sneak/Shared/NPC.cs

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

namespace SemiColinGames {
  class NPC {
    private Point position;

    private const int spriteWidth = 96;
    private const int spriteHeight = 81;
    private const int spriteCenterYOffset = 3;

    public NPC(Point position) {
      this.position = position;
    }

    public int Facing { get; private set; } = 1;

    public void Update(float modelTime, AABB[] collisionTargets) {
      int moveSpeed = 120;
      int desiredX = position.X + (int) (moveSpeed * Facing * modelTime);
      // TODO: define the box modularly & correctly.
      AABB npcBox = new AABB(new Vector2(desiredX, position.Y), new Vector2(11, 33));
      Debug.AddRect(npcBox, Color.Cyan);
      bool foundBox = false;
      foreach (AABB box in collisionTargets) {
        if (box.Intersect(npcBox) != null) {
          foundBox = true;
          break;
        }
      }

      if (!foundBox) {
        Facing *= -1;
      }
      position.X = desiredX;
    }

    public void Draw(SpriteBatch spriteBatch) {
      Rectangle textureSource = Sprites.Executioner.GetTextureSource(
          "run", (int) Clock.ModelTime.TotalMilliseconds);
      // TODO: move this into Sprite metadata.
      Vector2 spriteCenter = new Vector2(spriteWidth / 2, spriteHeight / 2 + spriteCenterYOffset);
      SpriteEffects effect = Facing == 1 ?
        SpriteEffects.None : SpriteEffects.FlipHorizontally;
      Color color = Color.White;
      spriteBatch.Draw(Textures.Executioner.Get, position.ToVector2(), textureSource, color, 0f,
        spriteCenter, Vector2.One, effect, 0f);
    }
  }
}