using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using MonoGame.Framework.Utilities;
using System;

namespace SemiColinGames {
  public class SneakGame : Game {
    const int TARGET_FPS = 60;
    const double TARGET_FRAME_TIME = 1.0 / TARGET_FPS;

    readonly GraphicsDeviceManager graphics;

    bool fullScreen = false;
    bool paused = false;
    IDisplay display;

    readonly History<Input> input = new History<Input>(2);

    readonly FpsCounter fpsCounter = new FpsCounter();
    readonly Timer updateTimer = new Timer(TARGET_FRAME_TIME / 2.0, "UpdateTimer");
    readonly Timer drawTimer = new Timer(TARGET_FRAME_TIME / 2.0, "DrawTimer");

    IScene scene;
    IWorld world;

    public SneakGame() {
      Debug.WriteLine("MonoGame platform: " + PlatformInfo.MonoGamePlatform +
          " w/ graphics backend: " + PlatformInfo.GraphicsBackend);
      graphics = new GraphicsDeviceManager(this) {
        SynchronizeWithVerticalRetrace = true,
        GraphicsProfile = GraphicsProfile.HiDef
      };
      IsFixedTimeStep = true;
      TargetElapsedTime = TimeSpan.FromSeconds(TARGET_FRAME_TIME);
      IsMouseVisible = true;
      Content.RootDirectory = "Content";
    }

    // Performs initialization that's needed before starting to run.
    protected override void Initialize() {
      display = (IDisplay) Services.GetService(typeof(IDisplay));
      display.Initialize(Window, graphics);
      display.SetFullScreen(fullScreen);

      Debug.Initialize(GraphicsDevice);

      RasterizerState rasterizerState = new RasterizerState() {
        CullMode = CullMode.None
      };
      GraphicsDevice.RasterizerState = rasterizerState;

      base.Initialize();
    }

    // Called once per game. Loads all game content.
    protected override void LoadContent() {
      base.LoadContent();
      SoundEffects.Load(Content);
      Textures.Load(Content);
      Sprites.Load(Content);
      LoadLevel();
    }

    private void LoadLevel() {
      world?.Dispose();
      world = new World(GraphicsDevice, Content.LoadString("levels/demo.json"));
      scene?.Dispose();
      scene = new Scene(GraphicsDevice, world.Camera);

      GC.Collect();
      GC.WaitForPendingFinalizers();
    }

    // Called once per game. Unloads all game content.
    protected override void UnloadContent() {
      base.UnloadContent();
      updateTimer.DumpStats();
      drawTimer.DumpStats();
    }

    // Updates the game world.
    protected override void Update(GameTime gameTime) {
      updateTimer.Start();
      input.Add(new Input(GamePad.GetState(PlayerIndex.One), Keyboard.GetState()));

      if (input[0].Exit) {
        Exit();
      }

      if (input[0].Pause && !input[1].Pause) {
        paused = !paused;
      }

      if (input[0].FullScreen && !input[1].FullScreen) {
        fullScreen = !fullScreen;
        display.SetFullScreen(fullScreen);
      }

      if (input[0].Restart && !input[1].Restart) {
        LoadLevel();
      }

      Debug.Clear(paused);
      if (input[0].Debug && !input[1].Debug) {
        Debug.Enabled = !Debug.Enabled;
      }

      if (!paused) {
        double modelTime = gameTime.ElapsedGameTime.TotalSeconds;
        // To prevent huge diffs, never update by more than 4 frames' worth of time.
        modelTime = Math.Min(modelTime, TARGET_FRAME_TIME * 4.0f);
        Clock.AddModelTime(modelTime);
        world.Update((float) modelTime, input);
      }

      base.Update(gameTime);
      updateTimer.Stop();
    }

    // Called when the game should draw itself.
    protected override void Draw(GameTime gameTime) {
      drawTimer.Start();

      // We need to update the FPS counter in Draw() since Update() might get called more
      // frequently, especially when gameTime.IsRunningSlowly.
      fpsCounter.Update();
      string fpsText = $"{GraphicsDevice.Viewport.Width}x{GraphicsDevice.Viewport.Height}, " +
        $"{fpsCounter.Fps} FPS";
      if (paused) {
        fpsText += " (paused)";
      }

      Debug.SetFpsText(fpsText);

      scene.Draw(gameTime.IsRunningSlowly, world, paused);

      base.Draw(gameTime);
      drawTimer.Stop();
    }
  }
}