#include "pch.h"
#include <iostream>
#include <fstream>
#include <cstring>
#include <string>
#include <math.h>

using namespace std;

const int HEAD[8] = {-119, 80, 78, 71, 13, 10, 26, 10};

bool check_png(string file_name)
{
    ifstream file;
    int length;
    int position = 8;

    cout << "Attempting to open " << file_name << endl;

    file.open(file_name, ios::binary);
    length = file.rdbuf()->pubseekoff(0, ios_base::end);
    file.rdbuf()->pubseekoff(0, ios_base::beg);

    char *array = new char[length];

    file.read(array, length);

    for (int i = 0; i < position; i++)
    {
        if ((int)array[i] != HEAD[i])
        {

            cout << "PNG signature ERROR" << endl;
            break;
            return -1;
        }
    }

    bool idat = false; .


    while (position < length)

    {
        cout << "Position[" << position << "]\t";

        int length_block = 0;
        string name_block = "";
        string crc = "";

        for (int i = 0; i < 4; i++)
        {
            length_block += abs((uint8_t)array[position + i]) * pow(16, 2 * (3 - i));
        }

        position += 4;

        for (int i = 0; i < 4; i++)
        {
            name_block += array[position + i];
        }
        if (position == 12)
        {
            if (name_block != "IHDR")
            {
                cout << " IHDR ERROR" << endl;
                return false;
            }
        }
        if ((int)length_block + 8 > length - position)
        {
            cout << " IEND ERROR" << endl;
            return false;
        }
        cout << " Name[" << name_block << "]\t";
        cout << " CRC[";
        for (int i = length_block + 4; i < length_block + 8; i++)
        {

            cout << dec << (int)array[position + i] << " ";
        }
        cout << "]" << endl;


        if (name_block == "IDAT")
        {
            idat = true;
        }

    }

    if (idat = false)
    {
        cout << endl << "IDAT ERROR (not found)" << endl;
        return false;
    }

    return true;
}

int main()
{
        string filename;
        cout << "Enter path to file: ";
        cin >> filename;
        cout << endl;

        if (check_png(filename)==1)
        {
            cout << "File correct" << endl;
        }

    system("pause");
    return 0;
}