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 sceneTarget;
    RenderTarget2D lightingTarget;

    BasicEffect lightingEffect;

    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);

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

      lightingEffect = new BasicEffect(GraphicsDevice);
      lightingEffect.World = Matrix.CreateTranslation(0, 0, 0);
      lightingEffect.View = Matrix.CreateLookAt(Vector3.Backward, Vector3.Zero, Vector3.Up);
      lightingEffect.VertexColorEnabled = true;

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

      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"), Levels.ONE_ONE);
      grasslandBg1 = Content.Load<Texture2D>("grassland_bg1");
      grasslandBg2 = Content.Load<Texture2D>("grassland_bg2");
    }

    // Called once per game. Unloads all game content.
    protected override void 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);
      }

      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 sceneTarget.
      GraphicsDevice.SetRenderTarget(sceneTarget);
      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);
      spriteBatch.End();

      // Set up transformation matrix for drawing world objects.
      Matrix transform = Matrix.CreateTranslation(-camera.Left, -camera.Top, 0);
      spriteBatch.Begin(
          SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null, null, transform);

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

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

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

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

      // Draw lighting to lightingTarget.
      GraphicsDevice.SetRenderTarget(lightingTarget);
      GraphicsDevice.Clear(new Color(0, 0, 0, 0f));
      lightingEffect.Projection = camera.Projection;
      DrawFov();

      // Draw sceneTarget 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(sceneTarget, drawRect, Color.White);
        spriteBatch.Draw(lightingTarget, drawRect, Color.White);

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

        spriteBatch.End();
      }

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

    private void DrawFov() {
      // TODO: DrawIndexedPrimitives
      Color color = Color.FromNonPremultiplied(new Vector4(0, 0, 1, 0.6f));
      Vector2 eyePos = player.EyePosition;
      int numConePoints = 60;
      // TODO: don't new[] every frame.
      VertexPositionColor[] conePoints = new VertexPositionColor[numConePoints];
      float visionRange = 150;
      float visionRangeSq = visionRange * visionRange;
      float fov = FMath.DegToRad(120);
      float fovStep = fov / (numConePoints - 1);

      Vector2 ray = new Vector2(visionRange * player.GetFacing, 0);
      if (player.GetPose == Player.Pose.Stretching) {
        ray = ray.Rotate(player.GetFacing * FMath.DegToRad(-30));
      }
      if (player.GetPose == Player.Pose.Crouching) {
        ray = ray.Rotate(player.GetFacing * FMath.DegToRad(30));
      }

      for (int i = 0; i < conePoints.Length; i++) {
        float angle = -fov / 2 + fovStep * i;
        Vector2 rotated = ray.Rotate(angle);
        Vector2 closestHit = Vector2.Add(eyePos, rotated);
        float hitTime = 1f;

        Vector2 halfTileSize = new Vector2(World.TileSize / 2.0f, World.TileSize / 2.0f);
        for (int j = 0; j < world.CollisionTargets.Length; j++) {
          AABB box = world.CollisionTargets[j];
          if (Math.Abs(box.Position.X - player.Position.X) > visionRange + halfTileSize.X) {
            continue;
          }
          Vector2 delta = Vector2.Add(halfTileSize, Vector2.Subtract(box.Position, eyePos));
          if (delta.LengthSquared() > visionRangeSq) {
            continue;
          }
          Hit? maybeHit = box.IntersectSegment(eyePos, rotated);
          if (maybeHit != null) {
            Hit hit = maybeHit.Value;
            if (hit.Time < hitTime) {
              hitTime = hit.Time;
              closestHit = hit.Position;
            }
          }
        }

        float tint = 0.6f - hitTime / 2;
        Color tinted = Color.FromNonPremultiplied(new Vector4(0, 0, 1, tint));
        conePoints[i] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
      }

      // TODO: don't new[] every frame.
      VertexPositionColor[] vertices = new VertexPositionColor[numConePoints * 3];
      VertexPositionColor eyeVertex = new VertexPositionColor(new Vector3(eyePos, 0), color);
      for (int i = 0; i < numConePoints - 1; i++) {
        vertices[i * 3] = eyeVertex;
        vertices[i * 3 + 1] = conePoints[i];
        vertices[i * 3 + 2] = conePoints[i + 1];
      }

      VertexBuffer vertexBuffer = new VertexBuffer(
          GraphicsDevice, typeof(VertexPositionColor), vertices.Length, BufferUsage.WriteOnly);
      vertexBuffer.SetData<VertexPositionColor>(vertices);

      GraphicsDevice.SetVertexBuffer(vertexBuffer);

      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
        pass.Apply();
        GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, vertices.Length / 3);
      }
    }
  }
}