#include <GL/glew.h>
#include <SDL3/SDL_error.h>
#include <algorithm>
/* FINE LSP!! I'll play your games!!!! */
#include <SDL3/SDL_events.h> /* ~HJAPPY?!?!?! */
#include <SDL3/SDL_stdinc.h>
#include <SDL3/SDL_timer.h>
#include <SDL3/SDL_video.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <cstdlib>
#include <set>
#include <cstdio>
#include <string>

#include "bettola.h"
#include "bettola/network/net_common.h"
#include "game/remote_player.h"
#include "math/mat4.h"
#include "network/message.h"
#include "network/game_state_message.h"
#include "network/player_input_message.h"

/* Dacav's resolution ;) */
const int SCREEN_WIDTH  = 800;
const int SCREEN_HEIGHT = 600;

Bettola::Bettola(void) :
    _is_running(false),
    _window(nullptr),
    _gl_context(nullptr),
    _vao(0),
    _vbo(0),
    _our_player_id(0),
    _input_sequence_number(0) {

  memset(&_server_addr, 0, sizeof(_server_addr));
}

Bettola::~Bettola(void) {
  if(_gl_context) {
    SDL_GL_DestroyContext(_gl_context);
  }

  /* Explicitly close client socket. */
  _tcp_socket.close();
  _udp_socket.close();

  if(_window) {
    SDL_DestroyWindow(_window);
  }

  SDL_Quit();

  if(_gl_context) {
    /* Should only be deleted if it was successfully created
     * and if _gl_context is valid.
     */
    glDeleteVertexArrays(1, &_vao);
    glDeleteBuffers(1, &_vbo);
  }
}

int Bettola::run(void) {
  if(!init_sdl())               return -1;
  if(!create_window())          return -1;
  if(!create_gl_context())      return -1;
  if(!init_client_connection()) return -1;
  if(!init_glew())              return -1;

  if(!_shader.load_from_files("assets/shaders/simple.vert",
                             "assets/shaders/simple.frag")) {
    return -1;
  }

  _projection = BettolaMath::Mat4::orthographic(0.0f, 800.0f, 600.0f, 0.0f, -1.0f, 1.0f);
  _shader.use();
  unsigned int proj_loc = glGetUniformLocation(_shader.get_id(), "projection");
  glUniformMatrix4fv(proj_loc, 1, GL_FALSE, _projection.get_ptr());

  setup_quad();

  glViewport(0,0,SCREEN_WIDTH, SCREEN_HEIGHT);

  _is_running = true;

  Uint64 perf_freq  = SDL_GetPerformanceFrequency();
  Uint64 last_count = SDL_GetPerformanceCounter();
  double delta_time = 0;

  while(_is_running) {
    Uint64 current_counter = SDL_GetPerformanceCounter();
    delta_time = (double)(current_counter-last_count) / (double)perf_freq;
    last_count = current_counter;

    process_events();
    process_network();
    update(delta_time);
    render();
  }

  return 0;
}

void Bettola::process_events(void) {
  SDL_Event event;
  while(SDL_PollEvent(&event)) {
    if(event.type == SDL_EVENT_QUIT) {
      _is_running = false;
    } else if(event.type == SDL_EVENT_KEY_DOWN) {
      switch(event.key.key) {
        case SDLK_W: _input.up    = true; break;
        case SDLK_S: _input.down  = true; break;
        case SDLK_A: _input.left  = true; break;
        case SDLK_D: _input.right = true; break;
      }
    } else if(event.type == SDL_EVENT_KEY_UP) {
      switch(event.key.key) {
        case SDLK_W: _input.up    = false; break;
        case SDLK_S: _input.down  = false; break;
        case SDLK_A: _input.left  = false; break;
        case SDLK_D: _input.right = false; break;
      }
    }
  }
}

void Bettola::process_network(void) {
  fd_set read_fds;
  FD_ZERO(&read_fds);

  int tcp_fd = _tcp_socket.get_sockfd();
  int udp_fd = _udp_socket.get_sockfd();

  FD_SET(tcp_fd, &read_fds);
  FD_SET(udp_fd, &read_fds);

  int max_fd = std::max(tcp_fd, udp_fd);

  struct timeval tv;
  tv.tv_sec = 0;
  tv.tv_usec = 0; /* Non-blocking. */

  int activity = select(max_fd+1, &read_fds, nullptr, nullptr, &tv);

  if(activity > 0) {
    if(FD_ISSET(tcp_fd, &read_fds)) {
      /* We only expect player ID assignment for now. */
      if(_our_player_id == 0) {
        BettolaLib::Network::MessageHeader id_header;
        ssize_t id_bytes_received = _tcp_socket.recv(&id_header, sizeof(id_header));
        if(id_bytes_received > 0 && id_header.type == BettolaLib::Network::MessageType::PlayerId) {
          _tcp_socket.recv(&_our_player_id, sizeof(_our_player_id));
          printf("Bettola: Assigned player ID: %u\n", _our_player_id);
        }
      }
    }

    if(FD_ISSET(udp_fd, &read_fds)) {
      process_udp_messages();
    }
  }
}

void Bettola::process_udp_messages(void) {
  char buffer[1024];
  sockaddr_in from_addr;
  ssize_t id_bytes_received;

  while((id_bytes_received = _udp_socket.recv_from(buffer,sizeof(buffer),from_addr))>0) {
    if(id_bytes_received < sizeof(BettolaLib::Network::MessageHeader)) {
      continue;
    }

    BettolaLib::Network::MessageHeader header;
    memcpy(&header, buffer, sizeof(header));
    memcpy(&header, buffer, sizeof(header));

    const char* payload = buffer + sizeof(BettolaLib::Network::MessageHeader);
    size_t payload_size = id_bytes_received-sizeof(BettolaLib::Network::MessageHeader);

    if(header.type == BettolaLib::Network::MessageType::GameState) {
      if(payload_size >= sizeof(BettolaLib::Network::GameStateMessage)) {
        BettolaLib::Network::GameStateMessage msg;
        memcpy(&msg, payload, sizeof(msg));
        process_game_state(msg);
      }
    }
  }
}

void Bettola::update(double dt) {
  float dir_x = 0.0f;
  float dir_y = 0.0f;
  if(_input.up)     dir_y -= 1.0f;
  if(_input.down)   dir_y += 1.0f;
  if(_input.left)   dir_x -= 1.0f;
  if(_input.right)  dir_x += 1.0f;
  _player.set_velocity_direction(dir_x, dir_y);

  _player.update(dt);

  for(auto& remote_player : _remote_players) {
    remote_player.update(dt);
  }

  if(_our_player_id > 0) {
    /* Sent our current input state to the server. */
    BettolaLib::Network::PlayerInputMessage input_msg;
    input_msg.player_id = _our_player_id;
    input_msg.sequence_number = ++_input_sequence_number;
    input_msg.up    = _input.up;
    input_msg.down  = _input.down;
    input_msg.left  = _input.left;
    input_msg.right = _input.right;
    input_msg.dt = dt;

    BettolaLib::Network::MessageHeader header;
    header.type = BettolaLib::Network::MessageType::PlayerInput;
    header.size = sizeof(input_msg);

    char buffer[sizeof(header) + sizeof(input_msg)];
    memcpy(buffer, &header, sizeof(header));
    memcpy(buffer+sizeof(header), &input_msg, sizeof(input_msg));

    _udp_socket.send_to(buffer, sizeof(buffer), _server_addr);

    /* Store for reconciliation. */
    _pending_inputs.push_back(input_msg);
  }

  static char window_title[256];
  static double time_since_title_update = 0.0;

  time_since_title_update += dt;
  if(time_since_title_update > 0.25) {
    snprintf(window_title, 256, "Bettola - FPS %.2f", 1.0/dt);
    SDL_SetWindowTitle(_window, window_title);
    time_since_title_update = 0.0;
  }
}

void Bettola::render(void) {
  glClearColor(0.1f, 0.1f, 0.3f, 1.0f);
  glClear(GL_COLOR_BUFFER_BIT);

  _shader.use();

  BettolaMath::Mat4 trans_matrix = BettolaMath::Mat4::translation(_player.get_x(),
                                                                  _player.get_y(), 0.0f);

  BettolaMath::Mat4 scale_matrix = BettolaMath::Mat4::scale(_player.get_width(),
                                                            _player.get_height(), 1.0f);

  BettolaMath::Mat4 model= trans_matrix.multiply(scale_matrix);

  unsigned int model_loc = glGetUniformLocation(_shader.get_id(), "model");
  glUniformMatrix4fv(model_loc, 1, GL_FALSE, model.get_ptr());

  glBindVertexArray(_vao);
  glDrawArrays(GL_TRIANGLES, 0, 6);
  glBindVertexArray(0);

  /* Render remote players. */
  for(const auto& remote_player : _remote_players) {
    BettolaMath::Mat4 remote_trans_matrix =
      BettolaMath::Mat4::translation(remote_player.get_x(),
                                     remote_player.get_y(),
                                     0.0f);

    BettolaMath::Mat4 remote_scale_matrix =
      /* Assuming remote players have same size as local player. */
      BettolaMath::Mat4::scale(50.0f, 50.0f, 1.0f);

    BettolaMath::Mat4 remote_model = remote_trans_matrix.multiply(remote_scale_matrix);

    glUniformMatrix4fv(model_loc, 1, GL_FALSE, remote_model.get_ptr());

    glBindVertexArray(_vao);
    glDrawArrays(GL_TRIANGLES, 0, 6);
    glBindVertexArray(0);
  }

  SDL_GL_SwapWindow(_window);
}

void Bettola::process_game_state(const BettolaLib::Network::GameStateMessage& msg) {
  /* Track remote players each update. */
  std::set<unsigned int> players_in_message;

  for(unsigned int i = 0; i < msg.num_players; ++i) {
    const auto& player_state = msg.players[i];

    if(player_state.player_id == _our_player_id) {
      /* This is our player. Reconcile. */
      _player.set_position(player_state.x, player_state.y);

      /* Remove all inputs from our history that the server has processed. */
      while(!_pending_inputs.empty() &&
          _pending_inputs.front().sequence_number <= player_state.last_processed_sequence) {

        _pending_inputs.pop_front();
      }

      /* Now, re-apply any remaining inputs that the server hasn't
       * seen yet. This'll bring the client up to date with most recent inputs.
       */
      for(const auto& input : _pending_inputs) {
        float dir_x = (input.right ? 1.0f : 0.0f) - (input.left ? 1.0f : 0.0f);
        float dir_y = (input.down  ? 1.0f : 0.0f) - (input.up   ? 1.0f : 0.0f);
        _player.set_velocity_direction(dir_x, dir_y);
        _player.update(input.dt);
      }
    } else {
      /* Remote player. Find if we already know about them.. */
      players_in_message.insert(player_state.player_id);
      auto it = std::find_if(_remote_players.begin(), _remote_players.end(),
                             [&](const RemotePlayer& p) {
                                return p.get_id() == player_state.player_id;
                             });

      if(it != _remote_players.end()) {
        /* Found 'em! update their target pos. */
        it->set_target_position(player_state.x, player_state.y);
      } else {
        /* They are new, add them to our list. */
        _remote_players.emplace_back(player_state.player_id, player_state.x, player_state.y);
      }
    }
  }
  _remote_players.erase(
    std::remove_if(_remote_players.begin(), _remote_players.end(),
                   [&](const RemotePlayer& p) {
                      return players_in_message.find(p.get_id()) == players_in_message.end();
                   }),

    _remote_players.end());
}

bool Bettola::init_sdl(void) {
  if(!SDL_Init(SDL_INIT_VIDEO)) {
    fprintf(stderr, "Failed to iniit SDL! SDL ERROR: %s\n", SDL_GetError());
    return false;
  }
  return true;
}

bool Bettola::init_glew(void) {
  glewExperimental = GL_TRUE;
  GLenum glew_error = glewInit();
  if(glew_error != GLEW_OK) {
    fprintf(stderr, "Failed to init GLEW! %s\n", glewGetErrorString(glew_error));
    return false;
  }
  return true;
}

bool Bettola::create_window(void) {
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

  /* Don't you dare f.ckin fail to open!!!!! */
  _window = SDL_CreateWindow("Bettola Makes No Sense!", SCREEN_WIDTH, SCREEN_HEIGHT,
                              SDL_WINDOW_OPENGL);

  if(!_window) {
    fprintf(stderr, "Failed to create window! SDL_ERROR: %s\n", SDL_GetError());
    return false;
  }

  return true;
}

bool Bettola::create_gl_context(void) {
  _gl_context = SDL_GL_CreateContext(_window);
  if(!_gl_context) {
    fprintf(stderr, "Failed to create OpenGL context! SDL_ERROR: %s\n", SDL_GetError());
    return false;
  }
  return true;
}

void Bettola::setup_quad(void) {
  float vertices[] = {
    /* Should be a quad??!?? */
    -0.5f, -0.5f, 0.0f,
     0.5f, -0.5f, 0.0f,
     0.5f,  0.5f, 0.0f,
     0.5f,  0.5f, 0.0f,
    -0.5f,  0.5f, 0.0f,
    -0.5f, -0.5f, 0.0f,
  };

  glGenVertexArrays(1, &_vao);
  glGenBuffers(1, &_vbo);

  glBindVertexArray(_vao);

  glBindBuffer(GL_ARRAY_BUFFER, _vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

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

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

bool Bettola::init_client_connection(void) {
  SDL_Delay(1000); /* Wait a second before trying to connect. */
  if(!_tcp_socket.create()) {
    printf("Bettola client: Failed to create socket.\n");
    return false;
  }

  if(!_tcp_socket.connect("127.0.0.1", BettolaLib::Network::DEFAULT_PORT)) {
    perror("Bettola Client: Failed to connect to server.\n");
    return false;
  }

  if(!_udp_socket.create()) {
    printf("Bettola Client: Failed to create UDP socket.\n");
    return false;
  }

  /* Setup server address for UDP. */
  _server_addr.sin_family = AF_INET;
  _server_addr.sin_port = htons(BettolaLib::Network::DEFAULT_PORT);
  inet_pton(AF_INET, "127.0.0.1", &_server_addr.sin_addr);

  /* Set the socket to non-blocking. */
  int flags = fcntl(_tcp_socket.get_sockfd(), F_GETFL, 0);
  if(flags == -1) {
    perror("fcntl F_GETFL failed.");
    return false;
  }
  fcntl(_tcp_socket.get_sockfd(), F_SETFL, flags | O_NONBLOCK);
  fcntl(_udp_socket.get_sockfd(), F_SETFL, flags | O_NONBLOCK);

  printf("Bettola Client: Connected to server at 127.0.01.:%hu\n", BettolaLib::Network::DEFAULT_PORT);
  return true;
}