using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;

namespace SemiColinGames {
  class Scene : IDisposable {
    const float DESIRED_ASPECT_RATIO = 1920.0f / 1080.0f;

    public bool Enabled = false;

    Color backgroundColor = Color.CornflowerBlue;

    readonly GraphicsDevice graphics;
    readonly Camera camera;

    readonly RenderTarget2D sceneTarget;
    readonly BasicEffect basicEffect;
    readonly SpriteBatch spriteBatch;

    public Scene(GraphicsDevice graphics, Camera camera) {
      this.graphics = graphics;
      this.camera = camera;

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

      basicEffect = new BasicEffect(graphics) {
        World = Matrix.CreateTranslation(0, 0, 0),
        View = Matrix.CreateLookAt(Vector3.Backward, Vector3.Zero, Vector3.Up),
        VertexColorEnabled = true
      };

      spriteBatch = new SpriteBatch(graphics);
    }

    ~Scene() {
      Dispose();
    }

    public void Dispose() {
      sceneTarget.Dispose();
      basicEffect.Dispose();
      spriteBatch.Dispose();
      GC.SuppressFinalize(this);
    }

    public void Draw(World world, Player player, LinesOfSight linesOfSight) {
      graphics.SetRenderTarget(null);
      graphics.Clear(backgroundColor);
      if (!Enabled) {
        return;
      }

      // Draw scene to sceneTarget.
      graphics.SetRenderTarget(sceneTarget);
      graphics.Clear(backgroundColor);

      // Draw parallax backgrounds.
      spriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null);
      Rectangle bgTarget = new Rectangle(0, 0, camera.Width, camera.Height);

      float xScale = 1f / 16;
      for (int i = 0; i < Textures.Backgrounds.Length; i++) {
        int yOffset = Textures.Backgrounds[i].Get.Height - camera.Height - 24;
        Rectangle bgSource = new Rectangle(
          (int) (camera.Left * xScale), yOffset, camera.Width, camera.Height);
        spriteBatch.Draw(Textures.Backgrounds[i].Get, bgTarget, bgSource, Color.White);
        xScale *= 2;
      }
      spriteBatch.End();

      // Draw lines of sight.
      basicEffect.Projection = camera.Projection;
      if (Debug.Enabled) {
        linesOfSight.Draw(graphics, basicEffect);
      }

      // 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 background tiles.
      world.DrawBackground(spriteBatch);

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

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

      // Draw debug rects & lines on top.
      Debug.Draw(graphics, basicEffect);

      // Get ready to draw sceneTarget to screen.
      graphics.SetRenderTarget(null);

      // Letterbox the scene if needed.
      float aspectRatio = 1.0f * graphics.Viewport.Width / graphics.Viewport.Height;
      Rectangle drawRect;
      if (aspectRatio > DESIRED_ASPECT_RATIO) {
        // Need to letterbox the sides.
        int desiredWidth = (int) (graphics.Viewport.Height * DESIRED_ASPECT_RATIO);
        int padding = (graphics.Viewport.Width - desiredWidth) / 2;
        drawRect = new Rectangle(padding, 0, desiredWidth, graphics.Viewport.Height);
      } else {
        // Need to letterbox the top / bottom.
        int desiredHeight = (int) (graphics.Viewport.Width / DESIRED_ASPECT_RATIO);
        int padding = (graphics.Viewport.Height - desiredHeight) / 2;
        drawRect = new Rectangle(0, padding, graphics.Viewport.Width, desiredHeight);
      }

      // Actually draw to screen.
      spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend,
          SamplerState.PointClamp, DepthStencilState.Default,
          RasterizerState.CullNone);
      spriteBatch.Draw(sceneTarget, drawRect, Color.White);

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

      spriteBatch.End();
    }
  }
}