#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "GL/glfw.h"

#define S_WIDTH 640
#define S_HEIGHT 480

// Bad Global Variables:
//int width, height;													// Window dimensions
double t;																// Time (seconds)
GLuint texture;															// Texture reference

// Function prototypes:
void reSizeGLScene( GLsizei width, GLsizei height );
bool initGL();
bool loadTexture( const char* path );
bool drawGLScene();
void cleanUp();

int main( int argc, char** argv )
{
	// Initialize variables:
	bool status = true;		// Is the program okay?
	bool done = false;		// Is the program done?
	
	// Start up GLFW
	glfwInit();
	
	// Open up a window
	status = glfwOpenWindow(
		S_WIDTH, S_HEIGHT,
		8, 8, 8, 8,
		24,
		0,
		GLFW_WINDOW
	);
	
	// Exit if there is an error opening the window
	if ( !status )
	{
		glfwTerminate();
		fprintf( stderr, "ERROR OPENING GLFW WINDOW\n" );
		return 1;
	}
	
	// Set the window title
	glfwSetWindowTitle( "My OpenGL Program" );
	
	// Enable sticky keys
	glfwEnable( GLFW_STICKY_KEYS );
	
	initGL();
	loadTexture( "data/test.tga" );
	
	// Game loop:
	while ( !done )
	{
		reSizeGLScene( S_WIDTH, S_HEIGHT );
		// Call the render function:
		status = drawGLScene();
		
		// Flip buffers:
		glfwSwapBuffers();
		
		done = glfwGetKey( GLFW_KEY_ESC ) || !glfwGetWindowParam( GLFW_OPENED );
	}
	
	// Clean up:
	cleanUp();
}

/*~~~~~~~~~~~ reSizeGLScene() ~~~~~~~~~~~~*/
/*  - Resize and initialize the GL window
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
void reSizeGLScene( GLsizei width, GLsizei height )
{
	
	// Make sure the height is non-zero
	if ( height < 1 )
	{
		height = 1;
	}
	
	// Set the viewport:
	glViewport( 0, 0, width, height );
	
	// Now set up the projection matrix:
	glMatrixMode( GL_PROJECTION );										// Change the matrix mode to projection
	glLoadIdentity();													// Identity Matrix
	gluPerspective( 65.0, (double)width/(double)height, 1.0, 100.0 );	// Set the perspective
	
	// Set up the modelview matrix:
	glMatrixMode( GL_MODELVIEW );										// Modelview matrix
	glLoadIdentity();													// Identity matrix
}

/*~~~~~~~~~~~~~~~ initGL() ~~~~~~~~~~~~~~~*/
/*  - Initializes OpenGL
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
bool initGL()
{
	glEnable( GL_TEXTURE_2D );											// Enable texture mapping
	glShadeModel( GL_SMOOTH );											// Use the smooth shader model
	glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );								// Set a black background
	glClearDepth( 1.0f );												// Setup the depth buffer
	glEnable( GL_DEPTH_TEST );											// Enable depth testing
	glDepthFunc( GL_LEQUAL );											// The type of depth test to do
	glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );				// Really Nice perspective calculations
	return true;														// Return success
};	

/*~~~~~~~~~~~~ loadTexture() ~~~~~~~~~~~~~*/
/*  - Initializes Textures
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
bool loadTexture( const char* path )
{
	glGenTextures( 0, &texture );
	glBindTexture( GL_TEXTURE_2D, texture );
	glfwLoadTexture2D( path, 0 );
	
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
	return true;
}

/*~~~~~~~~~~~~ drawGLScene() ~~~~~~~~~~~~~*/
/*  - Main OpenGL draw function
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
bool drawGLScene()
{
	// Now let's get the system time
	t = glfwGetTime();

	// Clear colour and depth buffers:
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );				// Clear the screen and depth buffer
	glLoadIdentity();													// Reset the ModelView Matrix
	
	
	glTranslatef( 0.0f, 0.0f,-6.0f );									// Set the offset
	glEnable( GL_TEXTURE_2D );
	glBindTexture( GL_TEXTURE_2D, texture );							// Select texture
	fprintf( stderr, "Texture id: %d\n", texture );
	glBegin( GL_QUADS );
	{
		glTexCoord2f( 0.0f, 0.0f ); glVertex3f(-2.0f, 2.0f, 0.0f );
		glTexCoord2f( 1.0f, 0.0f ); glVertex3f( 2.0f, 2.0f, 0.0f );
		glTexCoord2f( 1.0f, 1.0f ); glVertex3f( 2.0f,-2.0f, 0.0f );
		glTexCoord2f( 0.0f, 1.0f ); glVertex3f(-2.0f,-2.0f, 0.0f );
	}
	glEnd();
	glDisable( GL_TEXTURE_2D );
	glPopMatrix();
	return true;														// Return success
}

/*~~~~~~~~~~~~~~ cleanUp() ~~~~~~~~~~~~~~~*/
/*  - Clean everything up
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
void cleanUp()
{
	glfwTerminate();
}