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

namespace TestGame
{
    public sealed class Npc
    {
        // FIFO collection for storing tasks.
        public Queue<KeyValuePair<NpcTasks, object[]>> Tasks;

        private Vector2[] path;
        private bool stopThread;
        private Thread thread;  // Task update thread

        public Npc()
        {
            Tasks = new Queue<KeyValuePair<NpcTasks, object[]>>();
            path = new Vector2[0];

            InitThread();
        }

        public void Load()
        {
            if (thread.ThreadState == ThreadState.Running) throw new InvalidOperationException();
            if (thread.ThreadState != ThreadState.Unstarted) InitThread();

            thread.Start();
        }

        public void UnLoad()
        {
            stopThread = true; // Request a thread stop
        }

        public void Update()
        {
            // gamelogic update
        }

        private void InitThread()
        {
            // Set thread to its function
            thread = new Thread(RunThread);
        }

        private void RunThread()
        {
            // message loop
            while (!stopThread)
            {
                if (Tasks.Count > 0) TickThread();  // tick when task is available
                else Thread.Sleep(100);             // do nothing for 100 ms
            }
        }

        private void TickThread()
        {
            KeyValuePair<NpcTasks, object[]> task = Tasks.Dequeue();    // get current task.

            switch (task.Key)
            {
                case NpcTasks.Walk:
                    lock(path)      // lock path to prevent interthread exceptions
                    {
                        path = new Vector2[] { Vector2.Zero, Vector2.One };
                    }
                    break;
            }
        }
    }

    public enum NpcTasks
    {
        Walk
    }
}