using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

using System;
using System.Collections.Generic;

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

    readonly GraphicsDeviceManager graphics;
    RenderTarget2D renderTarget;

    SpriteBatch spriteBatch;
    SpriteFont font;
    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");
    // Draw() needs to be called without IsRunningSlowly this many times before we actually
    // attempt to draw the scene. This is a workaround for the fact that otherwise the first few
    // frames can be really slow to draw.
    int framesToSuppress = 2;
    Texture2D grasslandBg1;
    Texture2D grasslandBg2;

    Player player;
    World world;
    readonly Camera camera = new Camera();

    public SneakGame() {
      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);

      renderTarget = new RenderTarget2D(
        GraphicsDevice, camera.Width, camera.Height, false /* mipmap */,
        GraphicsDevice.PresentationParameters.BackBufferFormat, DepthFormat.Depth24);

      base.Initialize();
    }

    // Called once per game. Loads all game content.
    protected override void LoadContent() {
      spriteBatch = new SpriteBatch(GraphicsDevice);
      font = Content.Load<SpriteFont>("font");

      player = new Player(Content.Load<Texture2D>("Ninja_Female"));
      world = new World(Content.Load<Texture2D>("grassland"));
      grasslandBg1 = Content.Load<Texture2D>("grassland_bg1");
      grasslandBg2 = Content.Load<Texture2D>("grassland_bg2");
    }

    // Called once per game. Unloads all game content.
    protected override void UnloadContent() {
    }

    // 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);
      }

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

      if (!paused) {
        float modelTime = (float) gameTime.ElapsedGameTime.TotalSeconds;
        Clock.AddModelTime(modelTime);
        player.Update(modelTime, input, world.CollisionTargets);
        camera.Update(player.Position, world.Width);
      }

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

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

      if (framesToSuppress > 0 && !gameTime.IsRunningSlowly) {
        framesToSuppress--;
      }

      // 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);

      // Draw scene to RenderTarget.
      GraphicsDevice.SetRenderTarget(renderTarget);
      GraphicsDevice.Clear(Color.CornflowerBlue);
      spriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null);

      // Draw background.
      Rectangle bgSource = new Rectangle(
        (int) (camera.Left * 0.25), 0, camera.Width, camera.Height);
      Rectangle bgTarget = new Rectangle(0, 0, camera.Width, camera.Height);
      spriteBatch.Draw(grasslandBg2, bgTarget, bgSource, Color.White);
      bgSource = new Rectangle(
        (int) (camera.Left * 0.5), 0, camera.Width, camera.Height);
      spriteBatch.Draw(grasslandBg1, bgTarget, bgSource, Color.White);

      // Draw player.
      player.Draw(spriteBatch, camera);

      // Draw foreground tiles.
      world.Draw(spriteBatch, camera);

      // Draw debug rects & lines.
      Debug.Draw(spriteBatch, camera);

      // Aaaaand we're done.
      spriteBatch.End();

      // Draw RenderTarget to screen.
      GraphicsDevice.SetRenderTarget(null);
      GraphicsDevice.Clear(Color.CornflowerBlue);
      if (framesToSuppress == 0) {
        spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend,
              SamplerState.PointClamp, DepthStencilState.Default,
              RasterizerState.CullNone);
        Rectangle drawRect = new Rectangle(
          0, 0, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height);
        spriteBatch.Draw(renderTarget, drawRect, Color.White);

        // Draw debug toasts.
        Debug.DrawToasts(spriteBatch, font);

        spriteBatch.End();
      }

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