/************************************************************************************
Copyright : Copyright (c) Facebook Technologies, LLC and its affiliates. All rights reserved.

Your use of this SDK or tool is subject to the Oculus SDK License Agreement, available at
https://developer.oculus.com/licenses/oculussdk/

Unless required by applicable law or agreed to in writing, the Utilities SDK distributed
under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
ANY KIND, either express or implied. See the License for the specific language governing
permissions and limitations under the License.
************************************************************************************/

using UnityEngine;
using UnityEngine.Events;
using UnityEngine.Assertions;

namespace Oculus.Interaction.Samples
{
    /// <summary>
    /// Raises events when an object is scaled up or down. Events are raised in steps,
    /// meaning scale changes are only responded to when the scale magnitude delta since
    /// last step exceeds a provided amount.
    /// </summary>
    public class ScaleAudioEvents : MonoBehaviour
    {
        private enum Direction
        {
            None,
            ScaleUp,
            ScaleDown,
        }

        [SerializeField, Interface(typeof(IInteractableView))]
        private MonoBehaviour _interactableView;

        [Tooltip("Transform to track scale of. If not provided, transform of this component is used.")]
        [SerializeField, Optional]
        private Transform _trackedTransform;

        [Tooltip("The increase in scale magnitude that will fire the step event")]
        [SerializeField]
        private float _stepSize = 0.4f;

        [Tooltip("Events will not be fired more frequently than this many times per second")]
        [SerializeField]
        private int _maxEventFreq = 20;

        [SerializeField]
        private UnityEvent _whenScalingStarted = new UnityEvent();

        [SerializeField]
        private UnityEvent _whenScalingEnded = new UnityEvent();

        [SerializeField]
        private UnityEvent _whenScaledUp = new UnityEvent();

        [SerializeField]
        private UnityEvent _whenScaledDown = new UnityEvent();

        public UnityEvent WhenScalingStarted => _whenScalingStarted;

        public UnityEvent WhenScalingEnded => _whenScalingEnded;

        public UnityEvent WhenScaledUp => _whenScaledUp;

        public UnityEvent WhenScaledDown => _whenScaledDown;

        private IInteractableView InteractableView;

        private Transform TrackedTransform
        {
            get => _trackedTransform == null ? transform : _trackedTransform;
        }

        private bool _isScaling;
        private Vector3 _lastStep;
        private float _lastEventTime;
        private Direction _direction = Direction.None;

        protected bool _started;

        private void ScalingStarted()
        {
            _lastStep = TrackedTransform.localScale;
            _whenScalingStarted.Invoke();
        }

        private void ScalingEnded()
        {
            _whenScalingEnded.Invoke();
        }

        private float GetTotalDelta(out Direction direction)
        {
            float prevMagnitude = _lastStep.magnitude;
            float newMagnitude = TrackedTransform.localScale.magnitude;
            if (newMagnitude == prevMagnitude)
            {
                direction = Direction.None;
            }
            else
            {
                direction = newMagnitude > prevMagnitude ? Direction.ScaleUp : Direction.ScaleDown;
            }

            return direction == Direction.ScaleUp ?
                   newMagnitude - prevMagnitude :
                   prevMagnitude - newMagnitude;
        }

        private void UpdateScaling()
        {
            if (_stepSize <= 0 || _maxEventFreq <= 0)
            {
                return;
            }

            float effectiveStepSize = _stepSize;
            float totalDelta = GetTotalDelta(out _direction);
            if (totalDelta > effectiveStepSize)
            {
                _lastStep = TrackedTransform.localScale;
                float timeSince = Time.time - _lastEventTime;
                if (timeSince >= 1f / _maxEventFreq)
                {
                    _lastEventTime = Time.time;
                    if (_direction == Direction.ScaleUp)
                    {
                        _whenScaledUp.Invoke();
                    }
                    else
                    {
                        _whenScaledDown.Invoke();
                    }
                }
            }
        }

        protected virtual void Awake()
        {
            InteractableView = _interactableView as IInteractableView;
        }

        protected virtual void Start()
        {
            this.BeginStart(ref _started);
            Assert.IsNotNull(InteractableView);
            Assert.IsNotNull(TrackedTransform);
            this.EndStart(ref _started);
        }

        protected virtual void Update()
        {
            bool wasScaling = _isScaling;
            _isScaling = InteractableView.State == InteractableState.Select;

            if (!_isScaling)
            {
                if (wasScaling)
                {
                    ScalingEnded();
                }
            }
            else
            {
                if (!wasScaling)
                {
                    ScalingStarted();
                }
                UpdateScaling();
            }
        }
    }
}