using System.ComponentModel;
using System.Runtime.CompilerServices;
using XSDVisualiser.Core;

namespace XSDVisualiser.Desktop.ViewModels;

/// <summary>
/// View model exposing the parsed schema for binding in the main window.
/// Provides selection state and information about the currently loaded XSD file.
/// </summary>
public class MainWindowViewModel(SchemaModel model) : INotifyPropertyChanged
{
    private string? _currentFilePath;
    private SchemaModel _model = model ?? throw new ArgumentNullException(nameof(model));
    private SchemaNode? _selectedNode;
    private SchemaNode? _selectedRootElement;

    /// <summary>
    /// Parsed schema model currently displayed by the UI.
    /// Setting this property updates dependent properties and notifies bindings.
    /// </summary>
    public SchemaModel Model
    {
        get => _model;
        set
        {
            if (ReferenceEquals(_model, value)) return;
            _model = value ?? throw new ArgumentNullException(nameof(value));
            OnPropertyChanged();
            OnPropertyChanged(nameof(RootElements));
            OnPropertyChanged(nameof(VisibleRootElements));
        }
    }

    /// <summary>
    /// All global elements defined in the loaded schema.
    /// </summary>
    public IEnumerable<SchemaNode> RootElements => _model?.RootElements ?? Enumerable.Empty<SchemaNode>();

    /// <summary>
    /// If set, filters the view to show only this root element and its subtree.
    /// </summary>
    public SchemaNode? SelectedRootElement
    {
        get => _selectedRootElement;
        set
        {
            if (EqualityComparer<SchemaNode?>.Default.Equals(_selectedRootElement, value)) return;
            _selectedRootElement = value;
            OnPropertyChanged();
            OnPropertyChanged(nameof(VisibleRootElements));
        }
    }

    public SchemaNode? SelectedNode
    {
        get => _selectedNode;
        set
        {
            if (EqualityComparer<SchemaNode?>.Default.Equals(_selectedNode, value)) return;
            _selectedNode = value;
            OnPropertyChanged();
        }
    }

    public IEnumerable<SchemaNode> VisibleRootElements =>
        SelectedRootElement != null ? [SelectedRootElement] : RootElements;

    public string? CurrentFilePath
    {
        get => _currentFilePath;
        set
        {
            if (string.Equals(_currentFilePath, value, StringComparison.Ordinal)) return;
            _currentFilePath = value;
            OnPropertyChanged();
            OnPropertyChanged(nameof(CurrentFileName));
            OnPropertyChanged(nameof(CurrentDirectory));
        }
    }

    public string? CurrentFileName =>
        string.IsNullOrEmpty(_currentFilePath) ? null : Path.GetFileName(_currentFilePath);

    public string? CurrentDirectory =>
        string.IsNullOrEmpty(_currentFilePath) ? null : Path.GetDirectoryName(_currentFilePath);

    public event PropertyChangedEventHandler? PropertyChanged;

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