sneak/Shared/World.cs

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

namespace SemiColinGames {

  public class Terrain {

    public static Terrain FromSymbol(char symbol) {
      if (mapping.ContainsKey(symbol)) {
        return mapping[symbol];
      } else {
        return null;
      }
    }

    private readonly static Dictionary<char, Terrain> mapping = new Dictionary<char, Terrain>();

    public static Terrain Empty =
        new Terrain('\0', Textures.Grassland, 0, 0);
    public static Terrain Spike =
        new Terrain('^', Textures.Grassland, 11, 8, isObstacle: true, isHarmful: true);
    public static Terrain Grass =
        new Terrain('=', Textures.Grassland, 3, 0, isObstacle: true);
    public static Terrain GrassL =
        new Terrain('<', Textures.Grassland, 2, 0, isObstacle: true);
    public static Terrain GrassR =
        new Terrain('>', Textures.Grassland, 4, 0, isObstacle: true);
    public static Terrain Rock =
        new Terrain('.', Textures.Grassland, 3, 1, isObstacle: true);
    public static Terrain RockL =
        new Terrain('[', Textures.Grassland, 1, 2, isObstacle: true);
    public static Terrain RockR =
        new Terrain(']', Textures.Grassland, 5, 2, isObstacle: true);
    public static Terrain Block =
        new Terrain('X', Textures.Ruins, 2, 0, isObstacle: true);
    public static Terrain Wood =
        new Terrain('_', Textures.Grassland, 10, 3, isObstacle: true);
    public static Terrain WoodL =
        new Terrain('(', Textures.Grassland, 9, 3, isObstacle: true);
    public static Terrain WoodR =
        new Terrain(')', Textures.Grassland, 12, 3, isObstacle: true);
    public static Terrain WoodVert =
        new Terrain('|', Textures.Grassland, 9, 5);
    public static Terrain WoodVertL =
        new Terrain('/', Textures.Grassland, 9, 4);
    public static Terrain WoodVertR =
        new Terrain('\\', Textures.Grassland, 12, 4);
    public static Terrain WoodBottom =
        new Terrain('v', Textures.Grassland, 10, 5);
    public static Terrain WaterL =
        new Terrain('~', Textures.Grassland, 9, 2);
    public static Terrain WaterR =
        new Terrain('`', Textures.Grassland, 10, 2);
    public static Terrain FenceL =
        new Terrain('d', Textures.Grassland, 5, 4);
    public static Terrain Fence =
        new Terrain('f', Textures.Grassland, 6, 4);
    public static Terrain FencePost =
        new Terrain('x', Textures.Grassland, 7, 4);
    public static Terrain FenceR =
        new Terrain('b', Textures.Grassland, 8, 4);
    public static Terrain VineTop =
        new Terrain('{', Textures.Ruins, 12, 5);
    public static Terrain VineMid =
        new Terrain(';', Textures.Ruins, 12, 6);
    public static Terrain VineBottom =
        new Terrain('}', Textures.Ruins, 12, 7);
    public static Terrain GrassTall =
        new Terrain('q', Textures.Grassland, 13, 0);
    public static Terrain GrassShort =
        new Terrain('w', Textures.Grassland, 14, 0);
    public static Terrain Shoots =
        new Terrain('e', Textures.Grassland, 15, 0);
    public static Terrain Bush =
        new Terrain('r', Textures.Grassland, 13, 2);
    public static Terrain Mushroom =
        new Terrain('t', Textures.Grassland, 17, 2);

    public bool IsObstacle { get; private set; }
    public bool IsHarmful { get; private set; }
    public TextureRef Texture { get; private set; }
    public Rectangle TextureSource { get; private set; }

    private Terrain(
        char symbol, TextureRef texture, int x, int y,
        bool isObstacle = false, bool isHarmful = false) {
      if (mapping.ContainsKey(symbol)) {
        throw new ArgumentException("already have a terrain with symbol " + symbol);
      }
      mapping[symbol] = this;
      IsObstacle = isObstacle;
      IsHarmful = isHarmful;
      Texture = texture;
      int size = World.TileSize;
      TextureSource = new Rectangle(x * size, y * size, size, size);
    }
  }

  class Tile {
    public Tile(Terrain terrain, Rectangle position) {
      Terrain = terrain;
      Position = position;
    }

    public Rectangle Position { get; private set; }
    public Terrain Terrain { get; private set; }

    public void Draw(SpriteBatch spriteBatch) {
      spriteBatch.Draw(
          Terrain.Texture.Get, Position.Location.ToVector2(), Terrain.TextureSource, Color.White);
    }
  }

  public class World {

    public const int TileSize = 16;
    readonly Tile[] tiles;
    readonly Tile[] decorations;
    readonly NPC[] npcs = new NPC[4];

    // Size of World in terms of tile grid.
    private readonly int tileWidth;
    private readonly int tileHeight;

    public Player Player { get; private set; }

    // Size of World in pixels.
    public int Width {
      get { return tileWidth * TileSize; }
    }

    public int Height {
      get { return tileHeight * TileSize; }
    }

    public World(string levelSpecification) {
      Player = new Player();
      npcs[0] = new NPC(new Point(16 * 8, 16 * 6));
      npcs[1] = new NPC(new Point(16 * 28, 16 * 6));
      npcs[2] = new NPC(new Point(16 * 36, 16 * 6));
      npcs[3] = new NPC(new Point(16 * 36, 16 * 12));

      var tilesList = new List<Tile>();
      var decorationsList = new List<Tile>();
      string[] worldDesc = levelSpecification.Substring(1).Split('\n');
      tileWidth = worldDesc.AsQueryable().Max(a => a.Length);
      tileHeight = worldDesc.Length;
      Debug.WriteLine("world size: {0}x{1}", tileWidth, tileHeight);
      for (int i = 0; i < tileWidth; i++) {
        for (int j = 0; j < tileHeight; j++) {
          if (i < worldDesc[j].Length) {
            char key = worldDesc[j][i];
            Terrain terrain = Terrain.FromSymbol(key);
            if (terrain != null) {
              var position = new Rectangle(i * TileSize, j * TileSize, TileSize, TileSize);
              Tile tile = new Tile(terrain, position);
              if (tile.Terrain.IsObstacle) {
                tilesList.Add(tile);
              } else {
                decorationsList.Add(tile);
              }
            }
          }
        }
      }
      tiles = tilesList.ToArray();
      decorations = decorationsList.ToArray();

      // Because we added tiles from left to right, the CollisionTargets are sorted by x-position.
      // We maintain this invariant so that it's possible to efficiently find CollisionTargets that
      // are nearby a given x-position.
      CollisionTargets = new AABB[tiles.Length + 2];

      // Add a synthetic collisionTarget on the left side of the world.
      CollisionTargets[0] = new AABB(new Vector2(-1, 0), new Vector2(1, float.MaxValue));

      // Now add all the normal collisionTargets for every static terrain tile.
      Vector2 halfSize = new Vector2(TileSize / 2, TileSize / 2);
      for (int i = 0; i < tiles.Length; i++) {
        Vector2 center = new Vector2(
          tiles[i].Position.Left + halfSize.X, tiles[i].Position.Top + halfSize.Y);
        CollisionTargets[i + 1] = new AABB(center, halfSize, tiles[i].Terrain);
      }

      // Add a final synthetic collisionTarget on the right side of the world.
      CollisionTargets[tiles.Length + 1] = new AABB(
          new Vector2(Width + 1, 0), new Vector2(1, float.MaxValue));
    }

    public void Update(float modelTime, History<Input> input) {
      Player.Update(modelTime, this, input);
      foreach (NPC npc in npcs) {
        npc.Update(modelTime, this);
      }
      if (Player.Health <= 0) {
        Reset();
      }
    }

    void Reset() {
      Player = new Player();
    }

    public void DrawBackground(SpriteBatch spriteBatch) {
      foreach (Tile t in decorations) {
        t.Draw(spriteBatch);
      }
      foreach (NPC npc in npcs) {
        npc.Draw(spriteBatch);
      }
    }

    public void DrawForeground(SpriteBatch spriteBatch) {
      foreach (Tile t in tiles) {
        t.Draw(spriteBatch);
      }
    }

    public AABB[] CollisionTargets { get; }
  }
}