using Prism.Services.Dialogs;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;

namespace Store.Management.Framework.Controls;

internal static class ViewLifecycle
{
    // 卸载时 DataContext 可能已改变，记录实际收到 OnLoaded 的实例。
    private static readonly DependencyProperty LoadedViewModelProperty =
        DependencyProperty.RegisterAttached("LoadedViewModel", typeof(ViewModelBase), typeof(ViewLifecycle));

    internal static void Register()
    {
        foreach (Type type in new[] { typeof(UserControl), typeof(Window) })
        {
            FrameworkElement.DataContextProperty.OverrideMetadata(type,
                new FrameworkPropertyMetadata(null, OnDataContextChanged));
        }
    }

    private static void OnDataContextChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        if (sender is Window window)
        {
            if (e.OldValue is ViewModelBase)
            {
                window.Activated -= OnActivated;
                window.Deactivated -= OnDeactivated;
                window.Closing -= OnClosing;
                window.Closed -= OnClosed;
            }
            if (e.NewValue is ViewModelBase)
            {
                window.Activated += OnActivated;
                window.Deactivated += OnDeactivated;
                window.Closing += OnClosing;
                window.Closed += OnClosed;
            }
            if (window is IDialogWindow) return; // Prism 弹窗由内容页接收加载与卸载。
        }
        var view = (FrameworkElement)sender;
        if (e.OldValue is ViewModelBase)
        {
            view.Loaded -= OnLoaded;
            view.Unloaded -= OnUnloaded;
        }
        if (e.NewValue is ViewModelBase)
        {
            view.Loaded += OnLoaded;
            view.Unloaded += OnUnloaded;
        }
        if (view.IsLoaded || view.GetValue(LoadedViewModelProperty) != null)
            UpdateViewModel(view);
    }

    private static void OnLoaded(object sender, RoutedEventArgs e)
        => UpdateViewModel((FrameworkElement)sender);

    private static void OnActivated(object? sender, EventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnActivated();
    private static void OnDeactivated(object? sender, EventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnDeactivated();
    private static void OnClosing(object? sender, CancelEventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnClosing(e);
    private static void OnClosed(object? sender, EventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnClosed();

    private static void UpdateViewModel(FrameworkElement view)
    {
        // 共享父级 DataContext 的页眉、导航栏等子控件不拥有页面生命周期。
        var source = DependencyPropertyHelper.GetValueSource(view, FrameworkElement.DataContextProperty);
        var next = source.BaseValueSource == BaseValueSource.Inherited ? null : view.DataContext as ViewModelBase;
        var previous = (ViewModelBase?)view.GetValue(LoadedViewModelProperty);
        if (ReferenceEquals(previous, next)) return;
        view.SetValue(LoadedViewModelProperty, next);
        previous?.OnUnloaded();
        next?.NotifyLoaded();
    }

    private static void OnUnloaded(object sender, RoutedEventArgs e)
    {
        var view = (FrameworkElement)sender;
        var previous = (ViewModelBase?)view.GetValue(LoadedViewModelProperty);
        view.ClearValue(LoadedViewModelProperty);
        previous?.OnUnloaded();
    }
}