/**
 * resize.c
 *
 * Computer Science 50
 * Problem Set 5
 *
 * Resizes a BMP.
 */

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

#include "bmp.h"

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

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

    // turn the scale into an int
    int scale = atoi(argv[1]);

    // 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);
    BITMAPINFOHEADER old_bi = bi;

    // 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;
    }

    // update outfile's header

    printf("Old file size: %i\n", bf.bfSize);
    bf.bfSize *= scale;
    printf("New file size: %i\n\n", bf.bfSize);

    printf("Old image size: %i\n", bi.biSizeImage);
    bi.biSizeImage *= scale;
    printf("New image size: %i\n\n", bi.biSizeImage);

    printf("Old image width: %i\n", bi.biWidth);
    bi.biWidth *= scale;
    printf("New image width: %i\n\n", bi.biWidth);

    printf("Old image height: %i\n", bi.biHeight);
    bi.biHeight *= scale;
    printf("New image height: %i\n\n", bi.biHeight);


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

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

    // determine padding for scanlines
    int padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    int old_padding =  (4 - (old_bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(old_bi.biHeight); i < biHeight; i++)
    {
        // repeat the row scale number of times
        for (int m = 0; m < scale; m++)
        {
            // get current position
            int f_pos = ftell(inptr);
            printf("%i\n", f_pos);

            // iterate over pixels in scanline
            for (int j = 0; j < old_bi.biWidth; j++)
            {
                // temporary storage
                RGBTRIPLE triple;

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

                // write RGB triple to outfile scale number of times
                for (int k = 0; k < scale; k++)
                {
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
            }

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

            // then add it back (to demonstrate how)
            for (int l = 0; l < padding; l++)
            {
                fputc(0x00, outptr);
            }

            // go back to original line in infile
            long offset = -(old_bi.biWidth * sizeof(RGBTRIPLE)) - old_padding;
            fseek(inptr, offset, SEEK_CUR);

            // get current position
            f_pos = ftell(inptr);
            printf("%i\n", f_pos);
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}