using System;
using Unity.Mathematics;
using UnityEngine;
using UnityEngine.Splines;

namespace Unity.Splines.Examples
{
	// Visualize the nearest point on a spline to a roving sphere.
	[RequireComponent(typeof(LineRenderer))]
	public class ShowNearestPoint : MonoBehaviour
	{
		// Boundary setup for the wandering sphere
		Vector3 m_Center = Vector3.zero;
		float m_Size = 50f;

		// Store a collection of Splines to test for nearest to our position.
		SplineContainer[] m_SplineContainer;

		LineRenderer m_LineRenderer;

		// This GameObject will be used to visualize the nearest point on the nearest spline to this transform.
		[SerializeField]
		Transform m_NearestPoint;

		void Start()
		{
			if (!TryGetComponent(out m_LineRenderer))
				Debug.LogError("ShowNearestPoint requires a LineRenderer.");
			m_LineRenderer.positionCount = 2;
			m_SplineContainer = FindObjectsOfType<SplineContainer>();
			if (m_NearestPoint == null)
				Debug.LogError("Nearest Point GameObject is null");
		}

		void Update()
		{
			var position = CalculatePosition();
			var nearest = new float4(0, 0, 0, float.PositiveInfinity);

			foreach (var container in m_SplineContainer)
			{
				using var native = new NativeSpline(container.Spline, container.transform.localToWorldMatrix);
				float d = SplineUtility.GetNearestPoint(native, transform.position, out float3 p, out float t);
				if (d < nearest.w)
					nearest = new float4(p, d);
			}

			m_LineRenderer.SetPosition(0, position);
			m_LineRenderer.SetPosition(1, nearest.xyz);
			m_NearestPoint.position = nearest.xyz;
			transform.position = position;
		}

		Vector3 CalculatePosition()
		{
			float time = Time.time * .2f, time1 = time + 1;
			float half = m_Size * .5f;

			return m_Center + new Vector3(
				Mathf.PerlinNoise(time, time) * m_Size - half,
				0,
				Mathf.PerlinNoise(time1, time1) * m_Size - half
			);
		}

		void OnDrawGizmosSelected()
		{
			Gizmos.DrawWireCube(m_Center, new Vector3(m_Size, .1f, m_Size));
		}
	}
}