using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using LZ4;
using MareSynchronos.API;
using MareSynchronos.FileCacheDB;
using MareSynchronos.Utils;
using MareSynchronos.WebAPI.Utils;
using Microsoft.AspNetCore.SignalR.Client;

namespace MareSynchronos.WebAPI
{
    public partial class ApiController
    {
        public void CancelUpload()
        {
            if (_uploadCancellationTokenSource != null)
            {
                Logger.Warn("Cancelling upload");
                _uploadCancellationTokenSource?.Cancel();
                _fileHub!.SendAsync(FilesHubAPI.SendAbortUpload);
                CurrentUploads.Clear();
            }
        }

        public async Task DeleteAllMyFiles()
        {
            await _fileHub!.SendAsync(FilesHubAPI.SendDeleteAllFiles);
        }

        public async Task<string> DownloadFile(string hash, CancellationToken ct)
        {
            var reader = _fileHub!.StreamAsync<byte[]>(FilesHubAPI.StreamDownloadFileAsync, hash, ct);
            string fileName = Path.GetTempFileName();
            await using var fs = File.OpenWrite(fileName);
            await foreach (var data in reader.WithCancellation(ct))
            {
                //Logger.Debug("Getting chunk of " + hash);
                CurrentDownloads.Single(f => f.Hash == hash).Transferred += data.Length;
                await fs.WriteAsync(data, ct);
            }
            return fileName;
        }

        public async Task DownloadFiles(List<FileReplacementDto> fileReplacementDto, CancellationToken ct)
        {
            Logger.Debug("Downloading files");
            List<FileTransfer> fileTransferList = new List<FileTransfer>();
            List<DownloadFileDto> downloadFiles = new List<DownloadFileDto>();
            foreach (var file in fileReplacementDto)
            {
                downloadFiles.Add(await _fileHub!.InvokeAsync<DownloadFileDto>(FilesHubAPI.InvokeGetFileSize, file.Hash, ct));
            }

            downloadFiles = downloadFiles.Distinct().ToList();

            foreach (var dto in downloadFiles)
            {
                var downloadFileTransfer = new DownloadFileTransfer(dto);
                if (CurrentDownloads.All(f => f.Hash != downloadFileTransfer.Hash))
                {
                    CurrentDownloads.Add(downloadFileTransfer);
                }

                fileTransferList.Add(downloadFileTransfer);
            }

            foreach (var file in CurrentDownloads.Where(c => c.IsForbidden))
            {
                if (ForbiddenTransfers.All(f => f.Hash != file.Hash))
                {
                    ForbiddenTransfers.Add(file);
                }
            }

            foreach (var file in fileTransferList.Where(f => f.CanBeTransferred))
            {
                var hash = file.Hash;
                var tempFile = await DownloadFile(hash, ct);
                if (ct.IsCancellationRequested)
                {
                    File.Delete(tempFile);
                    CurrentDownloads.RemoveAll(d => fileReplacementDto.Any(f => f.Hash == d.Hash));
                    break;
                }

                var tempFileData = await File.ReadAllBytesAsync(tempFile, ct);
                var extractedFile = LZ4Codec.Unwrap(tempFileData);
                File.Delete(tempFile);
                var filePath = Path.Combine(_pluginConfiguration.CacheFolder, file.Hash);
                await File.WriteAllBytesAsync(filePath, extractedFile, ct);
                var fi = new FileInfo(filePath);
                Func<DateTime> RandomDayFunc()
                {
                    DateTime start = new DateTime(1995, 1, 1);
                    Random gen = new Random();
                    int range = (DateTime.Today - start).Days;
                    return () => start.AddDays(gen.Next(range));
                }

                fi.CreationTime = RandomDayFunc().Invoke();
                fi.LastAccessTime = RandomDayFunc().Invoke();
                fi.LastWriteTime = RandomDayFunc().Invoke();
            }

            var allFilesInDb = false;
            while (!allFilesInDb && !ct.IsCancellationRequested)
            {
                await using (var db = new FileCacheContext())
                {
                    allFilesInDb = fileTransferList.Where(c => c.CanBeTransferred).All(h => db.FileCaches.Any(f => f.Hash == h.Hash));
                }

                await Task.Delay(250, ct);
            }

            if (ct.IsCancellationRequested)
            {
                CurrentDownloads.RemoveAll(d => fileReplacementDto.Any(f => f.Hash == d.Hash));
            }

            CurrentDownloads.RemoveAll(d => d.Transferred == d.Total || !d.CanBeTransferred);
        }

        public async Task PushCharacterData(CharacterCacheDto character, List<string> visibleCharacterIds)
        {
            if (!IsConnected || SecretKey == "-") return;
            Logger.Debug("Sending Character data to service " + ApiUri);

            CancelUpload();
            _uploadCancellationTokenSource = new CancellationTokenSource();
            var uploadToken = _uploadCancellationTokenSource.Token;
            Logger.Verbose("New Token Created");

            var filesToUpload = await _fileHub!.InvokeAsync<List<UploadFileDto>>(FilesHubAPI.InvokeSendFiles, character.FileReplacements.Select(c => c.Hash).Distinct(), uploadToken);

            foreach (var file in filesToUpload.Where(f => !f.IsForbidden))
            {
                await using var db = new FileCacheContext();
                try
                {
                    CurrentUploads.Add(new UploadFileTransfer(file)
                    {
                        Total = new FileInfo(db.FileCaches.FirstOrDefault(f => f.Hash.ToLower() == file.Hash.ToLower())
                            ?.Filepath ?? string.Empty).Length
                    });
                }
                catch (Exception ex)
                {
                    Logger.Warn("Tried to request file " + file.Hash + " but file was not present");
                    Logger.Warn(ex.StackTrace!);
                }
            }

            await using (var db = new FileCacheContext())
            {
                foreach (var file in filesToUpload.Where(c => c.IsForbidden))
                {
                    if (ForbiddenTransfers.All(f => f.Hash != file.Hash))
                    {
                        ForbiddenTransfers.Add(new UploadFileTransfer(file)
                        {
                            LocalFile = db.FileCaches.FirstOrDefault(f => f.Hash == file.Hash)?.Filepath ?? string.Empty
                        });
                    }
                }
            }

            var totalSize = CurrentUploads.Sum(c => c.Total);
            Logger.Verbose("Compressing and uploading files");
            foreach (var file in CurrentUploads.Where(f => f.CanBeTransferred && !f.IsTransferred))
            {
                Logger.Verbose("Compressing and uploading " + file);
                var data = await GetCompressedFileData(file.Hash, uploadToken);
                CurrentUploads.Single(e => e.Hash == data.Item1).Total = data.Item2.Length;
                await UploadFile(data.Item2, file.Hash, uploadToken);
                if (!uploadToken.IsCancellationRequested) continue;
                Logger.Warn("Cancel in filesToUpload loop detected");
                CurrentUploads.Clear();
                break;
            }

            if (CurrentUploads.Any())
            {
                var compressedSize = CurrentUploads.Sum(c => c.Total);
                Logger.Debug($"Compressed {totalSize} to {compressedSize} ({(compressedSize / (double)totalSize):P2})");
            }

            Logger.Verbose("Upload tasks complete, waiting for server to confirm");
            var anyUploadsOpen = await _fileHub!.InvokeAsync<bool>(FilesHubAPI.InvokeIsUploadFinished, uploadToken);
            Logger.Verbose("Uploads open: " + anyUploadsOpen);
            while (anyUploadsOpen && !uploadToken.IsCancellationRequested)
            {
                anyUploadsOpen = await _fileHub!.InvokeAsync<bool>(FilesHubAPI.InvokeIsUploadFinished, uploadToken);
                await Task.Delay(TimeSpan.FromSeconds(0.5), uploadToken);
                Logger.Verbose("Waiting for uploads to finish");
            }

            CurrentUploads.Clear();

            if (!uploadToken.IsCancellationRequested)
            {
                Logger.Verbose("=== Pushing character data ===");
                await _userHub!.InvokeAsync(UserHubAPI.InvokePushCharacterDataToVisibleClients, character, visibleCharacterIds, uploadToken);
            }
            else
            {
                Logger.Warn("=== Upload operation was cancelled ===");
            }

            Logger.Verbose("Upload complete for " + character.Hash);
            _uploadCancellationTokenSource = null;
        }

        private async Task<(string, byte[])> GetCompressedFileData(string fileHash, CancellationToken uploadToken)
        {
            await using var db = new FileCacheContext();
            var fileCache = db.FileCaches.First(f => f.Hash == fileHash);
            return (fileHash, LZ4Codec.WrapHC(await File.ReadAllBytesAsync(fileCache.Filepath, uploadToken), 0,
                (int)new FileInfo(fileCache.Filepath).Length));
        }

        private async Task UploadFile(byte[] compressedFile, string fileHash, CancellationToken uploadToken)
        {
            if (uploadToken.IsCancellationRequested) return;

            async IAsyncEnumerable<byte[]> AsyncFileData([EnumeratorCancellation] CancellationToken token)
            {
                var chunkSize = 1024 * 512; // 512kb
                using var ms = new MemoryStream(compressedFile);
                var buffer = new byte[chunkSize];
                int bytesRead;
                while ((bytesRead = await ms.ReadAsync(buffer, 0, chunkSize, token)) > 0 && !token.IsCancellationRequested)
                {
                    CurrentUploads.Single(f => f.Hash == fileHash).Transferred += bytesRead;
                    token.ThrowIfCancellationRequested();
                    yield return bytesRead == chunkSize ? buffer.ToArray() : buffer.Take(bytesRead).ToArray();
                }
            }

            await _fileHub!.SendAsync(FilesHubAPI.SendUploadFileStreamAsync, fileHash, AsyncFileData(uploadToken), uploadToken);
        }
    }

}