using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Media;
using TeamAAS.FlowEditor.Models;

namespace TeamAAS.FlowEditor.Controls
{
    /// <summary>
    /// 节点拖拽手柄 - 处理节点选择和拖动
    /// </summary>
    public class MoveThumb : Thumb
    {
        private FlowCanvas _canvas;

        // 拖拽锚点：起点时鼠标在画布坐标系的位置 + 各节点的起始坐标。
        // 用 Mouse.GetPosition(画布) 实时计算位移，而不是累加 DragDelta——
        // 后者在 PerMonitorV2 + 高 DPI 下是物理像素，会导致节点移动速度 ≠ 鼠标（4K 200% 缩放下节点跑飞）。
        private Point _dragStartMouseOnCanvas;
        private readonly List<FlowNode> _dragNodes = new List<FlowNode>();
        private readonly List<double> _startXs = new List<double>();
        private readonly List<double> _startYs = new List<double>();
        private int _diagCounter; // TODO 拖拽诊断，问题定位后删除

        public MoveThumb()
        {
            DragStarted += OnDragStartedHandler;
            DragDelta += OnDragDeltaHandler;
            DragCompleted += OnDragCompletedHandler;
        }

        private FlowCanvas FindCanvas()
        {
            if (_canvas != null) return _canvas;
            DependencyObject parent = VisualTreeHelper.GetParent(this);
            while (parent != null && !(parent is FlowCanvas))
                parent = VisualTreeHelper.GetParent(parent);
            _canvas = parent as FlowCanvas;
            return _canvas;
        }

        protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
        {
            // 选择由 FlowCanvas.OnMouseLeftButtonDown 统一处理（含 Ctrl 多选）
            base.OnMouseLeftButtonDown(e);
        }

        private void OnDragStartedHandler(object sender, DragStartedEventArgs e)
        {
            var canvas = FindCanvas();
            var node = DataContext as FlowNode;
            if (canvas == null || node == null) return;

            _dragStartMouseOnCanvas = Mouse.GetPosition(canvas);
            _dragNodes.Clear();
            _startXs.Clear();
            _startYs.Clear();

            var selectedNodes = canvas.GetSelectedNodes();
            if (selectedNodes != null && selectedNodes.Count > 1 && selectedNodes.Contains(node))
            {
                foreach (var selNode in selectedNodes)
                {
                    _dragNodes.Add(selNode);
                    _startXs.Add(selNode.X);
                    _startYs.Add(selNode.Y);
                }
            }
            else
            {
                _dragNodes.Add(node);
                _startXs.Add(node.X);
                _startYs.Add(node.Y);
            }

            // TODO 拖拽诊断，问题定位后删除
            AppLogger.Info($"[DragDiag] started node={node.NodeName} mouseOnCanvas=({_dragStartMouseOnCanvas.X:F1},{_dragStartMouseOnCanvas.Y:F1}) nodePos=({node.X:F1},{node.Y:F1})", "DragDiag");
        }

        private void OnDragDeltaHandler(object sender, DragDeltaEventArgs e)
        {
            var node = DataContext as FlowNode;
            if (node == null) return;

            var canvas = FindCanvas();

            // 流程运行中 / 只读监控模式禁止移动节点
            if (canvas != null && (canvas.IsRunning || canvas.IsReadOnly)) return;
            if (_dragNodes.Count == 0) return;

            // 鼠标相对拖拽起点的位移（画布本地坐标，DPI / 缩放换算均正确）
            var mouse = Mouse.GetPosition(canvas);
            double dx = mouse.X - _dragStartMouseOnCanvas.X;
            double dy = mouse.Y - _dragStartMouseOnCanvas.Y;

            // TODO 拖拽诊断，问题定位后删除
            if ((++_diagCounter % 10) == 0)
                AppLogger.Info($"[DragDiag] delta mouse=({mouse.X:F1},{mouse.Y:F1}) d=({dx:F1},{dy:F1}) node0=({_dragNodes[0].X:F1},{_dragNodes[0].Y:F1}) startPos=({_startXs[0]:F1},{_startYs[0]:F1})", "DragDiag");

            if (_dragNodes.Count > 1)
            {
                // 整组硬墙语义：先预判每个成员的目标位置，
                // 只要有一个成员越出画布边界、或与非同组成员的节点碰撞，
                // 整组本次一动不动（碰壁即停），之后把鼠标拖回自由方向才能继续移动。
                // 同组成员以相同位移整体平移、相对位置不变，彼此不可能相撞，故不算障碍。
                for (int i = 0; i < _dragNodes.Count; i++)
                {
                    double sx = _startXs[i] + dx;
                    double sy = _startYs[i] + dy;
                    if (sx < 0 || sy < 0 || canvas.CheckNodeCollision(_dragNodes[i], Math.Max(0, sx), Math.Max(0, sy), _dragNodes))
                        return;
                }

                for (int i = 0; i < _dragNodes.Count; i++)
                {
                    _dragNodes[i].X = Math.Max(0, _startXs[i] + dx);
                    _dragNodes[i].Y = Math.Max(0, _startYs[i] + dy);
                }
                canvas.UpdateCanvasSize();
                return;
            }

            // 单选拖拽
            double newX = Math.Max(0, _startXs[0] + dx);
            double newY = Math.Max(0, _startYs[0] + dy);

            // 节点碰撞检测
            if (canvas != null)
            {
                if (canvas.CheckNodeCollision(node, newX, newY))
                {
                    // 尝试只移动X
                    if (!canvas.CheckNodeCollision(node, newX, node.Y))
                        node.X = newX;
                    // 尝试只移动Y
                    else if (!canvas.CheckNodeCollision(node, node.X, newY))
                        node.Y = newY;
                    return;
                }

                // 对齐引导线检测
                canvas.CheckAlignment(node, ref newX, ref newY);
            }

            node.X = newX;
            node.Y = newY;

            // 自动拉线预览
            canvas?.UpdateAutoConnectPreview(node);

            // 通知画布更新大小
            canvas?.UpdateCanvasSize();
        }

        private void OnDragCompletedHandler(object sender, DragCompletedEventArgs e)
        {
            var canvas = FindCanvas();
            if (canvas == null) return;
            canvas.ClearAlignLines();

            // 自动拉线：仅单节点拖拽时生效（多节点移动不触发）
            var node = DataContext as FlowNode;
            var selectedNodes = canvas.GetSelectedNodes();
            if (node != null && (selectedNodes == null || selectedNodes.Count <= 1))
                canvas.TryAutoConnect(node);
        }
    }
}