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

namespace SemiColinGames {
  static class Debug {
    struct DebugRect {
      public Rectangle Rect;
      public Color Color;

      public DebugRect(Rectangle rect, Color color) {
        Rect = rect;
        Color = color;
      }
    }

    struct DebugLine {
      public Point Start;
      public Point End;
      public Color Color;

      public DebugLine(Point start, Point end, Color color) {
        Start = start;
        End = end;
        Color = color;
      }
    }

    public static bool Enabled = true;
    // Lines in excess of MAX_LINES get dropped on the floor.
    const int MAX_LINES = 1000;
    const int MAX_LINE_VERTICES = MAX_LINES * 2;
    // This is a LinkedList instead of a List because SetFpsText() adds to its front.
    static readonly LinkedList<string> toasts = new LinkedList<string>();
    static readonly List<DebugRect> rects = new List<DebugRect>();
    static int lineIdx = 0;
    static readonly VertexPositionColor[] lineVertices = new VertexPositionColor[MAX_LINE_VERTICES];
    static VertexBuffer vertexBuffer;

    static Texture2D whiteTexture;

    public static void Initialize(GraphicsDevice graphics, Texture2D white) {
      whiteTexture = white;
      vertexBuffer = new VertexBuffer(
          graphics, typeof(VertexPositionColor), MAX_LINE_VERTICES, BufferUsage.WriteOnly);
    }

    public static void WriteLine(string s) {
      System.Diagnostics.Debug.WriteLine(s);
    }

    public static void WriteLine(string s, params object[] args) {
      System.Diagnostics.Debug.WriteLine(s, args);
    }

    public static void Clear(bool paused) {
      toasts.Clear();
      if (!paused) {
        rects.Clear();
        lineIdx = 0;
      }
    }

    public static void AddToast(string s) {
      toasts.AddLast(s);
    }

    // FPS text is always displayed as the first toast (if set).
    public static void SetFpsText(string s) {
      toasts.AddFirst(s);
    }

    public static void AddRect(Rectangle rect, Color color) {
      rects.Add(new DebugRect(rect, color));
    }

    public static void AddRect(AABB box, Color color) {
      Rectangle rect = new Rectangle(
          (int) (box.Position.X - box.HalfSize.X), (int) (box.Position.Y - box.HalfSize.Y),
          (int) (box.HalfSize.X * 2), (int) (box.HalfSize.Y * 2));
      AddRect(rect, color);
    }

    public static void AddLine(Point start, Point end, Color color) {
      if (lineIdx >= MAX_LINE_VERTICES) {
        return;
      }
      lineVertices[lineIdx] = new VertexPositionColor(new Vector3(start.X, start.Y, 0), color);
      lineVertices[lineIdx + 1] = new VertexPositionColor(new Vector3(end.X, end.Y, 0), color);
      lineIdx += 2;
    }

    public static void AddLine(int p1x, int p1y, int p2x, int p2y, Color color) {
      AddLine(new Point(p1x, p1y), new Point(p2x, p2y), color);
    }

    public static void AddLine(Vector2 start, Vector2 end, Color color) {
      AddLine(start.ToPoint(), end.ToPoint(), color);
    }

    public static void DrawToasts(SpriteBatch spriteBatch, SpriteFont font) {
      if (!Enabled) {
        return;
      }
      int y = 10;
      foreach (var toast in toasts) {
        spriteBatch.DrawString(font, toast, new Vector2(10, y), Color.Teal);
        y += 30;
      }
    }

    public static void Draw(
        SpriteBatch spriteBatch, GraphicsDevice graphics, BasicEffect lightingEffect) {
      if (!Enabled) {
        return;
      }

      // Draw rects.
      foreach (var debugRect in rects) {
        var rect = debugRect.Rect;
        var color = debugRect.Color;
        // top side
        spriteBatch.Draw(
          whiteTexture, new Rectangle(rect.Left, rect.Top, rect.Width, 1), color);
        // bottom side
        spriteBatch.Draw(
          whiteTexture, new Rectangle(rect.Left, rect.Bottom - 1, rect.Width, 1), color);
        // left side
        spriteBatch.Draw(
          whiteTexture, new Rectangle(rect.Left, rect.Top, 1, rect.Height), color);
        // right side
        spriteBatch.Draw(
          whiteTexture, new Rectangle(rect.Right - 1, rect.Top, 1, rect.Height), color);
      }

      // Draw lines.
      graphics.SetVertexBuffer(vertexBuffer);
      vertexBuffer.SetData(lineVertices);
      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
        pass.Apply();
        graphics.DrawPrimitives(PrimitiveType.LineList, 0, lineIdx / 2);
      }
    }
  }
}