/*************************************************************************
 * ModernUO                                                              *
 * Copyright (C) 2020 - ModernUO Development Team                        *
 * Email: hi@modernuo.com                                                *
 * File: AsyncWriter.cs                                                  *
 * Created: 2020/12/30 - Updated: 2020/04/25                             *
 *                                                                       *
 * 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.Generic;
using System.IO;
using System.Net;
using System.Threading;
using Server.Guilds;

namespace Server
{
    public sealed class AsyncWriter : IGenericWriter
    {
        private readonly int m_BufferSize;
        private readonly FileStream m_File;
        private readonly bool m_PrefixStrings;

        private readonly Queue<MemoryStream> m_WriteQueue;
        private BinaryWriter m_Bin;
        private bool m_Closed;

        private long m_LastPos;

        private MemoryStream m_Mem;
        private Thread m_WorkerThread;

        public AsyncWriter(string filename, bool prefix)
            : this(filename, 1048576, prefix) // 1 mb buffer
        {
        }

        public AsyncWriter(string filename, int buffSize, bool prefix)
        {
            m_PrefixStrings = prefix;
            m_Closed = false;
            m_WriteQueue = new Queue<MemoryStream>();
            m_BufferSize = buffSize;

            m_File = new FileStream(filename, FileMode.Create, FileAccess.Write, FileShare.None);
            m_Mem = new MemoryStream(m_BufferSize + 1024);
            m_Bin = new BinaryWriter(m_Mem, Utility.UTF8WithEncoding);
        }

        public static int ThreadCount { get; private set; }

        public MemoryStream MemStream
        {
            get => m_Mem;
            set
            {
                if (m_Mem.Length > 0)
                    Enqueue(m_Mem);

                m_Mem = value;
                m_Bin = new BinaryWriter(m_Mem, Utility.UTF8WithEncoding);
                m_LastPos = 0;
                Position = m_Mem.Length;
                m_Mem.Seek(0, SeekOrigin.End);
            }
        }

        public long Position { get; private set; }

        public void Close()
        {
            Enqueue(m_Mem);
            m_Closed = true;
        }

        public void Write(IPAddress value)
        {
            m_Bin.Write(Utility.GetLongAddressValue(value));
            OnWrite();
        }

        public void Write(string value)
        {
            if (m_PrefixStrings)
            {
                if (value == null)
                {
                    m_Bin.Write((byte)0);
                }
                else
                {
                    m_Bin.Write((byte)1);
                    m_Bin.Write(value);
                }
            }
            else
            {
                m_Bin.Write(value);
            }

            OnWrite();
        }

        public void WriteDeltaTime(DateTime value)
        {
            var ticks = value.Ticks;
            var now = DateTime.UtcNow.Ticks;

            TimeSpan d;

            try
            {
                d = new TimeSpan(ticks - now);
            }
            catch
            {
                d = TimeSpan.MaxValue;
            }

            Write(d);
        }

        public void Write(DateTime value)
        {
            m_Bin.Write(value.Ticks);
            OnWrite();
        }

        public void Write(DateTimeOffset value)
        {
            m_Bin.Write(value.Ticks);
            m_Bin.Write(value.Offset.Ticks);
            OnWrite();
        }

        public void Write(TimeSpan value)
        {
            m_Bin.Write(value.Ticks);
            OnWrite();
        }

        public void Write(decimal value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(long value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(ulong value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void WriteEncodedInt(int value)
        {
            var v = (uint)value;

            while (v >= 0x80)
            {
                m_Bin.Write((byte)(v | 0x80));
                v >>= 7;
            }

            m_Bin.Write((byte)v);
            OnWrite();
        }

        public void Write(int value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(uint value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(short value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(ushort value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(double value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(float value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(char value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(byte value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(byte[] value)
        {
            Write(value, value.Length);
        }

        public void Write(byte[] value, int length)
        {
            m_Bin.Write(value, 0, length);
            OnWrite();
        }

        public void Write(sbyte value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(bool value)
        {
            m_Bin.Write(value);
            OnWrite();
        }

        public void Write(Point3D value)
        {
            Write(value.m_X);
            Write(value.m_Y);
            Write(value.m_Z);
        }

        public void Write(Point2D value)
        {
            Write(value.m_X);
            Write(value.m_Y);
        }

        public void Write(Rectangle2D value)
        {
            Write(value.Start);
            Write(value.End);
        }

        public void Write(Rectangle3D value)
        {
            Write(value.Start);
            Write(value.End);
        }

        public void Write(Map value)
        {
            if (value != null)
                Write((byte)value.MapIndex);
            else
                Write((byte)0xFF);
        }

        public void Write(Race value)
        {
            if (value != null)
                Write((byte)value.RaceIndex);
            else
                Write((byte)0xFF);
        }

        public void WriteEntity(IEntity value)
        {
            if (value?.Deleted != false)
                Write(Serial.MinusOne);
            else
                Write(value.Serial);
        }

        public void Write(Item value)
        {
            if (value?.Deleted != false)
                Write(Serial.MinusOne);
            else
                Write(value.Serial);
        }

        public void Write(Mobile value)
        {
            if (value?.Deleted != false)
                Write(Serial.MinusOne);
            else
                Write(value.Serial);
        }

        public void Write(BaseGuild value)
        {
            if (value == null)
                Write(0);
            else
                Write(value.Serial);
        }

        public void WriteItem<T>(T value) where T : Item
        {
            Write(value);
        }

        public void WriteMobile<T>(T value) where T : Mobile
        {
            Write(value);
        }

        public void WriteGuild<T>(T value) where T : BaseGuild
        {
            Write(value);
        }

        public void Write(List<Item> list)
        {
            WriteItemList(list);
        }

        public void Write(List<Item> list, bool tidy)
        {
            WriteItemList(list, tidy);
        }

        public void WriteItemList<T>(List<T> list) where T : Item
        {
            WriteItemList(list, false);
        }

        public void WriteItemList<T>(List<T> list, bool tidy) where T : Item
        {
            if (tidy)
                for (var i = 0; i < list.Count;)
                    if (list[i].Deleted)
                        list.RemoveAt(i);
                    else
                        ++i;

            Write(list.Count);

            for (var i = 0; i < list.Count; ++i)
                Write(list[i]);
        }

        public void Write(HashSet<Item> set)
        {
            Write(set, false);
        }

        public void Write(HashSet<Item> set, bool tidy)
        {
            if (tidy) set.RemoveWhere(item => item.Deleted);

            Write(set.Count);

            foreach (var item in set) Write(item);
        }

        public void WriteItemSet<T>(HashSet<T> set) where T : Item
        {
            WriteItemSet(set, false);
        }

        public void WriteItemSet<T>(HashSet<T> set, bool tidy) where T : Item
        {
            if (tidy) set.RemoveWhere(item => item.Deleted);

            Write(set.Count);

            foreach (var item in set) Write(item);
        }

        public void Write(List<Mobile> list)
        {
            Write(list, false);
        }

        public void Write(List<Mobile> list, bool tidy)
        {
            if (tidy)
                for (var i = 0; i < list.Count;)
                    if (list[i].Deleted)
                        list.RemoveAt(i);
                    else
                        ++i;

            Write(list.Count);

            for (var i = 0; i < list.Count; ++i)
                Write(list[i]);
        }

        public void WriteMobileList<T>(List<T> list) where T : Mobile
        {
            WriteMobileList(list, false);
        }

        public void WriteMobileList<T>(List<T> list, bool tidy) where T : Mobile
        {
            if (tidy)
                for (var i = 0; i < list.Count;)
                    if (list[i].Deleted)
                        list.RemoveAt(i);
                    else
                        ++i;

            Write(list.Count);

            for (var i = 0; i < list.Count; ++i)
                Write(list[i]);
        }

        public void Write(HashSet<Mobile> set)
        {
            Write(set, false);
        }

        public void Write(HashSet<Mobile> set, bool tidy)
        {
            if (tidy) set.RemoveWhere(mobile => mobile.Deleted);

            Write(set.Count);

            foreach (var mob in set) Write(mob);
        }

        public void WriteMobileSet<T>(HashSet<T> set) where T : Mobile
        {
            WriteMobileSet(set, false);
        }

        public void WriteMobileSet<T>(HashSet<T> set, bool tidy) where T : Mobile
        {
            if (tidy) set.RemoveWhere(mob => mob.Deleted);

            Write(set.Count);

            foreach (var mob in set) Write(mob);
        }

        public void Write(List<BaseGuild> list)
        {
            Write(list, false);
        }

        public void Write(List<BaseGuild> list, bool tidy)
        {
            if (tidy)
                for (var i = 0; i < list.Count;)
                    if (list[i].Disbanded)
                        list.RemoveAt(i);
                    else
                        ++i;

            Write(list.Count);

            for (var i = 0; i < list.Count; ++i)
                Write(list[i]);
        }

        public void WriteGuildList<T>(List<T> list) where T : BaseGuild
        {
            WriteGuildList(list, false);
        }

        public void WriteGuildList<T>(List<T> list, bool tidy) where T : BaseGuild
        {
            if (tidy)
                for (var i = 0; i < list.Count;)
                    if (list[i].Disbanded)
                        list.RemoveAt(i);
                    else
                        ++i;

            Write(list.Count);

            for (var i = 0; i < list.Count; ++i)
                Write(list[i]);
        }

        public void Write(HashSet<BaseGuild> set)
        {
            Write(set, false);
        }

        public void Write(HashSet<BaseGuild> set, bool tidy)
        {
            if (tidy) set.RemoveWhere(guild => guild.Disbanded);

            Write(set.Count);

            foreach (var guild in set) Write(guild);
        }

        public void WriteGuildSet<T>(HashSet<T> set) where T : BaseGuild
        {
            WriteGuildSet(set, false);
        }

        public void WriteGuildSet<T>(HashSet<T> set, bool tidy) where T : BaseGuild
        {
            if (tidy) set.RemoveWhere(guild => guild.Disbanded);

            Write(set.Count);

            foreach (var guild in set) Write(guild);
        }

        private void Enqueue(MemoryStream mem)
        {
            lock (m_WriteQueue)
            {
                m_WriteQueue.Enqueue(mem);
            }

            if (m_WorkerThread.IsAlive != true)
            {
                m_WorkerThread = new Thread(new WorkerThread(this).Worker) { Priority = ThreadPriority.BelowNormal };
                m_WorkerThread.Start();
            }
        }

        private void OnWrite()
        {
            var curlen = m_Mem.Length;
            Position += curlen - m_LastPos;
            m_LastPos = curlen;
            if (curlen >= m_BufferSize)
            {
                Enqueue(m_Mem);
                m_Mem = new MemoryStream(m_BufferSize + 1024);
                m_Bin = new BinaryWriter(m_Mem, Utility.UTF8WithEncoding);
                m_LastPos = 0;
            }
        }

        private class WorkerThread
        {
            private readonly AsyncWriter m_Owner;

            public WorkerThread(AsyncWriter owner) => m_Owner = owner;

            public void Worker()
            {
                ThreadCount++;

                int lastCount;

                do
                {
                    MemoryStream mem = null;

                    lock (m_Owner.m_WriteQueue)
                    {
                        if ((lastCount = m_Owner.m_WriteQueue.Count) > 0)
                            mem = m_Owner.m_WriteQueue.Dequeue();
                    }

                    if (mem?.Length > 0)
                        mem.WriteTo(m_Owner.m_File);
                } while (lastCount > 1);

                if (m_Owner.m_Closed)
                    m_Owner.m_File.Close();

                ThreadCount--;

                if (ThreadCount <= 0)
                    World.NotifyDiskWriteComplete();
            }
        }
    }
}