using System.IO;
using System.Linq;
using System.Collections.Generic;

using Lidgren.Network;

namespace CoopServer
{
    internal static class DownloadManager
    {
        private static readonly List<long> ClientsToDelete = new();
        private static List<DownloadClient> _clients = new();
        private static readonly List<DownloadFile> _files = new();
        public static bool AnyFileExists = false;

        public static void InsertClient(long nethandle)
        {
            lock (_clients)
            {
                _clients.Add(new DownloadClient(nethandle, new(_files)));
            }
        }

        public static bool CheckForDirectoryAndFiles()
        {
            if (!Directory.Exists("clientside"))
            {
                return false;
            }

            string[] filePaths = Directory.GetFiles("clientside");
            if (filePaths.Length == 0)
            {
                return false;
            }

            byte fileCount = 0;

            foreach (string file in filePaths)
            {
                FileInfo fileInfo = new(file);

                // ONLY JAVASCRIPT AND JSON FILES!
                if (!new string[] { ".js", ".json" }.Any(x => x == fileInfo.Extension))
                {
                    Logging.Warning("Only files with \"*.js\" and \"*.json\" can be sent!");
                    continue;
                }

                const int MAX_BUFFER = 5120; // 5KB
                byte[] buffer = new byte[MAX_BUFFER];
                ushort bytesRead = 0;
                bool fileCreated = false;
                DownloadFile newFile = null;

                using (FileStream fs = File.Open(file, FileMode.Open, FileAccess.Read))
                using (BufferedStream bs = new(fs))
                {
                    while ((bytesRead = (ushort)bs.Read(buffer, 0, MAX_BUFFER)) != 0) // Reading 5KB chunks at time
                    {
                        if (!fileCreated && (fileCreated = true))
                        {
                            newFile = new() { FileID = fileCount, FileName = fileInfo.Name, FileLength = fileInfo.Length, FileChunks = new() };
                        }

                        newFile.FileChunks.Add(buffer.Take(bytesRead).ToArray());
                    }
                }

                _files.Add(newFile);
                fileCount++;
            }

            AnyFileExists = true;
            return true;
        }

        public static void Tick()
        {
            lock (_clients)
            {
                lock (ClientsToDelete)
                {
                    foreach (long nethandle in ClientsToDelete)
                    {
                        DownloadClient client = _clients.FirstOrDefault(x => x.NetHandle == nethandle);
                        if (client != null)
                        {
                            client.Finish();
                            _clients.Remove(client);
                        }
                    }
                    ClientsToDelete.Clear();
                }

                _clients.ForEach(client =>
                {
                    if (client.SendFiles())
                    {
                        lock (Server.Clients)
                        {
                            Client x = Server.Clients.FirstOrDefault(x => x.NetHandle == client.NetHandle);
                            if (x != null)
                            {
                                x.FilesReceived = true;
                            }
                        }

                        AddClientToRemove(client.NetHandle);
                    }
                });
            }
        }

        public static void RemoveClient(long nethandle)
        {
            lock (_clients)
            {
                DownloadClient client = _clients.FirstOrDefault(x => x.NetHandle == nethandle);
                if (client != null)
                {
                    _clients.Remove(client);
                }
            }
        }

        /// <summary>
        /// We try to remove the client when all files have been sent
        /// </summary>
        /// <param name="nethandle"></param>
        /// <param name="id">Not currently used but maybe we can need this sometime</param>
        public static void TryToRemoveClient(long nethandle, int id)
        {
            lock (_clients)
            {
                DownloadClient client = _clients.FirstOrDefault(x => x.NetHandle == nethandle);
                if (client == null)
                {
                    return;
                }

                client.FilePosition++;

                if (client.DownloadComplete())
                {
                    client.Finish();
                    _clients.Remove(client);
                }
            }
        }

        public static void AddClientToRemove(long nethandle)
        {
            lock (ClientsToDelete)
            {
                ClientsToDelete.Add(nethandle);
            }
        }
    }

    internal class DownloadClient
    {
        public long NetHandle = 0;
        private readonly List<DownloadFile> _files = null;
        public int FilePosition = 0;
        private int _fileDataPosition = 0;

        public DownloadClient(long nethandle, List<DownloadFile> files)
        {
            NetHandle = nethandle;
            _files = files;

            NetConnection conn = Server.MainNetServer.Connections.FirstOrDefault(x => x.RemoteUniqueIdentifier == NetHandle);
            if (conn == null)
            {
                DownloadManager.AddClientToRemove(NetHandle);
                return;
            }

            _files.ForEach(file =>
            {
                NetOutgoingMessage outgoingMessage = Server.MainNetServer.CreateMessage();

                new Packets.FileTransferRequest()
                {
                    ID = file.FileID,
                    FileType = (byte)Packets.DataFileType.Script,
                    FileName = file.FileName,
                    FileLength = file.FileLength
                }.PacketToNetOutGoingMessage(outgoingMessage);

                Server.MainNetServer.SendMessage(outgoingMessage, conn, NetDeliveryMethod.ReliableOrdered, (byte)ConnectionChannel.File);
            });
        }

        public void Finish()
        {
            NetConnection conn = Server.MainNetServer.Connections.FirstOrDefault(x => x.RemoteUniqueIdentifier == NetHandle);
            if (conn == null)
            {
                return;
            }

            NetOutgoingMessage outgoingMessage = Server.MainNetServer.CreateMessage();

            new Packets.FileTransferComplete()
            {
                ID = 0x0
            }.PacketToNetOutGoingMessage(outgoingMessage);

            Server.MainNetServer.SendMessage(outgoingMessage, conn, NetDeliveryMethod.ReliableOrdered, (byte)ConnectionChannel.File);
        }

        /// <summary>
        /// 
        /// </summary>
        /// <returns>true if we are done otherwise false</returns>
        public bool SendFiles()
        {
            DownloadFile file = _files[FilePosition];

            Send(NetHandle, file);

            if (_fileDataPosition >= file.FileChunks.Count)
            {
                FilePosition++;
                _fileDataPosition = 0;
            }

            return DownloadComplete();
        }

        private void Send(long nethandle, DownloadFile file)
        {
            NetConnection conn = Server.MainNetServer.Connections.FirstOrDefault(x => x.RemoteUniqueIdentifier == nethandle);
            if (conn == null)
            {
                DownloadManager.AddClientToRemove(NetHandle);
                return;
            }

            NetOutgoingMessage outgoingMessage = Server.MainNetServer.CreateMessage();

            new Packets.FileTransferTick() { ID = file.FileID, FileChunk = file.FileChunks[_fileDataPosition++] }.PacketToNetOutGoingMessage(outgoingMessage);

            Server.MainNetServer.SendMessage(outgoingMessage, conn, NetDeliveryMethod.ReliableUnordered, (byte)ConnectionChannel.File);
        }

        public bool DownloadComplete()
        {
            return FilePosition >= _files.Count;
        }
    }

    internal class DownloadFile
    {
        public byte FileID { get; set; } = 0;
        public string FileName { get; set; } = string.Empty;
        public long FileLength { get; set; } = 0;
        public List<byte[]> FileChunks { get; set; } = null;
    }
}