#include <iostream>
#include <vgl.h>
#include <LoadShaders.h>

using namespace std;

enum VAO_IDs {Triangles, NumVAOs};
enum Buffer_IDs {ArrayBuffer, NumBuffers};
enum Attrib_IDs {vPosition, vColor, Scalefactor};

GLuint VAOs[NumVAOs];
GLuint Buffers[NumBuffers];

const GLuint NumVertices = 6;
const GLuint VertexSize = 9;

struct Vstruct {
    GLfloat  vertex[2*NumVertices];
    GLfloat  colors[4*NumVertices];
    GLfloat  scale [3*NumVertices];
};

Vstruct vertices = {
       .vertex = {{ -0.90, -0.90}, {  0.85, -0.90}, 
                 { -0.90,  0.85}, {  0.90, -0.85}, 
                 {  0.90,  0.90}, { -0.85,  0.90}}, 
       .colors = {{1.0, 1.0 , 0.0, 1.0}, {0.0, 1.0 , 0.0, 1.0},
        {0.0, 0.0 , 1.0, 1.0}, {1.0, 1.0 , 0.0, 1.0},
        {1.0, 0.0 , 1.0, 1.0}, {0.0, 1.0 , 1.0, 1.0}},
       .scale = {{1.0, 1.0, 1.0}, {1.0, 1.0, 1.0}, {1.0, 1.0, 1.0},
	{0.9, 0.9, 0.9}, {0.3, 0.3, 0.3}, {0.5, 0.5, 0.5}}
};

ShaderInfo shaders[] = {
    { GL_VERTEX_SHADER, "color.vert" },
    { GL_FRAGMENT_SHADER, "triangles.frag"},
    { GL_NONE, NULL}
};

void DoErrorReport(string header ) {
    GLenum err = GL_NO_ERROR;
    bool firstPass = true;
    while ((err = glGetError()) != GL_NO_ERROR) {
        if(firstPass) {
	   cout << header << endl;
	   firstPass = false;
        }
        cout << "Got error " << err << ": " ;
	cout << gluErrorString(err) << endl;
    }
}

void setup() {
   GLuint program;

   program = LoadShaders(shaders);
   glUseProgram(program);

   glGenVertexArrays(NumVAOs, VAOs);
   glBindVertexArray(VAOs[Triangles]);

   // set up the triangles
   glGenBuffers(NumBuffers, Buffers);
   glBindBuffer(GL_ARRAY_BUFFER, Buffers[ArrayBuffer]);
   glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

   GLsizei stride =0; 

   glVertexAttribPointer(vPosition, 2, GL_FLOAT, GL_FALSE, stride, 
       BUFFER_OFFSET(0));
   glEnableVertexAttribArray(vPosition);
   glVertexAttribPointer(vColor, 4, GL_FLOAT, GL_FALSE, stride, 
       BUFFER_OFFSET(vertices.colors));
   glEnableVertexAttribArray(vColor);
   glVertexAttribPointer(Scalefactor, 3, GL_FLOAT, GL_FALSE, stride, 
       BUFFER_OFFSET(vertices.scale));
   glEnableVertexAttribArray(Scalefactor);

   DoErrorReport("End of Setup");

   return;
}

void display(){

   glClear(GL_COLOR_BUFFER_BIT);

   glBindVertexArray(VAOs[Triangles]);
   glDrawArrays(GL_TRIANGLES, 0, NumVertices);

   glFlush();
   DoErrorReport("End of Display");

   return;
}


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

    switch(key) {
       case 'q':
          exit(0);
    }

    glutPostRedisplay();
    return;
}


int main(int argc, char * argv[]) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA);
    glutInitWindowSize(512, 512);
    glutInitContextVersion(3,0);
    glutInitContextProfile(GLUT_CORE_PROFILE);
    glutCreateWindow(argv[0]);

    glutDisplayFunc(display);
    glutKeyboardFunc(keypress);

    glewExperimental = GL_TRUE;
    if (glewInit()) {
        cerr << "Unable to initialize glew, exiting " << endl;
	exit (-1);
    }

    setup();

    glutMainLoop();

    return 0;
}