using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Net;
using System.Threading;
using System;
using NeonTea.Quakeball.TeaNet.Packets;
using UnityEngine;

namespace NeonTea.Quakeball.TeaNet.Peers {
    /// <summary>Manages connections for Peer, sends them keepalives and sends and handles incoming messages.</summary>
    public class ConnectionManager {
        private ulong ConnectionCounter;
        private Dictionary<ulong, Connection> Connections = new Dictionary<ulong, Connection>();
        private Dictionary<IPEndPoint, ulong> IPtoID = new Dictionary<IPEndPoint, ulong>();
        private Dictionary<ulong, ConcurrentQueue<Packet>> PacketQueue = new Dictionary<ulong, ConcurrentQueue<Packet>>();
        private Peer Peer;

        public Dictionary<ulong, Queue<ProtocolAction>> ProtocolActionQueues = new Dictionary<ulong, Queue<ProtocolAction>>();
        private Queue<Connection> ConnectionsToRemove = new Queue<Connection>();

        private Thread UpdateThread;

        public long Timeout = 8000;
        public long Interval = 100;

        /// <summary>The amount of bytes sent since the last clear interval from Peer</summary>
        public int BytesSent;
        public ConcurrentDictionary<Type, int> SentByPacket = new ConcurrentDictionary<Type, int>();
        public ConcurrentDictionary<Type, int> ReceivedByPacket = new ConcurrentDictionary<Type, int>();

        public ConnectionManager(Peer peer) {
            Peer = peer;
            UpdateThread = new Thread(new ThreadStart(UpdateThreadMethod));
            UpdateThread.Start();
        }

        public void StopThread() {
            UpdateThread.Abort();
        }

        /// <summary>Find a given Connection. Should not be used, unless expecting to establish a connection with the endpoint.</summary>
        public Connection Find(IPEndPoint endpoint) {
            if (IPtoID.ContainsKey(endpoint)) {
                return Connections[IPtoID[endpoint]];
            }
            Connection conn = new Connection(endpoint, ConnectionStatus.Awaiting);
            AddConnection(conn);
            return conn;
        }

        /// <summary>Start establishing a connection to a given endpoint with the given protocol</summary>
        public bool StartConnection(IPEndPoint endpoint, byte protocolIdent) {
            if (IPtoID.ContainsKey(endpoint)) {
                return false;
            }
            Connection conn = new Connection(endpoint);
            conn.Internal.AssignedProtocol = protocolIdent;
            AddConnection(conn);
            return true;
        }

        /// <summary>Get the connection instance from the given uid, if such exists. Null otherwise.</summary>
        public Connection GetConnection(ulong uid) {
            Connection conn;
            Connections.TryGetValue(uid, out conn);
            return conn;
        }

        /// <summary>Soft-closes the connection with the given uid, meaning it will wait for them to acknowledge the closing</summary>
        public void CloseConnection(ulong uid, ClosingReason reason) {
            if (Connections.ContainsKey(uid)) {
                Connections[uid].ClosingReason = reason;
                Connections[uid].Status = ConnectionStatus.Rejected;
            }
        }

        /// <summary>Add a reliable packet to the packet queue, to be sent on the next update, or when SendPacketQueue is called.</summary>
        public void AddPacketToQueue(ulong uid, Packet p) {
            if (!Connections.ContainsKey(uid)) {
                return;
            }
            p = p.ShallowCopy();
            p.PacketId = Connections[uid].Internal.ReliablePacketIDCounter++;
            PacketQueue[uid].Enqueue(p);
        }

        /// <summary>Send the current packet queue instantly.</summary>
        public void SendPacketQueue(ulong uid) {
            if (!Connections.ContainsKey(uid)) {
                return;
            }
            Connection conn = Connections[uid];
            Protocol protocol = Peer.GetProtocol(conn.Internal.AssignedProtocol);
            if (protocol != null && conn.IsReady()) {
                Packet[] list = PacketQueue[uid].ToArray();
                int firstId = Int32.MaxValue;
                if (list.Length > 0) {
                    firstId = list[0].PacketId;
                }
                ByteBuffer buffer = protocol.BuildMessage(conn, firstId, true);
                buffer.Write(list.Length);
                foreach (Packet p in list) {
                    buffer.WritePacket(protocol, p);

                    // Do the analytics dance!
                    int OldSentByPacket;
                    SentByPacket.TryGetValue(p.GetType(), out OldSentByPacket);
                    SentByPacket[p.GetType()] = OldSentByPacket + p.Size;
                }
                Send(conn, buffer);
            }
        }

        /// <summary>Send a single unreliable packet.</summary>
        public void SendSingleUnreliable(ulong uid, Packet p) {
            if (!Connections.ContainsKey(uid)) {
                return;
            }
            Connection conn = Connections[uid];
            p = p.ShallowCopy();
            p.PacketId = conn.Internal.UnreliablePacketIDCounter++;
            p.PacketIsReliable = false;
            Protocol protocol = Peer.GetProtocol(conn.Internal.AssignedProtocol);
            if (protocol != null && conn.IsReady()) {
                ByteBuffer buffer = protocol.BuildMessage(conn, p.PacketId, false);
                buffer.Write(1);
                buffer.WritePacket(protocol, p);
                Send(conn, buffer);

                // Do the analytics dance!
                int OldSentByPacket;
                SentByPacket.TryGetValue(p.GetType(), out OldSentByPacket);
                SentByPacket[p.GetType()] = OldSentByPacket + p.Size;
            }
        }

        /// <summary>Go through queue of networking actions that have happened since last update.</summary>
        public void Update() {
            foreach (byte id in ProtocolActionQueues.Keys) {
                Protocol protocol = Peer.GetProtocol(id);
                while (ProtocolActionQueues[id].Count > 0) {
                    ProtocolAction action = ProtocolActionQueues[id].Dequeue();
                    if (action is ReceiveAction) {
                        ReceiveAction receive = (ReceiveAction)action;
                        protocol.Receive(receive.Connection, receive.Packet);
                    } else if (action is ConnectionChangedAction) {
                        ConnectionChangedAction changed = (ConnectionChangedAction)action;
                        protocol.ConnectionStatusChanged(changed.OldStatus, changed.NewStatus, changed.Connection);
                    } else if (action is TimeoutAction) {
                        TimeoutAction changed = (TimeoutAction)action;
                        protocol.Timeout(changed.Connection);
                    }
                }
            }
            while (ConnectionsToRemove.Count > 0) {
                Connection conn = ConnectionsToRemove.Dequeue();
                RemoveConnection(conn);
            }
        }

        private void AddConnection(Connection conn) {
            conn.uid = ConnectionCounter++;
            Connections.Add(conn.uid, conn);
            IPtoID.Add(conn.Endpoint, conn.uid);
            PacketQueue.Add(conn.uid, new ConcurrentQueue<Packet>());
        }

        private void RemoveConnection(Connection conn) {
            Connections.Remove(conn.uid);
            IPtoID.Remove(conn.Endpoint);
            PacketQueue.Remove(conn.uid);
        }

        private void SendPlain(Connection conn) {
            Protocol protocol = Peer.GetProtocol(conn.Internal.AssignedProtocol);
            if (protocol != null) {
                ByteBuffer buffer = protocol.BuildMessage(conn, Int32.MaxValue, false);
                Send(conn, buffer);
            }
        }

        private void Send(Connection conn, ByteBuffer buffer) {
            if (conn.Status == ConnectionStatus.Lost) {
                return;
            }
            BytesSent += buffer.Size;
            byte[] bytes = buffer.Pack();
            Peer.ListenerThread.LastSentConnection = conn;
            Peer.UdpClient.Send(bytes, bytes.Length, conn.Endpoint);
        }

        public void Handle(IPEndPoint endpoint, ByteBuffer buffer) {


            Connection conn = Find(endpoint);
            conn.Internal.LastMessage = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
            ConnectionStatus oldStatus = conn.Status;
            byte protocolId = buffer.Read();
            Protocol protocol = Peer.GetProtocol(protocolId);
            PacketStage stage = buffer.ReadStage();
            switch (stage) {
                case PacketStage.Establishing:
                    if (conn.Status == ConnectionStatus.Awaiting) {
                        conn.Internal.AssignedProtocol = protocolId;
                        string version = buffer.ReadString();
                        if (protocol == null || !version.Equals(protocol.Version)) {
                            conn.Status = ConnectionStatus.Rejected;
                            conn.ClosingReason = ClosingReason.IncorrectVersion;
                        } else {
                            conn.Status = ConnectionStatus.Ready;
                        }
                        if (protocol != null) {
                            ProtocolActionQueues[protocol.Identifier].Enqueue(new ConnectionChangedAction(oldStatus, conn.Status, conn));
                        }
                    }
                    break;
                case PacketStage.Rejected:
                    conn.Status = ConnectionStatus.Closed;
                    conn.ClosingReason = buffer.ReadClosingReason();
                    if (protocol != null) {
                        ProtocolActionQueues[protocol.Identifier].Enqueue(new ConnectionChangedAction(oldStatus, conn.Status, conn));
                    }
                    break;
                case PacketStage.Closed:
                    if (conn.Status == ConnectionStatus.Stopped) {
                        break;
                    }
                    conn.Status = ConnectionStatus.Stopped;
                    if (protocol != null) {
                        ProtocolActionQueues[protocol.Identifier].Enqueue(new ConnectionChangedAction(oldStatus, conn.Status, conn));
                    }
                    break;
                case PacketStage.Ready:
                    if (conn.Internal.AssignedProtocol != protocolId || protocol == null) {
                        break;
                    }
                    if (oldStatus == ConnectionStatus.Establishing) { // Update connection status
                        conn.Status = ConnectionStatus.Ready;
                        ProtocolActionQueues[protocol.Identifier].Enqueue(new ConnectionChangedAction(oldStatus, conn.Status, conn));
                    }
                    if (!(oldStatus == ConnectionStatus.Establishing || oldStatus == ConnectionStatus.Ready)) {
                        break; // No cheating at this table! For realsies this time!
                    }

                    conn.Internal.LatestOutwardReliable = buffer.ReadInt();
                    int FirstPacketId = buffer.ReadInt();
                    bool Reliable = buffer.ReadBool();

                    ConcurrentQueue<Packet> queue = PacketQueue[conn.uid];
                    Packet peeked;
                    while (queue.TryPeek(out peeked)) {
                        if (peeked.PacketId > conn.Internal.LatestOutwardReliable) {
                            break;
                        } else {
                            Packet LastRemoved;
                            queue.TryDequeue(out LastRemoved);
                        }
                    }
                    PacketQueue[conn.uid] = queue;

                    int PacketAmount = buffer.ReadInt();
                    for (int i = 0; i < PacketAmount; i++) {
                        Packet p = buffer.ReadPacket(protocol);
                        p.PacketId = FirstPacketId + i;
                        p.PacketIsReliable = Reliable;
                        if (p.PacketIsReliable) {
                            if (p.PacketId > conn.Internal.LatestInwardReliable) {
                                conn.Internal.LatestInwardReliable = p.PacketId;
                                ProtocolActionQueues[protocol.Identifier].Enqueue(new ReceiveAction(conn, p));
                            }
                        } else if (p.PacketId > conn.Internal.LatestInwardUnreliable) {
                            conn.Internal.LatestInwardUnreliable = p.PacketId;
                            ProtocolActionQueues[protocol.Identifier].Enqueue(new ReceiveAction(conn, p));
                        }

                        // Do some analytics!
                        int OldReceivedByPacket;
                        ReceivedByPacket.TryGetValue(p.GetType(), out OldReceivedByPacket);
                        ReceivedByPacket[p.GetType()] = OldReceivedByPacket + p.Size;
                    }
                    break;
            }
        }

        private void UpdateThreadMethod() {
            try {
                while (Thread.CurrentThread.IsAlive) {
                    long now = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
                    List<ulong> timedOut = new List<ulong>();
                    foreach (ulong uid in Connections.Keys) {
                        Connection conn = Connections[uid];
                        if ((now - conn.Internal.LastMessage) > Timeout || conn.Status == ConnectionStatus.Lost) {
                            timedOut.Add(uid);
                        }
                        if (conn.Status != ConnectionStatus.Awaiting || conn.Status != ConnectionStatus.Stopped) {
                            if (conn.Status == ConnectionStatus.Ready) {
                                SendPacketQueue(uid);
                            } else {
                                SendPlain(conn);
                            }
                        }
                    }
                    foreach (ulong uid in timedOut) {
                        Connection conn = Connections[uid];
                        ConnectionsToRemove.Enqueue(conn);
                        if (conn.Status == ConnectionStatus.Ready
                            || conn.Status == ConnectionStatus.Establishing
                            || conn.Status == ConnectionStatus.Awaiting
                            || conn.Status == ConnectionStatus.Lost) {
                            Protocol protocol = Peer.GetProtocol(conn.Internal.AssignedProtocol);
                            if (protocol != null) {
                                conn.ClosingReason = ClosingReason.Timeout;
                                ProtocolActionQueues[conn.Internal.AssignedProtocol].Enqueue(new TimeoutAction(conn));
                            }
                        }
                    }
                    Thread.Sleep((int)Interval);
                }
            } catch (ThreadAbortException) {
                Peer.MessageListener.Message("Connection Thread Stopped");
            }
        }
    }

    public abstract class ProtocolAction { };

    class ReceiveAction : ProtocolAction {
        public Connection Connection;
        public Packet Packet;

        public ReceiveAction(Connection connection, Packet packet) {
            Connection = connection;
            Packet = packet;
        }
    }

    class ConnectionChangedAction : ProtocolAction {
        public ConnectionStatus OldStatus;
        public ConnectionStatus NewStatus;
        public Connection Connection;

        public ConnectionChangedAction(ConnectionStatus old, ConnectionStatus newstatus, Connection connection) {
            Connection = connection;
            OldStatus = old;
            NewStatus = newstatus;
        }
    }

    class TimeoutAction : ProtocolAction {
        public Connection Connection;

        public TimeoutAction(Connection connection) {
            Connection = connection;
        }
    }
}