using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

namespace XP.Common.Controls
{
    /// <summary>
    /// 虚拟摇杆自定义控件，提供圆形区域内的鼠标拖拽操控能力 | Virtual joystick custom control providing mouse drag interaction within a circular area
    /// </summary>
    /// <remarks>
    /// 支持双轴/单轴 Y 模式、死区配置、归一化比例输出（-1.0 ~ 1.0）、鼠标左右键区分及四向功能图标切换。
    /// Supports dual-axis/single-axis Y mode, dead zone configuration, normalized proportional output (-1.0 ~ 1.0),
    /// left/right mouse button differentiation, and four-directional icon switching.
    /// </remarks>
    [TemplatePart(Name = PART_Thumb, Type = typeof(UIElement))]
    public class VirtualJoystick : Control
    {
        /// <summary>
        /// 操控点模板部件名称 | Thumb template part name
        /// </summary>
        private const string PART_Thumb = "PART_Thumb";

        #region 私有字段 | Private Fields

        /// <summary>
        /// 是否正在拖拽 | Whether dragging is in progress
        /// </summary>
        private bool _isDragging;

        /// <summary>
        /// 控件中心点坐标 | Control center point coordinates
        /// </summary>
        private Point _centerPoint;

        /// <summary>
        /// 操控点的平移变换，用于跟随鼠标移动 | Translate transform for thumb element to follow mouse movement
        /// </summary>
        private TranslateTransform _thumbTransform = new TranslateTransform();

        #endregion
        #region 静态构造函数 | Static Constructor

        static VirtualJoystick()
        {
            DefaultStyleKeyProperty.OverrideMetadata(
                typeof(VirtualJoystick),
                new FrameworkPropertyMetadata(typeof(VirtualJoystick)));
        }

        #endregion

        #region JoystickMode 依赖属性 | JoystickMode Dependency Property

        /// <summary>
        /// 摇杆轴模式依赖属性 | Joystick axis mode dependency property
        /// </summary>
        public static readonly DependencyProperty JoystickModeProperty =
            DependencyProperty.Register(
                nameof(JoystickMode),
                typeof(JoystickMode),
                typeof(VirtualJoystick),
                new PropertyMetadata(JoystickMode.DualAxis));

        /// <summary>
        /// 获取或设置摇杆轴模式（双轴或单轴 Y）| Gets or sets the joystick axis mode (DualAxis or SingleAxisY)
        /// </summary>
        public JoystickMode JoystickMode
        {
            get => (JoystickMode)GetValue(JoystickModeProperty);
            set => SetValue(JoystickModeProperty, value);
        }

        #endregion

        #region OutputX 只读依赖属性 | OutputX Read-Only Dependency Property

        /// <summary>
        /// OutputX 只读依赖属性键 | OutputX read-only dependency property key
        /// </summary>
        private static readonly DependencyPropertyKey OutputXPropertyKey =
            DependencyProperty.RegisterReadOnly(
                nameof(OutputX),
                typeof(double),
                typeof(VirtualJoystick),
                new PropertyMetadata(0.0));

        /// <summary>
        /// X 轴归一化输出依赖属性 | X-axis normalized output dependency property
        /// </summary>
        public static readonly DependencyProperty OutputXProperty = OutputXPropertyKey.DependencyProperty;

        /// <summary>
        /// 获取 X 轴归一化输出值，范围 [-1.0, 1.0] | Gets the X-axis normalized output value, range [-1.0, 1.0]
        /// </summary>
        public double OutputX
        {
            get => (double)GetValue(OutputXProperty);
            internal set => SetValue(OutputXPropertyKey, value);
        }

        #endregion

        #region OutputY 只读依赖属性 | OutputY Read-Only Dependency Property

        /// <summary>
        /// OutputY 只读依赖属性键 | OutputY read-only dependency property key
        /// </summary>
        private static readonly DependencyPropertyKey OutputYPropertyKey =
            DependencyProperty.RegisterReadOnly(
                nameof(OutputY),
                typeof(double),
                typeof(VirtualJoystick),
                new PropertyMetadata(0.0));

        /// <summary>
        /// Y 轴归一化输出依赖属性 | Y-axis normalized output dependency property
        /// </summary>
        public static readonly DependencyProperty OutputYProperty = OutputYPropertyKey.DependencyProperty;

        /// <summary>
        /// 获取 Y 轴归一化输出值，范围 [-1.0, 1.0] | Gets the Y-axis normalized output value, range [-1.0, 1.0]
        /// </summary>
        public double OutputY
        {
            get => (double)GetValue(OutputYProperty);
            internal set => SetValue(OutputYPropertyKey, value);
        }

        #endregion

        #region DeadZone 依赖属性 | DeadZone Dependency Property

        /// <summary>
        /// 死区比例依赖属性 | Dead zone ratio dependency property
        /// </summary>
        public static readonly DependencyProperty DeadZoneProperty =
            DependencyProperty.Register(
                nameof(DeadZone),
                typeof(double),
                typeof(VirtualJoystick),
                new PropertyMetadata(0.05));

        /// <summary>
        /// 获取或设置死区比例，范围 [0.0, 1.0]，默认值 0.05 | Gets or sets the dead zone ratio, range [0.0, 1.0], default 0.05
        /// </summary>
        public double DeadZone
        {
            get => (double)GetValue(DeadZoneProperty);
            set => SetValue(DeadZoneProperty, value);
        }

        #endregion

        #region ActiveMouseButton 只读依赖属性 | ActiveMouseButton Read-Only Dependency Property

        /// <summary>
        /// ActiveMouseButton 只读依赖属性键 | ActiveMouseButton read-only dependency property key
        /// </summary>
        private static readonly DependencyPropertyKey ActiveMouseButtonPropertyKey =
            DependencyProperty.RegisterReadOnly(
                nameof(ActiveMouseButton),
                typeof(MouseButtonType),
                typeof(VirtualJoystick),
                new PropertyMetadata(MouseButtonType.None));

        /// <summary>
        /// 当前激活的鼠标按键依赖属性 | Active mouse button dependency property
        /// </summary>
        public static readonly DependencyProperty ActiveMouseButtonProperty = ActiveMouseButtonPropertyKey.DependencyProperty;

        /// <summary>
        /// 获取当前激活的鼠标按键（None、Left、Right）| Gets the currently active mouse button (None, Left, Right)
        /// </summary>
        public MouseButtonType ActiveMouseButton
        {
            get => (MouseButtonType)GetValue(ActiveMouseButtonProperty);
            internal set => SetValue(ActiveMouseButtonPropertyKey, value);
        }

        #endregion

        #region 左键四向图标依赖属性 | Left Button Directional Icon Dependency Properties

        /// <summary>
        /// 左键拖动时上方图标内容依赖属性 | Left button top icon content dependency property
        /// </summary>
        public static readonly DependencyProperty LeftButtonTopIconProperty =
            DependencyProperty.Register(
                nameof(LeftButtonTopIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置左键拖动时上方图标内容 | Gets or sets the top icon content when left button is dragging
        /// </summary>
        public object? LeftButtonTopIcon
        {
            get => GetValue(LeftButtonTopIconProperty);
            set => SetValue(LeftButtonTopIconProperty, value);
        }

        /// <summary>
        /// 左键拖动时下方图标内容依赖属性 | Left button bottom icon content dependency property
        /// </summary>
        public static readonly DependencyProperty LeftButtonBottomIconProperty =
            DependencyProperty.Register(
                nameof(LeftButtonBottomIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置左键拖动时下方图标内容 | Gets or sets the bottom icon content when left button is dragging
        /// </summary>
        public object? LeftButtonBottomIcon
        {
            get => GetValue(LeftButtonBottomIconProperty);
            set => SetValue(LeftButtonBottomIconProperty, value);
        }

        /// <summary>
        /// 左键拖动时左方图标内容依赖属性 | Left button left icon content dependency property
        /// </summary>
        public static readonly DependencyProperty LeftButtonLeftIconProperty =
            DependencyProperty.Register(
                nameof(LeftButtonLeftIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置左键拖动时左方图标内容 | Gets or sets the left icon content when left button is dragging
        /// </summary>
        public object? LeftButtonLeftIcon
        {
            get => GetValue(LeftButtonLeftIconProperty);
            set => SetValue(LeftButtonLeftIconProperty, value);
        }

        /// <summary>
        /// 左键拖动时右方图标内容依赖属性 | Left button right icon content dependency property
        /// </summary>
        public static readonly DependencyProperty LeftButtonRightIconProperty =
            DependencyProperty.Register(
                nameof(LeftButtonRightIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置左键拖动时右方图标内容 | Gets or sets the right icon content when left button is dragging
        /// </summary>
        public object? LeftButtonRightIcon
        {
            get => GetValue(LeftButtonRightIconProperty);
            set => SetValue(LeftButtonRightIconProperty, value);
        }

        #endregion

        #region 右键四向图标依赖属性 | Right Button Directional Icon Dependency Properties

        /// <summary>
        /// 右键拖动时上方图标内容依赖属性 | Right button top icon content dependency property
        /// </summary>
        public static readonly DependencyProperty RightButtonTopIconProperty =
            DependencyProperty.Register(
                nameof(RightButtonTopIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置右键拖动时上方图标内容 | Gets or sets the top icon content when right button is dragging
        /// </summary>
        public object? RightButtonTopIcon
        {
            get => GetValue(RightButtonTopIconProperty);
            set => SetValue(RightButtonTopIconProperty, value);
        }

        /// <summary>
        /// 右键拖动时下方图标内容依赖属性 | Right button bottom icon content dependency property
        /// </summary>
        public static readonly DependencyProperty RightButtonBottomIconProperty =
            DependencyProperty.Register(
                nameof(RightButtonBottomIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置右键拖动时下方图标内容 | Gets or sets the bottom icon content when right button is dragging
        /// </summary>
        public object? RightButtonBottomIcon
        {
            get => GetValue(RightButtonBottomIconProperty);
            set => SetValue(RightButtonBottomIconProperty, value);
        }

        /// <summary>
        /// 右键拖动时左方图标内容依赖属性 | Right button left icon content dependency property
        /// </summary>
        public static readonly DependencyProperty RightButtonLeftIconProperty =
            DependencyProperty.Register(
                nameof(RightButtonLeftIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置右键拖动时左方图标内容 | Gets or sets the left icon content when right button is dragging
        /// </summary>
        public object? RightButtonLeftIcon
        {
            get => GetValue(RightButtonLeftIconProperty);
            set => SetValue(RightButtonLeftIconProperty, value);
        }

        /// <summary>
        /// 右键拖动时右方图标内容依赖属性 | Right button right icon content dependency property
        /// </summary>
        public static readonly DependencyProperty RightButtonRightIconProperty =
            DependencyProperty.Register(
                nameof(RightButtonRightIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置右键拖动时右方图标内容 | Gets or sets the right icon content when right button is dragging
        /// </summary>
        public object? RightButtonRightIcon
        {
            get => GetValue(RightButtonRightIconProperty);
            set => SetValue(RightButtonRightIconProperty, value);
        }

        #endregion

        #region ThumbElement 内部属性 | ThumbElement Internal Property

        /// <summary>
        /// 操控点 UI 元素引用（从模板获取）| Thumb UI element reference (obtained from template)
        /// </summary>
        internal UIElement? ThumbElement { get; private set; }

        #endregion

        #region 默认四向图标依赖属性 | Default Directional Icon Dependency Properties

        /// <summary>
        /// 默认状态上方图标内容依赖属性 | Default top icon content dependency property
        /// </summary>
        public static readonly DependencyProperty DefaultTopIconProperty =
            DependencyProperty.Register(
                nameof(DefaultTopIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置默认状态上方图标内容 | Gets or sets the top icon content in default state
        /// </summary>
        public object? DefaultTopIcon
        {
            get => GetValue(DefaultTopIconProperty);
            set => SetValue(DefaultTopIconProperty, value);
        }

        /// <summary>
        /// 默认状态下方图标内容依赖属性 | Default bottom icon content dependency property
        /// </summary>
        public static readonly DependencyProperty DefaultBottomIconProperty =
            DependencyProperty.Register(
                nameof(DefaultBottomIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置默认状态下方图标内容 | Gets or sets the bottom icon content in default state
        /// </summary>
        public object? DefaultBottomIcon
        {
            get => GetValue(DefaultBottomIconProperty);
            set => SetValue(DefaultBottomIconProperty, value);
        }

        /// <summary>
        /// 默认状态左方图标内容依赖属性 | Default left icon content dependency property
        /// </summary>
        public static readonly DependencyProperty DefaultLeftIconProperty =
            DependencyProperty.Register(
                nameof(DefaultLeftIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置默认状态左方图标内容 | Gets or sets the left icon content in default state
        /// </summary>
        public object? DefaultLeftIcon
        {
            get => GetValue(DefaultLeftIconProperty);
            set => SetValue(DefaultLeftIconProperty, value);
        }

        /// <summary>
        /// 默认状态右方图标内容依赖属性 | Default right icon content dependency property
        /// </summary>
        public static readonly DependencyProperty DefaultRightIconProperty =
            DependencyProperty.Register(
                nameof(DefaultRightIcon),
                typeof(object),
                typeof(VirtualJoystick),
                new PropertyMetadata(null));

        /// <summary>
        /// 获取或设置默认状态右方图标内容 | Gets or sets the right icon content in default state
        /// </summary>
        public object? DefaultRightIcon
        {
            get => GetValue(DefaultRightIconProperty);
            set => SetValue(DefaultRightIconProperty, value);
        }

        #endregion

        #region 模板应用 | Template Application

        /// <summary>
        /// 应用控件模板时查找操控点元素并设置平移变换 | Find thumb element and set up translate transform when template is applied
        /// </summary>
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            // 查找模板中的操控点元素 | Find the thumb element in the template
            ThumbElement = GetTemplateChild(PART_Thumb) as UIElement;

            if (ThumbElement != null)
            {
                // 设置平移变换用于拖拽跟随 | Set translate transform for drag following
                ThumbElement.RenderTransform = _thumbTransform;
            }
        }

        #endregion

        #region 鼠标交互事件处理 | Mouse Interaction Event Handlers

        /// <summary>
        /// 鼠标左键按下时开始拖拽 | Start dragging when left mouse button is pressed
        /// </summary>
        protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
        {
            base.OnMouseLeftButtonDown(e);

            // 如果已在拖拽中或控件未启用，忽略 | Ignore if already dragging or control is disabled
            if (_isDragging || !IsEnabled)
                return;

            StartDrag(MouseButtonType.Left);
            e.Handled = true;
        }

        /// <summary>
        /// 鼠标右键按下时开始拖拽 | Start dragging when right mouse button is pressed
        /// </summary>
        protected override void OnMouseRightButtonDown(MouseButtonEventArgs e)
        {
            base.OnMouseRightButtonDown(e);

            // 如果已在拖拽中或控件未启用，忽略 | Ignore if already dragging or control is disabled
            if (_isDragging || !IsEnabled)
                return;

            StartDrag(MouseButtonType.Right);
            e.Handled = true;
        }

        /// <summary>
        /// 鼠标移动时更新操控点位置和输出值 | Update thumb position and output values when mouse moves
        /// </summary>
        protected override void OnMouseMove(MouseEventArgs e)
        {
            base.OnMouseMove(e);

            if (!_isDragging)
                return;

            try
            {
                // 获取鼠标相对于控件的位置 | Get mouse position relative to the control
                var mousePosition = e.GetPosition(this);

                // 计算相对于中心的偏移量 | Calculate displacement from center
                var dx = mousePosition.X - _centerPoint.X;
                var dy = mousePosition.Y - _centerPoint.Y;

                // 计算可用半径（取宽高较小值的一半）| Calculate available radius (half of the smaller dimension)
                var radius = GetRadius();
                if (radius <= 0)
                    return;

                // 将位移限制在圆形区域内 | Clamp displacement within circular area
                var (clampedDx, clampedDy) = JoystickCalculator.ClampToRadius(dx, dy, radius);

                // 计算归一化输出（含死区映射）| Calculate normalized output (with dead zone mapping)
                var (outputX, outputY) = JoystickCalculator.CalculateOutput(dx, dy, radius, DeadZone, JoystickMode);

                // 更新输出值 | Update output values
                OutputX = outputX;
                OutputY = outputY;

                // 更新操控点的平移变换位置（使用限制后的位移）| Update thumb translate transform (using clamped displacement)
                _thumbTransform.X = clampedDx;
                _thumbTransform.Y = clampedDy;
            }
            catch
            {
                // 异常时重置到中心位置并输出归零 | Reset to center and zero output on exception
                ResetToCenter();
            }

            e.Handled = true;
        }

        /// <summary>
        /// 鼠标左键释放时结束拖拽 | End dragging when left mouse button is released
        /// </summary>
        protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
        {
            base.OnMouseLeftButtonUp(e);

            // 仅当正在拖拽且激活按键为左键时处理 | Only handle when dragging with left button active
            if (!_isDragging || ActiveMouseButton != MouseButtonType.Left)
                return;

            EndDrag();
            e.Handled = true;
        }

        /// <summary>
        /// 鼠标右键释放时结束拖拽 | End dragging when right mouse button is released
        /// </summary>
        protected override void OnMouseRightButtonUp(MouseButtonEventArgs e)
        {
            base.OnMouseRightButtonUp(e);

            // 仅当正在拖拽且激活按键为右键时处理 | Only handle when dragging with right button active
            if (!_isDragging || ActiveMouseButton != MouseButtonType.Right)
                return;

            EndDrag();
            e.Handled = true;
        }

        #endregion

        #region 拖拽辅助方法 | Drag Helper Methods

        /// <summary>
        /// 开始拖拽操作 | Start drag operation
        /// </summary>
        /// <param name="buttonType">触发拖拽的鼠标按键类型 | Mouse button type that initiated the drag</param>
        private void StartDrag(MouseButtonType buttonType)
        {
            // 捕获鼠标以接收控件外的鼠标事件 | Capture mouse to receive events outside the control
            CaptureMouse();

            // 设置激活的鼠标按键 | Set the active mouse button
            ActiveMouseButton = buttonType;

            // 计算控件中心点 | Calculate control center point
            _centerPoint = new Point(ActualWidth / 2.0, ActualHeight / 2.0);

            // 标记拖拽状态 | Mark dragging state
            _isDragging = true;
        }

        /// <summary>
        /// 结束拖拽操作 | End drag operation
        /// </summary>
        private void EndDrag()
        {
            // 重置到中心位置并归零输出 | Reset to center and zero output
            ResetToCenter();

            // 释放鼠标捕获 | Release mouse capture
            ReleaseMouseCapture();
        }

        /// <summary>
        /// 重置操控点到中心位置，输出归零，清除拖拽状态 | Reset thumb to center, zero output, clear drag state
        /// </summary>
        internal void ResetToCenter()
        {
            // 输出值归零 | Zero output values
            OutputX = 0.0;
            OutputY = 0.0;

            // 清除激活的鼠标按键 | Clear active mouse button
            ActiveMouseButton = MouseButtonType.None;

            // 清除拖拽状态 | Clear dragging state
            _isDragging = false;

            // 重置操控点平移变换到中心 | Reset thumb translate transform to center
            _thumbTransform.X = 0.0;
            _thumbTransform.Y = 0.0;
        }

        /// <summary>
        /// 获取可用半径（取宽高较小值的一半）| Get available radius (half of the smaller dimension)
        /// </summary>
        /// <returns>可用半径 | Available radius</returns>
        private double GetRadius()
        {
            return Math.Min(ActualWidth, ActualHeight) / 2.0;
        }

        #endregion
    }
}