using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using CommonIO;
using MediaBrowser.Common.Configuration;
using MediaBrowser.Controller.MediaEncoding;
using MediaBrowser.Model.Dto;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.Logging;
using MediaBrowser.Model.Serialization;

namespace MediaBrowser.Server.Implementations.LiveTv.EmbyTV
{
    public class EncodedRecorder : IRecorder
    {
        private readonly ILogger _logger;
        private readonly IFileSystem _fileSystem;
        private readonly IMediaEncoder _mediaEncoder;
        private readonly IApplicationPaths _appPaths;
        private bool _hasExited;
        private Stream _logFileStream;
        private string _targetPath;
        private Process _process;
        private readonly IJsonSerializer _json;

        public EncodedRecorder(ILogger logger, IFileSystem fileSystem, IMediaEncoder mediaEncoder, IApplicationPaths appPaths, IJsonSerializer json)
        {
            _logger = logger;
            _fileSystem = fileSystem;
            _mediaEncoder = mediaEncoder;
            _appPaths = appPaths;
            _json = json;
        }

        public async Task Record(MediaSourceInfo mediaSource, string targetFile, Action onStarted, CancellationToken cancellationToken)
        {
            _targetPath = targetFile;
            _fileSystem.CreateDirectory(Path.GetDirectoryName(targetFile));

            var process = new Process
            {
                StartInfo = new ProcessStartInfo
                {
                    CreateNoWindow = true,
                    UseShellExecute = false,

                    // Must consume both stdout and stderr or deadlocks may occur
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    RedirectStandardInput = true,

                    FileName = _mediaEncoder.EncoderPath,
                    Arguments = GetCommandLineArgs(mediaSource, targetFile),

                    WindowStyle = ProcessWindowStyle.Hidden,
                    ErrorDialog = false
                },

                EnableRaisingEvents = true
            };

            _process = process;

            var commandLineLogMessage = process.StartInfo.FileName + " " + process.StartInfo.Arguments;
            _logger.Info(commandLineLogMessage);

            var logFilePath = Path.Combine(_appPaths.LogDirectoryPath, "record-transcode-" + Guid.NewGuid() + ".txt");
            _fileSystem.CreateDirectory(Path.GetDirectoryName(logFilePath));

            // FFMpeg writes debug/error info to stderr. This is useful when debugging so let's put it in the log directory.
            _logFileStream = _fileSystem.GetFileStream(logFilePath, FileMode.Create, FileAccess.Write, FileShare.Read, true);

            var commandLineLogMessageBytes = Encoding.UTF8.GetBytes(_json.SerializeToString(mediaSource) + Environment.NewLine + Environment.NewLine + commandLineLogMessage + Environment.NewLine + Environment.NewLine);
            await _logFileStream.WriteAsync(commandLineLogMessageBytes, 0, commandLineLogMessageBytes.Length, cancellationToken).ConfigureAwait(false);

            process.Exited += (sender, args) => OnFfMpegProcessExited(process);

            process.Start();

            cancellationToken.Register(Stop);

            // MUST read both stdout and stderr asynchronously or a deadlock may occurr
            process.BeginOutputReadLine();

            // Important - don't await the log task or we won't be able to kill ffmpeg when the user stops playback
            StartStreamingLog(process.StandardError.BaseStream, _logFileStream);

            onStarted();

            // Wait for the file to exist before proceeeding
            while (!_hasExited)
            {
                await Task.Delay(100, cancellationToken).ConfigureAwait(false);
            }
        }

        private string GetCommandLineArgs(MediaSourceInfo mediaSource, string targetFile)
        {
            string videoArgs;
            if (EncodeVideo(mediaSource))
            {
                var maxBitrate = 25000000;
                videoArgs = string.Format(
                        "-codec:v:0 libx264 -force_key_frames expr:gte(t,n_forced*5) {0} -pix_fmt yuv420p -preset superfast -crf 23 -b:v {1} -maxrate {1} -bufsize ({1}*2) -vsync vfr -profile:v high -level 41",
                        GetOutputSizeParam(),
                        maxBitrate.ToString(CultureInfo.InvariantCulture));
            }
            else
            {
                videoArgs = "-codec:v:0 copy";
            }

            var commandLineArgs = "-fflags +genpts -async 1 -vsync -1 -i \"{0}\" -sn {2} -map_metadata -1 -threads 0 {3} -y \"{1}\"";

            if (mediaSource.ReadAtNativeFramerate)
            {
                commandLineArgs = "-re " + commandLineArgs;
            }

            commandLineArgs = string.Format(commandLineArgs, mediaSource.Path, targetFile, videoArgs, GetAudioArgs(mediaSource));

            return commandLineArgs;
        }

        private string GetAudioArgs(MediaSourceInfo mediaSource)
        {
            var copyAudio = new[] { "aac", "mp3" };
            var mediaStreams = mediaSource.MediaStreams ?? new List<MediaStream>();
            if (mediaStreams.Any(i => i.Type == MediaStreamType.Audio && copyAudio.Contains(i.Codec, StringComparer.OrdinalIgnoreCase)))
            {
                return "-codec:a:0 copy";
            }

            var audioChannels = 2;
            var audioStream = mediaStreams.FirstOrDefault(i => i.Type == MediaStreamType.Audio);
            if (audioStream != null)
            {
                audioChannels = audioStream.Channels ?? audioChannels;
            }
            return "-codec:a:0 aac -strict experimental -ab 320000";
        }

        private bool EncodeVideo(MediaSourceInfo mediaSource)
        {
            var mediaStreams = mediaSource.MediaStreams ?? new List<MediaStream>();
            return !mediaStreams.Any(i => i.Type == MediaStreamType.Video && string.Equals(i.Codec, "h264", StringComparison.OrdinalIgnoreCase) && !i.IsInterlaced);
        }

        protected string GetOutputSizeParam()
        {
            var filters = new List<string>();

            filters.Add("yadif=0:-1:0");

            var output = string.Empty;

            if (filters.Count > 0)
            {
                output += string.Format(" -vf \"{0}\"", string.Join(",", filters.ToArray()));
            }

            return output;
        }

        private void Stop()
        {
            if (!_hasExited)
            {
                try
                {
                    _logger.Info("Killing ffmpeg recording process for {0}", _targetPath);

                    //process.Kill();
                    _process.StandardInput.WriteLine("q");

                    // Need to wait because killing is asynchronous
                    _process.WaitForExit(5000);
                }
                catch (Exception ex)
                {
                    _logger.ErrorException("Error killing transcoding job for {0}", ex, _targetPath);
                }
            }
        }

        /// <summary>
        /// Processes the exited.
        /// </summary>
        /// <param name="process">The process.</param>
        private void OnFfMpegProcessExited(Process process)
        {
            _hasExited = true;

            _logger.Debug("Disposing stream resources");
            DisposeLogStream();

            try
            {
                _logger.Info("FFMpeg exited with code {0}", process.ExitCode);
            }
            catch
            {
                _logger.Error("FFMpeg exited with an error.");
            }
        }

        private void DisposeLogStream()
        {
            if (_logFileStream != null)
            {
                try
                {
                    _logFileStream.Dispose();
                }
                catch (Exception ex)
                {
                    _logger.ErrorException("Error disposing log stream", ex);
                }

                _logFileStream = null;
            }
        }

        private async void StartStreamingLog(Stream source, Stream target)
        {
            try
            {
                using (var reader = new StreamReader(source))
                {
                    while (!reader.EndOfStream)
                    {
                        var line = await reader.ReadLineAsync().ConfigureAwait(false);

                        var bytes = Encoding.UTF8.GetBytes(Environment.NewLine + line);

                        await target.WriteAsync(bytes, 0, bytes.Length).ConfigureAwait(false);
                        await target.FlushAsync().ConfigureAwait(false);
                    }
                }
            }
            catch (ObjectDisposedException)
            {
                // Don't spam the log. This doesn't seem to throw in windows, but sometimes under linux
            }
            catch (Exception ex)
            {
                _logger.ErrorException("Error reading ffmpeg log", ex);
            }
        }
    }
}