#include "ppmImage.h"
#include <iostream>

/**
 * Constructor
 */
ppmImage::ppmImage() : pixels(NULL)
{
    imageW = imageH = 0;
}

/**
 *  Destrctor
 */
ppmImage::~ppmImage()
{
    if (pixels) free(pixels);
}

/**
 *
 */
bool ppmImage::readFile(const std::string& filename)
{
    FILE * file = fopen(filename.c_str(), "rb");
    if (file == NULL)
    {
        std::cerr << "Unable to open " << filename << " for reading\n";
        return false;
    }
    char buffer[100];
    // read file identifier (magic number)
    fgets (buffer, sizeof (buffer), file);
    if ((buffer[0] != 'P') || (buffer[1] != '6'))
    {
        std::cerr << "Not a ppm file\n";
        return false;
    }
    // read image size
    do
        fgets (buffer, sizeof (buffer), file);

    // Skip all comments "#"
    // Also skip any newlines that might (but shouldn't) be there 
    // thanks Stephen Nerbetski for finding this bug.
    while (buffer[0] == '#' || buffer[0] == 10);
    
    // Read the width and height of the  image
    sscanf (buffer, "%d %d", &imageW, &imageH);

    // Allocate the buffer
    if (pixels)
        delete pixels; // don't leak!!
    pixels = new unsigned char[imageW*imageH*3*sizeof(char)];  // 3 bytes per pixel

// read maximum pixel value (usually 255) and ignore
    do
        fgets (buffer, sizeof (buffer), file);
    while (buffer[0] == '#');
    int maxval;
    sscanf (buffer, "%d", &maxval);

    // Read in the pixel array row-by-row: 1st row = top scanline, so flip for openGL
    int rowsize = imageW * 3*sizeof(char); // the sized of each row
    unsigned char *ptr = pixels + (imageH-1) * rowsize;
    for (int i = imageH; i > 0; --i)
    {
        fread(ptr, sizeof(char), rowsize, file);
        ptr -= rowsize;
    }

    fclose(file);
    return true;
}


/**
 * Write the pixel buffer to disk using the ppm formate
 */
bool ppmImage::writeFile(const std::string& filename)
{
    FILE * file = fopen(filename.c_str(), "wb");
    if (file == NULL)
    {
        std::cerr << "Unable to open " << filename << " for writing\n";
        return false;
    }
    char tmp[20];
    tmp[0] = 'P';
    tmp[1] = '6';
    tmp[2] = 10;
    fwrite(tmp, sizeof(char), 3, file);
    sprintf(tmp, "%d %d", imageW, imageH);
    fwrite(tmp, strlen(tmp), 1, file);
    tmp[0] = 10;
    tmp[1] = '2';
    tmp[2] = '5';
    tmp[3] = '5';
    tmp[4] = 10;
    fwrite(tmp, sizeof(char), 5, file);

    // Write the image row by row, flip back for ppm
    int rowsize = imageW * 3; // the sized of each row
    unsigned char *ptr = pixels + (imageH-1) * rowsize;
    for (int i = imageH; i > 0; --i)
    {
        fwrite((void *)ptr, sizeof(unsigned char), rowsize, file);
        ptr -= rowsize;
    }
    
    fclose(file);
    return true;
}