using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Microsoft.UI.Xaml.Media;

namespace FluidExplorer.Models;

/// <summary>轻量文件系统条目：由快速枚举一次性填充（不产生额外系统调用）。</summary>
public sealed class FileEntry
{
    public required string Name { get; init; }
    public required string FullPath { get; init; }
    public bool IsDirectory { get; init; }
    public long Size { get; init; }
    public DateTime ModifiedUtc { get; init; }
    public DateTime CreatedUtc { get; init; }
    public DateTime AccessedUtc { get; init; }
    public FileAttributes Attributes { get; init; }

    public string Extension
    {
        get
        {
            if (IsDirectory) return string.Empty;
            var i = Name.LastIndexOf('.');
            return i > 0 && i < Name.Length - 1 ? Name[(i + 1)..] : string.Empty;
        }
    }

    public string TypeKey => IsDirectory ? "folder" : (Extension.Length == 0 ? "file" : Extension.ToLowerInvariant());

    public bool IsHidden => (Attributes & FileAttributes.Hidden) != 0;
    public bool IsSystem => (Attributes & FileAttributes.System) != 0;
    public bool IsReparsePoint => (Attributes & FileAttributes.ReparsePoint) != 0;
    public bool IsReadOnly => (Attributes & FileAttributes.ReadOnly) != 0;
    public bool IsOffline => (Attributes & FileAttributes.Offline) != 0;

    public DateTime ModifiedLocal => ModifiedUtc.ToLocalTime();
    public DateTime CreatedLocal => CreatedUtc.ToLocalTime();

    /// <summary>Windows 资源管理器风格的尺寸文本（已按 1024 进制并为文件夹留空）。</summary>
    public string SizeText => IsDirectory ? string.Empty : FormatSize(Size);

    /// <summary>类型描述：优先使用注册表里的友好类型名（惰性、带缓存）。</summary>
    public string TypeText => IsDirectory ? "文件夹" : Services.Shell.TypeNameResolver.GetTypeName(Extension, IsDirectory);

    public static string FormatSize(long bytes)
    {
        if (bytes < 0) return string.Empty;
        if (bytes < 1024) return $"{bytes} 字节";
        string[] units = ["KB", "MB", "GB", "TB", "PB"];
        double v = bytes;
        int u = -1;
        do { v /= 1024.0; u++; } while (v >= 1024 && u < units.Length - 1);
        return v >= 100 ? $"{v:0} {units[u]}" : v >= 10 ? $"{v:0.0} {units[u]}" : $"{v:0.00} {units[u]}";
    }
}

/// <summary>列表里的一行：可观察包装，缩略图/图标异步补齐，不阻塞滚动。</summary>
public sealed class ExplorerItem : INotifyPropertyChanged
{
    private ImageSource? _icon;
    private bool _isSelected;
    private bool _isRenaming;
    private string _renameText = string.Empty;
    private string? _displayName;
    private int _iconSize = 16;

    public ExplorerItem(FileEntry entry) => Entry = entry;

    public FileEntry Entry { get; }
    public string Name => Entry.Name;

    /// <summary>界面显示名（"显示文件扩展名"关闭时隐藏扩展名，与资源管理器一致）。</summary>
    public string DisplayName
    {
        get => _displayName ?? Entry.Name;
        set { if (_displayName != value) { _displayName = value; OnPropertyChanged(); } }
    }

    /// <summary>是否为新建/重命名中的占位项（这些项要滚动到可见并进入编辑状态）。</summary>
    public bool IsPending { get; set; }
    public string FullPath => Entry.FullPath;
    public bool IsDirectory => Entry.IsDirectory;
    public long Size => Entry.Size;
    public string SizeText => Entry.SizeText;
    public string TypeText => Entry.TypeText;
    public DateTime ModifiedLocal => Entry.ModifiedLocal;
    public string ModifiedText => Entry.ModifiedLocal.ToString("yyyy/MM/dd HH:mm");
    public string CreatedText => Entry.CreatedLocal.ToString("yyyy/MM/dd HH:mm");

    /// <summary>图标或缩略图（ImageSource 由 UI 线程创建后写入；先给几何图标占位，避免跳动）。</summary>
    public ImageSource? Icon
    {
        get => _icon;
        set { if (!ReferenceEquals(_icon, value)) { _icon = value; OnPropertyChanged(); } }
    }

    /// <summary>是否已经替换为真实缩略图（用于淡入动画）。</summary>
    public bool HasThumbnail { get; set; }

    public bool IsSelected
    {
        get => _isSelected;
        set
        {
            if (_isSelected == value) return;
            _isSelected = value;
            OnPropertyChanged();
            OnPropertyChanged(nameof(ShowCheckBox));
        }
    }

    /// <summary>复选框是否可见（对齐资源管理器：选中时显示，或用户开启了"始终显示项目复选框"）。</summary>
    public bool ShowCheckBox => _isSelected || AlwaysShowCheckBoxes;

    /// <summary>全局设置：始终显示项目复选框。</summary>
    public static bool AlwaysShowCheckBoxes { get; set; }

    /// <summary>当前视图所需的图标像素尺寸（由窗格在切换视图方式时写入）。</summary>
    public int IconSize
    {
        get => _iconSize;
        set { if (_iconSize != value) { _iconSize = value; OnPropertyChanged(); } }
    }

    public bool IsRenaming
    {
        get => _isRenaming;
        set { if (_isRenaming != value) { _isRenaming = value; OnPropertyChanged(); } }
    }

    public string RenameText
    {
        get => _renameText;
        set { if (_renameText != value) { _renameText = value; OnPropertyChanged(); } }
    }

    public string Extension => Entry.Extension;
    public bool IsHidden => Entry.IsHidden;
    public bool IsReparsePoint => Entry.IsReparsePoint;

    public event PropertyChangedEventHandler? PropertyChanged;

    private void OnPropertyChanged([CallerMemberName] string? name = null)
        => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}

/// <summary>当前文件夹的内容集合。</summary>
public sealed class FolderListing
{
    public required string Path { get; set; }
    public ObservableCollection<ExplorerItem> Items { get; } = [];
    public bool IsLoading { get; set; }
    public bool IsComplete { get; set; }
    public string? Error { get; set; }
    public int TotalCount => Items.Count;
}