sneak/Shared/World.cs

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

namespace SemiColinGames {
  enum Terrain {
    Grass,
    GrassL,
    GrassR,
    Rock,
    RockL,
    RockR,
    Water,
    Block
  }

  enum TileSet {
    Cemetery,
    Crypt,
    Dungeon,
    Forest,
    Garden,
    Grassland,
    Ruins,
    Sewer,
    Temple,
    Village,
  }

  class TileFactory {
    struct TileSetAndPoint {
      public TileSet tileSet;
      public Point point;

      public TileSetAndPoint(TileSet tileSet, int x, int y) {
        this.tileSet = tileSet;
        point = new Point(x, y);
      }
    }

    static readonly Dictionary<TileSet, string> tileSetToContentPath =
      new Dictionary<TileSet, string>() {
        { TileSet.Cemetery,  "tiles/anokolisa/cemetery"  },
        { TileSet.Crypt,     "tiles/anokolisa/crypt"     },
        { TileSet.Dungeon,   "tiles/anokolisa/dungeon"   },
        { TileSet.Forest,    "tiles/anokolisa/forest"    },
        { TileSet.Garden,    "tiles/anokolisa/garden"    },
        { TileSet.Grassland, "tiles/anokolisa/grassland" },
        { TileSet.Ruins,     "tiles/anokolisa/ruins"     },
        { TileSet.Sewer,     "tiles/anokolisa/sewer"     },
        { TileSet.Temple,    "tiles/anokolisa/temple"    },
        { TileSet.Village,   "tiles/anokolisa/village"   },
      };

    static readonly Dictionary<Terrain, TileSetAndPoint> terrainToTilePosition =
      new Dictionary<Terrain, TileSetAndPoint>() {
        { Terrain.Grass,  new TileSetAndPoint(TileSet.Grassland, 3, 0) },
        { Terrain.GrassL, new TileSetAndPoint(TileSet.Grassland, 2, 0) },
        { Terrain.GrassR, new TileSetAndPoint(TileSet.Grassland, 4, 0) },
        { Terrain.Rock,   new TileSetAndPoint(TileSet.Grassland, 3, 1) },
        { Terrain.RockL,  new TileSetAndPoint(TileSet.Grassland, 1, 2) },
        { Terrain.RockR,  new TileSetAndPoint(TileSet.Grassland, 5, 2) },
        { Terrain.Water,  new TileSetAndPoint(TileSet.Grassland, 9, 2) },
        { Terrain.Block,  new TileSetAndPoint(TileSet.Grassland, 6, 3) },
      };

    readonly Texture2D[] textures;

    public TileFactory(ContentManager content) {
      Array tileSets = Enum.GetValues(typeof(TileSet));
      textures = new Texture2D[tileSets.Length];
      foreach (TileSet tileSet in tileSets) {
        textures[(int) tileSet] = content.Load<Texture2D>(tileSetToContentPath[tileSet]);
      }
    }

    public Tile MakeTile(Terrain terrain, Rectangle position) {
      TileSet tileSet = terrainToTilePosition[terrain].tileSet;
      Texture2D texture = textures[(int) tileSet];
      return new Tile(terrain, position, texture, TextureSource(terrain));
    }

    private static Rectangle TextureSource(Terrain terrain) {
      int size = World.TileSize;
      Point pos = terrainToTilePosition[terrain].point;
      return new Rectangle(pos.X * size, pos.Y * size, size, size);
    }
  }

  class Tile {
    readonly Texture2D texture;
    readonly Rectangle textureSource;

    public Tile(Terrain terrain, Rectangle position, Texture2D texture, Rectangle textureSource) {
      Terrain = terrain;
      Position = position;
      this.texture = texture;
      this.textureSource = textureSource;
    }

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

    public void Draw(SpriteBatch spriteBatch) {
      spriteBatch.Draw(texture, Position.Location.ToVector2(), textureSource, Color.White);
    }
  }

  class World {

    public const int TileSize = 16;
    readonly Tile[] tiles;

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

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

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

    private static readonly Dictionary<char, Terrain> charToTerrain =
        new Dictionary<char, Terrain>() {
      { '=', Terrain.Grass },
      { '<', Terrain.GrassL },
      { '>', Terrain.GrassR },
      { '.', Terrain.Rock },
      { '[', Terrain.RockL },
      { ']', Terrain.RockR },
      { '~', Terrain.Water },
      { 'X', Terrain.Block }
    };

    public World(ContentManager content, string levelSpecification) {
      TileFactory factory = new TileFactory(content);
      var tilesList = new List<Tile>();
      string[] worldDesc = levelSpecification.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];
            if (charToTerrain.ContainsKey(key)) {
              Terrain terrain = charToTerrain[key];
              var position = new Rectangle(i * TileSize, j * TileSize, TileSize, TileSize);
              tilesList.Add(factory.MakeTile(terrain, position));
            }
          }
        }
      }
      tiles = tilesList.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);
      }

      // 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 Draw(SpriteBatch spriteBatch) {
      foreach (Tile t in tiles) {
        t.Draw(spriteBatch);
      }
    }

    public AABB[] CollisionTargets { get; }
  }
}