using System.Collections;
using System.Collections.Generic;
#if UNITY_EDITOR
using UnityEditor;
#endif
using UnityEngine;
using UnityEngine.UI;

public class UILineRenderer : Graphic
{
    public List<Vector2> points = new List<Vector2>();
    public float thickness = 10f;

    float GetAngle(Vector2 source, Vector2 target)
    {
        return (float)(Mathf.Atan2(target.y - source.y, target.x - source.x)) * Mathf.Rad2Deg;
    }
    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear();

        if (points.Count < 2) return;

        float angle = 0;
        for (int i = 0; i < points.Count; i++)
        {
            Vector2 point = points[i];

            if (i < points.Count - 1)
            {
                angle = GetAngle(points[i], points[i + 1]) + 45f;
            }

            DrawVertices(point, vh, angle);
        }

        for (int i = 0; i < points.Count - 1; ++i)
        {
            int index = i * 2;
            vh.AddTriangle(index + 0, index + 1, index + 3);
            vh.AddTriangle(index + 3, index + 2, index + 0);
        }
    }

    void DrawVertices(Vector2 point, VertexHelper vh, float angle)
    {
        UIVertex vertex = UIVertex.simpleVert;
        vertex.color = color;

        vertex.position = Quaternion.Euler(0, 0, angle) * new Vector3(-thickness / 2, 0);
        vertex.position += new Vector3(point.x, point.y);
        vh.AddVert(vertex);

        vertex.position = Quaternion.Euler(0, 0, angle) * new Vector3(thickness / 2, 0);
        vertex.position += new Vector3(point.x, point.y);
        vh.AddVert(vertex);
    }

    private Color previousColor;
    public void Select()
    {
        previousColor = color;
        color = Color.yellow;
        transform.SetAsLastSibling();
    }
    public void Deselect()
    {
        color = previousColor;
    }

#if UNITY_EDITOR
    [MenuItem("GameObject/Gather and Defend/UILineRenderer")]
    public static void CreateUILineRenderer()
    {
        var line = new GameObject("UILineRenderer");
        line.transform.parent = Selection.activeTransform;
        line.AddComponent<CanvasRenderer>();
        line.AddComponent<UILineRenderer>();
        EditorUtility.SetDirty(line);
    }
#endif
}