using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;

public interface IPinchHandler
{
    void OnPinchStart();
    void OnPinchEnd();
    void OnPinchZoom(float gapDelta);
}
public class PinchZoomModule : MonoBehaviour, IPointerUpHandler,IPointerDownHandler, IDragHandler
{
    private int firstEnterFingerID = -1;
    private int lastEnterFingerID = -1;
    private int nowFingersCount = 0;

    private Vector2 firstFingerPosition;
    private Vector2 lastFingerPosition;
    private float distance = 0.0f;

    public float zoomSpeed = 0.5f;
    public float minZoom = 0.5f;
    public float maxZoom = 2.0f;

    float scale = 1.0f;

    public float zoomGap = 0.0f;
    public float zoomGapDelta = 0.0f;
    public float zoomGapDeltaSpeed = 0.1f;

    private bool isPinchZooming = false;

    public IPinchHandler pinchHandler;

    void Awake()
    {
        if(GetComponent(typeof(IPinchHandler)) as IPinchHandler == null)
        {
            var add = gameObject.AddComponent<UIMultiScaleTool>();
            add.minScale = minZoom;
            add.maxScale = maxZoom;
            add.enabled = false;
        }
        pinchHandler = GetComponent(typeof(IPinchHandler)) as IPinchHandler;
    }

    private void OnEnable()
    {
        GetComponent<UIMultiScaleTool>().enabled = true;
        zoomGap = 0.0f;
        scale = 1.0f;
    }
    private void OnDisable()
    {
        GetComponent<UIMultiScaleTool>().enabled = false;
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        nowFingersCount++;
        DebugUtil.Log("add new finger, nowFingersCount: " + nowFingersCount);
        if (nowFingersCount == 1)
        {
            firstEnterFingerID = eventData.pointerId;
            firstFingerPosition = eventData.position;
        }
        else if (nowFingersCount == 2)
        {
            lastEnterFingerID = eventData.pointerId;
            lastFingerPosition = eventData.position;

            distance = Vector2.Distance(firstFingerPosition, lastFingerPosition);

            isPinchZooming = true;
            pinchHandler?.OnPinchStart();
        }
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        nowFingersCount--;
        DebugUtil.Log("remove a finger, nowFingersCount: " + nowFingersCount);
        if (eventData.pointerId == firstEnterFingerID)
        {
            firstEnterFingerID = lastEnterFingerID;
            firstFingerPosition = lastFingerPosition;

            lastEnterFingerID = -1;
            if (isPinchZooming)
            {
                isPinchZooming = false;
                pinchHandler?.OnPinchEnd();
            }
        }
        else if(eventData.pointerId == lastEnterFingerID)
        {
            lastEnterFingerID = -1;
            if (isPinchZooming)
            {
                isPinchZooming = false;
                pinchHandler?.OnPinchEnd();
            }
        }
    }

    public void OnDrag(PointerEventData eventData)
    {
        if (isPinchZooming)
        {
            if(eventData.pointerId == firstEnterFingerID)
            {
                firstFingerPosition = eventData.position;
            }
            else if(eventData.pointerId == lastEnterFingerID)
            {
                lastFingerPosition = eventData.position;
            }

            float nowDistance = Vector2.Distance(firstFingerPosition, lastFingerPosition);
            zoomGapDelta = nowDistance - distance;
            zoomGap = zoomGapDelta * zoomSpeed;
            distance = nowDistance;

            scale = Mathf.Clamp(scale + zoomGap * zoomGapDeltaSpeed, minZoom, maxZoom);

            pinchHandler?.OnPinchZoom(scale);
        }
    }
}