/**
 * From the OpenGL Programming wikibook: http://en.wikibooks.org/wiki/OpenGL_Programming
 * This file is in the public domain.
 * Contributors: Sylvain Beucler
 */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
/* Use glew.h instead of gl.h to get all the GL prototypes declared */
#include <GL/glew.h>
/* Using the GLUT library for the base windowing setup */
#include <GL/freeglut.h>
/* GLM */
// #define GLM_MESSAGES
#define GLM_FORCE_RADIANS
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include "../common/shader_utils.h"

#include "res_texture.c"

int screen_width=800, screen_height=600;
GLuint vbo_cube_vertices, vbo_cube_texcoords;
GLuint ibo_cube_elements;
GLuint program;
GLuint texture_id;
GLint attribute_coord3d, attribute_texcoord;
GLint uniform_mvp, uniform_mytexture;

int init_resources()
{
  GLfloat cube_vertices[] = {
    // front
    -1.0, -1.0,  1.0,
     1.0, -1.0,  1.0,
     1.0,  1.0,  1.0,
    -1.0,  1.0,  1.0,
    // top
    -1.0,  1.0,  1.0,
     1.0,  1.0,  1.0,
     1.0,  1.0, -1.0,
    -1.0,  1.0, -1.0,
    // back
     1.0, -1.0, -1.0,
    -1.0, -1.0, -1.0,
    -1.0,  1.0, -1.0,
     1.0,  1.0, -1.0,
    // bottom
    -1.0, -1.0, -1.0,
     1.0, -1.0, -1.0,
     1.0, -1.0,  1.0,
    -1.0, -1.0,  1.0,
    // left
    -1.0, -1.0, -1.0,
    -1.0, -1.0,  1.0,
    -1.0,  1.0,  1.0,
    -1.0,  1.0, -1.0,
    // right
     1.0, -1.0,  1.0,
     1.0, -1.0, -1.0,
     1.0,  1.0, -1.0,
     1.0,  1.0,  1.0,
  };
  glGenBuffers(1, &vbo_cube_vertices);
  glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_vertices);
  glBufferData(GL_ARRAY_BUFFER, sizeof(cube_vertices), cube_vertices, GL_STATIC_DRAW);

  GLfloat cube_texcoords[2*4*6] = {
    // front
    0.0, 0.0,
    1.0, 0.0,
    1.0, 1.0,
    0.0, 1.0,
  };
  for (int i = 1; i < 6; i++)
    memcpy(&cube_texcoords[i*4*2], &cube_texcoords[0], 2*4*sizeof(GLfloat));
  glGenBuffers(1, &vbo_cube_texcoords);
  glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_texcoords);
  glBufferData(GL_ARRAY_BUFFER, sizeof(cube_texcoords), cube_texcoords, GL_STATIC_DRAW);

  GLushort cube_elements[] = {
    // front
    0,  1,  2,
    2,  3,  0,
    // top
    4,  5,  6,
    6,  7,  4,
    // back
    8,  9, 10,
    10, 11,  8,
    // bottom
    12, 13, 14,
    14, 15, 12,
    // left
    16, 17, 18,
    18, 19, 16,
    // right
    20, 21, 22,
    22, 23, 20,
  };
  glGenBuffers(1, &ibo_cube_elements);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo_cube_elements);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(cube_elements), cube_elements, GL_STATIC_DRAW);

  glGenTextures(1, &texture_id);
  glBindTexture(GL_TEXTURE_2D, texture_id);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexImage2D(GL_TEXTURE_2D, // target
	       0,  // level, 0 = base, no minimap,
	       GL_RGB, // internalformat
	       res_texture.width,  // width
	       res_texture.height,  // height
	       0,  // border, always 0 in OpenGL ES
	       GL_RGB,  // format
	       GL_UNSIGNED_BYTE, // type
	       res_texture.pixel_data);

  GLint link_ok = GL_FALSE;

  GLuint vs, fs;
  if ((vs = create_shader("cube.v.glsl", GL_VERTEX_SHADER))   == 0) return 0;
  if ((fs = create_shader("cube.f.glsl", GL_FRAGMENT_SHADER)) == 0) return 0;

  program = glCreateProgram();
  glAttachShader(program, vs);
  glAttachShader(program, fs);
  glLinkProgram(program);
  glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
  if (!link_ok) {
    fprintf(stderr, "glLinkProgram:");
    print_log(program);
    return 0;
  }

  const char* attribute_name;
  attribute_name = "coord3d";
  attribute_coord3d = glGetAttribLocation(program, attribute_name);
  if (attribute_coord3d == -1) {
    fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
    return 0;
  }
  attribute_name = "texcoord";
  attribute_texcoord = glGetAttribLocation(program, attribute_name);
  if (attribute_texcoord == -1) {
    fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
    return 0;
  }
  const char* uniform_name;
  uniform_name = "mvp";
  uniform_mvp = glGetUniformLocation(program, uniform_name);
  if (uniform_mvp == -1) {
    fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
    return 0;
  }
  uniform_name = "mytexture";
  uniform_mytexture = glGetUniformLocation(program, uniform_name);
  if (uniform_mytexture == -1) {
    fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
    return 0;
  }

  return 1;
}

void onIdle() {
  float angle = glutGet(GLUT_ELAPSED_TIME) / 1000.0 * glm::radians(15.0);  // base 15° per second
  glm::mat4 anim = \
    glm::rotate(glm::mat4(1.0f), angle*3.0f, glm::vec3(1, 0, 0)) *  // X axis
    glm::rotate(glm::mat4(1.0f), angle*2.0f, glm::vec3(0, 1, 0)) *  // Y axis
    glm::rotate(glm::mat4(1.0f), angle*4.0f, glm::vec3(0, 0, 1));   // Z axis

  glm::mat4 model = glm::translate(glm::mat4(1.0f), glm::vec3(0.0, 0.0, -4.0));
  glm::mat4 view = glm::lookAt(glm::vec3(0.0, 2.0, 0.0), glm::vec3(0.0, 0.0, -4.0), glm::vec3(0.0, 1.0, 0.0));
  glm::mat4 projection = glm::perspective(45.0f, 1.0f*screen_width/screen_height, 0.1f, 10.0f);

  glm::mat4 mvp = projection * view * model * anim;
  glUseProgram(program);
  glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, glm::value_ptr(mvp));
  glutPostRedisplay();
}

void onDisplay()
{
  glClearColor(1.0, 1.0, 1.0, 1.0);
  glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

  glUseProgram(program);

  glActiveTexture(GL_TEXTURE0);
  glBindTexture(GL_TEXTURE_2D, texture_id);
  glUniform1i(uniform_mytexture, /*GL_TEXTURE*/0);

  glEnableVertexAttribArray(attribute_coord3d);
  // Describe our vertices array to OpenGL (it can't guess its format automatically)
  glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_vertices);
  glVertexAttribPointer(
    attribute_coord3d, // attribute
    3,                 // number of elements per vertex, here (x,y,z)
    GL_FLOAT,          // the type of each element
    GL_FALSE,          // take our values as-is
    0,                 // no extra data between each position
    0                  // offset of first element
  );

  glEnableVertexAttribArray(attribute_texcoord);
  glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_texcoords);
  glVertexAttribPointer(
    attribute_texcoord, // attribute
    2,                  // number of elements per vertex, here (x,y)
    GL_FLOAT,           // the type of each element
    GL_FALSE,           // take our values as-is
    0,                  // no extra data between each position
    0                   // offset of first element
  );

  /* Push each element in buffer_vertices to the vertex shader */
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo_cube_elements);
  int size;  glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, GL_BUFFER_SIZE, &size);
  glDrawElements(GL_TRIANGLES, size/sizeof(GLushort), GL_UNSIGNED_SHORT, 0);

  glDisableVertexAttribArray(attribute_coord3d);
  glDisableVertexAttribArray(attribute_texcoord);
  glutSwapBuffers();
}

void onReshape(int width, int height) {
  screen_width = width;
  screen_height = height;
  glViewport(0, 0, screen_width, screen_height);
}

void free_resources()
{
  glDeleteProgram(program);
  glDeleteBuffers(1, &vbo_cube_vertices);
  glDeleteBuffers(1, &vbo_cube_texcoords);
  glDeleteBuffers(1, &ibo_cube_elements);
  glDeleteTextures(1, &texture_id);
}


int main(int argc, char* argv[]) {
  glutInit(&argc, argv);
  glutInitContextVersion(2,0);
  glutInitDisplayMode(GLUT_RGBA|GLUT_ALPHA|GLUT_DOUBLE|GLUT_DEPTH);
  glutInitWindowSize(screen_width, screen_height);
  glutCreateWindow("My Textured Cube");

  GLenum glew_status = glewInit();
  if (glew_status != GLEW_OK) {
    fprintf(stderr, "Error: %s\n", glewGetErrorString(glew_status));
    return 1;
  }

  if (!GLEW_VERSION_2_0) {
    fprintf(stderr, "Error: your graphic card does not support OpenGL 2.0\n");
    return 1;
  }

  if (init_resources()) {
    glutDisplayFunc(onDisplay);
    glutReshapeFunc(onReshape);
    glutIdleFunc(onIdle);
    glEnable(GL_BLEND);
    glEnable(GL_DEPTH_TEST);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glutMainLoop();
  }

  free_resources();
  return 0;
}