//   SparkleShare, a collaboration and sharing tool.
//   Copyright (C) 2010  Hylke Bons <hylkebons@gmail.com>
//
//   This program is free software: you can redistribute it and/or modify
//   it under the terms of the GNU General Public License as published by
//   the Free Software Foundation, either version 3 of the License, or
//   (at your option) any later version.
//
//   This program is distributed in the hope that it will be useful,
//   but WITHOUT ANY WARRANTY; without even the implied warranty of
//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
//   GNU General Public License for more details.
//
//   You should have received a copy of the GNU General Public License
//   along with this program. If not, see <http://www.gnu.org/licenses/>.


using System;
using System.Collections;
using System.Collections.Generic;
using System.Timers;
using System.Linq;

namespace SparkleLib {

    public class SparkleAnnouncement {

        public readonly string FolderIdentifier;
        public readonly string Message;


        public SparkleAnnouncement (string folder_identifier, string message)
        {
            FolderIdentifier = folder_identifier;
            Message          = message;
        }
    }


    public static class SparkleListenerFactory {

        private static List<SparkleListenerBase> listeners = new List<SparkleListenerBase> ();

        public static SparkleListenerBase CreateListener (string folder_name, string folder_identifier)
        {
            string uri = SparkleConfig.DefaultConfig.GetFolderOptionalAttribute (
                folder_name, "announcements_url");

            if (uri == null) {
                // This is SparkleShare's centralized notification service.
                // Don't worry, we only use this server as a backup if you
                // don't have your own. All data needed to connect is hashed and
                // we don't store any personal information ever

                uri = "tcp://notifications.sparkleshare.org:1986";
            }

            Uri announce_uri = new Uri (uri);

            // We use only one listener per server to keep
            // the number of connections as low as possible
            foreach (SparkleListenerBase listener in listeners) {
                if (listener.Server.Equals (announce_uri)) {
                    SparkleHelpers.DebugInfo ("ListenerFactory",
                        "Refered to existing listener for " + announce_uri);

                    listener.AlsoListenTo (folder_identifier);
                    return (SparkleListenerBase) listener;
                }
            }

            // Create a new listener with the appropriate
            // type if one doesn't exist yet for that server
            switch (announce_uri.Scheme) {
            case "tcp":
                listeners.Add (new SparkleListenerTcp (announce_uri, folder_identifier));
                break;
            default:
                listeners.Add (new SparkleListenerTcp (announce_uri, folder_identifier));
                break;
            }

            SparkleHelpers.DebugInfo ("ListenerFactory", "Issued new listener for " + announce_uri);
            return (SparkleListenerBase) listeners [listeners.Count - 1];
        }
    }


    // A persistent connection to the server that
    // listens for change notifications
    public abstract class SparkleListenerBase {

        // We've connected to the server
        public event ConnectedEventHandler Connected;
        public delegate void ConnectedEventHandler ();

        // We've disconnected from the server
        public event DisconnectedEventHandler Disconnected;
        public delegate void DisconnectedEventHandler ();

        // We've been notified about a remote
        // change by the channel
        public event AnnouncementEventHandler Announcement;
        public delegate void AnnouncementEventHandler (SparkleAnnouncement announcement);

        public abstract void Connect ();
        public abstract void Announce (SparkleAnnouncement announcent);
        public abstract void AlsoListenTo (string folder_identifier);
        public abstract bool IsConnected { get; }

        protected List<string> channels = new List<string> ();
        protected Dictionary<string,List<SparkleAnnouncement>> recent_announcements = new Dictionary<string, List<SparkleAnnouncement>> ();
        protected int max_recent_announcements = 10;
        protected Dictionary<string, SparkleAnnouncement> queue_up  = new Dictionary<string, SparkleAnnouncement> ();
        protected Dictionary<string,SparkleAnnouncement> queue_down = new Dictionary<string, SparkleAnnouncement> ();
        protected bool is_connecting;
        protected Uri server;
        protected Timer reconnect_timer = new Timer { Interval = 60 * 1000, Enabled = true };


        public SparkleListenerBase (Uri server, string folder_identifier)
        {
            this.server = server;

            this.reconnect_timer.Elapsed += delegate {
                if (!IsConnected && !this.is_connecting)
                    Reconnect ();
            };

            this.reconnect_timer.Start ();
        }


        public void AnnounceBase (SparkleAnnouncement announcement)
        {
            if (!this.IsRecentAnnounement (announcement)) {
                if (IsConnected) {
                    SparkleHelpers.DebugInfo ("Listener",
                        "Announcing message " + announcement.Message + " to " + announcement.FolderIdentifier + " on " + this.server);

                    Announce (announcement);
                    this.AddRecentAnnouncement (announcement);
                } else {
                    SparkleHelpers.DebugInfo ("Listener", "Can't send message to " + this.server + ". Queuing message");
                    this.queue_up [announcement.FolderIdentifier] = announcement;
                }

            } else {
                SparkleHelpers.DebugInfo ("Listener",
                    "Already processed message " + announcement.Message + " to " + announcement.FolderIdentifier + " from " + this.server);
            }

        }


        public void Reconnect ()
        {
            SparkleHelpers.DebugInfo ("Listener", "Trying to reconnect to " + this.server);
            Connect ();
        }


        public void OnConnected ()
        {
            SparkleHelpers.DebugInfo ("Listener", "Listening for announcements on " + Server);

            if (Connected != null)
                Connected ();

            if (this.queue_up.Count > 0) {
                SparkleHelpers.DebugInfo ("Listener", "Delivering " + this.queue_up.Count + " queued messages...");

                foreach (KeyValuePair<string, SparkleAnnouncement> item in this.queue_up) {
                    SparkleAnnouncement announcement = item.Value;
                    AnnounceBase (announcement);
                }

                this.queue_down.Clear ();
            }
        }


        public void OnDisconnected ()
        {
            SparkleHelpers.DebugInfo ("Listener", "Signal of " + Server + " lost");

            if (Disconnected != null)
                Disconnected ();
        }


        public void OnAnnouncement (SparkleAnnouncement announcement)
        {
            SparkleHelpers.DebugInfo ("Listener",
              "Got message " + announcement.Message + " from " + announcement.FolderIdentifier + " on " + this.server);

            if (IsRecentAnnounement(announcement) ){
                SparkleHelpers.DebugInfo ("Listener",
                    "Ignoring previously processed message " + announcement.Message + 
                    " from " + announcement.FolderIdentifier + " on " + this.server);
                
                  return;
            }

            SparkleHelpers.DebugInfo ("Listener",
                "Processing message " + announcement.Message + " from " + announcement.FolderIdentifier + " on " + this.server);

            AddRecentAnnouncement (announcement);
            this.queue_down [announcement.FolderIdentifier] = announcement;

            if (Announcement != null)
                Announcement (announcement);
        }


        private bool IsRecentAnnounement (SparkleAnnouncement announcement)
        {
            if (!HasRecentAnnouncements (announcement.FolderIdentifier)) {
                return false;

            } else {
                foreach (SparkleAnnouncement recent_announcement in GetRecentAnnouncements (announcement.FolderIdentifier)) {
                    if (recent_announcement.Message.Equals (announcement.Message))
                        return true;
                }

                return false;
            }
        }


        private List<SparkleAnnouncement> GetRecentAnnouncements (string folder_identifier)
        {
            if (!this.recent_announcements.ContainsKey (folder_identifier))
                this.recent_announcements [folder_identifier] = new List<SparkleAnnouncement> ();

            return (List<SparkleAnnouncement>) this.recent_announcements [folder_identifier];
        }


        private void AddRecentAnnouncement (SparkleAnnouncement announcement)
        {
            List<SparkleAnnouncement> recent_announcements = this.GetRecentAnnouncements (announcement.FolderIdentifier);

            if (!IsRecentAnnounement (announcement))
                recent_announcements.Add (announcement);

            if (recent_announcements.Count > this.max_recent_announcements)
                recent_announcements.RemoveRange (0, (recent_announcements.Count - this.max_recent_announcements));
        }


        private bool HasRecentAnnouncements (string folder_identifier)
        {
            return this.recent_announcements.ContainsKey (folder_identifier);
        }


        public virtual void Dispose ()
        {
            this.reconnect_timer.Dispose ();
        }


        public Uri Server {
            get {
                return this.server;
            }
        }


        public bool IsConnecting {
            get {
               return this.is_connecting;
            }
        }
    }
}