#include <cstdio>
#include "GL/Shaders.h"
#include "GL/ImmediateMode.h"


BEGIN_NAMESPACE


static GLfloat vertices[] = {
     0.5f,  1.0f,    1.0f, 0.0f, 0.0f, // Top-left
     1.0f,  1.0f,    0.0f, 1.0f, 0.0f, // Top-right
     1.0f,  0.5f,    0.0f, 0.0f, 1.0f, // Bottom-right
     0.5f,  0.5f,    1.0f, 1.0f, 1.0f  // Bottom-left
};


static GLuint elements[] = {
    0, 1, 2,
    2, 3, 0
};


static const char* vertextShaderSource = "\
#version 150\n\
\n\
in vec2 position;\n\
in vec3 color;\n\
out vec3 Color;\n\
\n\
void main()\n\
{\n\
	Color = color;\n\
    gl_Position = vec4(position, 0.0, 1.0);\n\
}\n\
";


static const char* fragmentShaderSource = "\
#version 150\n\
\n\
in vec3 Color;\n\
out vec4 outColor;\n\
\n\
void main()\n\
{\n\
    outColor = vec4(Color, 1.0);\n\
}\n\
";


struct GLProgramContext
{
	GLuint shaderProgram;
	GLuint vao;
	GLuint vbo;
    GLuint ebo;
	GLuint vertexShader;
	GLuint fragmentShader;
};


static GLProgramContext ctx;


void SetupObjects()
{
	glGenVertexArrays(1, &ctx.vao);
	glBindVertexArray(ctx.vao);

	glGenBuffers(1, &ctx.vbo); // Generate 1 buffer
	glBindBuffer(GL_ARRAY_BUFFER, ctx.vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    // Create an element array
    glGenBuffers(1, &ctx.ebo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ctx.ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

/*
}
static void CompileShader()
{
*/
	GLint status;

	ctx.vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(ctx.vertexShader, 1, &vertextShaderSource, NULL);
	glCompileShader(ctx.vertexShader);
	glGetShaderiv(ctx.vertexShader, GL_COMPILE_STATUS, &status);
	if ( status != GL_TRUE ) {
		char buffer[512];
		glGetShaderInfoLog(ctx.vertexShader, 512, NULL, buffer);
		printf("Vertex shader error: %s\n", buffer);
	}

	ctx.fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(ctx.fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(ctx.fragmentShader);
	glGetShaderiv(ctx.fragmentShader, GL_COMPILE_STATUS, &status);
	if ( status != GL_TRUE ) {
		char buffer[512];
		glGetShaderInfoLog(ctx.fragmentShader, 512, NULL, buffer);
		printf("Fragment shader error: %s\n", buffer);
	}

	ctx.shaderProgram = glCreateProgram();
	glAttachShader(ctx.shaderProgram, ctx.vertexShader);
	glAttachShader(ctx.shaderProgram, ctx.fragmentShader);
	glBindFragDataLocation(ctx.shaderProgram, 0, "outColor");
	glLinkProgram(ctx.shaderProgram);
	glUseProgram(ctx.shaderProgram);

    // Specify the layout of the vertex data
    GLint posAttrib = glGetAttribLocation(ctx.shaderProgram, "position");
    glEnableVertexAttribArray(posAttrib);
    glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), 0);
	//glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);

    GLint colAttrib = glGetAttribLocation(ctx.shaderProgram, "color");
    glEnableVertexAttribArray(colAttrib);
    glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));
}


void DrawShaderObjects()
{
	glUseProgram(ctx.shaderProgram);
	glBindVertexArray(ctx.vao);
	glDrawElements(GL_TRIANGLES, sizeof(elements) / sizeof(GLuint), GL_UNSIGNED_INT, 0);
	glUseProgram(0);
}


void CleanupObjects()
{
    glDeleteProgram(ctx.shaderProgram);
    glDeleteShader(ctx.fragmentShader);
    glDeleteShader(ctx.vertexShader);
    glDeleteBuffers(1, &ctx.ebo);
    glDeleteBuffers(1, &ctx.vbo);
    glDeleteVertexArrays(1, &ctx.vao);
}


END_NAMESPACE