/**
 * resize.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * Resizes a BMP image
 */

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

#include "bmp.h"

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

    // ensure proper usage
if (argc != 4)
    {
        printf("Usage: ./resize n infile outfile\n");
        return 1;
    }

    // remember factor and filenames
    int n = atoi(argv[1]);
    if(n < 0 || n > 100)
    {
        printf("The resize factor should be a positive integer less than 100.\n");
        return 2;
    }
    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 3;
    }

    // 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;
    }


    //Store old values of width and height before resize
    int width = bi.biWidth;
    int height = bi.biHeight;

    //Resize the width and height
    bi.biWidth = bi.biWidth * n;
    bi.biHeight = bi.biHeight * n;

    // determine padding for scanlines for input file
    int in_padding =  (4 - (width * sizeof(RGBTRIPLE)) % 4) % 4;

    // determine padding for scanlines for output file
    int out_padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;


    //Resize the header file info
    bi.biSizeImage = (bi.biWidth * abs(bi.biHeight)) + (out_padding * abs(bi.biHeight));
    bf.bfSize = 54 +  bi.biSizeImage;

    // 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(height); i++)
    {
        //iterate over each scanline n times
        for (int x = 0; x < n; x++)
        {


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

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



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

            }

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

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

            }

            //Go back to the beggining of the input file scanline
            fseek(inptr, -(width * 3 + in_padding ), SEEK_CUR);

        }
        fseek(inptr, width * sizeof(RGBTRIPLE) + in_padding, SEEK_CUR);

    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}