using System;
using System.Collections.Generic;
using System.Linq;
using NLog;
using NzbDrone.Common.Cache;
using NzbDrone.Common.Extensions;
using NzbDrone.Core.History;
using NzbDrone.Core.Messaging.Events;
using NzbDrone.Core.Parser;

namespace NzbDrone.Core.Download.TrackedDownloads
{
    public interface ITrackedDownloadService
    {
        TrackedDownload Find(string downloadId);
        void StopTracking(string downloadId);
        void StopTracking(List<string> downloadIds);
        TrackedDownload TrackDownload(DownloadClientDefinition downloadClient, DownloadClientItem downloadItem);
        List<TrackedDownload> GetTrackedDownloads();
        void UpdateTrackable(List<TrackedDownload> trackedDownloads);
    }

    public class TrackedDownloadService : ITrackedDownloadService
    {
        private readonly IParsingService _parsingService;
        private readonly IHistoryService _historyService;
        private readonly IEventAggregator _eventAggregator;
        private readonly Logger _logger;
        private readonly ICached<TrackedDownload> _cache;

        public TrackedDownloadService(IParsingService parsingService,
                                      ICacheManager cacheManager,
                                      IHistoryService historyService,
                                      IEventAggregator eventAggregator,
                                      Logger logger)
        {
            _parsingService = parsingService;
            _historyService = historyService;
            _eventAggregator = eventAggregator;
            _cache = cacheManager.GetCache<TrackedDownload>(GetType());
            _logger = logger;
        }

        public TrackedDownload Find(string downloadId)
        {
            return _cache.Find(downloadId);
        }

        public void StopTracking(string downloadId)
        {
            var trackedDownload = _cache.Find(downloadId);

            _cache.Remove(downloadId);
            _eventAggregator.PublishEvent(new TrackedDownloadsRemovedEvent(new List<TrackedDownload> { trackedDownload }));
        }

        public void StopTracking(List<string> downloadIds)
        {
            var trackedDownloads = new List<TrackedDownload>();

            foreach (var downloadId in downloadIds)
            {
                var trackedDownload = _cache.Find(downloadId);
                _cache.Remove(downloadId);
                trackedDownloads.Add(trackedDownload);
            }

            _eventAggregator.PublishEvent(new TrackedDownloadsRemovedEvent(trackedDownloads));
        }

        public TrackedDownload TrackDownload(DownloadClientDefinition downloadClient, DownloadClientItem downloadItem)
        {
            var existingItem = Find(downloadItem.DownloadId);

            if (existingItem != null && existingItem.State != TrackedDownloadStage.Downloading)
            {
                LogItemChange(existingItem, existingItem.DownloadItem, downloadItem);

                existingItem.DownloadItem = downloadItem;
                existingItem.IsTrackable = true;

                return existingItem;
            }

            var trackedDownload = new TrackedDownload
            {
                DownloadClient = downloadClient.Id,
                DownloadItem = downloadItem,
                Protocol = downloadClient.Protocol,
                IsTrackable = true
            };

            try
            {
                var parsedAlbumInfo = Parser.Parser.ParseAlbumTitle(trackedDownload.DownloadItem.Title);
                var historyItems = _historyService.FindByDownloadId(downloadItem.DownloadId);

                if (parsedAlbumInfo != null)
                {
                    trackedDownload.RemoteAlbum = _parsingService.Map(parsedAlbumInfo);
                }

                if (historyItems.Any())
                {
                    var firstHistoryItem = historyItems.OrderByDescending(h => h.Date).First();
                    trackedDownload.State = GetStateFromHistory(firstHistoryItem.EventType);

                    var grabbedEvent = historyItems.FirstOrDefault(v => v.EventType == HistoryEventType.Grabbed);
                    trackedDownload.Indexer = grabbedEvent?.Data["indexer"];


                    if (parsedAlbumInfo == null ||
                        trackedDownload.RemoteAlbum == null ||
                        trackedDownload.RemoteAlbum.Artist == null ||
                        trackedDownload.RemoteAlbum.Albums.Empty())
                    {
                        // Try parsing the original source title and if that fails, try parsing it as a special
                        // TODO: Pass the TVDB ID and TVRage IDs in as well so we have a better chance for finding the item
                        parsedAlbumInfo = Parser.Parser.ParseAlbumTitle(firstHistoryItem.SourceTitle);

                        if (parsedAlbumInfo != null)
                        {
                            trackedDownload.RemoteAlbum = _parsingService.Map(parsedAlbumInfo, firstHistoryItem.ArtistId, historyItems.Where(v => v.EventType == HistoryEventType.Grabbed).Select(h => h.AlbumId).Distinct());
                        }
                    }
                }

                if (trackedDownload.RemoteAlbum == null)
                {
                    _logger.Trace("No Album found for download '{0}', not tracking.", trackedDownload.DownloadItem.Title);
                    return null;
                }
            }
            catch (Exception e)
            {
                _logger.Debug(e, "Failed to find album for " + downloadItem.Title);
                return null;
            }

            LogItemChange(trackedDownload, existingItem?.DownloadItem, trackedDownload.DownloadItem);

            _cache.Set(trackedDownload.DownloadItem.DownloadId, trackedDownload);
            return trackedDownload;
        }

        public List<TrackedDownload> GetTrackedDownloads()
        {
            return _cache.Values.ToList();
        }

        public void UpdateTrackable(List<TrackedDownload> trackedDownloads)
        {
            var untrackable = GetTrackedDownloads().ExceptBy(t => t.DownloadItem.DownloadId, trackedDownloads, t => t.DownloadItem.DownloadId, StringComparer.CurrentCulture).ToList();

            foreach (var trackedDownload in untrackable)
            {
                trackedDownload.IsTrackable = false;
            }
        }

        private void LogItemChange(TrackedDownload trackedDownload, DownloadClientItem existingItem, DownloadClientItem downloadItem)
        {
            if (existingItem == null ||
                existingItem.Status != downloadItem.Status ||
                existingItem.CanBeRemoved != downloadItem.CanBeRemoved ||
                existingItem.CanMoveFiles != downloadItem.CanMoveFiles)
            {
                _logger.Debug("Tracking '{0}:{1}': ClientState={2}{3} SonarrStage={4} Episode='{5}' OutputPath={6}.",
                    downloadItem.DownloadClient, downloadItem.Title,
                    downloadItem.Status, downloadItem.CanBeRemoved ? "" :
                                         downloadItem.CanMoveFiles ? " (busy)" : " (readonly)",
                    trackedDownload.State,
                    trackedDownload.RemoteAlbum?.ParsedAlbumInfo,
                    downloadItem.OutputPath);
            }
        }


        private static TrackedDownloadStage GetStateFromHistory(HistoryEventType eventType)
        {
            switch (eventType)
            {
                case HistoryEventType.DownloadFolderImported:
                    return TrackedDownloadStage.Imported;
                case HistoryEventType.DownloadFailed:
                    return TrackedDownloadStage.DownloadFailed;
                default:
                    return TrackedDownloadStage.Downloading;
            }
        }
    }
}
