/**
 * copy.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * Copies a BMP piece by piece, just because.
 */

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

#include "bmp.h"

int main(int argc, char* argv[])
{
    // ensure proper usage
    if (argc != 4)
    {
        printf("Usage: ./copy infile outfile\n");
        return 1;
    }

    // remember filenames
    int n = atoi(argv[1]);
    char* infile = argv[2];
    char* outfile = argv[3];

    // open input file
    FILE* inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        printf("Could not open %s.\n", infile);
        return 2;
    }

    // open output file
    FILE* outptr = fopen(outfile, "w");
    if (outptr == NULL)
    {
        fclose(inptr);
        fprintf(stderr, "Could not create %s.\n", outfile);
        return 3;
    }

    // read infile's BITMAPFILEHEADER
    BITMAPFILEHEADER bf;
    fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);

    // read infile's BITMAPINFOHEADER
    BITMAPINFOHEADER bi;
    fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);

    // ensure infile is (likely) a 24-bit uncompressed BMP 4.0
    if (bf.bfType != 0x4d42 || bf.bfOffBits != 54 || bi.biSize != 40 ||
        bi.biBitCount != 24 || bi.biCompression != 0)
    {
        fclose(outptr);
        fclose(inptr);
        fprintf(stderr, "Unsupported file format.\n");
        return 4;
    }

    //Save original values just in case (UNLOCK AS NEEDED OR ELSE STUPID UNUSED VARIABLE ERROR)
    LONG old_biWidth = bi.biWidth;
    LONG old_biHeight = bi.biHeight;
    int old_padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    //DWORD old_biSizeImage = bi.biSizeImage;
    //DWORD old_bfSize = bf.bfSize;

    //Modify headers for outfile
    bi.biWidth = bi.biWidth * n;
    bi.biHeight =  bi.biHeight * n;
    int padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + padding) * abs(bi.biHeight);
    bf.bfSize = bi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    // write outfile's BITMAPFILEHEADER
    fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);

    // write outfile's BITMAPINFOHEADER
    fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);

    // temporary storage variables
    RGBTRIPLE triple;
    RGBTRIPLE array[bi.biWidth]; //size of modified height

    // iterate over infile's scanlines
    for (int i = 0; i < abs(old_biHeight); i++)
    {
        // copy row into array
        for (int j = 0; j < old_biWidth; j++)
        {
            // read RGB triple from infile
            fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
            array[j] = triple; //put it in an array
        }

        //skip over any padding
        fseek(inptr, old_padding, SEEK_CUR);

        for (int w = 0; w < bi.biWidth; w++)
        {
            triple = array[w];
            fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
        }
        //add padding new padding
        for (int k = 0; k < padding; k++)
        {
            fputc(0x00, outptr);
        }

    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}