// Copyright (C) 2024 Intro-Skipper contributors <intro-skipper.org>
// SPDX-License-Identifier: GPL-3.0-only.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using IntroSkipper.Analyzers;
using IntroSkipper.Configuration;
using IntroSkipper.Data;
using IntroSkipper.Db;
using IntroSkipper.Manager;
using MediaBrowser.Controller.Library;
using Microsoft.Extensions.Logging;

namespace IntroSkipper.ScheduledTasks;

/// <summary>
/// Common code shared by all media item analyzer tasks.
/// </summary>
/// <remarks>
/// Initializes a new instance of the <see cref="BaseItemAnalyzerTask"/> class.
/// </remarks>
/// <param name="logger">Task logger.</param>
/// <param name="loggerFactory">Logger factory.</param>
/// <param name="libraryManager">Library manager.</param>
/// <param name="mediaSegmentUpdateManager">MediaSegmentUpdateManager.</param>
public class BaseItemAnalyzerTask(
    ILogger logger,
    ILoggerFactory loggerFactory,
    ILibraryManager libraryManager,
    MediaSegmentUpdateManager mediaSegmentUpdateManager)
{
    private readonly ILogger _logger = logger;
    private readonly ILoggerFactory _loggerFactory = loggerFactory;
    private readonly ILibraryManager _libraryManager = libraryManager;
    private readonly MediaSegmentUpdateManager _mediaSegmentUpdateManager = mediaSegmentUpdateManager;
    private readonly PluginConfiguration _config = Plugin.Instance?.Configuration ?? new PluginConfiguration();

    /// <summary>
    /// Analyze all media items on the server.
    /// </summary>
    /// <param name="progress">Progress reporter.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <param name="seasonsToAnalyze">Season IDs to analyze.</param>
    /// <returns>A task representing the asynchronous operation.</returns>
    public async Task AnalyzeItemsAsync(
        IProgress<double> progress,
        CancellationToken cancellationToken,
        IReadOnlyCollection<Guid>? seasonsToAnalyze = null)
    {
        // Assert that ffmpeg with chromaprint is installed
        if (_config.WithChromaprint && !FFmpegWrapper.CheckFFmpegVersion())
        {
            throw new FingerprintException(
                "Analysis terminated! Chromaprint is not enabled in the current ffmpeg. If Jellyfin is running natively, install jellyfin-ffmpeg7. If Jellyfin is running in a container, upgrade to version 10.10.0 or newer.");
        }

        HashSet<AnalysisMode> modes = [
            .. _config.ScanIntroduction ? [AnalysisMode.Introduction] : Array.Empty<AnalysisMode>(),
            .. _config.ScanCredits ? [AnalysisMode.Credits] : Array.Empty<AnalysisMode>(),
            .. _config.ScanRecap ? [AnalysisMode.Recap] : Array.Empty<AnalysisMode>(),
            .. _config.ScanPreview ? [AnalysisMode.Preview] : Array.Empty<AnalysisMode>()
        ];

        var queueManager = new QueueManager(
            _loggerFactory.CreateLogger<QueueManager>(),
            _libraryManager);

        var queue = queueManager.GetMediaItems();

        if (seasonsToAnalyze?.Count > 0)
        {
            queue = queue.Where(kvp => seasonsToAnalyze.Contains(kvp.Key))
                         .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
        }

        int totalQueued = queue.Sum(kvp => kvp.Value.Count) * modes.Count;
        if (totalQueued == 0)
        {
            throw new FingerprintException(
                "No libraries selected for analysis. Please visit the plugin settings to configure.");
        }

        int totalProcessed = 0;
        var options = new ParallelOptions
        {
            MaxDegreeOfParallelism = Math.Max(1, _config.MaxParallelism),
            CancellationToken = cancellationToken
        };

        await Parallel.ForEachAsync(queue, options, async (season, ct) =>
        {
            var updateMediaSegments = false;

            var (episodes, requiredModes) = queueManager.VerifyQueue(season.Value, modes);
            if (episodes.Count == 0)
            {
                return;
            }

            try
            {
                var firstEpisode = episodes[0];
                if (modes.Count != requiredModes.Count)
                {
                    Interlocked.Add(ref totalProcessed, episodes.Count * (modes.Count - requiredModes.Count));
                    progress.Report((double)totalProcessed / totalQueued * 100);
                }

                foreach (var mode in requiredModes)
                {
                    ct.ThrowIfCancellationRequested();
                    int analyzed = await AnalyzeItemsAsync(
                        episodes,
                        mode,
                        ct).ConfigureAwait(false);
                    Interlocked.Add(ref totalProcessed, analyzed);

                    updateMediaSegments = analyzed > 0 || updateMediaSegments;
                    progress.Report((double)totalProcessed / totalQueued * 100);
                }
            }
            catch (OperationCanceledException)
            {
                _logger.LogInformation("Analysis was canceled.");
            }
            catch (FingerprintException ex)
            {
                _logger.LogWarning(ex, "Fingerprint exception during analysis.");
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "An unexpected error occurred during analysis.");
                throw;
            }

            if (_config.RebuildMediaSegments || (updateMediaSegments && _config.UpdateMediaSegments))
            {
                await _mediaSegmentUpdateManager.UpdateMediaSegmentsAsync(episodes, ct).ConfigureAwait(false);
            }
        }).ConfigureAwait(false);

        Plugin.Instance!.AnalyzeAgain = false;

        if (_config.RebuildMediaSegments)
        {
            _logger.LogInformation("Regenerated media segments.");
            _config.RebuildMediaSegments = false;
            Plugin.Instance!.SaveConfiguration();
        }
    }

    /// <summary>
    /// Analyze a group of media items for skippable segments.
    /// </summary>
    /// <param name="items">Media items to analyze.</param>
    /// <param name="mode">Analysis mode.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Number of items successfully analyzed.</returns>
    private async Task<int> AnalyzeItemsAsync(
        IReadOnlyList<QueuedEpisode> items,
        AnalysisMode mode,
        CancellationToken cancellationToken)
    {
        var first = items[0];
        if (!first.IsMovie && first.SeasonNumber == 0 && !_config.AnalyzeSeasonZero)
        {
            return 0;
        }

        // Reset the IsAnalyzed flag for all items
        foreach (var item in items)
        {
            item.IsAnalyzed = false;
        }

        // Get the analyzer action for the current mode
        var action = Plugin.Instance!.GetAnalyzerAction(first.SeasonId, mode);

        _logger.LogInformation(
            "[Mode: {Mode}] Analyzing {Count} files from {Name} season {Season}",
            mode,
            items.Count,
            first.SeriesName,
            first.SeasonNumber);

        // Create a list of analyzers to use for the current mode
        var analyzers = new List<IMediaFileAnalyzer>();

        if (action is AnalyzerAction.Chapter or AnalyzerAction.Default)
        {
            analyzers.Add(new ChapterAnalyzer(_loggerFactory.CreateLogger<ChapterAnalyzer>()));
        }

        if (first.IsAnime && _config.WithChromaprint &&
            mode is not (AnalysisMode.Recap or AnalysisMode.Preview) &&
            action is AnalyzerAction.Default or AnalyzerAction.Chromaprint)
        {
            analyzers.Add(new ChromaprintAnalyzer(_loggerFactory.CreateLogger<ChromaprintAnalyzer>()));
        }

        if (mode is AnalysisMode.Credits &&
            action is AnalyzerAction.Default or AnalyzerAction.BlackFrame)
        {
            analyzers.Add(new BlackFrameAnalyzer(_loggerFactory.CreateLogger<BlackFrameAnalyzer>()));
        }

        if (!first.IsAnime && !first.IsMovie &&
            mode is not (AnalysisMode.Recap or AnalysisMode.Preview) &&
            action is AnalyzerAction.Default or AnalyzerAction.Chromaprint)
        {
            analyzers.Add(new ChromaprintAnalyzer(_loggerFactory.CreateLogger<ChromaprintAnalyzer>()));
        }

        // Use each analyzer to find skippable ranges in all media files, removing successfully
        // analyzed items from the queue.
        foreach (var analyzer in analyzers)
        {
            cancellationToken.ThrowIfCancellationRequested();
            items = await analyzer.AnalyzeMediaFiles(items, mode, cancellationToken).ConfigureAwait(false);
        }

        // Set the episode IDs for the analyzed items
        await Plugin.Instance!.SetEpisodeIdsAsync(first.SeasonId, mode, items.Select(i => i.EpisodeId)).ConfigureAwait(false);

        return items.Where(i => i.IsAnalyzed).Count();
    }
}