#region File Description
//-----------------------------------------------------------------------------
// NetworkSessionComponent.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion

#region Using Statements
using System;
using System.Linq;
using System.Diagnostics;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.GamerServices;
#endregion

namespace NetworkStateManagement
{
    /// <summary>
    /// Component in charge of owning and updating the current NetworkSession object.
    /// This is responsible for calling NetworkSession.Update at regular intervals,
    /// and also exposes the NetworkSession as a game service which can easily be
    /// looked up by any other code that needs to access it.
    /// </summary>
    class NetworkSessionComponent : GameComponent
    {
        #region Fields

        public const int MaxGamers = 16;
        public const int MaxLocalGamers = 4;

        ScreenManager screenManager;
        NetworkSession networkSession;
        IMessageDisplay messageDisplay;

        bool notifyWhenPlayersJoinOrLeave;

        string sessionEndMessage;

        #endregion

        #region Initialization


        /// <summary>
        /// The constructor is private: external callers should use the Create method.
        /// </summary>
        NetworkSessionComponent(ScreenManager screenManager,
                                NetworkSession networkSession)
            : base(screenManager.Game)
        {
            this.screenManager = screenManager;
            this.networkSession = networkSession;

            // Hook up our session event handlers.
            networkSession.GamerJoined += GamerJoined;
            networkSession.GamerLeft += GamerLeft;
            networkSession.SessionEnded += NetworkSessionEnded;
        }


        /// <summary>
        /// Creates a new NetworkSessionComponent.
        /// </summary>
        public static void Create(ScreenManager screenManager,
                                  NetworkSession networkSession)
        {
            Game game = screenManager.Game;

            // Register this network session as a service.
            game.Services.AddService(typeof(NetworkSession), networkSession);

            // Create a NetworkSessionComponent, and add it to the Game.
            game.Components.Add(new NetworkSessionComponent(screenManager,
                                                            networkSession));
        }


        /// <summary>
        /// Initializes the component.
        /// </summary>
        public override void Initialize()
        {
            base.Initialize();

            // Look up the IMessageDisplay service, which will
            // be used to report gamer join/leave notifications.
            messageDisplay = (IMessageDisplay)Game.Services.GetService(
                                                              typeof(IMessageDisplay));

            if (messageDisplay != null)
                notifyWhenPlayersJoinOrLeave = true;
        }


        /// <summary>
        /// Shuts down the component.
        /// </summary>
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                // Remove the NetworkSessionComponent.
                Game.Components.Remove(this);

                // Remove the NetworkSession service.
                Game.Services.RemoveService(typeof(NetworkSession));

                // Dispose the NetworkSession.
                if (networkSession != null)
                {
                    networkSession.Dispose();
                    networkSession = null;
                }
            }

            base.Dispose(disposing);
        }


        #endregion

        #region Update


        /// <summary>
        /// Updates the network session.
        /// </summary>
        public override void Update(GameTime gameTime)
        {
            if (networkSession == null)
                return;

            try
            {
                networkSession.Update();

                // Has the session ended?
                if (networkSession.SessionState == NetworkSessionState.Ended)
                {
                    LeaveSession();
                }
            }
            catch (Exception exception)
            {
                // Handle any errors from the network session update.
                Debug.WriteLine("NetworkSession.Update threw " + exception);

                sessionEndMessage = Resources.ErrorNetwork;

                LeaveSession();
            }
        }


        #endregion

        #region Event Handlers


        /// <summary>
        /// Event handler called when a gamer joins the session.
        /// Displays a notification message.
        /// </summary>
        void GamerJoined(object sender, GamerJoinedEventArgs e)
        {
            if (notifyWhenPlayersJoinOrLeave)
            {
                messageDisplay.ShowMessage(Resources.MessageGamerJoined,
                                           e.Gamer.Gamertag);
            }
        }


        /// <summary>
        /// Event handler called when a gamer leaves the session.
        /// Displays a notification message.
        /// </summary>
        void GamerLeft(object sender, GamerLeftEventArgs e)
        {
            if (notifyWhenPlayersJoinOrLeave)
            {
                messageDisplay.ShowMessage(Resources.MessageGamerLeft,
                                           e.Gamer.Gamertag);
            }
        }


        /// <summary>
        /// Event handler called when the network session ends.
        /// Stores the end reason, so this can later be displayed to the user.
        /// </summary>
        void NetworkSessionEnded(object sender, NetworkSessionEndedEventArgs e)
        {
            switch (e.EndReason)
            {
                case NetworkSessionEndReason.ClientSignedOut:
                    sessionEndMessage = null;
                    break;

                case NetworkSessionEndReason.HostEndedSession:
                    sessionEndMessage = Resources.ErrorHostEndedSession;
                    break;

                case NetworkSessionEndReason.RemovedByHost:
                    sessionEndMessage = Resources.ErrorRemovedByHost;
                    break;

                case NetworkSessionEndReason.Disconnected:
                default:
                    sessionEndMessage = Resources.ErrorDisconnected;
                    break;
            }

            notifyWhenPlayersJoinOrLeave = false;
        }


        /// <summary>
        /// Event handler called when the system delivers an invite notification.
        /// This can occur when the user accepts an invite that was sent to them by
        /// a friend (pull mode), or if they choose the "Join Session In Progress"
        /// option in their friends screen (push mode). The handler leaves the
        /// current session (if any), then joins the session referred to by the
        /// invite. It is not necessary to prompt the user before doing this, as
        /// the Guide will already have taken care of the necessary confirmations
        /// before the invite was delivered to you.
        /// </summary>
        public static void InviteAccepted(ScreenManager screenManager,
                                          InviteAcceptedEventArgs e)
        {
            // If we are already in a network session, leave it now.
            NetworkSessionComponent self = FindSessionComponent(screenManager.Game);

            if (self != null)
                self.Dispose();

            try
            {
                // Which local profiles should we include in this session?
                IEnumerable<SignedInGamer> localGamers =
                    ChooseGamers(NetworkSessionType.PlayerMatch, e.Gamer.PlayerIndex);

                // Begin an asynchronous join-from-invite operation.
                IAsyncResult asyncResult = NetworkSession.BeginJoinInvited(localGamers,
                                                                           null, null);

                // Use the loading screen to replace whatever screens were previously
                // active. This will completely reset the screen state, regardless of
                // whether we were in the menus or playing a game when the invite was
                // delivered. When the loading screen finishes, it will activate the
                // network busy screen, which displays an animation as it waits for
                // the join operation to complete.
                NetworkBusyScreen busyScreen = new NetworkBusyScreen(asyncResult);

                busyScreen.OperationCompleted += JoinInvitedOperationCompleted;

                LoadingScreen.Load(screenManager, false, null, new BackgroundScreen(),
                                                               busyScreen);
            }
            catch (Exception exception)
            {
                NetworkErrorScreen errorScreen = new NetworkErrorScreen(exception);

                LoadingScreen.Load(screenManager, false, null, new BackgroundScreen(),
                                                               new MainMenuScreen(),
                                                               errorScreen);
            }
        }


        /// <summary>
        /// Event handler for when the asynchronous join-from-invite
        /// operation has completed.
        /// </summary>
        static void JoinInvitedOperationCompleted(object sender,
                                                  OperationCompletedEventArgs e)
        {
            ScreenManager screenManager = ((GameScreen)sender).ScreenManager;

            try
            {
                // End the asynchronous join-from-invite operation.
                NetworkSession networkSession =
                                        NetworkSession.EndJoinInvited(e.AsyncResult);

                // Create a component that will manage the session we just created.
                NetworkSessionComponent.Create(screenManager, networkSession);

                // Go to the lobby screen.
                screenManager.AddScreen(new LobbyScreen(networkSession), null);
            }
            catch (Exception exception)
            {
                screenManager.AddScreen(new MainMenuScreen(), null);
                screenManager.AddScreen(new NetworkErrorScreen(exception), null);
            }
        }


        #endregion

        #region Methods


        /// <summary>
        /// Checks whether the specified session type is online.
        /// Online sessions cannot be used by local profiles, or if
        /// parental controls are enabled, or when running in trial mode.
        /// </summary>
        public static bool IsOnlineSessionType(NetworkSessionType sessionType)
        {
            switch (sessionType)
            {
                case NetworkSessionType.Local:
                case NetworkSessionType.SystemLink:
                    return false;

                case NetworkSessionType.PlayerMatch:
                case NetworkSessionType.Ranked:
                    return true;

                default:
                    throw new NotSupportedException();
            }
        }


        /// <summary>
        /// Decides which local gamer profiles should be included in a network session.
        /// This is passed the index of the primary gamer (the profile who selected the
        /// relevant menu option, or who is responding to an invite). The primary gamer
        /// will always be included in the session. Other gamers may also be added if
        /// there are suitable profiles signed in. To control how many gamers can be
        /// returned by this method, adjust the MaxLocalGamers constant.
        /// </summary>
        public static IEnumerable<SignedInGamer> ChooseGamers(
                                                        NetworkSessionType sessionType,
                                                        PlayerIndex playerIndex)
        {
            List<SignedInGamer> gamers = new List<SignedInGamer>();

            // Look up the primary gamer, and make sure they are signed in.
            SignedInGamer primaryGamer = Gamer.SignedInGamers[playerIndex];

            if (primaryGamer == null)
                throw new GamerPrivilegeException();

            gamers.Add(primaryGamer);

            // Check whether any other profiles should also be included.
            foreach (SignedInGamer gamer in Gamer.SignedInGamers)
            {
                // Never include more profiles than the MaxLocalGamers constant.
                if (gamers.Count >= MaxLocalGamers)
                    break;

                // Don't want two copies of the primary gamer!
                if (gamer == primaryGamer)
                    continue;

                // If this is an online session, make sure the profile is signed
                // in to Live, and that it has the privilege for online gameplay.
                if (IsOnlineSessionType(sessionType))
                {
                    if (!gamer.IsSignedInToLive)
                        continue;

                    if (!gamer.Privileges.AllowOnlineSessions)
                        continue;
                }

                if (primaryGamer.IsGuest && !gamer.IsGuest && gamers[0] == primaryGamer)
                {
                    // Special case: if the primary gamer is a guest profile,
                    // we should insert some other non-guest at the start of the
                    // output list, because guests aren't allowed to host sessions.
                    gamers.Insert(0, gamer);
                }
                else
                {
                    gamers.Add(gamer);
                }
            }

            return gamers;
        }


        /// <summary>
        /// Public method called when the user wants to leave the network session.
        /// Displays a confirmation message box, then disposes the session, removes
        /// the NetworkSessionComponent, and returns them to the main menu screen.
        /// </summary>
        public static void LeaveSession(ScreenManager screenManager,
                                        PlayerIndex playerIndex)
        {
            NetworkSessionComponent self = FindSessionComponent(screenManager.Game);

            if (self != null)
            {
                // Display a message box to confirm the user really wants to leave.
                string message;

                if (self.networkSession.IsHost)
                    message = Resources.ConfirmEndSession;
                else
                    message = Resources.ConfirmLeaveSession;

                MessageBoxScreen confirmMessageBox = new MessageBoxScreen(message);

                // Hook the messge box ok event to actually leave the session.
                confirmMessageBox.Accepted += delegate
                {
                    self.LeaveSession();
                };

                screenManager.AddScreen(confirmMessageBox, playerIndex);
            }
        }


        /// <summary>
        /// Internal method for leaving the network session. This disposes the 
        /// session, removes the NetworkSessionComponent, and returns the user
        /// to the main menu screen.
        /// </summary>
        void LeaveSession()
        {
            // Destroy this NetworkSessionComponent.
            Dispose();

            // If we have a sessionEndMessage string explaining why the session has
            // ended (maybe this was a network disconnect, or perhaps the host kicked
            // us out?) create a message box to display this reason to the user.
            MessageBoxScreen messageBox;

            if (!string.IsNullOrEmpty(sessionEndMessage))
                messageBox = new MessageBoxScreen(sessionEndMessage, false);
            else
                messageBox = null;

            // At this point we want to return the user all the way to the main
            // menu screen. But what if they just joined a session? In that case
            // they went through this flow of screens:
            //
            //  - MainMenuScreen
            //  - CreateOrFindSessionsScreen
            //  - JoinSessionScreen (if joining, skipped if creating a new session)
            //  - LobbyScreeen
            //
            // If we have these previous screens on the history stack, and the user
            // backs out of the LobbyScreen, the right thing is just to pop off the
            // intermediate screens, returning them to the existing MainMenuScreen
            // instance without bothering to reload everything. But if the user is
            // in gameplay, or has been in gameplay and then returned to the lobby,
            // the screen stack will have been emptied.
            //
            // To do the right thing in both cases, we scan through the screen history
            // stack looking for a MainMenuScreen. If we find one, we pop any
            // subsequent screens so as to return back to it, while if we don't
            // find it, we just reset everything via the LoadingScreen.

            GameScreen[] screens = screenManager.GetScreens();

            // Look for the MainMenuScreen.
            for (int i = 0; i < screens.Length; i++)
            {
                if (screens[i] is MainMenuScreen)
                {
                    // If we found one, pop everything since then to return back to it.
                    for (int j = i + 1; j < screens.Length; j++)
                        screens[j].ExitScreen();

                    // Display the why-did-the-session-end message box.
                    if (messageBox != null)
                        screenManager.AddScreen(messageBox, null);

                    return;
                }
            }

            // If we didn't find an existing MainMenuScreen, reload everything.
            // The why-did-the-session-end message box will be displayed after
            // the loading screen has completed.
            LoadingScreen.Load(screenManager, false, null, new BackgroundScreen(),
                                                           new MainMenuScreen(),
                                                           messageBox);
        }


        /// <summary>
        /// Searches through the Game.Components collection to
        /// find the NetworkSessionComponent (if any exists).
        /// </summary>
        static NetworkSessionComponent FindSessionComponent(Game game)
        {
            return game.Components.OfType<NetworkSessionComponent>().FirstOrDefault();
        }


        #endregion
    }
}