using System.Collections;

using UnityEngine;
using UnityEngine.UI;

[RequireComponent(typeof(Image))]
[ExecuteInEditMode]
public class SubstanceController : MonoBehaviour
{

    private const string ShaderName = "UI/Substance";
    public const string PercentageProperty = "_Percentage";

    private Image image;
    private void Awake()
    {
        image = GetComponent<Image>();

        if (image.material.shader.name != ShaderName)
        {
            Debug.LogError("Bad shader on image material attached!");
        }
    }

    // Use this method for instant substance percentage fill change
    public void ChangePercentage(float toValue)
    {
        image.material.SetFloat(PercentageProperty, Mathf.Clamp(toValue, 0.0f, 1.0f));
    }

    // Use this method for substance percentage fill change in time
    public void ChangePercentageInTime(float toValue, float time)
    {
        // clamping values to match range defined in shader
        StartCoroutine(ChangeValueInMaterial(Mathf.Clamp(toValue, 0.0f, 1.0f), PercentageProperty, time));
    }

    private IEnumerator ChangeValueInMaterial(float toValue, string propertyName, float time)
    {
        float startingValue = image.material.GetFloat(propertyName);

        float curTime = 0.0f;
        while (curTime <= time)
        {
            curTime += Time.deltaTime;
            image.material.SetFloat(propertyName, Mathf.Lerp(startingValue, toValue, curTime / time));
            yield return null;
        }

        image.material.SetFloat(propertyName, toValue);
        yield return null;
    }
}