////////////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2007-2020 , Inc.  All Rights Reserved.
//
////////////////////////////////////////////////////////////////////////////////

using UnityEngine;
using UnityEngine.EventSystems;

using GCSeries.Core.EventSystems;
using GCSeries.Core.Input;

namespace GCSeries.Core.Samples
{
    public class Draggable :
        ZPointerInteractable, IBeginDragHandler, IDragHandler, IEndDragHandler
    {
        public bool Active = true;

        ////////////////////////////////////////////////////////////////////////
        // Public Methods
        ////////////////////////////////////////////////////////////////////////

        public override ZPointer.DragPolicy GetDragPolicy(ZPointer pointer)
        {
            if (pointer is ZMouse)
            {
                return ZPointer.DragPolicy.LockToScreenAlignedPlane;
            }

            if (pointer is ZStylus)
            {
                return ZPointer.DragPolicy.LockHitPosition;
            }

            return base.GetDragPolicy(pointer);
        }

        public virtual void OnBeginDrag(PointerEventData eventData)
        {
            if (!this.Active) return;

            ZPointerEventData pointerEventData = eventData as ZPointerEventData;
            if (pointerEventData == null ||
                pointerEventData.button != PointerEventData.InputButton.Left)
            {
                return;
            }

            Pose pose = pointerEventData.Pointer.EndPointWorldPose;

            // Cache the initial grab state.
            this._initialGrabOffset =
                Quaternion.Inverse(this.transform.rotation) *
                (this.transform.position - pose.position);

            this._initialGrabRotation =
                Quaternion.Inverse(pose.rotation) *
                this.transform.rotation;

            // If the grabbable object has a rigidbody component,
            // mark it as kinematic during the grab.
            var rigidbody = this.GetComponent<Rigidbody>();
            if (rigidbody != null)
            {
                this._isKinematic = rigidbody.isKinematic;
                rigidbody.isKinematic = true;
            }

            // Capture pointer events.
            pointerEventData.Pointer.CapturePointer(this.gameObject);
        }

        public virtual void OnDrag(PointerEventData eventData)
        {
            if (!this.Active) return;
            if (_initialGrabOffset == Vector3.zero) return;

            ZPointerEventData pointerEventData = eventData as ZPointerEventData;
            if (pointerEventData == null ||
                pointerEventData.button != PointerEventData.InputButton.Left)
            {
                return;
            }

            Pose pose = pointerEventData.Pointer.EndPointWorldPose;

            // Update the grab object's rotation.
            this.transform.rotation =
                pose.rotation * this._initialGrabRotation;

            // Update the grab object's position.
            this.transform.position =
                pose.position +
                (this.transform.rotation * this._initialGrabOffset);
        }

        public virtual void OnEndDrag(PointerEventData eventData)
        {
            if (!this.Active) return;

            ZPointerEventData pointerEventData = eventData as ZPointerEventData;
            if (pointerEventData == null ||
                pointerEventData.button != PointerEventData.InputButton.Left)
            {
                return;
            }

            // Release the pointer.
            pointerEventData.Pointer.CapturePointer(null);

            // If the grabbable object has a rigidbody component,
            // restore its original isKinematic state.
            var rigidbody = this.GetComponent<Rigidbody>();
            if (rigidbody != null)
            {
                rigidbody.isKinematic = this._isKinematic;
            }

            _initialGrabOffset = Vector3.zero;
        }

        ////////////////////////////////////////////////////////////////////////
        // Private Members
        ////////////////////////////////////////////////////////////////////////

        private Vector3 _initialGrabOffset = Vector3.zero;
        private Quaternion _initialGrabRotation = Quaternion.identity;
        private bool _isKinematic = false;
    }
}