using System.Collections.ObjectModel;
using System.Diagnostics;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using FluidExplorer.Navigation;
using FluidExplorer.Services;
using FluidExplorer.Services.FileSystem;
using FluidExplorer.Services.Icons;
using FluidExplorer.Services.ItemVisuals;
using FluidExplorer.Services.Operations;
using FluidExplorer.Services.Search;
using FluidExplorer.Services.Shell;
using FluidExplorer.Helpers;
using Microsoft.UI.Dispatching;
using PathHelper = FluidExplorer.Services.FileSystem.PathHelper;

namespace FluidExplorer.ViewModels;

/// <summary>主视图模型：标签页、侧边栏、索引状态、操作队列、设置。</summary>
public sealed partial class MainViewModel : ObservableObject
{
    private readonly IFileSystemService _fs;
    private readonly SearchService _search;
    private readonly IFileOperationService _operations;
    private readonly AppSettings _settings;
    private readonly DispatcherQueue _ui;

    public MainViewModel(
        IFileSystemService fs,
        SearchService search,
        IFileOperationService operations,
        IIconService icons,
        AppSettings settings,
        DispatcherQueue ui)
    {
        _fs = fs;
        _search = search;
        _operations = operations;
        _settings = settings;
        _ui = ui;

        Clipboard = new FileClipboard();
        Visuals = new ItemVisualService(icons, ui);

        ShowHiddenFiles = settings.ShowHiddenFiles;
        ShowSystemFiles = settings.ShowSystemFiles;
        ShowFileExtensions = settings.ShowFileExtensions;
        AlwaysShowCheckBoxes = settings.AlwaysShowCheckBoxes;
        DeleteToRecycleBin = settings.DeleteToRecycleBin;
        AnimationsEnabled = settings.AnimationsEnabled;
        SearchInCurrentFolderOnly = settings.SearchScope == SearchScope.CurrentFolder;
        ThemeMode = settings.ThemeMode;

        _operations.JobsChanged += (_, _) => RefreshJobs();
        _search.IndexStateChanged += (_, _) => _ui.Post(RefreshIndexState);

        _jobTimer = _ui.CreateTimer();
        _jobTimer.Interval = TimeSpan.FromMilliseconds(250);
        _jobTimer.IsRepeating = true;
        _jobTimer.Tick += OnJobTimerTick;

        BuildSidebar();
        RefreshIndexState();
        RefreshJobs();
    }

    public ItemVisualService Visuals { get; }
    public IFileClipboard Clipboard { get; }
    public AppSettings Settings => _settings;

    // ── 标签页 ──────────────────────────────────────────────────────────────
    public ObservableCollection<ExplorerTabViewModel> Tabs { get; } = [];
    [ObservableProperty] private ExplorerTabViewModel? _selectedTab;

    public ExplorerPaneViewModel? ActivePane => SelectedTab?.ActivePane;

    public ExplorerTabViewModel AddTab(NavigationLocation? start = null, bool select = true)
    {
        var location = start ?? DefaultStartLocation();
        var tab = new ExplorerTabViewModel(_fs, _search, _operations, Visuals, Clipboard, _settings, _ui, location);
        tab.PropertyChanged += (_, _) => { if (ReferenceEquals(tab, SelectedTab)) OnPropertyChanged(nameof(ActivePane)); };
        Tabs.Add(tab);
        if (select) SelectedTab = tab;
        SaveOpenTabs();
        return tab;
    }

    [RelayCommand]
    private void NewTab() => AddTab();

    [RelayCommand]
    private void CloseTab(ExplorerTabViewModel? tab)
    {
        tab ??= SelectedTab;
        if (tab is null) return;
        var index = Tabs.IndexOf(tab);
        tab.Dispose();
        Tabs.Remove(tab);
        if (Tabs.Count == 0)
        {
            AddTab();
            return;
        }
        SelectedTab = Tabs[Math.Clamp(index, 0, Tabs.Count - 1)];
        SaveOpenTabs();
    }

    [RelayCommand]
    private void DuplicateTab(ExplorerTabViewModel? tab)
    {
        tab ??= SelectedTab;
        if (tab is null) return;
        AddTab(NavigationLocation.FromPath(tab.Primary.CurrentPath));
    }

    [RelayCommand]
    private void ToggleDualPane()
    {
        SelectedTab?.ToggleDualPane();
        _settings.DualPane = SelectedTab?.IsDualPane ?? false;
        _settings.Save();
    }

    partial void OnSelectedTabChanged(ExplorerTabViewModel? value)
    {
        OnPropertyChanged(nameof(ActivePane));
        if (value is not null) UpdateSidebarSelection(value.ActivePane.CurrentPath);
    }

    private NavigationLocation DefaultStartLocation()
    {
        if (!string.IsNullOrWhiteSpace(_settings.DefaultStartPath) && Directory.Exists(_settings.DefaultStartPath))
            return NavigationLocation.FromPath(_settings.DefaultStartPath);
        var downloads = KnownFolders.Downloads;
        return Directory.Exists(downloads) ? NavigationLocation.FromPath(downloads) : NavigationLocation.Home;
    }

    // ── 侧边栏 ──────────────────────────────────────────────────────────────
    public ObservableCollection<SidebarNode> SidebarRoots { get; } = [];
    [ObservableProperty] private SidebarNode? _selectedSidebarNode;

    private void BuildSidebar()
    {
        SidebarRoots.Clear();
        SidebarRoots.Add(SidebarNode.Create("主页", "\uE80F", NavigationLocation.Home));
        SidebarRoots.Add(SidebarNode.Create("图库", "\uE91B", NavigationLocation.Gallery));

        if (_settings.PinnedFolders.Count == 0)
        {
            foreach (var path in new[] { KnownFolders.Desktop, KnownFolders.Downloads, KnownFolders.Documents, KnownFolders.Pictures })
                if (!string.IsNullOrWhiteSpace(path) && Directory.Exists(path)) _settings.PinnedFolders.Add(path);
        }

        var quick = SidebarNode.Create("快速访问", "\uE8B7", NavigationLocation.Home, expandable: true);
        quick.IsExpanded = true;
        foreach (var path in _settings.PinnedFolders)
        {
            if (!Directory.Exists(path)) continue;
            quick.Children.Add(SidebarNode.Create(PathHelper.GetName(path), "\uE8B7", NavigationLocation.FromPath(path), canPin: true));
        }
        SidebarRoots.Add(quick);

        var thisPc = SidebarNode.Create("此电脑", "\uE977", NavigationLocation.ThisPc, expandable: true);
        thisPc.IsExpanded = true;
        foreach (var drive in DriveItem.Enumerate())
        {
            thisPc.Children.Add(SidebarNode.Create(drive.DisplayName, drive.Glyph,
                new NavigationLocation(LocationKind.Drive, drive.RootPath, drive.DisplayName, drive.Glyph)));
        }
        SidebarRoots.Add(thisPc);

        SidebarRoots.Add(SidebarNode.Create("网络", "\uE968", NavigationLocation.Network));
        SidebarRoots.Add(SidebarNode.Create("回收站", "\uE74D", NavigationLocation.RecycleBin));
    }

    public void UpdateSidebarSelection(string path)
    {
        if (string.IsNullOrEmpty(path)) return;
        foreach (var node in EnumerateNodes(SidebarRoots))
        {
            var match = node.Location.Kind switch
            {
                LocationKind.Home or LocationKind.Gallery or LocationKind.ThisPc or LocationKind.Network or LocationKind.RecycleBin
                    => string.Equals(node.Location.Path, path, StringComparison.OrdinalIgnoreCase),
                LocationKind.Drive => string.Equals(node.Location.Path.TrimEnd('\\'), path.TrimEnd('\\'), StringComparison.OrdinalIgnoreCase),
                _ => false
            };
            if (match)
            {
                SelectedSidebarNode = node;
                return;
            }
        }
    }

    private static IEnumerable<SidebarNode> EnumerateNodes(IEnumerable<SidebarNode> nodes)
    {
        foreach (var node in nodes)
        {
            yield return node;
            foreach (var child in EnumerateNodes(node.Children)) yield return child;
        }
    }

    [RelayCommand]
    private async Task NavigateSidebarAsync(SidebarNode? node)
    {
        if (node is null) return;
        var pane = ActivePane ?? AddTab(node.Location).Primary;
        await pane.NavigateAsync(node.Location);
        UpdateSidebarSelection(node.Location.Path);
    }

    [RelayCommand]
    private void PinFolder()
    {
        var pane = ActivePane;
        if (pane is null || pane.Location.Kind is not (LocationKind.Folder or LocationKind.Drive)) return;
        if (_settings.PinnedFolders.Contains(pane.CurrentPath, StringComparer.OrdinalIgnoreCase)) return;
        _settings.PinnedFolders.Add(pane.CurrentPath);
        _settings.Save();
        BuildSidebar();
    }

    [RelayCommand]
    private void UnpinFolder(SidebarNode? node)
    {
        if (node is null) return;
        _settings.PinnedFolders.RemoveAll(p => string.Equals(p, node.Location.Path, StringComparison.OrdinalIgnoreCase));
        _settings.Save();
        BuildSidebar();
    }

    // ── 索引状态 ────────────────────────────────────────────────────────────
    [ObservableProperty] private string _indexSummary = "索引：未启动";
    [ObservableProperty] private bool _isIndexing;
    [ObservableProperty] private double _indexProgress;
    [ObservableProperty] private bool _indexNeedsElevation;
    [ObservableProperty] private string _indexDetail = string.Empty;

    private void RefreshIndexState()
    {
        var state = _search.AggregateState;
        var count = _search.TotalIndexedEntries;
        IndexDetail = _search.AllIndexes.FirstOrDefault() is { } first
            ? first.GetType().Name
            : string.Empty;

        switch (state)
        {
            case IndexState.NotStarted:
                IndexSummary = "索引：未启动（搜索将退化为实时扫描）";
                IsIndexing = false;
                break;
            case IndexState.Building:
                IndexSummary = $"索引：正在建立…（已索引 {count:N0} 项）";
                IsIndexing = true;
                break;
            case IndexState.RequiresElevation:
                IndexSummary = "索引：需要管理员权限才能读取 NTFS 主文件表";
                IsIndexing = false;
                IndexNeedsElevation = true;
                break;
            case IndexState.Failed:
                IndexSummary = "索引：不可用（该卷不是 NTFS）";
                IsIndexing = false;
                break;
            default:
                IndexSummary = $"索引：{count:N0} 项 · 已就绪";
                IsIndexing = false;
                IndexNeedsElevation = false;
                break;
        }
    }

    [RelayCommand]
    private async Task BuildIndexAsync()
    {
        if (IsIndexing) return;
        IsIndexing = true;
        IndexSummary = "索引：正在建立…";

        var volumes = DriveItem.Enumerate()
            .Where(d => d.DriveType == 3 && d.IsReady)
            .Select(d => d.RootPath)
            .ToList();
        if (volumes.Count == 0) volumes.Add(Path.GetPathRoot(Environment.SystemDirectory) ?? "C:\\");

        _settings.IndexedVolumes = volumes;
        _settings.Save();

        var progress = new Progress<(string Volume, double Progress)>(p => _ui.Post(() =>
        {
            IndexProgress = p.Progress;
            IndexSummary = $"索引：正在读取 {p.Volume} … {p.Progress:P0}";
        }));

        try
        {
            await _search.BuildIndexesAsync(volumes, progress, CancellationToken.None);
        }
        catch (Exception ex)
        {
            IndexSummary = $"索引：失败（{ex.Message}）";
        }
        finally
        {
            IsIndexing = false;
            RefreshIndexState();
        }
    }

    [RelayCommand]
    private void RestartElevated()
    {
        try
        {
            var exe = Environment.ProcessPath;
            if (string.IsNullOrEmpty(exe)) return;
            Process.Start(new ProcessStartInfo(exe) { UseShellExecute = true, Verb = "runas" });
            Microsoft.UI.Xaml.Application.Current.Exit();
        }
        catch
        {
            // 用户拒绝了 UAC
        }
    }

    // ── 操作队列 ────────────────────────────────────────────────────────────
    public ObservableCollection<JobRowViewModel> JobRows { get; } = [];
    [ObservableProperty] private bool _isQueueExpanded;
    [ObservableProperty] private int _activeJobCount;
    private readonly DispatcherQueueTimer _jobTimer;

    private void RefreshJobs()
    {
        _ui.Post(() =>
        {
            JobRows.Clear();
            foreach (var job in _operations.Jobs) JobRows.Add(new JobRowViewModel(job));
            ActiveJobCount = JobRows.Count(j => !j.IsFinished);
            OnPropertyChanged(nameof(HasJobs));

            // 有活动作业时以 250ms 刷新快照（作业本身在后台线程更新，不能直接绑 UI）
            if (ActiveJobCount > 0) _jobTimer.Start();
            else _jobTimer.Stop();
        });
    }

    private void OnJobTimerTick(DispatcherQueueTimer sender, object args)
    {
        var anyActive = false;
        foreach (var row in JobRows)
        {
            row.Refresh();
            if (!row.IsFinished) anyActive = true;
        }
        ActiveJobCount = JobRows.Count(r => !r.IsFinished);
        if (!anyActive) sender.Stop();
    }

    public bool HasJobs => JobRows.Count > 0;

    [RelayCommand]
    private void PauseJob(JobRowViewModel? row)
    {
        if (row is null) return;
        if (row.Job.State == JobState.Paused) _operations.Resume(row.Job.Id);
        else _operations.Pause(row.Job.Id);
    }

    [RelayCommand]
    private void CancelJob(JobRowViewModel? row)
    {
        if (row is null) return;
        _operations.Cancel(row.Job.Id);
    }

    [RelayCommand]
    private void ClearFinishedJobs()
    {
        _operations.ClearFinished();
        RefreshJobs();
    }

    [RelayCommand]
    private async Task UndoAsync()
    {
        var result = await _operations.UndoAsync();
        if (!result.Success) ErrorMessage = result.Error;
        await (ActivePane?.RefreshCommand.ExecuteAsync(null) ?? Task.CompletedTask);
    }

    [ObservableProperty] private string? _errorMessage;

    // ── 设置（改动即时生效） ────────────────────────────────────────────────
    [ObservableProperty] private bool _showHiddenFiles;
    [ObservableProperty] private bool _showSystemFiles;
    [ObservableProperty] private bool _showFileExtensions;
    [ObservableProperty] private bool _alwaysShowCheckBoxes;
    [ObservableProperty] private bool _deleteToRecycleBin;
    [ObservableProperty] private bool _animationsEnabled;
    [ObservableProperty] private bool _searchInCurrentFolderOnly;
    [ObservableProperty] private AppThemeMode _themeMode;

    partial void OnShowHiddenFilesChanged(bool value)
    {
        _settings.ShowHiddenFiles = value;
        _settings.Save();
        _ = ActivePane?.RefreshCommand.ExecuteAsync(null);
    }

    partial void OnShowSystemFilesChanged(bool value)
    {
        _settings.ShowSystemFiles = value;
        _settings.Save();
        _ = ActivePane?.RefreshCommand.ExecuteAsync(null);
    }

    partial void OnShowFileExtensionsChanged(bool value)
    {
        _settings.ShowFileExtensions = value;
        _settings.Save();
        foreach (var pane in AllPanes()) pane.RebuildDisplayNames();
    }

    partial void OnAlwaysShowCheckBoxesChanged(bool value)
    {
        _settings.AlwaysShowCheckBoxes = value;
        _settings.Save();
    }

    partial void OnDeleteToRecycleBinChanged(bool value)
    {
        _settings.DeleteToRecycleBin = value;
        _settings.Save();
    }

    partial void OnAnimationsEnabledChanged(bool value)
    {
        _settings.AnimationsEnabled = value;
        _settings.Save();
        AnimationsToggled?.Invoke(this, value);
    }

    public event EventHandler<bool>? AnimationsToggled;
    public event EventHandler<AppThemeMode>? ThemeModeChanged;

    partial void OnThemeModeChanged(AppThemeMode value)
    {
        _settings.ThemeMode = value;
        _settings.Save();
        ThemeModeChanged?.Invoke(this, value);
    }

    partial void OnSearchInCurrentFolderOnlyChanged(bool value)
    {
        _settings.SearchScope = value ? SearchScope.CurrentFolder : SearchScope.Global;
        _settings.Save();
    }

    private IEnumerable<ExplorerPaneViewModel> AllPanes()
    {
        foreach (var tab in Tabs)
        {
            yield return tab.Primary;
            if (tab.Secondary is not null) yield return tab.Secondary;
        }
    }

    public void SaveOpenTabs()
    {
        _settings.OpenTabs = Tabs
            .Select(t => t.Primary.CurrentPath)
            .Where(p => !string.IsNullOrEmpty(p) && !p.StartsWith("::", StringComparison.Ordinal))
            .ToList();
        _settings.Save();
    }

    /// <summary>启动：恢复上次的标签页并建立索引。</summary>
    public async Task InitializeAsync()
    {
        if (_settings.RestoreTabsOnStartup && _settings.OpenTabs.Count > 0)
        {
            foreach (var path in _settings.OpenTabs.Take(8))
            {
                if (Directory.Exists(path)) AddTab(NavigationLocation.FromPath(path), select: false);
            }
        }
        if (Tabs.Count == 0) AddTab();
        SelectedTab = Tabs[0];

        if (_settings.DualPane) SelectedTab?.ToggleDualPane();

        if (_settings.IndexOnStartup)
        {
            await BuildIndexAsync();
        }
    }
}