/*
 *
 */

#include <time.h>
#include <stdio.h>
#include <windows.h>

#include <GL/gl.h>
#include <GL/glut.h>

/* globals */
time_t g_time;
time_t g_begintime;

//GLuint g_quad; // quad display list for screen "back buffer"
GLuint g_tex; // texture for screen "back buffer" (FBO soon)

GLuint g_width;
GLuint g_height;

unsigned char* g_screenpixels; // array of pixels on the screen

#define NUMCHANNELS     4

/* print errors from OpenGL */
void printglerror( )
{
    int error = glGetError();
    if (error != GL_NO_ERROR)
        printf("An OpenGL error has occured: %s\n", gluErrorString(error));
}

/* set the color of the pixels to red */
void redpixels( void )
{
    for( GLuint y=0; y<g_height; y++ )
    {
        for( GLuint x=0; x<g_width; x++ )
        {
            g_screenpixels[y*g_width*NUMCHANNELS+x*NUMCHANNELS+0]=255;
            g_screenpixels[y*g_width*NUMCHANNELS+x*NUMCHANNELS+1]=0;
            g_screenpixels[y*g_width*NUMCHANNELS+x*NUMCHANNELS+2]=0;
            g_screenpixels[y*g_width*NUMCHANNELS+x*NUMCHANNELS+3]=255;
        }
    }
}

/* create display lists here */
//void buildlists( )
//{
//  g_quad = glGenLists(1);
//
//  // textured quad for screen
//  glNewList(g_quad,GL_COMPILE);
//      glLoadIdentity( );
//      glTranslatef( 0.0f,0.0f,0.0f );
//      glBegin(GL_QUADS);
//          glTexCoord2f(0.0f, 1.0f);   glVertex3f(-1.0f, 1.0f, 0.0f);
//          glTexCoord2f(1.0f, 1.0f);   glVertex3f( 1.0f, 1.0f, 0.0f);
//          glTexCoord2f(1.0f, 0.0f);   glVertex3f( 1.0f,-1.0f, 0.0f);
//          glTexCoord2f(0.0f, 0.0f);   glVertex3f(-1.0f,-1.0f, 0.0f);
//      glEnd();
//  glEndList();
//}

/* initialize variables and gl properties */
void init ( )
{
    // begin timer
    g_begintime = clock( );
    g_time = g_begintime;

    // gl preparations
    glShadeModel( GL_FLAT );
    glClearColor( 0.0f, 0.0f, 0.0f, 0.5f );
    glClearDepth( 1.0f );
    glEnable( GL_DEPTH_TEST );
    glDepthFunc( GL_LEQUAL );
    glEnable ( GL_COLOR_MATERIAL );
    glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );

    // prepare backbuffer texture
    glEnable( GL_TEXTURE_2D );
    glGenTextures( 1, &g_tex );
    glBindTexture( GL_TEXTURE_2D, g_tex );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT ); // tried here as well
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );

    g_screenpixels = new unsigned char[g_width*g_height*NUMCHANNELS];
    redpixels( );

    glTexImage2D( GL_TEXTURE_2D, 0, NUMCHANNELS, g_width, g_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, g_screenpixels);
}

/* frame render */
void display( void )
{
    // update time
    double elapsed = difftime( clock( ),g_time )/1000.0;
    g_time = clock( );

    // clear the screen
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    // draw the backbuffer quad
    glBindTexture( GL_TEXTURE_2D, g_tex );
    glLoadIdentity( );
    glTranslatef( 0.0f,0.0f,0.0f );
    glScalef( 0.5f, 0.5f, 0.5f );
    glBegin(GL_QUADS);
        glTexCoord2f(0.0f, 0.0f);   glVertex3f(-1.0f,-1.0f, 0.0f);
        glTexCoord2f(0.0f, 1.0f);   glVertex3f(-1.0f, 1.0f, 0.0f);
        glTexCoord2f(1.0f, 1.0f);   glVertex3f( 1.0f, 1.0f, 0.0f);
        glTexCoord2f(1.0f, 0.0f);   glVertex3f( 1.0f,-1.0f, 0.0f);
    glEnd();

    // swap to screen
    glutSwapBuffers( );
}

/* window resize */
void reshape( int w, int h )
{
    g_width = w;
    g_height = h;

    delete g_screenpixels;
    g_screenpixels = new unsigned char[g_width*g_height*NUMCHANNELS];
    redpixels( );

    glBindTexture( GL_TEXTURE_2D, g_tex );
    glTexImage2D( GL_TEXTURE_2D, 0, NUMCHANNELS, g_width, g_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, g_screenpixels);

    glViewport( 0, 0, w, h );
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity( );
    gluOrtho2D(-1.0,1.0,-1.0,1.0);
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity( );
}

/* keyboard callback */
void keyboard( unsigned char key, int x, int y )
{
    switch( key ) {
        case VK_ESCAPE:
            exit ( 0 );
        default:
            break;
    }
}

/* arrow key callback */
void arrow_keys( int a_keys, int x, int y ) // Create Special Function (required for arrow keys)
{
    switch( a_keys ) {
        case GLUT_KEY_UP:
            glutFullScreen( );
            break;
        case GLUT_KEY_DOWN:
            g_width = 512;
            g_height = 512;
            glutReshapeWindow( g_width, g_height );
            break;
        default:
            break;
    }
}

/* main is main */
int main ( int argc, char** argv )
{
    g_width = 512;
    g_height = 512;

    glutInit( &argc, argv );
    init( );

    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
    glutInitWindowSize( g_width, g_height );
    glutCreateWindow( "TahoeVis" );
    //buildlists( );

    glutDisplayFunc( display );
    glutIdleFunc( display );
    glutReshapeFunc( reshape );
    glutKeyboardFunc( keyboard );
    glutSpecialFunc( arrow_keys );
    glutMainLoop( );

    return 0;
}