// Copies a BMP file

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

#include "bmp.h"

int main(int argc, char *argv[])
{

    // Resize factor
    int n = atoi(argv[1]);

    // Ensure proper usage
    if (argc != 4)
    {
        printf("Usage: ./resize n infile outfile\n");
        return 1;
    }
    if (n < 0 || n > 100)
    {
        printf("Usage: ./resize n infile outfile\n");
        return 1;
    }

    // Remember filenames
    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);
        printf("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);

    // Adjust Height and Width
    bi.biHeight = bi.biHeight * n;
    bi.biWidth = bi.biWidth * n;

    // Determine padding for scanlines
    int newPadding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    int oldPadding = (4 - (((bi.biWidth) / n) * sizeof(RGBTRIPLE)) % 4) % 4;

    // Adjust image and file size
    bi.biSizeImage = ((bi.biWidth * sizeof(RGBTRIPLE)) + newPadding) * abs(bi.biHeight);
    bf.bfSize = bi.biSizeImage + sizeof(BITMAPINFOHEADER) + sizeof(BITMAPFILEHEADER);


    // 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);
        printf("Unsupported file format.\n");
        return 4;
    }

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


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

    // Iterate over infile's scanlines
    for (int i = 0, biHeight = abs((bi.biHeight) / n); i < biHeight; i++)
    {

        // Make every row n times
        for (int l = 0; l < n; l++)
        {
            // Iterate over pixels in scanline
            for (int j = 0; j < (bi.biWidth) / n; j++)
            {

                // Make every pixel n times
                for (int m = 0; m < n; m++)
                {
                    // Temporary storage
                    RGBTRIPLE triple;

                    // Read RGB triple from infile
                    fread(&triple, sizeof(RGBTRIPLE), 1, inptr);

                    // Write RGB triple n times to outfile
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);

                    // Move infile cursor 1 RGB triple back
                    fseek(inptr, -(sizeof(RGBTRIPLE)), SEEK_CUR);
                }

                // Move infile cursor 1 RGB triple forward
                fseek(inptr, sizeof(RGBTRIPLE), SEEK_CUR);
            }

            // Add padding
            for (int k = 0; k < newPadding; k++)
            {
                fputc(0x00, outptr);
            }

            // Send infile cursor back
            fseek(inptr, -(bi.biWidth / n) * sizeof(RGBTRIPLE), SEEK_CUR);
        }

        // Send infile cursor forward
        fseek(inptr, (bi.biWidth / n) * sizeof(RGBTRIPLE), SEEK_CUR);

        // Skip over padding, if any
        fseek(inptr, oldPadding, SEEK_CUR);

    }

    // Close infile
    fclose(inptr);

    // Close outfile
    fclose(outptr);

    // Success
    return 0;
}