using UnityEngine;
using System.Collections;
using System.Net;
using System.Net.Sockets;

/// <summary>
/// This component is responsible for continously checking if there is an internet connection.
/// This is done by first checking the Application.internetReachability. But this can give false
/// positives, e.g. connected to a wifi router but does not have an actual internet connection.
/// So the next step is pinging PING_DESTINATION every TIME_BETWEEN_PINGS seconds.
/// If the ping fails for FAILED_PINGS_DISCONNECTION_TRIGGER times, it means it has gone offline.
/// Whenever the connectivity changes, a ConnectivityChange notification is fired.
/// </summary>
public class ConnectivityPollManager : MonoBehaviour
{
	static bool _hasInternet;
	public static bool HasInternet { get { return _hasInternet; } }

	private const string PING_DESTINATION = "https://game.gamatic.com/ping_do_not_delete.html";
	const float TIME_BETWEEN_PINGS = 3; //seconds
	//sometimes the ping just fails every once in a while, so we should do multiple pings just to make sure
	const int FAILED_PINGS_DISCONNECTION_TRIGGER = 3;

	bool _hasPingedDestination;
	string _address;
	int _failedPings;
        
	void Start()
	{
		StartCoroutine(CheckForConnectivityCoroutine());
	}
        
	IEnumerator CheckForConnectivityCoroutine()
	{
		while (true)
		{
			bool isNetworkReachable = (Application.internetReachability != NetworkReachability.NotReachable);
			//If the api says that it is reachable, we need to test further by pinging a proper connection
			if (isNetworkReachable)
			{
				yield return StartCoroutine(TestConnectionCoroutine());

				if (_hasPingedDestination != _hasInternet)
				{
					if (!_hasPingedDestination)
					{
						++_failedPings;
						if (_failedPings >= FAILED_PINGS_DISCONNECTION_TRIGGER)
						{
							AVDebug.Log("Went offline");
							_hasInternet = false;
							CoreNotificationCenter.Post(CoreNotificationType.ConnectivityChange, _hasPingedDestination);
						}
						else
						{
							AVDebug.Log("Ping missed");
						}
					}
					else
					{
						AVDebug.Log("Back online");
						_hasInternet = true;
						_failedPings = 0;
						CoreNotificationCenter.Post(CoreNotificationType.ConnectivityChange, _hasPingedDestination);
					}
				}
			} else
			{
				//Network was not reachable
				if (_hasInternet)
				{
					AVDebug.Log("Went offline (airplane mode/wifi off?)");
					_hasInternet = false;
					CoreNotificationCenter.Post(CoreNotificationType.ConnectivityChange, _hasPingedDestination);
				}
			}

			yield return new WaitForSeconds(TIME_BETWEEN_PINGS);
		}
	}

	//Inspired from http://forum.unity3d.com/threads/68938-How-can-you-tell-if-there-exists-a-network-connection-of-any-kind
	//Its result is stored in _hasPingedDestination, since coroutines cannot return a value directly
	IEnumerator TestConnectionCoroutine()
	{
		_hasPingedDestination = false;
		WWW www = new WWW(PING_DESTINATION);
		yield return www;
		if (www.error == null)
		{
			_hasPingedDestination = true;
		}
	}
}