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

using System;
using System.Collections.Generic;

namespace Jumpy {
  public class JumpyGame : Game {
    GraphicsDeviceManager graphics;

    // TODO: use a History<RenderTarget2D> but implement functions that let us re-use the
    // RenderTargets instead of re-creating them every frame?
    const int numRenderTargets = 1;
    RenderTarget2D[] renderTargets = new RenderTarget2D[numRenderTargets];
    int renderTargetIdx = 0;

    SpriteBatch spriteBatch;
    SpriteFont font;
    bool fullScreen = false;
    IDisplay display;

    History<KeyboardState> keyboard = new History<KeyboardState>(2);
    History<GamePadState> gamePad = new History<GamePadState>(2);

    FpsCounter fpsCounter = new FpsCounter();
    Texture2D grasslandBg1;
    Texture2D grasslandBg2;

    Player player;
    World world;

    public JumpyGame() {
      graphics = new GraphicsDeviceManager(this);
      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);

      for (int i = 0; i < renderTargets.Length; i++) {
        renderTargets[i] = 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() {
      Console.WriteLine("LoadContent()");
      spriteBatch = new SpriteBatch(GraphicsDevice);
      font = Content.Load<SpriteFont>("font");
      // TODO: decouple things like Player and World from their textures.
      player = new Player(Content.Load<Texture2D>("player_1x"));
      world = new World(Content.Load<Texture2D>("grassland"));
      // TODO: move backgrounds into World.
      grasslandBg1 = Content.Load<Texture2D>("grassland_bg1");
      grasslandBg2 = Content.Load<Texture2D>("grassland_bg2");
    }

    // Called once per game. Unloads all game content.
    protected override void UnloadContent() {
      // TODO: Unload any non ContentManager content here.
    }

    // Updates the game world.
    protected override void Update(GameTime gameTime) {
      Debug.Clear();

      gamePad.Add(GamePad.GetState(PlayerIndex.One));
      keyboard.Add(Keyboard.GetState());

      if (keyboard[0].IsKeyDown(Keys.Escape) || gamePad[0].IsButtonDown(Buttons.Start)) {
        Exit();
      }

      if (keyboard[0].IsKeyDown(Keys.F12) && keyboard[1].IsKeyUp(Keys.F12) ||
          gamePad[0].IsButtonDown(Buttons.Back) && gamePad[1].IsButtonUp(Buttons.Back)) {
        fullScreen = !fullScreen;
        display.SetFullScreen(fullScreen);
      }

      if (gamePad[0].IsButtonDown(Buttons.LeftShoulder) &&
          gamePad[1].IsButtonUp(Buttons.LeftShoulder)) {
        Debug.Enabled = !Debug.Enabled;
      }

      List<Rectangle> collisionTargets = world.CollisionTargets();
      player.Update(gameTime, gamePad, collisionTargets);

      base.Update(gameTime);
    }

    // Called when the game should draw itself.
    protected override void Draw(GameTime gameTime) {
      // We need to update the FPS counter in Draw() since Update() might get called more
      // frequently, especially when gameTime.IsRunningSlowly.
      fpsCounter.Update();

      // Draw scene to RenderTarget.
      RenderTarget2D renderTarget = renderTargets[renderTargetIdx];
      renderTargetIdx = (renderTargetIdx + 1) % renderTargets.Length;
      GraphicsDevice.SetRenderTarget(renderTarget);
      GraphicsDevice.Clear(Color.CornflowerBlue);
      spriteBatch.Begin();

      // Draw background.
      Rectangle bgSource = new Rectangle(
        0, grasslandBg1.Height - Camera.Height, Camera.Width, Camera.Height);
      Rectangle bgTarget = new Rectangle(0, 0, Camera.Width, Camera.Height);
      spriteBatch.Draw(grasslandBg2, bgTarget, bgSource, Color.White);
      spriteBatch.Draw(grasslandBg1, bgTarget, bgSource, Color.White);

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

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

      // Draw debug rects.
      Debug.Draw(spriteBatch);

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

      // Draw RenderTarget to screen.
      GraphicsDevice.SetRenderTarget(null);
      GraphicsDevice.Clear(Color.Black);
      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);
      string fpsText = $"{GraphicsDevice.Viewport.Width}x{GraphicsDevice.Viewport.Height}, " +
        $"{fpsCounter.Fps} FPS";
      spriteBatch.DrawString(font, fpsText, new Vector2(10, 10), Color.White);
      spriteBatch.End();

      base.Draw(gameTime);
    }
  }
}