/**
 * resize.c
 *
 * Computer Science 50
 * Problem Set 5
 *
 * Copies a BMP piece by piece, and creates a another bmp with requested dimensions.
 */

#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;
    }

    // receive scale value and check for validity
    int n = atoi(argv[1]);
    if ( n < 1 || n > 100)
    {
        printf("Enter a value for scale between 1 and 100");
    }

    // 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);
        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;
    }

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

    // updating BITMAPINFOHEADER height and width varibles inorder to resize
    //int initialHeight = abs(bi.biHeight); // to be used for modifying offset
    int initialWidth = bi.biWidth;
    bi.biHeight *= n;
    bi.biWidth *= n;

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

    // update BITMAPINFOHEADER biSizeImage and BITMAPFILEHEADER bfSize
    bi.biSizeImage = ((bi.biWidth)* abs(bi.biHeight) * sizeof(RGBTRIPLE)) + paddingOutfile;
    bf.bfSize = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER) + bi.biSizeImage;

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

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

    // offset variable used to shift fseek
    int offset = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
    {
        // iterate over pixels in scanline
        for (int j = 0; j < initialWidth; j++)
        {
            // temporary storage
            RGBTRIPLE triple;

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

            // write RGB triple to outfile. Iterate n times to copy the pixels (n-1) times horizontally.
            for(int k = 0; k < n; k++)
            {
                fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
            }
        }

        // then add it back
        for (int k = 0; k < paddingOutfile; k++)
        {
            fputc(0x00, outptr);
        }

        ////////////////////////TEST///////////////////////////
        //printf("i : %i\n",i);
        //printf("offset : %i\n",offset);

        //Modifying offset inorder to change fseek SEEK_SET psition
        if(i%n == (n-1))
        {
            offset += ((initialWidth) * sizeof(RGBTRIPLE)) + paddingInfile;
        }

        // skip over padding, if any
        fseek(inptr, offset, SEEK_SET);
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}