using System.Collections;
using UnityEngine;
[RequireComponent(typeof(LinearMapping))]
public class MouseLinearObj : MonoBehaviour
{
    public Transform startPos, endPos;
    LinearMapping linearMapping;
    Vector3 m_Offset;
    Vector3 m_TargetScreenVec;
    Camera cam;
    private void Start()
    {
        cam = Camera.main;
        linearMapping = GetComponent<LinearMapping>();
        CalculateLinearMapping();
    }
    private void OnEnable()
    {
        transform.localPosition = startPos.localPosition;
    }
    private IEnumerator OnMouseDown()
    {
        if (!cam)
        {
            cam = Camera.main;
        }
        m_TargetScreenVec = cam.WorldToScreenPoint(transform.position);
        m_Offset = transform.position - cam.ScreenToWorldPoint(new Vector3
        (Input.mousePosition.x, Input.mousePosition.y, m_TargetScreenVec.z));
        while (Input.GetMouseButton(0))
        {
            Vector3 temp = cam.ScreenToWorldPoint(new Vector3(Input.mousePosition.x,
            Input.mousePosition.y, m_TargetScreenVec.z)) + m_Offset;
            transform.position = LineMapping(startPos.position,endPos.position, temp);
            linearMapping.value = Mathf.Round(CalculateLinearMapping() * 100) / 100f;
            yield return new WaitForFixedUpdate();
        }
    }
    private void OnMouseDrag()
    {
        if (TryGetComponent(out PC_DragEvent dragEvent))
        {
            dragEvent.stay?.Invoke(gameObject);
        }
    }
    /// <summary>
    /// 直线映射
    /// </summary>
    /// <param name="mAPoint">直线的开始点</param>
    /// <param name="mBPoint">直线的结束点</param>
    /// <param name="mCurrentPoint">当前点位置</param>
    /// <returns>映射位置</returns>
    Vector3 LineMapping(Vector3 mAPoint, Vector3 mBPoint, Vector3 mCurrentPoint)
    {
        Vector3 vectorAB = mBPoint - mAPoint;
        float dotProduct = vectorAB.x * (mCurrentPoint.x - mAPoint.x) + vectorAB.y * (mCurrentPoint.y - mAPoint.y) + vectorAB.z * (mCurrentPoint.z - mAPoint.z);
        float lengthSquared = vectorAB.x * vectorAB.x + vectorAB.y * vectorAB.y + vectorAB.z * vectorAB.z;
        if (dotProduct > lengthSquared) dotProduct = lengthSquared; if (dotProduct < 0) dotProduct = 0; //限制
        Vector3 PointA = mAPoint + vectorAB * dotProduct / lengthSquared;
        Vector3 PointB = mCurrentPoint + (PointA - mCurrentPoint);
        return PointB;
    }
    protected float CalculateLinearMapping()
    {
        Vector3 direction = endPos.position - startPos.position;
        float length = direction.magnitude;
        direction.Normalize();

        Vector3 displacement = transform.position - startPos.position;

        return Vector3.Dot(displacement, direction) / length;
    }
}