//triangles.cpp
#include <stdio.h>
#include <iostream>
using namespace std;
#include "vgl.h"
#include "LoadShaders.h"

//0 -> Triangles
//1 -> NumVAOs
enum VAO_IDs { Triangles, NumVAOs };
enum Buffer_IDs { ArrayBuffer, NumBuffers };


enum Attrib_IDs { vPosition = 0 };
//VAOs: vertex array object
GLuint VAOs[NumVAOs];
GLuint Buffers[NumBuffers];
const GLuint NumVertices = 6;
//---------------------------------------------------------------------
//
// init
//
void init(void){
    glGenVertexArrays(NumVAOs, VAOs);//VAOs: input & output var
    glBindVertexArray(VAOs[Triangles]);
    GLfloat vertices[NumVertices][2] = {
        { -0.90, -0.90 }, // Triangle 1
        { 0.85, -0.90 },
        { -0.90, 0.85 },
        { 0.90, -0.85 }, // Triangle 2
        { 0.90, 0.90 },
        { -0.85, 0.90 }
    };
    glGenBuffers(NumBuffers, Buffers);
    glBindBuffer(GL_ARRAY_BUFFER, Buffers[ArrayBuffer]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices),
            vertices, GL_STATIC_DRAW);
    ShaderInfo shaders[] = {
        { GL_VERTEX_SHADER, "triangles.vert" },
        { GL_FRAGMENT_SHADER, "triangles.frag" },
        { GL_NONE, NULL }
    };
    GLuint program = LoadShaders(shaders);
    glUseProgram(program);
    glVertexAttribPointer(vPosition, 2, GL_FLOAT,
            GL_FALSE, 0, BUFFER_OFFSET(0));
    glEnableVertexAttribArray(vPosition);
}
//---------------------------------------------------------------------
//
// display
//
    void
display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glBindVertexArray(VAOs[Triangles]);
    glDrawArrays(GL_TRIANGLES, 0, NumVertices);

    glFlush();
}
//---------------------------------------------------------------------
//
// main
//
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA);
    glutInitWindowSize(512, 512);
//  const char * v = (const char *)glGetString(GL_VERSION);
  glutInitContextVersion(2, 1);
//  glutInitContextProfile(GLUT_CORE_PROFILE);
    glutCreateWindow(argv[0]);
    if (glewInit()) {
        cerr << "Unable to initialize GLEW ...exiting" << endl;
        exit(EXIT_FAILURE);
    }
    init();
    glutDisplayFunc(display);
    glutMainLoop();
}