#include "stdlib.h"
#include "stdio.h"
#include "string.h"

struct frame{
    int size;
    char* value;
    char name[4];
    int pos;
};

int get_size(FILE* file)
{
    int a, ans;
    ans = 0;
    for (int i = 0; i < 4; i++) {
        fread(&a, 1, 1, file);
        ans = ans * 128 + a % 128;
    }
    return ans;
}

int get_frame_size(FILE* file)
{
    int a, ans;
    ans = 0;
    for (int i = 0; i < 4; i++){
        fread(&a, 1, 1, file);
        ans = ans * 256 + a % 128;
    }
    return ans;
}

struct frame T_frame_pos[38];
T_it = 0;
struct frame W_frame_pos[20];
W_it = 0;
struct frame comment;
int check_comment = 0;

void get_frame(FILE* file, int *i, char c){
    struct frame new_frame;
    new_frame.name[0] = c;
    for (int j = 1; j < 4; ++j){
        fread(&new_frame.name[j], 1, 1, file);
    }
    *i = *i + 3;
    new_frame.size = get_frame_size(file);
    *i += 4;
    for (int j = 0; j < 2; ++j){ fread(&c, 1, 1, file);}
    *i += 2;
    if (new_frame.name[0] == 'T'){
        fread(&c, 1, 1, file);
        new_frame.pos = ftell(file);
        new_frame.value = (char*)malloc((new_frame.size - 1) * sizeof(char));
        for (int j = 0; j < new_frame.size - 1; j++){
            fread(&new_frame.value[j], 1, 1, file);
        }
        *i += new_frame.size;
        T_frame_pos[T_it] = new_frame;
        T_it++;
        return;
    }
    else if (new_frame.name[0] == 'W'){
        new_frame.pos = ftell(file);
        new_frame.value = (char*)malloc((new_frame.size - 1) * sizeof(char));
        for (int j = 0; j < new_frame.size; j++)
            fread(&new_frame.value[j], 1, 1, file);
        *i += new_frame.size;
        W_frame_pos[W_it] = new_frame;
        W_it++;
        return;
    }
    else if (new_frame.name[0] == 'C' && new_frame.name[3] == 'M'){
        comment.name[0] = 'C';
        comment.name[1] = 'O';
        comment.name[2] = 'M';
        comment.name[3] = 'M';
        comment.size = new_frame.size;
        fread(&c, 1, 1, file);
        fread(&c, 1, 1, file);
        fread(&c, 1, 1, file);
        fread(&c, 1, 1, file);
        comment.pos = ftell(file);
        comment.value = (char *) malloc(sizeof(char) * (comment.size - 4));
        for (int j = 0; j < comment.size - 4; j++){
            fread(&comment.value[j], 1, 1, file);
        }
        *i += comment.size;
        check_comment = 1;
        return;
    }
    else{
        fread(&c, 1, 1, file);
        fread(&c, 1, 1, file);
        fread(&c, 1, 1, file);
        *i += 3;
        int skip_size = get_frame_size(file);
        fread(&c, 1, 1, file);
        fread(&c, 1, 1, file);
        *i += 2;
        for (int j = 0; j < skip_size; j++)
            fread(&c, 1, 1, file);
        *i += skip_size;
        return;
    }
}

void show()
{
    for (int i = 0; i < T_it; i++)
    {
        for(int j = 0; j < 4; ++j){
            printf("%c", T_frame_pos[i].name[j]);
        }
        printf(" ");
        for(int j = 0; j < T_frame_pos[i].size - 1; ++j){
            printf("%c", T_frame_pos[i].value[j]);
        }
        printf("\n");
    }
    for (int i = 0; i < W_it; i++)
    {
        for(int j = 0; j < 4; ++j){
            printf("%c", W_frame_pos[i].name[j]);
        }
        printf(" ");
        for(int j = 0; j < W_frame_pos[i].size; ++j){
            printf("%c", W_frame_pos[i].value[j]);
        }
        printf("\n");
    }
    if (check_comment == 1){
        for(int j = 0; j < 4; ++j){
            printf("%c", comment.name[j]);
        }
        printf(" ");
        for(int j = 0; j < comment.size - 4; ++j){
            printf("%c", comment.value[j]);
        }
        printf("\n");
    }
}

int frame_comp(char* x, char* y){
    int check = 1;
    for (int j = 0; j < 4; ++j){
        if (x[j] != y[j]){
            check = 0;
        }
    }
    return check;
}

void get_value(char* fr){
    if (fr[0] == 'T'){
        int j = 0;
        while ((j < T_it) && (frame_comp(fr, T_frame_pos[j].name) == 0)){
            ++j;
        }
        if (j != T_it){
            for (int k = 0; k < T_frame_pos[j].size - 1; ++k)
                printf("%c", T_frame_pos[j].value[k]);
            printf("\n");
        }
        else{
            printf("There are no such frames\n");
        }
    }
    else if (fr[0] == 'W'){
        int j = 0;
        while ((j < W_it) && (frame_comp(fr, W_frame_pos[j].name) == 0)){
            ++j;
        }
        if (j != W_it){
            for (int k = 0; k < W_frame_pos[j].size; ++k){
                printf("%c", W_frame_pos[j].value[k]);
            }
            printf("\n");
        }
        else{
            printf("There are no such frames\n");
        }
    }
    else if (fr[0] == 'C' && fr[1] == 'O' && fr[2] == 'M' && fr[3] == 'P'){
        for (int k = 0; k < comment.size - 4; ++k){
            printf("%c", comment.value[k]);
        }
        printf("\n");
    }
    else{
        printf("There are no such frames\n");
    }
}

void information(FILE* file)
{
    T_it = 0;
    W_it = 0;
    fseek(file, 0, SEEK_SET);
    char c;
    for (int i = 0; i < 6; ++i){
        fread(&c, 1, 1, file);
    }
    int size_all_frames = get_size(file);
    int i = 0;
    fread(&c, 1, 1, file);
    while (i < size_all_frames && c != '\0'){
        get_frame(file, &i, c);
        fread(&c, 1, 1, file);
        ++i;
    }
}

void change_frame(FILE* file, char* fr, char* value){
    char c = '\0';
    if (fr[0] == 'T') {
        int j = 0;
        while ((j < T_it) && (frame_comp(fr, T_frame_pos[j].name) == 0)){
            ++j;
        }
        if (j != T_it)
        {
            fseek(file, T_frame_pos[j].pos, 0);
            if (T_frame_pos[j].size - 1 < strlen(value)){
                for (int k = 0; k < T_frame_pos[j].size - 1; ++k){
                    fwrite(&value[k], 1, 1, file);
                }
            }
            else{
                for (int k = 0; k < strlen(value); ++k){
                    printf("%c ", value[k]);
                    fwrite(&value[k], 1, 1, file);
                }
                printf("\n");
                for (int k = strlen(value); k < T_frame_pos[j].size - 1; ++k){
                    fwrite(&c, 1, 1, file);
                }
            }
        }
        else
            printf("There are no such frames\n");
    } else
    if (fr[0] == 'W') {
        int j = 0;
        while ((j < W_it) && (frame_comp(fr, W_frame_pos[j].name) == 0))
            ++j;
        if (j != W_it)
        {
            fseek(file, W_frame_pos[j].pos, 0);
            if (W_frame_pos[j].size < strlen(value))
            {
                for (int k = 0; k < W_frame_pos[j].size; ++k)
                    fwrite(&value[k], 1, 1, file);
            }
            else {
                for (int k = 0; k < strlen(value); ++k){
                    fwrite(&value[k], 1, 1, file);
                }
                for (int k = strlen(value); k < W_frame_pos[j].size; ++k){
                    fwrite(&c, 1, 1, file);
                }
            }
        }
        else{
            printf("There are no such frames\n");
        }
    }
    else{
        if (frame_comp(fr, "COMM") != 0){
            fseek(file, comment.pos, 0);
            if (comment.size - 4 < strlen(value))
            {
                for (int j = 0; j < comment.size - 4; ++j)
                    fwrite(&value[j], 1, 1, file);
            }
            else {
                for (int j = 0; j < strlen(value); ++j){
                    fwrite(&value[j], 1, 1, file);
                }
                for (int j = strlen(value); j < comment.size - 4; ++j) {
                    fwrite(&c, 1, 1, file);
                }
            }
        }
        else
        printf("There are no such frames\n");
    }
    information(file);
}



int main(){
    /*char* name_file = (char*)malloc(sizeof(char));
    for (int i = 11; i < strlen(argv[1]); ++i){
        if (arg)
        name_file[i - 11] = argv[1][i];
    }*/
    FILE *file = fopen("test.mp3", "rb");
    information(file);
    show();
    change_frame(file, "TIT2", "assdvs");
    printf("\n");
    show();
    return 0;
}