using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.UI;

namespace LineUI
{
	[RequireComponent(typeof(CanvasRenderer))]
	[RequireComponent(typeof(RectTransform))]
	public class Line : Graphic
	{
		[SerializeField] private bool loop = false;
		[SerializeField] private float thickness = 1f;
		[SerializeField] private int roundCount = 0;
		[SerializeField] private List<Vector2> screenPositions = new List<Vector2>();

		public RectTransform RectTr { get => rectTransform; }

		//调用的话最少10宽度
		public float MyThickness
		{
			get { return thickness; }
			set {
				if (value >= 10)
				{

					thickness = value;
				}
			}
		}


    public void SetLine(List<Vector2> screenPositions)
		{
			this.screenPositions = screenPositions;
			SetVerticesDirty();
		}

		protected override void OnPopulateMesh(VertexHelper vh)
		{
			vh.Clear();
			SetVertex(vh);
			SetTriangles(vh);
		}

		private void SetVertex(VertexHelper vh)
		{
			UIVertex vert = UIVertex.simpleVert;
			vert.color = color;
			if (screenPositions.Count < 2)
				return;
			List<Vector2> _screenPositions = screenPositions.ToList();
			if (loop) {
				//添加多两个顶点。形成闭环
				_screenPositions.Add(screenPositions[0]);
				_screenPositions.Add(screenPositions[1]);
			}

			float lastAngle = 0;
			for (int i = 1; i < _screenPositions.Count; i++)
			{
				Vector2 previousPos = _screenPositions[i - 1];
				Vector2 currentPos = _screenPositions[i];
				Vector2 dif = currentPos - previousPos;
				float angle = Vector2.SignedAngle(Vector2.right, dif);
                if (i > 1)
                {
                    float anglePerRound = (angle - lastAngle) / roundCount;
                    for (int j = 0; j < roundCount; j++)
                    {
                        float ang = lastAngle + anglePerRound * j;
                        Vector2 roundOffset = Quaternion.Euler(0, 0, ang) * Vector2.up * thickness;
                        vert.position = previousPos - roundOffset;
                        vh.AddVert(vert);

                        vert.position = previousPos + roundOffset;
                        vh.AddVert(vert);
                    }
                }
                lastAngle = angle;

				Vector2 offset = (Vector2)(Quaternion.Euler(0, 0, angle) * Vector3.up * thickness);

				vert.position = previousPos - offset;
				vh.AddVert(vert);

				vert.position = previousPos + offset;
				vh.AddVert(vert);

				vert.position = currentPos - offset;
				vh.AddVert(vert);

				vert.position = currentPos + offset;
				vh.AddVert(vert);

			}
			
		}

        private static void SetTriangles(VertexHelper vh)
        {
            for (int i = 0; i < vh.currentVertCount - 2; i += 2)
            {
                int index = i;
                vh.AddTriangle(index, index + 1, index + 3);
                vh.AddTriangle(index + 3, index + 2, index);
            }
        }


    }
}