/// TaskManager.cs
/// Copyright (c) 2011, Ken Rockot  <k-e-n-@-REMOVE-CAPS-AND-HYPHENS-oz.gs>.  All rights reserved.
/// Everyone is granted non-exclusive license to do anything at all with this code.
///
/// This is a new coroutine interface for Unity.
///
/// The motivation for this is twofold:
///
/// 1. The existing coroutine API provides no means of stopping specific
///    coroutines; StopCoroutine only takes a string argument, and it stops
///    all coroutines started with that same string; there is no way to stop
///    coroutines which were started directly from an enumerator.  This is
///    not robust enough and is also probably pretty inefficient.
///
/// 2. StartCoroutine and friends are MonoBehaviour methods.  This means
///    that in order to start a coroutine, a user typically must have some
///    component reference handy.  There are legitimate cases where such a
///    constraint is inconvenient.  This implementation hides that
///    constraint from the user.
///
/// Example usage:
///
/// ----------------------------------------------------------------------------
/// IEnumerator MyAwesomeTask()
/// {
///     while(true) {
///         Debug.Log("Logcat iz in ur consolez, spammin u wif messagez.");
///         yield return null;
////    }
/// }
///
/// IEnumerator TaskKiller(float delay, Task t)
/// {
///     yield return new WaitForSeconds(delay);
///     t.Stop();
/// }
///
/// void SomeCodeThatCouldBeAnywhereInTheUniverse()
/// {
///     Task spam = new Task(MyAwesomeTask());
///     new Task(TaskKiller(5, spam));
/// }
/// ----------------------------------------------------------------------------
///
/// When SomeCodeThatCouldBeAnywhereInTheUniverse is called, the debug console
/// will be spammed with annoying messages for 5 seconds.
///
/// Simple, really.  There is no need to initialize or even refer to TaskManager.
/// When the first Task is created in an application, a "TaskManager" GameObject
/// will automatically be added to the scene root with the TaskManager component
/// attached.  This component will be responsible for dispatching all coroutines
/// behind the scenes.
///
/// Task also provides an event that is triggered when the coroutine exits.

using UnityEngine;
using System.Collections;

// Using the Fungus namespace to minimize conflicts with other assets.
namespace Fungus
{

	/// A Task object represents a coroutine.  Tasks can be started, paused, and stopped.
	/// It is an error to attempt to start a task that has been stopped or which has
	/// naturally terminated.
	public class Task
	{
	    /// Returns true if and only if the coroutine is running.  Paused tasks
	    /// are considered to be running.
	    public bool Running {
	        get {
	            return task.Running;
	        }
	    }

	    /// Returns true if and only if the coroutine is currently paused.
	    public bool Paused {
	        get {
	            return task.Paused;
	        }
	    }

	    /// Delegate for termination subscribers.  manual is true if and only if
	    /// the coroutine was stopped with an explicit call to Stop().
	    public delegate void FinishedHandler(bool manual);

	    /// Termination event.  Triggered when the coroutine completes execution.
	    public event FinishedHandler Finished;

	    /// Creates a new Task object for the given coroutine.
	    ///
	    /// If autoStart is true (default) the task is automatically started
	    /// upon construction.
	    public Task(IEnumerator c, bool autoStart = true)
	    {
	        task = TaskManager.CreateTask(c);
	        task.Finished += TaskFinished;
	        if(autoStart)
	            Start();
	    }

	    /// Begins execution of the coroutine
	    public void Start()
	    {
	        task.Start();
	    }

	    /// Discontinues execution of the coroutine at its next yield.
	    public void Stop()
	    {
	        task.Stop();
	    }

	    public void Pause()
	    {
	        task.Pause();
	    }

	    public void Unpause()
	    {
	        task.Unpause();
	    }

	    void TaskFinished(bool manual)
	    {
	        FinishedHandler handler = Finished;
	        if(handler != null)
	            handler(manual);
	    }

	    TaskManager.TaskState task;
	}

	class TaskManager : MonoBehaviour
	{
	    public class TaskState
	    {
	        public bool Running {
	            get {
	                return running;
	            }
	        }

	        public bool Paused  {
	            get {
	                return paused;
	            }
	        }

	        public delegate void FinishedHandler(bool manual);
	        public event FinishedHandler Finished;

	        IEnumerator coroutine;
	        bool running;
	        bool paused;
	        bool stopped;

	        public TaskState(IEnumerator c)
	        {
	            coroutine = c;
	        }

	        public void Pause()
	        {
	            paused = true;
	        }

	        public void Unpause()
	        {
	            paused = false;
	        }

	        public void Start()
	        {
	            running = true;
	            singleton.StartCoroutine(CallWrapper());
	        }

	        public void Stop()
	        {
	            stopped = true;
	            running = false;
	        }

	        IEnumerator CallWrapper()
	        {
	            yield return null;
	            IEnumerator e = coroutine;
	            while(running) {
	                if(paused)
	                    yield return null;
	                else {
	                    if(e != null && e.MoveNext()) {
	                        yield return e.Current;
	                    }
	                    else {
	                        running = false;
	                    }
	                }
	            }

	            FinishedHandler handler = Finished;
	            if(handler != null)
	                handler(stopped);
	        }
	    }

	    static TaskManager singleton;

	    public static TaskState CreateTask(IEnumerator coroutine)
	    {
	        if(singleton == null) {
	            GameObject go = new GameObject("TaskManager");
	            singleton = go.AddComponent<TaskManager>();
	        }
	        return new TaskState(coroutine);
	    }
	}

}