using UnityEngine;
using UnityEngine.UI;

public class QuantizedSlider : MonoBehaviour {

    public float epsilon = 0.01f;
    public float step = 1.0f;
    public float smoothDuration = 0.2f;
    private Slider slider;
    private Slider ctrl_slider;
    private float smooth;
    private float target;
    void copyTransform(GameObject dst, GameObject src)
    {
        RectTransform srcRect = src.transform as RectTransform;
        RectTransform dstRect = dst.transform as RectTransform;

        dstRect.anchorMin = srcRect.anchorMin;
        dstRect.anchorMax = srcRect.anchorMax;        
        dstRect.sizeDelta = srcRect.sizeDelta;
        dstRect.anchoredPosition = srcRect.anchoredPosition;

    }
	// Use this for initialization
	void Start () {
        slider = GetComponent<Slider>();
        ctrl_slider = transform.Find("ControllingSlider").GetComponent<Slider>();
        
        ctrl_slider.value = smooth = target = slider.value;
        ctrl_slider.minValue = slider.minValue;
        ctrl_slider.maxValue = slider.maxValue;
        ctrl_slider.onValueChanged.AddListener(OnValueChange);
        ctrl_slider.transform.hideFlags =  HideFlags.NotEditable;

        GameObject handle = Instantiate(slider.handleRect.gameObject, slider.handleRect.parent);
        copyTransform(handle, slider.handleRect.gameObject);
        ctrl_slider.handleRect = handle.transform as RectTransform;
        handle.GetComponent<Image>().color = new Color(1.0f, 0.0f, 0.0f, 0.0f);
        handle.transform.hideFlags =  HideFlags.NotEditable;
    }
	
    void OnValueChange(float f)
    {
        target = Mathf.Round((ctrl_slider.value - slider.minValue) / step)*step;
        target = Mathf.Clamp(target, slider.minValue, slider.maxValue);
    }
	// Update is called once per frame
	void Update () {

        float diff = target - smooth;        
        smooth = Mathf.Abs(diff)<epsilon?target: smooth + (diff) * Mathf.Min(1.0f, Time.deltaTime / smoothDuration);
        if(smooth != slider.value)
            slider.value = smooth;

    }
}