using System.Windows.Media;
using System.Windows;
using System.Windows.Threading;
using System.Windows.Controls;

namespace SeqEditor.Util
{
    public class DispatcherHelper
    {
        private static readonly DispatcherOperationCallback exitFrameCallback = ExitFrame;

        /// <summary>
        /// Processes all UI messages currently in the message queue.
        /// </summary>
        public static void WaitForPriority()
        {
            // Create new nested message pump.
            DispatcherFrame nestedFrame = new DispatcherFrame();

            // Dispatch a callback to the current message queue, when getting called,
            // this callback will end the nested message loop.
            // The priority of this callback should be lower than that of event message you want to process.
            DispatcherOperation exitOperation = Dispatcher.CurrentDispatcher.BeginInvoke(
                DispatcherPriority.ApplicationIdle, exitFrameCallback, nestedFrame);

            // pump the nested message loop, the nested message loop will immediately
            // process the messages left inside the message queue.
            Dispatcher.PushFrame(nestedFrame);

            // If the "exitFrame" callback is not finished, abort it.
            if (exitOperation.Status != DispatcherOperationStatus.Completed)
            {
                exitOperation.Abort();
            }
        }

        private static Object ExitFrame(Object state)
        {
            DispatcherFrame frame = state as DispatcherFrame;

            // Exit the nested message loop.
            frame.Continue = false;
            return null;
        }

        public static T FindControl<T>(object obj)
        {
            if (obj == null)
            {
                return default(T);
            }

            if (obj is T target)
            {
                return target;
            }
            return FindControl<T>(VisualTreeHelper.GetParent((DependencyObject)obj));
        }

        public static bool IsElementVisibleInScrollViewer(ScrollViewer scrollViewer, DependencyObject element)
        {
            if (scrollViewer == null || element == null)
                return false;

            // 将 element 转换为 FrameworkElement
            var frameworkElement = element as FrameworkElement;
            if (frameworkElement == null)
                return false;

            try
            {
                // 获取元素相对于 ScrollViewer 的坐标变换
                GeneralTransform transform = frameworkElement.TransformToVisual(scrollViewer);

                // 计算元素在 ScrollViewer 坐标系中的位置和大小
                Rect elementRect = new Rect(
                    transform.Transform(new Point(0, 0)),
                    transform.Transform(new Point(frameworkElement.ActualWidth, frameworkElement.ActualHeight))
                );

                // ScrollViewer 的视区矩形
                Rect viewportRect = new Rect(
                    0,
                    0,
                    scrollViewer.ViewportWidth,
                    scrollViewer.ViewportHeight
                );

                // 检查是否相交（部分可见也算可见）
                //return viewportRect.IntersectsWith(elementRect);

                // 如果需要完全可见，使用以下代码：
                 return viewportRect.Contains(elementRect);
            }
            catch (ArgumentException)
            {
                // 如果元素尚未加载或不可见，TransformToVisual 可能抛出异常
                return false;
            }
        }

        /// <summary>
        /// 查找第一个指定类型的子控件
        /// </summary>
        public static T FindVisualChild<T>(DependencyObject parent) where T : DependencyObject
        {
            if (parent == null)
                return null;

            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
            {
                var child = VisualTreeHelper.GetChild(parent, i);

                // 找到指定类型
                if (child is T t)
                    return t;

                // 递归查找
                var result = FindVisualChild<T>(child);
                if (result != null)
                    return result;
            }

            return null;
        }
    }
}