using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Media;
using Microsoft.Win32;

namespace TeamAAS
{
    /// <summary>
    /// 窗口分辨率/DPI 自适应助手。
    /// </summary>
    public static class UiScaler
    {
        private static double _globalScale = 1.0;

        /// <summary>当前全局缩放因子（弹窗读取用）</summary>
        public static double GlobalScale => _globalScale;

        /// <summary>全局因子变化通知（弹窗订阅后自动跟随）</summary>
        public static event Action ScaleChanged;

        private static readonly Dictionary<Window, Size> _designSizes = new Dictionary<Window, Size>();

        /// <summary>
        /// 主窗口：计算全局缩放因子并应用（设计基准默认 1600x900，钳制 minScale~maxScale）。
        /// </summary>
        public static void AttachMain(Window window, double refWidth = 1600, double refHeight = 900,
                                      double minScale = 0.6, double maxScale = 2.0)
        {
            if (window == null) return;
            var root = window.Content as FrameworkElement;
            if (root == null) return;
            if (root.Tag is UiScalerToken) return;
            root.Tag = new UiScalerToken();

            void Update()
            {
                double w = window.ActualWidth > 0 ? window.ActualWidth : refWidth;
                double h = window.ActualHeight > 0 ? window.ActualHeight : refHeight;

                double f = Math.Min(w / refWidth, h / refHeight);
                _globalScale = Math.Max(minScale, Math.Min(maxScale, f));

                ApplyTransform(window, _globalScale, resizeWindow: false);
                ScaleChanged?.Invoke();
            }

            window.SizeChanged += (s, e) => Update();
            window.DpiChanged += (s, e) => Update();
            window.Loaded += (s, e) => Update();
            SystemEvents.DisplaySettingsChanged += (s, e) => window.Dispatcher.Invoke(Update);
        }

        /// <summary>
        /// 弹窗/子窗体：跟随全局缩放因子（只放大不缩小，窗口尺寸与内容同步缩放）。
        /// 幂等：重复调用/全局钩子叠加均安全。
        /// </summary>
        public static void Attach(Window window)
        {
            if (window == null) return;
            var root = window.Content as FrameworkElement;
            if (root == null) return;
            if (root.Tag is UiScalerToken) return;
            root.Tag = new UiScalerToken();

            Action apply = () => ApplyTransform(window, _globalScale, resizeWindow: true);
            apply();

            // 全局因子变化时跟随；关闭时退订，避免事件泄漏
            ScaleChanged += apply;
            window.Closed += (s, e) => ScaleChanged -= apply;
        }

        private static void ApplyTransform(Window w, double f, bool resizeWindow)
        {
            var root = w.Content as FrameworkElement;
            if (root == null) return;

            // 弹窗只放大不缩小（f<1 时保持 1.0，避免小窗被缩到看不清）
            double effective = resizeWindow ? Math.Max(1.0, f) : f;

            if (Math.Abs(effective - 1.0) < 0.001)
            {
                root.LayoutTransform = null;
                return;
            }

            if (resizeWindow)
            {
                // 首次记录设计尺寸（XAML 声明值；NaN=自动/SizeToContent 交由内容自适应）
                if (!_designSizes.TryGetValue(w, out var design))
                {
                    design = new Size(w.Width, w.Height);
                    _designSizes[w] = design;
                }
                if (!double.IsNaN(design.Width) && design.Width > 0) w.Width = design.Width * effective;
                if (!double.IsNaN(design.Height) && design.Height > 0) w.Height = design.Height * effective;
            }

            root.LayoutTransform = new ScaleTransform(effective, effective);
        }

        private sealed class UiScalerToken { }
    }
}