using System.ComponentModel;
using FluidExplorer.ViewModels;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Input;

namespace FluidExplorer.Views;

/// <summary>一个标签页的宿主：负责单/双窗格布局与中间分隔条。</summary>
public sealed partial class ExplorerTabView : UserControl
{
    private bool _dragging;
    private double _startX;
    private double _startFirstWidth;
    private double _startSecondWidth;

    public ExplorerTabView()
    {
        InitializeComponent();
        Loaded += (_, _) => UpdatePaneLayout();
    }

    public static readonly DependencyProperty TabViewModelProperty = DependencyProperty.Register(
        nameof(TabViewModel),
        typeof(ExplorerTabViewModel),
        typeof(ExplorerTabView),
        new PropertyMetadata(null, OnTabChanged));

    public ExplorerTabViewModel? TabViewModel
    {
        get => (ExplorerTabViewModel?)GetValue(TabViewModelProperty);
        set => SetValue(TabViewModelProperty, value);
    }

    private static void OnTabChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var view = (ExplorerTabView)d;
        if (e.OldValue is ExplorerTabViewModel old) old.PropertyChanged -= view.OnTabPropertyChanged;
        if (e.NewValue is ExplorerTabViewModel tab) tab.PropertyChanged += view.OnTabPropertyChanged;
        view.UpdatePaneLayout();
    }

    private void OnTabPropertyChanged(object? sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == nameof(ExplorerTabViewModel.IsDualPane)) UpdatePaneLayout();
    }

    private void UpdatePaneLayout()
    {
        var dual = TabViewModel?.IsDualPane == true;

        if (dual)
        {
            Splitter.Visibility = Visibility.Visible;
            SecondaryPaneView.Visibility = Visibility.Visible;
            SplitterColumn.Width = new GridLength(4);
            if (FirstColumn.Width.IsAbsolute && SecondColumn.Width.IsAbsolute) return;
            FirstColumn.Width = new GridLength(1, GridUnitType.Star);
            SecondColumn.Width = new GridLength(1, GridUnitType.Star);
        }
        else
        {
            Splitter.Visibility = Visibility.Collapsed;
            SecondaryPaneView.Visibility = Visibility.Collapsed;
            SplitterColumn.Width = new GridLength(0);
            FirstColumn.Width = new GridLength(1, GridUnitType.Star);
            SecondColumn.Width = new GridLength(0);
        }
    }

    private void OnSplitterPointerPressed(object sender, PointerRoutedEventArgs e)
    {
        _dragging = true;
        _startX = e.GetCurrentPoint(LayoutRoot).Position.X;
        _startFirstWidth = FirstColumn.ActualWidth;
        _startSecondWidth = SecondColumn.ActualWidth;
        Splitter.CapturePointer(e.Pointer);
    }

    private void OnSplitterPointerMoved(object sender, PointerRoutedEventArgs e)
    {
        if (!_dragging) return;
        var delta = e.GetCurrentPoint(LayoutRoot).Position.X - _startX;
        var total = _startFirstWidth + _startSecondWidth;
        const double min = 240;

        var first = Math.Clamp(_startFirstWidth + delta, min, total - min);
        FirstColumn.Width = new GridLength(first, GridUnitType.Pixel);
        SecondColumn.Width = new GridLength(total - first, GridUnitType.Pixel);
    }

    private void OnSplitterPointerReleased(object sender, PointerRoutedEventArgs e)
    {
        if (!_dragging) return;
        _dragging = false;
        Splitter.ReleasePointerCapture(e.Pointer);
    }
}