////////////////////////////////////////////////////////////
// Load OpenGL textures from binary ppm files
////////////////////////////////////////////////////////////

#include <stdio.h>
#include <malloc.h>
//#include <GL/glut.h>
#include <glut.h>
#include "texture.h"

GLuint textureID = 0; //OpenGL texture ID to be returned

////////////////////////////////////////////////////////////
// FUNCTION LoadPPM(char *)
// Load a binary ppm file into an OpenGL texture and return the OpenGL texture reference ID
////////////////////////////////////////////////////////////

int loadPPM(char *filename) {

    FILE *inFile; //File pointer
	char buffer[100]; //Input buffer
    GLubyte *theTexture; //Texture buffer pointer
	unsigned char c; //Input character
	int width, height, maxVal, pixelSize; //Image characteristics from ppm file


	//Try to open the file for reading
	if( (inFile = fopen(filename, "rb")) == NULL) {
		fprintf (stderr, "cannot open %s\n", filename);
		exit(-1);
	}

	//Read file type identifier (magic number)
	fgets(buffer, sizeof(buffer), inFile);
	if ((buffer[0] != 'P') || (buffer[1] != '6')) {
		fprintf (stderr, "not a binary ppm file %s\n", filename);
		exit(-1);
    }

	if(buffer[2] == 'A')
		pixelSize = 4;
	else
		pixelSize = 3;

	//Read image size
	do fgets(buffer, sizeof (buffer), inFile);
	while (buffer[0] == '#');
	sscanf (buffer, "%d %d", &width, &height);

	//Read maximum pixel value (usually 255)
	do fgets (buffer, sizeof (buffer), inFile);
	while (buffer[0] == '#');
	sscanf (buffer, "%d", &maxVal);

	//Allocate RGBA texture buffer
	int memSize = width * height * 4 * sizeof(GLubyte);
	theTexture = (GLubyte *)malloc(memSize);

	// read RGB data and set alpha value
	for (int i = 0; i < memSize; i++) {
		if ((i % 4) < 3 || pixelSize == 4) {
			c = fgetc(inFile);
			theTexture[i]=(GLubyte) c;
        }
		else theTexture[i] = (GLubyte) 255; //Set alpha to opaque
    }
    fclose(inFile);


    glBindTexture(GL_TEXTURE_2D, ++textureID);

    //Set texture parameters
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
	//Ignore surface color
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    //Define the texture
    glTexImage2D(GL_TEXTURE_2D, 0, 4, (GLuint)width, (GLuint)height, 0, GL_RGBA, GL_UNSIGNED_BYTE, theTexture);

    //Create mipmaps
    gluBuild2DMipmaps(GL_TEXTURE_2D, 4, (GLuint)width, (GLuint)height, GL_RGBA, GL_UNSIGNED_BYTE, theTexture);

    free(theTexture);
    return(textureID);
}