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

namespace Michsky.UI.Heat
{
	[RequireComponent(typeof(Scrollbar))]
	public class SmoothScrollbar : MonoBehaviour
	{
		[Header("Settings")]
		[SerializeField]
		[Range(0.3f, 5f)]
		private float curveSpeed = 1.5f;

		[SerializeField]
		private AnimationCurve animationCurve = new AnimationCurve(new Keyframe(0f, 0f), new Keyframe(1f, 1f));

		private Scrollbar scrollbar;

		private void Awake()
		{
			scrollbar = GetComponent<Scrollbar>();
		}

		public void GoToTop()
		{
			StopCoroutine("GoBottom");
			StopCoroutine("GoTop");
			StartCoroutine("GoTop");
		}

		public void GoToBottom()
		{
			StopCoroutine("GoBottom");
			StopCoroutine("GoTop");
			StartCoroutine("GoBottom");
		}

		private IEnumerator GoTop()
		{
			float startingPoint = scrollbar.value;
			float elapsedTime = 0f;
			while (scrollbar.value < 0.999f)
			{
				elapsedTime += Time.unscaledDeltaTime;
				scrollbar.value = Mathf.Lerp(startingPoint, 1f, animationCurve.Evaluate(elapsedTime * curveSpeed));
				yield return null;
			}
			scrollbar.value = 1f;
		}

		private IEnumerator GoBottom()
		{
			float startingPoint = scrollbar.value;
			float elapsedTime = 0f;
			while (scrollbar.value > 0.001f)
			{
				elapsedTime += Time.unscaledDeltaTime;
				scrollbar.value = Mathf.Lerp(startingPoint, 0f, animationCurve.Evaluate(elapsedTime * curveSpeed));
				yield return null;
			}
			scrollbar.value = 0f;
		}
	}
}