using System.Collections;
using System.Collections.Generic;
using System.Linq;
using SkiaSharp;
using UnityEngine;
using UnityEngine.UIElements;

namespace BITKit.UX
{
	public class SkiaPainter : VisualElement
	{
		public new class UxmlFactory : UxmlFactory<SkiaPainter, UxmlTraits> { }
		public SkiaPainter()
		{
			RegisterCallback<GeometryChangedEvent>(OnGeometryChanged);
			RegisterCallback<MouseDownEvent>(OnMouseDown);
			RegisterCallback<MouseUpEvent>(OnMouseUp);
			RegisterCallback<MouseMoveEvent>(OnMouseMove);
		}

	
		private bool _isPainting;
		private readonly List<Vector2> _points = new();
		private SKImageInfo _info;
		private SKCanvas _canvas;
		private SKSurface _surface;
		private Rect _rect;
		private Optional<SKColor> _backgroundColor=new ();
		// private readonly SKPaint _linePaint = new()
		// {
		// 	Style = SKPaintStyle.Stroke,
		// 	Color = SKColors.Red,
		// 	StrokeWidth = 5,
		// };
		private readonly SKPaint _linePaint = new SKPaint
		{
			Style = SKPaintStyle.Stroke,
			Color = SKColors.Black, // 笔画颜色为黑色
			StrokeCap = SKStrokeCap.Round, // 笔画末端采用圆形
			StrokeJoin = SKStrokeJoin.Round, // 笔画连接处采用圆形
			StrokeWidth = 8, // 笔画宽度
			IsAntialias = true // 使用抗锯齿
		};
		public void ClearCanvas()
		{
			_points.Clear();
			Rebuild();
		}
		private void OnMouseMove(MouseMoveEvent evt)
		{
			if (_isPainting is false) return;
			var pos = evt.localMousePosition;
			pos.y = layout.height - pos.y;
			
			var last = _points.LastOrDefault();
			
			if (_rect.Contains(pos) is false)
			{
			
				if (last == default) return;
			
				_points.Add(default);
				return;
			}

			var originalPos = pos;
			if (last != default)
			{
				//pos = Vector2.Lerp(last, pos, 0.1f);
				
				_points.Add(Vector2.Lerp(last, pos, 0.1f));
				_points.Add(Vector2.Lerp(last, pos, 0.2f));
				//_points.Add(Vector2.Lerp(last, pos, 1f));
			}
			else
			{
				_points.Add(pos);
			}
			
			//_points.Add(pos);

			if (originalPos != pos)
			{
				//_points.Add(originalPos);
			}
			Rebuild();
		}

		private void OnMouseUp(MouseUpEvent evt)
		{
			_isPainting = false;
			var last = _points.LastOrDefault();
			if (last != default)
				_points.Add(default);
		}

		private void OnMouseDown(MouseDownEvent evt)
		{
			_isPainting = true;
		}
		private void OnGeometryChanged(GeometryChangedEvent evt)
		{
			if(float.IsNaN(layout.width) || layout.width < 16 || float.IsNaN(layout.height) || layout.height<16)
				return;
			_linePaint.Color = resolvedStyle.color.ToSKColor();
			_surface?.Dispose();
			_canvas?.Dispose();
			_info = new SKImageInfo((int)layout.width, (int)layout.height);
			_info.AlphaType = SKAlphaType.Premul;
			
			_surface = SKSurface.Create(_info);
			_canvas = _surface.Canvas;
			_rect = new Rect(0, 0, layout.width, layout.height);
			Rebuild();
		}
		private void Rebuild()
		{
			if (_canvas is null) return;
			
			_canvas.Clear(resolvedStyle.backgroundColor.ToSKColor());
			DoubleBuffer<Vector2> buffer = new();
			
			_linePaint.StrokeWidth = 4;
			
			foreach (var pos in _points)
			{
				if (pos == default)
				{
					buffer.Clear();
				}
				else
				{
					if (buffer.TryGetRelease(out var previousPoint))
					{
						_canvas.DrawLine(previousPoint.x, previousPoint.y, pos.x, pos.y, _linePaint);
					}
					buffer.Release(pos);
				}
			}
			var texture = _info.ToTexture2D(_surface);
			
			
			style.backgroundImage = texture;
		}
		public string Base64 => _surface?.GetBase64();
		public byte[] Bytes => _surface?.GetBytes();
	}
}