using System;
using System.Diagnostics;
using System.Collections.Concurrent;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using MediaBrowser.Common.Configuration;
using MediaBrowser.Common.Extensions;
using MediaBrowser.Controller.Entities;
using MediaBrowser.Controller.Library;
using MediaBrowser.Controller.MediaEncoding;
using MediaBrowser.Model.Dto;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.IO;
using MediaBrowser.Model.MediaInfo;
using Microsoft.Extensions.Logging;

namespace MediaBrowser.MediaEncoding.Attachments
{
    public class AttachmentExtractor : IAttachmentExtractor, IDisposable
    {
        private readonly ILogger _logger;
        private readonly IApplicationPaths _appPaths;
        private readonly IFileSystem _fileSystem;
        private readonly IMediaEncoder _mediaEncoder;
        private readonly IMediaSourceManager _mediaSourceManager;

        private readonly ConcurrentDictionary<string, SemaphoreSlim> _semaphoreLocks =
            new ConcurrentDictionary<string, SemaphoreSlim>();

        private bool _disposed = false;

        public AttachmentExtractor(
            ILogger<AttachmentExtractor> logger,
            IApplicationPaths appPaths,
            IFileSystem fileSystem,
            IMediaEncoder mediaEncoder,
            IMediaSourceManager mediaSourceManager)
        {
            _logger = logger;
            _appPaths = appPaths;
            _fileSystem = fileSystem;
            _mediaEncoder = mediaEncoder;
            _mediaSourceManager = mediaSourceManager;
        }

        /// <inheritdoc />
        public async Task<(MediaAttachment attachment, Stream stream)> GetAttachment(BaseItem item, string mediaSourceId, int attachmentStreamIndex, CancellationToken cancellationToken)
        {
            if (item == null)
            {
                throw new ArgumentNullException(nameof(item));
            }

            if (string.IsNullOrWhiteSpace(mediaSourceId))
            {
                throw new ArgumentNullException(nameof(mediaSourceId));
            }

            var mediaSources = await _mediaSourceManager.GetPlaybackMediaSources(item, null, true, false, cancellationToken).ConfigureAwait(false);
            var mediaSource = mediaSources
                .FirstOrDefault(i => string.Equals(i.Id, mediaSourceId, StringComparison.OrdinalIgnoreCase));
            if (mediaSource == null)
            {
                throw new ResourceNotFoundException($"MediaSource {mediaSourceId} not found");
            }

            var mediaAttachment = mediaSource.MediaAttachments
                .FirstOrDefault(i => i.Index == attachmentStreamIndex);
            if (mediaAttachment == null)
            {
                throw new ResourceNotFoundException($"MediaSource {mediaSourceId} has no attachment with stream index {attachmentStreamIndex}");
            }

            var attachmentStream = await GetAttachmentStream(mediaSource, mediaAttachment, cancellationToken)
                    .ConfigureAwait(false);

            return (mediaAttachment, attachmentStream);
        }

        private async Task<Stream> GetAttachmentStream(
            MediaSourceInfo mediaSource,
            MediaAttachment mediaAttachment,
            CancellationToken cancellationToken)
        {
            var attachmentPath = await GetReadableFile(mediaSource.Path, mediaSource.Path, mediaSource.Protocol, mediaAttachment, cancellationToken).ConfigureAwait(false);
            return File.OpenRead(attachmentPath);
        }

        private async Task<string> GetReadableFile(
            string mediaPath,
            string inputFile,
            MediaProtocol protocol,
            MediaAttachment mediaAttachment,
            CancellationToken cancellationToken)
        {
            var outputPath = GetAttachmentCachePath(mediaPath, protocol, mediaAttachment.Index);
            await ExtractAttachment(inputFile, protocol, mediaAttachment.Index, outputPath, cancellationToken)
                .ConfigureAwait(false);

            return outputPath;
        }

        private async Task ExtractAttachment(
            string inputFile,
            MediaProtocol protocol,
            int attachmentStreamIndex,
            string outputPath,
            CancellationToken cancellationToken)
        {
            var semaphore = _semaphoreLocks.GetOrAdd(outputPath, key => new SemaphoreSlim(1, 1));

            await semaphore.WaitAsync(cancellationToken).ConfigureAwait(false);

            try
            {
                if (!File.Exists(outputPath))
                {
                    await ExtractAttachmentInternal(
                        _mediaEncoder.GetInputArgument(new[] { inputFile }, protocol),
                        attachmentStreamIndex,
                        outputPath,
                        cancellationToken).ConfigureAwait(false);
                }
            }
            finally
            {
                semaphore.Release();
            }
        }

        private async Task ExtractAttachmentInternal(
            string inputPath,
            int attachmentStreamIndex,
            string outputPath,
            CancellationToken cancellationToken)
        {
            if (string.IsNullOrEmpty(inputPath))
            {
                throw new ArgumentNullException(nameof(inputPath));
            }

            if (string.IsNullOrEmpty(outputPath))
            {
                throw new ArgumentNullException(nameof(outputPath));
            }

            Directory.CreateDirectory(Path.GetDirectoryName(outputPath));

            var processArgs = string.Format(
                CultureInfo.InvariantCulture,
                "-dump_attachment:{1} {2} -i {0} -t 0 -f null null",
                inputPath,
                attachmentStreamIndex,
                outputPath);
            var startInfo = new ProcessStartInfo
            {
                Arguments = processArgs,
                FileName = _mediaEncoder.EncoderPath,
                UseShellExecute = false,
                CreateNoWindow = true,
                WindowStyle = ProcessWindowStyle.Hidden,
                ErrorDialog = false
            };

            int exitCode;

            using (var process = new Process { StartInfo = startInfo, EnableRaisingEvents = true })
            {
                _logger.LogInformation("{File} {Arguments}", process.StartInfo.FileName, process.StartInfo.Arguments);

                process.Start();

                var ranToCompletion = await process.WaitForExitAsync(cancellationToken).ConfigureAwait(false);

                if (!ranToCompletion)
                {
                    try
                    {
                        _logger.LogWarning("Killing ffmpeg attachment extraction process");
                        process.Kill();
                    }
                    catch (Exception ex)
                    {
                        _logger.LogError(ex, "Error killing attachment extraction process");
                    }
                }

                exitCode = ranToCompletion ? process.ExitCode : -1;
            }

            var failed = false;

            if (exitCode != 0)
            {
                failed = true;

                _logger.LogWarning("Deleting extracted attachment {Path} due to failure: {ExitCode}", outputPath, exitCode);
                try
                {
                    if (File.Exists(outputPath))
                    {
                        _fileSystem.DeleteFile(outputPath);
                    }
                }
                catch (IOException ex)
                {
                    _logger.LogError(ex, "Error deleting extracted attachment {Path}", outputPath);
                }
            }
            else if (!File.Exists(outputPath))
            {
                failed = true;
            }

            if (failed)
            {
                var msg = $"ffmpeg attachment extraction failed for {inputPath} to {outputPath}";

                _logger.LogError(msg);

                throw new InvalidOperationException(msg);
            }
            else
            {
                _logger.LogInformation("ffmpeg attachment extraction completed for {Path} to {Path}", inputPath, outputPath);
            }
        }

        private string GetAttachmentCachePath(string mediaPath, MediaProtocol protocol, int attachmentStreamIndex)
        {
            string filename;
            if (protocol == MediaProtocol.File)
            {
                var date = _fileSystem.GetLastWriteTimeUtc(mediaPath);
                filename = (mediaPath + attachmentStreamIndex.ToString(CultureInfo.InvariantCulture) + "_" + date.Ticks.ToString(CultureInfo.InvariantCulture)).GetMD5().ToString("D");
            }
            else
            {
                filename = (mediaPath + attachmentStreamIndex.ToString(CultureInfo.InvariantCulture)).GetMD5().ToString("D");
            }

            var prefix = filename.Substring(0, 1);
            return Path.Combine(_appPaths.DataPath, "attachments", prefix, filename);
        }

        /// <inheritdoc />
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            if (_disposed)
            {
                return;
            }

            if (disposing)
            {

            }

            _disposed = true;
        }
    }
}