#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
  // Initialize GLFW
  if (!glfwInit()) {
    return -1;
  }

  // Set the required options for GLFW
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

  // Create a windowed mode window and its OpenGL context
  GLFWmonitor *glfwMonitor = glfwGetPrimaryMonitor();
  const GLFWvidmode *mode = glfwGetVideoMode(glfwMonitor);
  GLFWwindow *window = glfwCreateWindow(mode->width, mode->height,
                                        "Blue screen", glfwMonitor, NULL);
  if (!window) {
    glfwTerminate();
    return -1;
  }

  glfwMakeContextCurrent(window);

  // Initialize GLEW
  GLenum glewStatus = glewInit();
  if (glewStatus != GLEW_OK) {
    printf("Failed to initialize GLEW: %s\n", glewGetErrorString(glewStatus));
    return -1;
  }

  float vertices[] = {-0.5f, -0.5f, 0.0f, 0.5f, -0.5f, 0.0f, 0.0f, 0.5f, 0.0f};

  unsigned int VBO;
  glGenBuffers(1, &VBO);
  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

  const char *vertex_shader_src =
      "#version 330 core\n"
      "layout (location = 0) in vec3 aPos;\n"
      "void main()\n"
      "{\n"
      "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
      "}\0";

  unsigned int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
  glShaderSource(vertex_shader, 1, &vertex_shader_src, NULL);
  glCompileShader(vertex_shader);

  int success;
  char info_log[512];
  glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);

  if (!success) {
    glGetShaderInfoLog(vertex_shader, 512, NULL, info_log);
    printf("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n%s\n", info_log);
  }

  const char *fragment_shader_src =
      "#version 330 core\n"
      "out vec4 FragColor;\n"
      "void main()\n"
      "{\n"
      " FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
      "}\0";

  unsigned int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
  glShaderSource(fragment_shader, 1, &fragment_shader_src, NULL);
  glCompileShader(fragment_shader);
  glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);

  if (!success) {
    glGetShaderInfoLog(fragment_shader, 512, NULL, info_log);
    printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n%s\n", info_log);
  }

  unsigned int shader_program = glCreateProgram();
  glAttachShader(shader_program, vertex_shader);
  glAttachShader(shader_program, fragment_shader);
  glLinkProgram(shader_program);

  glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
  if (!success) {
    glGetProgramInfoLog(shader_program, 512, NULL, info_log);
    printf("ERROR::SHADER::PROGRAM::LINK_FAILED\n%s\n", info_log);
  }

  glDeleteShader(vertex_shader);
  glDeleteShader(fragment_shader);

  unsigned int VAO;
  glGenVertexArrays(1, &VAO);
  glBindVertexArray(VAO);

  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
  glEnableVertexAttribArray(0);

  // Main loop
  while (!glfwWindowShouldClose(window)) {
    glClearColor(0.1f, 0.1f, 0.25f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glUseProgram(shader_program);
    glBindVertexArray(VAO);
    glDrawArrays(GL_TRIANGLES, 0, 3);

    glfwSwapBuffers(window);
    glfwPollEvents();
  }

  glfwTerminate();
  return 0;
}