using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using HTC.UnityPlugin.Vive;

//定义一个滑槽，可以让配件在碰到滑槽后吸附到滑槽上面
public class GunSlider : MonoBehaviour {
    private Vector3 startPoint;
    private Vector3 endPoint;
    public Vector3 sliderOffSet;
    [Range(0.0f, 1.0f)]
    public float offsetPercentage = 0f;
    public bool haveItem;
    private GameObject item;
    private GunItem itemScript_;
    private GameObject leftHand;
    private GameObject gun;
    public Transform startTransForm;
    public Transform endTransForm;


    // Use this for initialization
    void Start () {
        haveItem = false;
        leftHand = GameObject.FindGameObjectWithTag("leftHand");
        gun = GameObject.FindGameObjectWithTag("gun");
        startPoint = startTransForm.localPosition;
        endPoint = endTransForm.localPosition;
    }
	
	// Update is called once per frame
	void Update () {
        if (haveItem) {
            item.transform.localPosition = startPoint + offsetPercentage * (endPoint - startPoint);
            //当物品被拖动时，物品会在滑槽之间移动
            if (itemScript_.isSlide) {
                //float distanceStart = (leftHand.transform.position - (startPoint + sliderOffSet + gun.transform.position)).sqrMagnitude;
                //float distanceEnd = (leftHand.transform.position - (endPoint + sliderOffSet + gun.transform.position)).sqrMagnitude;
                float distanceStart = (leftHand.transform.position - startTransForm.position).sqrMagnitude;
                float distanceEnd = (leftHand.transform.position - endTransForm.position).sqrMagnitude;
                float distanceSE = (endPoint - startPoint).sqrMagnitude;
                if (distanceStart + distanceSE <= distanceEnd)
                {
                    offsetPercentage = 0f;
                }
                else if (distanceEnd + distanceSE <= distanceStart)
                {
                    offsetPercentage = 1f;
                }
                else {
                    //可以保证x大于0，且随着distance增大而增大
                    float x = distanceStart + distanceSE - distanceEnd;
                    //比例系数，使得当distanceStart == distanceEnd+distanceSE时，x*y==1
                    float y =  0.5f / distanceSE;
                    offsetPercentage = x * y;
                }
                
            }
            if (ViveInput.GetPressUp(HandRole.LeftHand,ControllerButton.Trigger)) {
                itemScript_.isSlide = false;
            }
        }
	}

    //检测到配件进入时，调用安装算法
    private void OnTriggerEnter(Collider other)
    {
        if (other.gameObject.tag == "gunItem") {
            //该滑槽没有配件的情况下,可以直接安装配件
            if (!haveItem)
            {
                InstallParts(other);
            }
            //该滑槽有配件的情况下,会把滑槽的配件与手上所持的配件进行更换
            else {
                itemScript_.itemBtn.GetComponent<GunItemButton>().ReturnItem();
                Destroy(item);
                //
                InstallParts(other);
                //
            }
        }
    }
    //安装&替换配件使用的方法
    private void InstallParts(Collider other_) {
        item = other_.gameObject;
        item.tag = "Untagged";
        itemScript_ = item.GetComponent<GunItem>();
        itemScript_.itemBtn.GetComponent<GunItemButton>().InstallItem(startPoint);
        //重置装配位置(如果不重置可能会导致配件偏移)
        startPoint = startTransForm.localPosition;
        endPoint = endTransForm.localPosition;
        //装配的配件放置在固定位置上面
        startPoint += itemScript_.itemBtn.GetComponent<GunItemButton>().self_.transform.position;
        endPoint += itemScript_.itemBtn.GetComponent<GunItemButton>().self_.transform.position;
        haveItem = true;
    }
}