MonoGame.Samples/BookSourceCode/XNAGameDevelopmentbyExampleCode/RobotRampage/Enemy.cs

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

namespace Robot_Rampage
{
    class Enemy
    {
        #region Declarations
        public Sprite EnemyBase;
        public Sprite EnemyClaws;
        public float EnemySpeed = 60f;
        public Vector2 currentTargetSquare;
        public bool Destroyed = false;
        private int collisionRadius = 14;
        #endregion

        #region Constructor
        public Enemy(
            Vector2 worldLocation,
            Texture2D texture,
            Rectangle initialFrame)
        {
            EnemyBase = new Sprite(
                worldLocation,
                texture,
                initialFrame,
                Vector2.Zero);

            EnemyBase.CollisionRadius = collisionRadius;

            Rectangle turretFrame = initialFrame;

            turretFrame.Offset(0, initialFrame.Height);
            EnemyClaws = new Sprite(
                worldLocation,
                texture,
                turretFrame,
                Vector2.Zero);
        }
        #endregion

        #region AI Methods
        private Vector2 determineMoveDirection()
        {
            if (reachedTargetSquare())
            {
                currentTargetSquare = getNewTargetSquare();
            }

            Vector2 squareCenter = TileMap.GetSquareCenter(
                currentTargetSquare);

            return squareCenter - EnemyBase.WorldCenter;
        }

        private bool reachedTargetSquare()
        {
            return (
                Vector2.Distance(
                    EnemyBase.WorldCenter,
                    TileMap.GetSquareCenter(currentTargetSquare))
                <= 2);
        }

        private Vector2 getNewTargetSquare()
        {
            List<Vector2> path = PathFinder.FindPath(
                TileMap.GetSquareAtPixel(EnemyBase.WorldCenter),
                TileMap.GetSquareAtPixel(Player.BaseSprite.WorldCenter));

            if (path.Count > 1)
            {
                return new Vector2(path[1].X, path[1].Y);
            }
            else
            {
                return TileMap.GetSquareAtPixel(
                    Player.BaseSprite.WorldCenter);
            }
        }
        #endregion

        #region Public Methods
        public void Update(GameTime gameTime)
        {
            if (!Destroyed)
            {
                Vector2 direction = determineMoveDirection();
                direction.Normalize();

                EnemyBase.Velocity = direction * EnemySpeed;
                EnemyBase.RotateTo(direction);
                EnemyBase.Update(gameTime);

                Vector2 directionToPlayer =
                    Player.BaseSprite.WorldCenter -
                    EnemyBase.WorldCenter;
                directionToPlayer.Normalize();

                EnemyClaws.WorldLocation = EnemyBase.WorldLocation;
                EnemyClaws.RotateTo(directionToPlayer);
            }
        }

        public void Draw(SpriteBatch spriteBatch)
        {
            if (!Destroyed)
            {
                EnemyBase.Draw(spriteBatch);
                EnemyClaws.Draw(spriteBatch);
            }
        }
        #endregion

    }
}