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

namespace GameWrapper
{
    [RequireComponent(typeof(CanvasRenderer))]
    public class UILineRenderer : MaskableGraphic
    {
        public List<Vector2> points = new List<Vector2>();
        public float thickness = 10f;

        protected override void Awake()
        {
            base.Awake();
            raycastTarget = false;
        }

        public void SetPoints(List<Vector2> points)
        {
            this.points = points ?? new List<Vector2>();
            SetVerticesDirty();
        }

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

            if (points.Count < 2)
                return;

            // If the graphic is transparent, do nothing.
            if (canvasRenderer.GetAlpha() == 0)
                 return;

            for (int i = 0; i < points.Count; i += 2)
            {
                if (i + 1 >= points.Count) break;

                DrawLineSegment(points[i], points[i + 1], vh);
            }
        }

        private void DrawLineSegment(Vector2 start, Vector2 end, VertexHelper vh)
        {
            Vector2 dir = (end - start).normalized;
            Vector2 perpendicular = new Vector2(-dir.y, dir.x) * (thickness / 2);

            UIVertex[] verts = new UIVertex[4];
            verts[0] = new UIVertex { position = start - perpendicular, color = this.color, uv0 = Vector2.zero };
            verts[1] = new UIVertex { position = start + perpendicular, color = this.color, uv0 = Vector2.up };
            verts[2] = new UIVertex { position = end + perpendicular,   color = this.color, uv0 = Vector2.one };
            verts[3] = new UIVertex { position = end - perpendicular,   color = this.color, uv0 = Vector2.right };

            vh.AddUIVertexQuad(verts);
        }
    }
}