0;

    while (tag.size > bytesReaded) {
        struct oframe buff = readoframe(fp, tag.size - bytesReaded);
        if (buff.size == 0)
            break;

        frames[i] = buff;
        if (strcmp(frames[i].name, framename) == 0) {
            printf("%s data: ", framename);
            for (int j = 0; j < frames[i].size - 1; j++) {
                printf("%c", frames[i].content[j]);
            }

            i++;
            for (int j = 0; j < buff.size; ++j) //clearing buff container
                buff.content[j] = 0;
            printf("\n");
            break;
        }
    }
}

void show(char *filepath) {
    FILE *fp = fopen(filepath, "rb");
    struct tagHeader tag = readTagHeader(fp);
    printf("%s%s%d%d%s%d\n", tag.name, " : ", tag.version[0], tag.version[1], " : ", tag.size);
    //END OF TAG HEADER

    int bytesReaded = 10;
    struct oframe frames[tag.size / 11 + 1];
    int i = 0;

    while (tag.size > bytesReaded) {
        struct oframe buff = readoframe(fp, tag.size - bytesReaded);
        if (buff.size == 0)
            break;

        frames[i] = buff;
        printf("%s %d ", frames[i].name, frames[i].size);
        bytesReaded += 10 + frames[i].size;
        for (int j = 0; j < frames[i].size - 1; j++)
            printf("%c", frames[i].content[j]);

        i++;
        for (int j = 0; j < buff.size; ++j) //clearing buff container
            buff.content[j] = 0;
        printf("\n");


    }
    //END OF FRAME

}

int main(int argc, char *argv[]) {
    setlocale(LC_ALL, "Rus");
    char* filepath;
     filepath = strpbrk(argv[1],"=") + 1;
     for (int i = 2; i < argc; i++){
         if (strcmp(argv[i], "--show") == 0) {
             show(filepath);
             continue;
         }
         if (strcmp(argv[i], "--get") == 0) {
             get(filepath, argv[i+1]);
             continue;
         }
         if (strcmp(argv[i], "--set") == 0) {
             set(filepath, argv[i+1], argv[i+2]);
             continue;
         }
     }
    return 0;
}