#include <GL/glew.h>

#include "shape_renderer.h"
#include "debug/debug_stats.h"
#include "math/math.h"

ShapeRenderer::ShapeRenderer(unsigned int screen_width, unsigned int screen_height) {
  math::ortho_proj(_projection, 0.0f, (float)screen_width, 0.0f, (float)screen_height, -1.0f, 1.0f);

  /* Load shader. */
  _shape_shader = new Shader("assets/shaders/shape.vert",
                             "assets/shaders/shape.frag");
  _shape_shader->use();
  _shape_shader->set_mat4("projection", _projection);

  /* Configure VAO/VBO for batch rendering. */
  glGenVertexArrays(1, &_vao);
  glGenBuffers(1, &_vbo);
  glBindVertexArray(_vao);
  glBindBuffer(GL_ARRAY_BUFFER, _vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(ShapeVertex) * MAX_SHAPE_VERTICES, nullptr, GL_DYNAMIC_DRAW);

  /* Position attribute. */
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(ShapeVertex), (void*)0);
  /* Colour attribute. */
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(ShapeVertex), (void*)offsetof(ShapeVertex, r));

  glBindBuffer(GL_ARRAY_BUFFER, 0);
  glBindVertexArray(0);

  _vertices.reserve(MAX_SHAPE_VERTICES);
}

ShapeRenderer::~ShapeRenderer(void) {
  delete _shape_shader;
}

void ShapeRenderer::begin(void) {
  _vertices.clear();
}

void ShapeRenderer::flush(void) {
  if(_vertices.empty()) return;

  _shape_shader->use();
  glBindVertexArray(_vao);

  glBindBuffer(GL_ARRAY_BUFFER, _vbo);
  glBufferSubData(GL_ARRAY_BUFFER, 0, _vertices.size() * sizeof(ShapeVertex), _vertices.data());

  DebugStats::draw_calls++;
  DebugStats::shape_vertices += _vertices.size();

  glDrawArrays(GL_TRIANGLES, 0, _vertices.size());

  glBindBuffer(GL_ARRAY_BUFFER, 0);
  glBindVertexArray(0);
}

void ShapeRenderer::draw_rect(int x, int y, int width, int height, const Color& color) {
  float x_f = (float)x;
  float y_f = (float)y;
  float w_f = (float)width;
  float h_f = (float)height;

  _vertices.push_back({x_f,       y_f+h_f,    color.r, color.g, color.b});
  _vertices.push_back({x_f,       y_f,        color.r, color.g, color.b});
  _vertices.push_back({x_f+w_f,   y_f,        color.r, color.g, color.b});

  _vertices.push_back({x_f,       y_f+h_f,    color.r, color.g, color.b});
  _vertices.push_back({x_f+w_f,   y_f,        color.r, color.g, color.b});
  _vertices.push_back({x_f+w_f,   y_f+h_f,    color.r, color.g, color.b});
}

void ShapeRenderer::draw_triangle(int x1, int y1, int x2, int y2, int x3,
                                  int y3, const Color& color) {
  _vertices.push_back({(float)x1, (float)y1, color.r, color.g, color.b});
  _vertices.push_back({(float)x2, (float)y2, color.r, color.g, color.b});
  _vertices.push_back({(float)x3, (float)y3, color.r, color.g, color.b});
}