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

void on_resize(GLFWwindow *win, int width, int height) {
  glViewport(0, 0, width, height);
}

void get_max_attrib_count(int *attrib_count) {
  glGetIntegerv(GL_MAX_VERTEX_ATTRIBS, attrib_count);
  printf("Max vertex attribs %d\n", *attrib_count);
}

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);

  GLFWwindow *window = glfwCreateWindow(320, 240, "Blue screen", NULL, NULL);
  if (!window) {
    glfwTerminate();
    return -1;
  }

  glfwSetFramebufferSizeCallback(window, (void *)on_resize);
  glfwMakeContextCurrent(window);

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

  int attrib_count;
  get_max_attrib_count(&attrib_count);

  float vertices[] = {
      0.5f,  0.5f,  0.0f, // top right
      0.5f,  -0.5f, 0.0f, // bottom right
      -0.5f, -0.5f, 0.0f, // bottom left
      -0.5f, 0.5f,  0.0f  // top left
  };
  unsigned int indices[] = {
      0, 1, 3, // first triangle
      1, 2, 3  // second triangle
  };

  unsigned int VBO;
  glGenBuffers(1, &VBO);
  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 6 * 3, vertices,
               GL_STATIC_DRAW);

  const char *vertex_shader_src =
      "#version 330 core\n"
      "layout (location = 0) in vec3 aPos;\n"
      "out vec4 vertexColor;\n"
      "void main()\n"
      "{\n"
      "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
      "   vertexColor = vec4(0.5, 0.0, 0.0, 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"
                                    "uniform vec4 ourColor;\n"
                                    "void main()\n"
                                    "{\n"
                                    " FragColor = ourColor;\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);

  unsigned int EBO;
  glGenBuffers(1, &EBO);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(float) * 2 * 3, indices,
               GL_STATIC_DRAW);

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

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

    glUseProgram(shader_program);
    float time_value = glfwGetTime();
    float green_value = (sin(time_value) / 2.0f) + 0.5f;
    int vertex_color_location =
        glGetUniformLocation(shader_program, "ourColor");

    glUniform4f(vertex_color_location, 0.0f, green_value, 0.0f, 1.0f);

    glBindVertexArray(VAO);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);

    glfwSwapBuffers(window);
    glfwPollEvents();
  }

  glfwTerminate();
  return 0;
}