/*
  Simple Demo for GLSL
  www.lighthouse3d.com
*/

#include "GL/glew.h"

#ifdef __linux__
#include <GL/glut.h>
#endif

#ifdef __APPLE__
#include <glut.h>
#endif

#ifdef _WIN32
#include "glut.h"
#endif

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

///////////////////////////////////////////////////////////////////////

GLhandleARB v,f,f2,p;
float lpos[4] = {1,0.5,1,0};
GLint loc;

char *textFileRead(char *fn) {


	FILE *fp;
	char *content = NULL;

	int count=0;

	if (fn != NULL) {
		fp = fopen(fn,"rt");

		if (fp != NULL) {
      
      fseek(fp, 0, SEEK_END);
      count = ftell(fp);
      rewind(fp);

			if (count > 0) {
				content = (char *)malloc(sizeof(char) * (count+1));
				count = fread(content,sizeof(char),count,fp);
				content[count] = '\0';
			}
			fclose(fp);
		}
	}

	if (content == NULL)
	   {
	   fprintf(stderr, "ERROR: could not load in file %s\n", fn);
	   exit(1);
	   }
	return content;
}

///////////////////////////////////////////////////////////////////////

int textFileWrite(char *fn, char *s) {

	FILE *fp;
	int status = 0;

	if (fn != NULL) {
		fp = fopen(fn,"w");

		if (fp != NULL) {
			
			if (fwrite(s,sizeof(char),strlen(s),fp) == strlen(s))
				status = 1;
			fclose(fp);
		}
	}
	return(status);
}

///////////////////////////////////////////////////////////////////////

void changeSize(int w, int h) {

	// Prevent a divide by zero, when window is too short
	// (you cant make a window of zero width).
	if(h == 0)
		h = 1;

	float ratio = 1.0* w / h;

	// Reset the coordinate system before modifying
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	
	// Set the viewport to be the entire window
    glViewport(0, 0, w, h);

	// Set the correct perspective.
	gluPerspective(45,ratio,1,1000);
	glMatrixMode(GL_MODELVIEW);


}

///////////////////////////////////////////////////////////////////////

float a = 0;

void renderScene(void) {

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glLoadIdentity();
	gluLookAt(0.0,0.0,10.0, 
		      0.0,0.0,-1.0,
			  0.0f,1.0f,0.0f);

	glLightfv(GL_LIGHT0, GL_POSITION, lpos);
	glRotatef(a,0,1,0);
	
	glColor3f(1.0, 0.0, 0.0);

	glBegin(GL_TRIANGLE_STRIP);
		glVertexAttrib1f(loc,2.0);
		glVertex2f(-1,1);

		glVertexAttrib1f(loc,2.0);
		glVertex2f(1,1);

		glVertexAttrib1f(loc,-2.0);
		glVertex2f(-1,-1);
		glVertexAttrib1f(loc,-2.0);
		glVertex2f(1,-1);

	glEnd();


	a+=0.1;

	glutSwapBuffers();
}

///////////////////////////////////////////////////////////////////////

void processNormalKeys(unsigned char key, int x, int y) {

	if (key == 27) 
		exit(0);
}

///////////////////////////////////////////////////////////////////////

#define printOpenGLError() printOglError(__FILE__, __LINE__)

int printOglError(char *file, int line)
{
    //
    // Returns 1 if an OpenGL error occurred, 0 otherwise.
    //
    GLenum glErr;
    int    retCode = 0;

    glErr = glGetError();
    while (glErr != GL_NO_ERROR)
    {
        printf("glError in file %s @ line %d: %s\n", file, line, gluErrorString(glErr));
        retCode = 1;
        glErr = glGetError();
    }
    return retCode;
}

///////////////////////////////////////////////////////////////////////

void printShaderLog(GLuint obj)
{
    GLint infoLogLength = 0;
    GLsizei charsWritten  = 0;
    GLchar *infoLog;

    glGetShaderiv(obj, GL_INFO_LOG_LENGTH, &infoLogLength);

    if (infoLogLength > 0)
    {
        infoLog = (char *) malloc(infoLogLength);
        glGetShaderInfoLog(obj, infoLogLength, &charsWritten, infoLog);
		printf("%s\n",infoLog);
        free(infoLog);
    }
}

void printProgramLog(GLuint obj)
{
    GLint infoLogLength = 0;
    GLsizei charsWritten  = 0;
    GLchar *infoLog;

    glGetProgramiv(obj, GL_INFO_LOG_LENGTH, &infoLogLength);

    if (infoLogLength > 0)
    {
        infoLog = (char *) malloc(infoLogLength);
        glGetProgramInfoLog(obj, infoLogLength, &charsWritten, infoLog);
		printf("%s\n",infoLog);
        free(infoLog);
    }
}


///////////////////////////////////////////////////////////////////////

void setShaders() {

	char *vs = NULL,*fs = NULL,*fs2 = NULL;

	v = glCreateShader(GL_VERTEX_SHADER_ARB);
	f = glCreateShader(GL_FRAGMENT_SHADER_ARB);
	f2 = glCreateShader(GL_FRAGMENT_SHADER_ARB);


	vs = textFileRead("height.vert");
	fs = textFileRead("height.frag");

	const char * vv = vs;
	const char * ff = fs;

	glShaderSource(v, 1, &vv,NULL);
	glShaderSource(f, 1, &ff,NULL);

	free(vs);free(fs);

	glCompileShaderARB(v);
	glCompileShaderARB(f);

	printShaderLog(v);
	printShaderLog(f);
	printProgramLog(f2);

	p = glCreateProgram();
	glAttachShader(p,v);
	glAttachShader(p,f);

	glLinkProgram(p);
	printProgramLog(p);

	glUseProgram(p);


	loc = glGetAttribLocation(p,"height");
}

///////////////////////////////////////////////////////////////////////

int main(int argc, char **argv) {
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
	glutInitWindowPosition(100,100);
	glutInitWindowSize(320,320);
	glutCreateWindow("MM 2004-05");

	glutDisplayFunc(renderScene);
	glutIdleFunc(renderScene);
	glutReshapeFunc(changeSize);
	glutKeyboardFunc(processNormalKeys);

	glEnable(GL_DEPTH_TEST);
	glClearColor(1.0,1.0,1.0,1.0);
//	glEnable(GL_CULL_FACE);

	glewInit();
	if (GLEW_ARB_vertex_program && GLEW_ARB_fragment_program)
		printf("Ready for GLSL\n");
	else {
		printf("No GLSL support\n");
		exit(1);
	}

	setShaders();

	glutMainLoop();

	return 0;
}