using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Diagnostics;
using System.IO;
using System.Threading;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using Futonizer.Models;
using Futonizer.Services;
using Futonizer.Views;
using Wpf.Ui.Controls;

namespace Futonizer;

public partial class MainWindow : FluentWindow
{
    private const int MaxConcurrentScans = 10;
    private const int MaxConcurrentStrips = 3;

    private AppSettings _settings = new();
    private readonly ObservableCollection<QueuedFileItem> _fileQueue = new();
    private readonly List<string> _pendingSubtitles = new();
    private readonly SemaphoreSlim _scanSemaphore = new(MaxConcurrentScans);
    private bool _isProcessing;
    private bool _propagatingSelection;

    public MainWindow()
    {
        Wpf.Ui.Appearance.SystemThemeWatcher.Watch(this);
        InitializeComponent();

        FileQueueList.ItemsSource = _fileQueue;

        _fileQueue.CollectionChanged += (_, _) => UpdateDropHint();

        LoadSettingsIntoUi();
        Closing += (_, _) => SaveSettingsFromUi();
        Loaded += MainWindow_Loaded;
    }

    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        EnsureRequiredSettingsConfigured();
    }

    /// <summary>
    /// Warns the user and opens Settings if mkvmerge.exe isn't configured (or
    /// no longer exists), or if a previously chosen output folder has since
    /// disappeared. Runs once on startup; does nothing once everything is
    /// already valid.
    /// </summary>
    private void EnsureRequiredSettingsConfigured()
    {
        bool mkvMissing = string.IsNullOrWhiteSpace(_settings.MkvMergePath) || !File.Exists(_settings.MkvMergePath);
        bool outputInvalid = !string.IsNullOrWhiteSpace(_settings.OutputFolder) && !Directory.Exists(_settings.OutputFolder);

        if (!mkvMissing && !outputInvalid) return;

        string message = mkvMissing
            ? "mkvmerge.exe could not be found. Please locate it to enable stripping tracks."
            : "The previously configured output folder no longer exists. Please choose a new one, or leave it blank to overwrite files in place.";

        System.Windows.MessageBox.Show(this, message, "Futonizer — Setup required",
            System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Warning);

        if (outputInvalid)
            _settings.OutputFolder = string.Empty;

        var win = new SettingsWindow(_settings) { Owner = this };
        if (win.ShowDialog() == true && win.Result != null)
        {
            _settings.MkvMergePath = win.Result.MkvMergePath;
            _settings.OutputFolder = win.Result.OutputFolder;
            SettingsService.Save(_settings);
        }
    }

    // ── Helpers ──────────────────────────────────────────────────────────────

    private static void RestartApplication()
    {
        try
        {
            string? exePath = Environment.ProcessPath;
            if (!string.IsNullOrEmpty(exePath))
                Process.Start(exePath);
        }
        catch
        {
        }
        System.Windows.Application.Current.Shutdown();
    }

    private void UpdateDropHint()
    {
        bool empty = _fileQueue.Count == 0;
        DropHint.Visibility = empty ? Visibility.Visible : Visibility.Collapsed;
        ClearQueueButton.IsEnabled = !empty;
    }

    /// <summary>
    /// Shows a blocking overlay with a simple "loaded / total" progress bar
    /// while any queued file is still being scanned, and keeps the Run button
    /// disabled until every dropped file has finished loading.
    /// </summary>
    private void UpdateLoadingOverlay()
    {
        int total = _fileQueue.Count;
        int loaded = _fileQueue.Count(f => !f.IsLoading);

        if (total > 0 && loaded < total)
        {
            LoadingOverlay.Visibility = Visibility.Visible;
            LoadingProgressBar.Maximum = total;
            LoadingProgressBar.Value = loaded;
            LoadingOverlayText.Text = $"Loading files... ({loaded}/{total})";
        }
        else
        {
            LoadingOverlay.Visibility = Visibility.Collapsed;
        }

        UpdateRunButtonEnabled();
    }

    private void UpdateRunButtonEnabled()
    {
        bool anyLoading = _fileQueue.Any(f => f.IsLoading);
        bool allCorrect = _fileQueue.Count > 0 && _fileQueue.All(f => f.IsCorrect);
        RunButton.IsEnabled = !_isProcessing && !anyLoading && allCorrect;
        RunButton.ToolTip = allCorrect
            ? null
            : "Every file in the queue needs exactly one audio and one subtitle track selected before stripping.";

        UpdateRunButtonLabel();
    }

    private void UpdateRunButtonLabel()
    {
        bool anyRename = _fileQueue.Any(f =>
            !string.Equals(f.DisplayFileName, f.FileName, StringComparison.Ordinal));
        RunButton.Content = anyRename ? "Rename and Strip Tracks" : "Strip Tracks";
    }

    private void QueuedFileItem_PropertyChanged(object? sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == nameof(QueuedFileItem.IsLoading))
            UpdateLoadingOverlay();
        if (e.PropertyName == nameof(QueuedFileItem.LoadState))
            UpdateRunButtonEnabled();
    }

    private static string GuessDefaultMkvMergePath()
    {
        string[] candidates =
        {
            @"C:\Program Files\MKVToolNix\mkvmerge.exe",
            @"C:\Program Files (x86)\MKVToolNix\mkvmerge.exe",
        };
        return candidates.FirstOrDefault(File.Exists) ?? string.Empty;
    }

    // ── Settings persistence ──────────────────────────────────────────────────

    private void LoadSettingsIntoUi()
    {
        _settings = SettingsService.Load();

        if (string.IsNullOrWhiteSpace(_settings.MkvMergePath))
            _settings.MkvMergePath = GuessDefaultMkvMergePath();
    }

    private void SaveSettingsFromUi()
    {
        SettingsService.Save(_settings);
    }

    // ── Settings button ───────────────────────────────────────────────────────

    private void SettingsButton_Click(object sender, RoutedEventArgs e)
    {
        var win = new SettingsWindow(_settings) { Owner = this };
        if (win.ShowDialog() == true && win.Result != null)
        {
            _settings.MkvMergePath = win.Result.MkvMergePath;
            _settings.OutputFolder = win.Result.OutputFolder;
            SettingsService.Save(_settings);
            RestartApplication();
        }
    }

    // ── Drag & Drop ───────────────────────────────────────────────────────────

    private void Window_DragOver(object sender, DragEventArgs e)
    {
        if (e.Data.GetDataPresent(DataFormats.FileDrop))
        {
            var paths = (string[])e.Data.GetData(DataFormats.FileDrop);
            bool hasAcceptedFile = paths.Any(p =>
                File.Exists(p) && (IsMkvFile(p) || SubtitleMatcher.IsSubtitleFile(p)));
            e.Effects = hasAcceptedFile ? DragDropEffects.Copy : DragDropEffects.None;
        }
        else
        {
            e.Effects = DragDropEffects.None;
        }
        e.Handled = true;
    }

    private static bool IsMkvFile(string path)
        => string.Equals(Path.GetExtension(path), ".mkv", StringComparison.OrdinalIgnoreCase);

    private void Window_Drop(object sender, DragEventArgs e)
    {
        if (!e.Data.GetDataPresent(DataFormats.FileDrop)) return;

        Activate();

        var paths = (string[])e.Data.GetData(DataFormats.FileDrop);

        var newVideoPaths = paths
            .Where(p => IsMkvFile(p)
                        && File.Exists(p)
                        && !_fileQueue.Any(q => string.Equals(q.FilePath, p, StringComparison.OrdinalIgnoreCase)))
            .ToList();

        var subtitlePaths = paths
            .Where(p => SubtitleMatcher.IsSubtitleFile(p) && File.Exists(p))
            .ToList();

        var newItems = new List<QueuedFileItem>();
        foreach (var path in newVideoPaths)
        {
            var item = new QueuedFileItem(path);
            item.PropertyChanged += QueuedFileItem_PropertyChanged;
            _fileQueue.Add(item);
            newItems.Add(item);
            _ = ScanFileItemAsync(item);
        }

        // Newly-added videos might satisfy subtitles dropped in earlier (or
        // in this same batch, if the subtitle sorts before its video).
        foreach (var item in newItems)
            MatchPendingSubtitlesToFile(item);

        int matchedSubtitles = 0;
        foreach (var subPath in subtitlePaths)
        {
            if (MatchSubtitleToQueue(subPath))
                matchedSubtitles++;
            else if (!_pendingSubtitles.Contains(subPath, StringComparer.OrdinalIgnoreCase))
                _pendingSubtitles.Add(subPath);
        }

        UpdateLoadingOverlay();

        if (newItems.Count > 0)
        {
            var first = _fileQueue.FirstOrDefault(q =>
                string.Equals(q.FilePath, newVideoPaths[0], StringComparison.OrdinalIgnoreCase));
            if (first != null) FileQueueList.SelectedItem = first;
        }

        int unmatchedSubtitles = subtitlePaths.Count - matchedSubtitles;
        if (matchedSubtitles > 0 || unmatchedSubtitles > 0)
        {
            StatusText.Text = unmatchedSubtitles > 0
                ? $"Matched {matchedSubtitles} subtitle(s); {unmatchedSubtitles} couldn't be matched to an episode (S04E06, E06, or plain episode number like 06/6/16)."
                : $"Matched {matchedSubtitles} subtitle(s) to their episode.";
        }
    }

    // ── Subtitle matching ───────────────────────────────────────────────────

    /// <summary>
    /// Attempts to attach a dropped subtitle file to whichever queued video(s)
    /// share the same episode. Prefers a full season+episode code (e.g.
    /// S04E06) when the subtitle's filename has one; otherwise falls back to
    /// matching by bare episode number alone (e.g. "06", "6", "16", "E06"),
    /// season-agnostic. Falls back further to the single queued file when
    /// there's exactly one and no episode info at all could be extracted
    /// from the subtitle's filename. Returns false if no target could be
    /// determined, in which case the file is kept pending until a matching
    /// video is dropped later.
    /// </summary>
    private bool MatchSubtitleToQueue(string subtitlePath)
    {
        string subFileName = Path.GetFileName(subtitlePath);
        string? subCode = SubtitleMatcher.ExtractEpisodeCode(subFileName);
        int? subEpisodeNumber = subCode == null ? SubtitleMatcher.ExtractEpisodeNumber(subFileName) : null;

        List<QueuedFileItem> targets;
        if (subCode != null)
        {
            targets = _fileQueue
                .Where(q => string.Equals(SubtitleMatcher.ExtractEpisodeCode(q.FileName), subCode, StringComparison.OrdinalIgnoreCase))
                .ToList();
        }
        else if (subEpisodeNumber != null)
        {
            targets = _fileQueue
                .Where(q => SubtitleMatcher.ExtractEpisodeNumber(q.FileName) == subEpisodeNumber)
                .ToList();
        }
        else if (_fileQueue.Count == 1)
        {
            targets = new List<QueuedFileItem> { _fileQueue[0] };
        }
        else
        {
            targets = new List<QueuedFileItem>();
        }

        if (targets.Count == 0) return false;

        foreach (var target in targets)
            AttachExternalSubtitle(target, subtitlePath);

        return true;
    }

    /// <summary>
    /// Called whenever a new video is added to the queue: checks the pending
    /// (previously unmatched) subtitle files for one matching this video's
    /// episode — by full season+episode code when both have one, or by bare
    /// episode number otherwise — and attaches + removes any matches from
    /// the pending list.
    /// </summary>
    private void MatchPendingSubtitlesToFile(QueuedFileItem item)
    {
        if (_pendingSubtitles.Count == 0) return;

        string? videoCode = SubtitleMatcher.ExtractEpisodeCode(item.FileName);
        int? videoEpisodeNumber = SubtitleMatcher.ExtractEpisodeNumber(item.FileName);
        if (videoCode == null && videoEpisodeNumber == null) return;

        var matches = _pendingSubtitles.Where(p =>
        {
            string subName = Path.GetFileName(p);
            string? subCode = SubtitleMatcher.ExtractEpisodeCode(subName);
            if (subCode != null)
                return videoCode != null && string.Equals(subCode, videoCode, StringComparison.OrdinalIgnoreCase);

            int? subEpisodeNumber = SubtitleMatcher.ExtractEpisodeNumber(subName);
            return subEpisodeNumber != null && subEpisodeNumber == videoEpisodeNumber;
        }).ToList();

        foreach (var match in matches)
        {
            AttachExternalSubtitle(item, match);
            _pendingSubtitles.Remove(match);
        }
    }

    private static void AttachExternalSubtitle(QueuedFileItem target, string subtitlePath)
    {
        if (target.ExternalSubtitles.Any(s => string.Equals(s.FilePath, subtitlePath, StringComparison.OrdinalIgnoreCase)))
            return;

        var info = SubtitleLanguageHelper.Detect(Path.GetFileName(subtitlePath));
        var sub = new ExternalSubtitleTrack(subtitlePath)
        {
            Language = info.Language,
            TrackName = info.TrackName,
            Forced = info.Forced,
            HearingImpaired = info.HearingImpaired,
            IsDefault = target.ExternalSubtitles.Count == 0,
        };
        target.ExternalSubtitles.Add(sub);
    }

    private void RemoveExternalSubtitle_Click(object sender, RoutedEventArgs e)
    {
        if (sender is not System.Windows.Controls.Button btn || btn.Tag is not ExternalSubtitleTrack sub) return;

        var owner = _fileQueue.FirstOrDefault(f => f.ExternalSubtitles.Contains(sub));
        if (owner == null) return;

        bool wasDefault = sub.IsDefault;
        owner.ExternalSubtitles.Remove(sub);

        if (wasDefault)
        {
            var next = owner.ExternalSubtitles.FirstOrDefault();
            if (next != null) next.IsDefault = true;
        }

        if (ReferenceEquals(FileQueueList.SelectedItem, owner))
            ExternalSubsPanel.Visibility = owner.HasExternalSubtitles ? Visibility.Visible : Visibility.Collapsed;

        e.Handled = true;
    }

    // ── File scanning ─────────────────────────────────────────────────────────

    private async Task ScanFileItemAsync(QueuedFileItem item)
    {
        item.IsScanning = true;
        item.Status = "Scanning...";
        item.Tracks.Clear();

        await _scanSemaphore.WaitAsync();
        try
        {
            if (string.IsNullOrWhiteSpace(_settings.MkvMergePath) || !File.Exists(_settings.MkvMergePath))
            {
                item.IsScanning = false;
                item.HasError = true;
                item.Status = "mkvmerge.exe not found — open Settings";
                return;
            }

            var service = new MkvService(_settings.MkvMergePath);
            var info = await service.IdentifyAsync(item.FilePath);
            var tracks = service.BuildTrackItems(info);

            foreach (var t in tracks)
            {
                item.Tracks.Add(t);
                if (t.Type is "audio" or "subtitles")
                {
                    t.PropertyChanged += (s, e) => OnTrackSelectionChanged(item, (TrackItem)s!, e);
                }
            }

            item.IsScanning = false;
            item.Status = $"{tracks.Count} track{(tracks.Count == 1 ? "" : "s")}";
        }
        catch (Exception ex)
        {
            item.IsScanning = false;
            item.HasError = true;
            item.Status = ex.Message;
        }
        finally
        {
            _scanSemaphore.Release();
        }
    }

    // ── Audio/subtitle selection propagation ────────────────────────────────────

    /// <summary>
    /// Propagates audio/subtitle selection/deselection to every other file in
    /// the queue:
    ///   - Checking a track matches it to other files by its exact
    ///     "Codec/Name" identity:
    ///       - If the source file had no other track of the same type
    ///         selected before this check ("adding"), other files that don't
    ///         have a matching track are left untouched.
    ///       - If the source file had a different track of the same type
    ///         selected before this check ("overriding"), other files that
    ///         don't have a matching track have their selection cleared.
    ///   - Unchecking a track clears the selection of that type in every
    ///     other file too, so a deselection always applies everywhere.
    /// Within the source file, only one track of a given type may ever be
    /// selected.
    /// </summary>
    private void OnTrackSelectionChanged(QueuedFileItem sourceFile, TrackItem track, PropertyChangedEventArgs e)
    {
        if (_propagatingSelection) return;
        if (e.PropertyName != nameof(TrackItem.Copy)) return;

        string type = track.Type;

        _propagatingSelection = true;
        try
        {
            if (track.Copy)
            {
                bool wasOverriding = sourceFile.Tracks.Any(t => t.Type == type && t != track && t.Copy);

                foreach (var other in sourceFile.Tracks.Where(t => t.Type == type && t != track))
                {
                    other.Copy = false;
                    other.DefaultTrack = false;
                }
                track.DefaultTrack = true;

                string key = track.PropagationKey;

                foreach (var otherFile in _fileQueue.Where(f => f != sourceFile))
                {
                    var match = otherFile.Tracks.FirstOrDefault(t => t.Type == type && t.PropagationKey == key);
                    if (match != null)
                    {
                        foreach (var sub in otherFile.Tracks.Where(t => t.Type == type))
                        {
                            sub.Copy = sub == match;
                            sub.DefaultTrack = sub == match;
                        }
                    }
                    else if (wasOverriding)
                    {
                        foreach (var sub in otherFile.Tracks.Where(t => t.Type == type))
                        {
                            sub.Copy = false;
                            sub.DefaultTrack = false;
                        }
                    }
                }
            }
            else
            {
                track.DefaultTrack = false;
                foreach (var otherFile in _fileQueue.Where(f => f != sourceFile))
                {
                    foreach (var sub in otherFile.Tracks.Where(t => t.Type == type))
                    {
                        sub.Copy = false;
                        sub.DefaultTrack = false;
                    }
                }
            }
        }
        finally
        {
            _propagatingSelection = false;
        }
    }

    // ── File queue UI ─────────────────────────────────────────────────────────

    private void RemoveFile_Click(object sender, RoutedEventArgs e)
    {
        if (sender is System.Windows.Controls.Button btn && btn.Tag is QueuedFileItem item)
        {
            item.PropertyChanged -= QueuedFileItem_PropertyChanged;
            _fileQueue.Remove(item);
            UpdateLoadingOverlay();
        }
        e.Handled = true;
    }

    /// <summary>
    /// Removes every currently-selected item from the queue (multi-select
    /// via Ctrl/Shift-click), for batch removal without clearing everything.
    /// </summary>
    private void FileQueueList_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
    {
        if (e.Key != System.Windows.Input.Key.Delete) return;

        var selected = FileQueueList.SelectedItems.Cast<QueuedFileItem>().ToList();
        if (selected.Count == 0) return;

        foreach (var item in selected)
        {
            item.PropertyChanged -= QueuedFileItem_PropertyChanged;
            _fileQueue.Remove(item);
        }
        UpdateLoadingOverlay();
        e.Handled = true;
    }

    /// <summary>
    /// Opens the currently-selected queue item with whatever application
    /// Windows has associated with .mkv files (typically the default video
    /// player), so the user can quickly preview a file without leaving the app.
    /// </summary>
    private void FileQueueList_MouseDoubleClick(object sender, System.Windows.Input.MouseButtonEventArgs e)
    {
        OpenSelectedFileInDefaultPlayer();
        e.Handled = true;
    }

    /// <summary>
    /// Same as <see cref="FileQueueList_MouseDoubleClick"/>, but for the track
    /// table. Ignores double-clicks on the "Copy" checkbox column so toggling
    /// it rapidly doesn't also launch the default player.
    /// </summary>
    private void TrackGrid_MouseDoubleClick(object sender, System.Windows.Input.MouseButtonEventArgs e)
    {
        if (e.OriginalSource is DependencyObject source && FindAncestor<CheckBox>(source) != null) return;
        OpenSelectedFileInDefaultPlayer();
        e.Handled = true;
    }

    /// <summary>
    /// Walks up the visual tree from <paramref name="source"/> looking for an
    /// ancestor (or the element itself) of type <typeparamref name="T"/>.
    /// </summary>
    private static T? FindAncestor<T>(DependencyObject source) where T : DependencyObject
    {
        var current = source;
        while (current != null)
        {
            if (current is T typed) return typed;
            current = System.Windows.Media.VisualTreeHelper.GetParent(current);
        }
        return null;
    }

    private void OpenSelectedFileInDefaultPlayer()
    {
        if (FileQueueList.SelectedItem is not QueuedFileItem item) return;

        try
        {
            Process.Start(new ProcessStartInfo(item.FilePath) { UseShellExecute = true });
        }
        catch (Exception ex)
        {
            StatusText.Text = $"Couldn't open {item.FileName}: {ex.Message}";
        }
    }

    private void ClearQueueButton_Click(object sender, RoutedEventArgs e)
    {
        foreach (var item in _fileQueue)
            item.PropertyChanged -= QueuedFileItem_PropertyChanged;
        _fileQueue.Clear();
        UpdateLoadingOverlay();
    }

    /// <summary>
    /// Scrolls the track grid or queue list by an amount proportional to the
    /// wheel delta instead of relying on WPF's default per-event line
    /// scrolling. Shared by both the file queue and track table so both
    /// panes scroll consistently.
    /// </summary>
    private void SmoothList_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
        => SmoothScrollHelper.HandlePreviewMouseWheel(sender, e);

    private void FileQueueList_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (FileQueueList.SelectedItem is QueuedFileItem file)
        {
            TrackGrid.ItemsSource = file.Tracks;
            TrackGrid.Visibility = Visibility.Visible;
            NoSelectionHint.Visibility = Visibility.Collapsed;
            ExternalSubsList.ItemsSource = file.ExternalSubtitles;
            ExternalSubsPanel.Visibility = file.HasExternalSubtitles ? Visibility.Visible : Visibility.Collapsed;
        }
        else
        {
            TrackGrid.ItemsSource = null;
            TrackGrid.Visibility = Visibility.Collapsed;
            NoSelectionHint.Visibility = Visibility.Visible;
            ExternalSubsList.ItemsSource = null;
            ExternalSubsPanel.Visibility = Visibility.Collapsed;
        }
    }

    // ── Keyboard shortcuts ───────────────────────────────────────────

    private void Window_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
    {
        if (e.Key == System.Windows.Input.Key.R
            && Keyboard.Modifiers == ModifierKeys.Control
            && RunButton.IsEnabled)
        {
            RunButton_Click(RunButton, new RoutedEventArgs());
            e.Handled = true;
        }
    }

    // ── Run ─────────────────────────────────────────────────────────────────────

    private void RunButton_Click(object sender, RoutedEventArgs e)
    {
        if (_isProcessing) return;
        if (_fileQueue.Any(f => f.IsLoading)) return;

        if (string.IsNullOrWhiteSpace(_settings.MkvMergePath) || !File.Exists(_settings.MkvMergePath))
        {
            StatusText.Text = "mkvmerge.exe not set — open Settings.";
            return;
        }

        var readyFiles = _fileQueue
            .Where(f => f.IsCorrect)
            .ToList();

        if (readyFiles.Count == 0)
        {
            StatusText.Text = _fileQueue.Count == 0
                ? "No files in queue."
                : "No files ready (need exactly one audio + one subtitle selected).";
            return;
        }

        SaveSettingsFromUi();

        _isProcessing = true;
        RunButton.IsEnabled = false;
        StatusText.Text = string.Empty;
        ProcessingOverlay.Visibility = Visibility.Visible;

        var progressWin = new ProgressWindow(readyFiles, _settings.MkvMergePath, _settings.OutputFolder, MaxConcurrentStrips)
        {
            Owner = this
        };
        progressWin.Closed += (_, _) =>
        {
            _isProcessing = false;
            ProcessingOverlay.Visibility = Visibility.Collapsed;
            if (progressWin.ShouldClearQueue)
            {
                foreach (var item in _fileQueue)
                    item.PropertyChanged -= QueuedFileItem_PropertyChanged;
                _fileQueue.Clear();
            }
            UpdateLoadingOverlay();
        };
        progressWin.Show();
    }
}