// Copies a BMP file

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

#include "bmp.h"

int main(int argc, char *argv[])
{
    // ensure proper usage
    if (argc != 4)
    {
        fprintf(stderr, "Usage: ./resize n infile outfile\n");
        return 1;
    }
    if (isdigit(argv[1][0]) == 0)
    {

        fprintf(stderr, "n is not an integer\n");
        return 1;
    }

    int n = atoi(argv[1]);
    printf("Scaling factor is: %i\n", n);

    if (n < 1 || n > 100)
    {
        fprintf(stderr, "1 < n < 101\n");
        return 1;
    }

    // remember filenames
    char *infile = argv[2];
    char *outfile = argv[3];

    // open input file
    FILE *inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        fprintf(stderr, "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;
    }

    // stores initial header and file values
    int biWidth0 = bi.biWidth;
    int biHeight0 = bi.biHeight;
    int padding0 = (4 - ((biWidth0) * sizeof(RGBTRIPLE)) % 4) % 4;
    int biSizeImage0 = ((sizeof(RGBTRIPLE) * biWidth0) + padding0) * abs(biHeight0);
    int bfSize0 = biSizeImage0 + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    // makes an update of header and file values
    bi.biWidth *= n;
    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);

    // iterate over infile's scanlines
    for (int i = 0; i < abs(biHeight0); i++)
    {
        // iterate over rows
        for (int r = 0 ; r < n - 1; r++)
        {
            // iterate over pixels in scanline
            for (int j = 0; j < biWidth0; j++)
            {
                // temporary storage
                RGBTRIPLE triple;

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

                // attempts to resize horizontally
                for (int k = 0; k < n; k++)
                {
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
            }
            // adds padding to outfile
            for (int q = 0; q < padding; q++)
            {
                fputc(0x00, outptr);
            }
            // sends infile cursor to the start of scanline
            fseek(inptr, -(biWidth0)*sizeof(RGBTRIPLE), SEEK_CUR);
        }

        // one last step in vertical scaling
        for (int a = 0; a < biWidth0; a++)
        {
            // temporary storage
            RGBTRIPLE triple;
            // read RGB triple from infile
            fread(&triple, sizeof(RGBTRIPLE), 1, inptr);

            // attempts to resize horizontally
            for (int b = 0; b < n; b++)
            {
                fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
            }
        }
        // adds padding to outfile
        for (int c = 0; c < padding; c++)
        {
            fputc(0x00, outptr);
        }
        // skip over padding, if any
        fseek(inptr, padding0, SEEK_CUR);
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;
}