using ARMeilleure.State;
using Ryujinx.Common.Logging;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.IO.Compression;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Threading;

using static ARMeilleure.Translation.PTC.PtcFormatter;

namespace ARMeilleure.Translation.PTC
{
    public static class PtcProfiler
    {
        private const string HeaderMagic = "Phd";

        private const uint InternalVersion = 1713; //! Not to be incremented manually for each change to the ARMeilleure project.

        private const int SaveInterval = 30; // Seconds.

        private const CompressionLevel SaveCompressionLevel = CompressionLevel.Fastest;

        private static readonly System.Timers.Timer _timer;

        private static readonly ManualResetEvent _waitEvent;

        private static readonly object _lock;

        private static bool _disposed;

        private static byte[] _lastHash;

        internal static Dictionary<ulong, FuncProfile> ProfiledFuncs { get; private set; }

        internal static bool Enabled { get; private set; }

        public static ulong StaticCodeStart { internal get; set; }
        public static ulong StaticCodeSize  { internal get; set; }

        static PtcProfiler()
        {
            _timer = new System.Timers.Timer((double)SaveInterval * 1000d);
            _timer.Elapsed += PreSave;

            _waitEvent = new ManualResetEvent(true);

            _lock = new object();

            _disposed = false;

            ProfiledFuncs = new Dictionary<ulong, FuncProfile>();

            Enabled = false;
        }

        internal static void AddEntry(ulong address, ExecutionMode mode, bool highCq)
        {
            if (IsAddressInStaticCodeRange(address))
            {
                Debug.Assert(!highCq);

                lock (_lock)
                {
                    ProfiledFuncs.TryAdd(address, new FuncProfile(mode, highCq: false));
                }
            }
        }

        internal static void UpdateEntry(ulong address, ExecutionMode mode, bool highCq)
        {
            if (IsAddressInStaticCodeRange(address))
            {
                Debug.Assert(highCq);

                lock (_lock)
                {
                    Debug.Assert(ProfiledFuncs.ContainsKey(address));

                    ProfiledFuncs[address] = new FuncProfile(mode, highCq: true);
                }
            }
        }

        internal static bool IsAddressInStaticCodeRange(ulong address)
        {
            return address >= StaticCodeStart && address < StaticCodeStart + StaticCodeSize;
        }

        internal static ConcurrentQueue<(ulong address, ExecutionMode mode, bool highCq)> GetProfiledFuncsToTranslate(ConcurrentDictionary<ulong, TranslatedFunction> funcs)
        {
            var profiledFuncsToTranslate = new ConcurrentQueue<(ulong address, ExecutionMode mode, bool highCq)>();

            foreach (var profiledFunc in ProfiledFuncs)
            {
                ulong address = profiledFunc.Key;

                if (!funcs.ContainsKey(address))
                {
                    profiledFuncsToTranslate.Enqueue((address, profiledFunc.Value.Mode, profiledFunc.Value.HighCq));
                }
            }

            return profiledFuncsToTranslate;
        }

        internal static void ClearEntries()
        {
            ProfiledFuncs.Clear();
            ProfiledFuncs.TrimExcess();
        }

        internal static void PreLoad()
        {
            _lastHash = Array.Empty<byte>();

            string fileNameActual = string.Concat(Ptc.CachePathActual, ".info");
            string fileNameBackup = string.Concat(Ptc.CachePathBackup, ".info");

            FileInfo fileInfoActual = new FileInfo(fileNameActual);
            FileInfo fileInfoBackup = new FileInfo(fileNameBackup);

            if (fileInfoActual.Exists && fileInfoActual.Length != 0L)
            {
                if (!Load(fileNameActual, false))
                {
                    if (fileInfoBackup.Exists && fileInfoBackup.Length != 0L)
                    {
                        Load(fileNameBackup, true);
                    }
                }
            }
            else if (fileInfoBackup.Exists && fileInfoBackup.Length != 0L)
            {
                Load(fileNameBackup, true);
            }
        }

        private static bool Load(string fileName, bool isBackup)
        {
            using (FileStream compressedStream = new FileStream(fileName, FileMode.Open))
            using (DeflateStream deflateStream = new DeflateStream(compressedStream, CompressionMode.Decompress, true))
            using (MemoryStream stream = new MemoryStream())
            using (MD5 md5 = MD5.Create())
            {
                try
                {
                    deflateStream.CopyTo(stream);
                }
                catch
                {
                    InvalidateCompressedStream(compressedStream);

                    return false;
                }

                int hashSize = md5.HashSize / 8;

                stream.Seek(0L, SeekOrigin.Begin);

                byte[] currentHash = new byte[hashSize];
                stream.Read(currentHash, 0, hashSize);

                byte[] expectedHash = md5.ComputeHash(stream);

                if (!CompareHash(currentHash, expectedHash))
                {
                    InvalidateCompressedStream(compressedStream);

                    return false;
                }

                stream.Seek((long)hashSize, SeekOrigin.Begin);

                Header header = ReadHeader(stream);

                if (header.Magic != HeaderMagic)
                {
                    InvalidateCompressedStream(compressedStream);

                    return false;
                }

                if (header.InfoFileVersion != InternalVersion)
                {
                    InvalidateCompressedStream(compressedStream);

                    return false;
                }

                try
                {
                    ProfiledFuncs = Deserialize(stream);
                }
                catch
                {
                    ProfiledFuncs = new Dictionary<ulong, FuncProfile>();

                    InvalidateCompressedStream(compressedStream);

                    return false;
                }

                _lastHash = expectedHash;
            }

            long fileSize = new FileInfo(fileName).Length;

            Logger.Info?.Print(LogClass.Ptc, $"{(isBackup ? "Loaded Backup Profiling Info" : "Loaded Profiling Info")} (size: {fileSize} bytes, profiled functions: {ProfiledFuncs.Count}).");

            return true;
        }

        private static bool CompareHash(ReadOnlySpan<byte> currentHash, ReadOnlySpan<byte> expectedHash)
        {
            return currentHash.SequenceEqual(expectedHash);
        }

        private static Header ReadHeader(Stream stream)
        {
            using (BinaryReader headerReader = new BinaryReader(stream, EncodingCache.UTF8NoBOM, true))
            {
                Header header = new Header();

                header.Magic = headerReader.ReadString();

                header.InfoFileVersion = headerReader.ReadUInt32();

                return header;
            }
        }

        private static Dictionary<ulong, FuncProfile> Deserialize(Stream stream)
        {
            return DeserializeDictionary<ulong, FuncProfile>(stream, (stream) => DeserializeStructure<FuncProfile>(stream));
        }

        private static void InvalidateCompressedStream(FileStream compressedStream)
        {
            compressedStream.SetLength(0L);
        }

        private static void PreSave(object source, System.Timers.ElapsedEventArgs e)
        {
            _waitEvent.Reset();

            string fileNameActual = string.Concat(Ptc.CachePathActual, ".info");
            string fileNameBackup = string.Concat(Ptc.CachePathBackup, ".info");

            FileInfo fileInfoActual = new FileInfo(fileNameActual);

            if (fileInfoActual.Exists && fileInfoActual.Length != 0L)
            {
                File.Copy(fileNameActual, fileNameBackup, true);
            }

            Save(fileNameActual);

            _waitEvent.Set();
        }

        private static void Save(string fileName)
        {
            int profiledFuncsCount;

            using (MemoryStream stream = new MemoryStream())
            using (MD5 md5 = MD5.Create())
            {
                int hashSize = md5.HashSize / 8;

                stream.Seek((long)hashSize, SeekOrigin.Begin);

                WriteHeader(stream);

                lock (_lock)
                {
                    Serialize(stream, ProfiledFuncs);

                    profiledFuncsCount = ProfiledFuncs.Count;
                }

                stream.Seek((long)hashSize, SeekOrigin.Begin);
                byte[] hash = md5.ComputeHash(stream);

                stream.Seek(0L, SeekOrigin.Begin);
                stream.Write(hash, 0, hashSize);

                if (CompareHash(hash, _lastHash))
                {
                    return;
                }

                using (FileStream compressedStream = new FileStream(fileName, FileMode.OpenOrCreate))
                using (DeflateStream deflateStream = new DeflateStream(compressedStream, SaveCompressionLevel, true))
                {
                    try
                    {
                        stream.WriteTo(deflateStream);

                        _lastHash = hash;
                    }
                    catch
                    {
                        compressedStream.Position = 0L;

                        _lastHash = Array.Empty<byte>();
                    }

                    if (compressedStream.Position < compressedStream.Length)
                    {
                        compressedStream.SetLength(compressedStream.Position);
                    }
                }
            }

            long fileSize = new FileInfo(fileName).Length;

            if (fileSize != 0L)
            {
                Logger.Info?.Print(LogClass.Ptc, $"Saved Profiling Info (size: {fileSize} bytes, profiled functions: {profiledFuncsCount}).");
            }
        }

        private static void WriteHeader(Stream stream)
        {
            using (BinaryWriter headerWriter = new BinaryWriter(stream, EncodingCache.UTF8NoBOM, true))
            {
                headerWriter.Write((string)HeaderMagic); // Header.Magic

                headerWriter.Write((uint)InternalVersion); // Header.InfoFileVersion
            }
        }

        private static void Serialize(Stream stream, Dictionary<ulong, FuncProfile> profiledFuncs)
        {
            SerializeDictionary<ulong, FuncProfile>(stream, profiledFuncs, (stream, structure) => SerializeStructure<FuncProfile>(stream, ref structure));
        }

        private struct Header
        {
            public string Magic;

            public uint InfoFileVersion;
        }

        [StructLayout(LayoutKind.Sequential, Pack = 1/*, Size = 5*/)]
        internal struct FuncProfile
        {
            public ExecutionMode Mode;
            public bool HighCq;

            public FuncProfile(ExecutionMode mode, bool highCq)
            {
                Mode = mode;
                HighCq = highCq;
            }
        }

        internal static void Start()
        {
            if (Ptc.State == PtcState.Enabled ||
                Ptc.State == PtcState.Continuing)
            {
                Enabled = true;

                _timer.Enabled = true;
            }
        }

        public static void Stop()
        {
            Enabled = false;

            if (!_disposed)
            {
                _timer.Enabled = false;
            }
        }

        internal static void Wait()
        {
            _waitEvent.WaitOne();
        }

        public static void Dispose()
        {
            if (!_disposed)
            {
                _disposed = true;

                _timer.Elapsed -= PreSave;
                _timer.Dispose();

                Wait();
                _waitEvent.Dispose();
            }
        }
    }
}