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

public class UIGridRenderer : Graphic
{
	public Vector2Int gridSize = new Vector2Int(1, 1); 
	public float thickness = 10f;

	float width;
	float height;
	float cellWidth;
	float cellHeight;
	
	protected override void OnPopulateMesh(VertexHelper vh)
	{
		vh.Clear();

		width = rectTransform.rect.width;
		height = rectTransform.rect.height;

		cellWidth = width / (float)gridSize.x;
		cellHeight = height / (float)gridSize.y;

		int count = 0;

		for (int y = 0; y < gridSize.y; y++)
		{
			for (int x = 0; x < gridSize.x; x++)
			{
				DrawCell(x, y,count, vh);
				count++;
			}
		}

	}

	private void DrawCell(int x, int y, int index, VertexHelper vh)
	{
		float xPos = cellWidth * x;
		float yPos = cellHeight * y;

		UIVertex vertex = UIVertex.simpleVert;
		vertex.color = color;

		vertex.position = new Vector3(xPos,yPos);
		vh.AddVert(vertex);

		vertex.position = new Vector3(xPos , yPos + cellHeight);
		vh.AddVert(vertex);

		vertex.position = new Vector3(xPos+cellWidth, yPos + cellHeight);
		vh.AddVert(vertex);

		vertex.position = new Vector3(xPos + cellWidth, yPos);
		vh.AddVert(vertex);

		//vh.AddTriangle(0, 1, 2);
		//vh.AddTriangle(2, 3, 0);

		float widthSqr = thickness * thickness;
		float distanceSqr = widthSqr / 2f;
		float distance = Mathf.Sqrt(distanceSqr);

		vertex.position = new Vector3(xPos +distance, yPos+distance);
		vh.AddVert(vertex);

		vertex.position = new Vector3(xPos + distance , yPos + (cellHeight - distance));
		vh.AddVert(vertex);

		vertex.position = new Vector3(xPos+(cellWidth - distance), yPos + (cellHeight - distance));
		vh.AddVert(vertex);

		vertex.position = new Vector3(xPos + (cellWidth - distance), yPos + distance);
		vh.AddVert(vertex);

		int offset = index * 8;


		//Left Edge
		vh.AddTriangle(offset + 0, offset + 1, offset + 5);
		vh.AddTriangle(offset + 5, offset + 4, offset + 0);

		//Top Edge
		vh.AddTriangle(offset + 1, offset + 2, offset + 6);
		vh.AddTriangle(offset + 6, offset + 5, offset + 1);

		//Right Edge
		vh.AddTriangle(offset + 2, offset + 3, offset + 7);
		vh.AddTriangle(offset + 7, offset + 6, offset + 2);

		//Bottom Edge
		vh.AddTriangle(offset + 3, offset + 0, offset + 4);
		vh.AddTriangle(offset + 4, offset + 7, offset + 3);

	}
}