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

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,
                                          IHandle<EpisodeInfoRefreshedEvent>,
                                          IHandle<SeriesDeletedEvent>
    {
        private readonly IParsingService _parsingService;
        private readonly IHistoryService _historyService;
        private readonly IEventAggregator _eventAggregator;
        private readonly IDownloadHistoryService _downloadHistoryService;
        private readonly Logger _logger;
        private readonly ICached<TrackedDownload> _cache;

        public TrackedDownloadService(IParsingService parsingService,
                                      ICacheManager cacheManager,
                                      IHistoryService historyService,
                                      IEventAggregator eventAggregator,
                                      IDownloadHistoryService downloadHistoryService,
                                      Logger logger)
        {
            _parsingService = parsingService;
            _historyService = historyService;
            _eventAggregator = eventAggregator;
            _downloadHistoryService = downloadHistoryService;
            _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 != TrackedDownloadState.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 parsedEpisodeInfo = Parser.Parser.ParseTitle(trackedDownload.DownloadItem.Title);
                var historyItems = _historyService.FindByDownloadId(downloadItem.DownloadId)
                                                  .OrderByDescending(h => h.Date)
                                                  .ToList();

                if (parsedEpisodeInfo != null)
                {
                    trackedDownload.RemoteEpisode = _parsingService.Map(parsedEpisodeInfo, 0, 0);
                }

                var downloadHistory = _downloadHistoryService.GetLatestDownloadHistoryItem(downloadItem.DownloadId);

                if (downloadHistory != null)
                {
                    var state = GetStateFromHistory(downloadHistory.EventType);
                    trackedDownload.State = state;
                }

                if (historyItems.Any())
                {
                    var firstHistoryItem = historyItems.First();
                    var grabbedEvent = historyItems.FirstOrDefault(v => v.EventType == EpisodeHistoryEventType.Grabbed);

                    trackedDownload.Indexer = grabbedEvent?.Data["indexer"];

                    if (parsedEpisodeInfo == null ||
                        trackedDownload.RemoteEpisode == null ||
                        trackedDownload.RemoteEpisode.Series == null ||
                        trackedDownload.RemoteEpisode.Episodes.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
                        parsedEpisodeInfo = Parser.Parser.ParseTitle(firstHistoryItem.SourceTitle) ?? _parsingService.ParseSpecialEpisodeTitle(parsedEpisodeInfo, firstHistoryItem.SourceTitle, 0, 0);

                        if (parsedEpisodeInfo != null)
                        {
                            trackedDownload.RemoteEpisode = _parsingService.Map(parsedEpisodeInfo, firstHistoryItem.SeriesId, historyItems.Where(v => v.EventType == EpisodeHistoryEventType.Grabbed).Select(h => h.EpisodeId).Distinct());
                        }
                    }
                }

                // Track it so it can be displayed in the queue even though we can't determine which series it is for
                if (trackedDownload.RemoteEpisode == null)
                {
                    _logger.Trace("No Episode found for download '{0}'", trackedDownload.DownloadItem.Title);
                }
            }
            catch (Exception e)
            {
                _logger.Debug(e, "Failed to find episode 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.DownloadClientInfo.Name, downloadItem.Title,
                    downloadItem.Status, downloadItem.CanBeRemoved ? "" :
                                         downloadItem.CanMoveFiles ? " (busy)" : " (readonly)",
                    trackedDownload.State,
                    trackedDownload.RemoteEpisode?.ParsedEpisodeInfo,
                    downloadItem.OutputPath);
            }
        }

        private void UpdateCachedItem(TrackedDownload trackedDownload)
        {
            var parsedEpisodeInfo = Parser.Parser.ParseTitle(trackedDownload.DownloadItem.Title);

            trackedDownload.RemoteEpisode = parsedEpisodeInfo == null ? null :_parsingService.Map(parsedEpisodeInfo, 0, 0);
        }

        private static TrackedDownloadState GetStateFromHistory(DownloadHistoryEventType eventType)
        {
            switch (eventType)
            {
                case DownloadHistoryEventType.DownloadImported:
                    return TrackedDownloadState.Imported;
                case DownloadHistoryEventType.DownloadFailed:
                    return TrackedDownloadState.Failed;
                case DownloadHistoryEventType.DownloadIgnored:
                    return TrackedDownloadState.Ignored;
                default:
                    return TrackedDownloadState.Downloading;
            }
        }

        public void Handle(EpisodeInfoRefreshedEvent message)
        {
            var needsToUpdate = false;

            foreach (var episode in message.Removed)
            {
                var cachedItems = _cache.Values.Where(t =>
                                            t.RemoteEpisode?.Episodes != null &&
                                            t.RemoteEpisode.Episodes.Any(e => e.Id == episode.Id))
                                        .ToList();

                if (cachedItems.Any())
                {
                    needsToUpdate = true;
                }

                cachedItems.ForEach(UpdateCachedItem);
            }

            if (needsToUpdate)
            {
                _eventAggregator.PublishEvent(new TrackedDownloadRefreshedEvent(GetTrackedDownloads()));
            }
        }

        public void Handle(SeriesDeletedEvent message)
        {
            var cachedItems = _cache.Values.Where(t =>
                                        t.RemoteEpisode?.Series != null &&
                                        t.RemoteEpisode.Series.Id == message.Series.Id)
                                    .ToList();

            if (cachedItems.Any())
            {
                cachedItems.ForEach(UpdateCachedItem);

                _eventAggregator.PublishEvent(new TrackedDownloadRefreshedEvent(GetTrackedDownloads()));
            }
        }
    }
}
