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

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

    Color backgroundColor = Color.CornflowerBlue;

    readonly GraphicsDevice graphics;
    readonly Camera camera;

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

    // 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;

    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);

      music = SoundEffects.IntroMusic.CreateInstance();
      music.IsLooped = true;
      music.Volume = 0.1f;
    }

    ~Scene() {
      Dispose();
    }

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

    public void Draw(bool isRunningSlowly, World world, bool paused) {
      graphics.SetRenderTarget(null);
      graphics.Clear(backgroundColor);

      // Enable the scene after we've gotten enough non-slow frames.
      if (framesToSuppress > 0 && !isRunningSlowly) {
        framesToSuppress--;
        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;
      world.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.
      world.Player.Draw(spriteBatch);

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

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

      // Draw in-world UI on top of everything.
      spriteBatch.Begin(
          SpriteSortMode.Deferred, null, SamplerState.PointClamp, null, null, null, null);
      for (int i = 0; i < world.Player.MaxHealth; i++) {
        Vector2 pos = new Vector2(16 + 15 * i, 8);
        if (world.Player.Health > i) {
          spriteBatch.Draw(Textures.Heart.Get, pos, new Rectangle(0, 0, 16, 16), Color.White);
        } else {
          spriteBatch.Draw(Textures.Heart.Get, pos, new Rectangle(16, 0, 16, 16), Color.White);
        }
      }

      if (paused) {
        string text = Strings.Paused;
        Vector2 position = Textures.BannerFont.CenteredOn(text, camera.HalfSize);
        Text.DrawOutlined(spriteBatch, Textures.BannerFont, text, position, Color.White);
        music.Pause();
      } else {
        music.Play();
      }
      spriteBatch.End();

      // 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.Deferred, BlendState.AlphaBlend,
          SamplerState.PointClamp, DepthStencilState.Default,
          RasterizerState.CullNone);
      spriteBatch.Draw(sceneTarget, drawRect, Color.White);

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

      spriteBatch.End();
    }
  }
}