/************************************************************************************
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 Oculus.Interaction.Input;
using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Assertions;
using UnityEngine.Serialization;

namespace Oculus.Interaction.PoseDetection
{
    internal class FingerFeatureStateDictionary
    {
        struct HandFingerState
        {
            public FeatureStateProvider<FingerFeature, string> StateProvider;
        }

        private readonly HandFingerState[] _fingerState = new HandFingerState[Constants.NUM_FINGERS];

        public void InitializeFinger(HandFinger finger,
            FeatureStateProvider<FingerFeature, string> stateProvider)
        {
            _fingerState[(int)finger] = new HandFingerState
            {
                StateProvider = stateProvider
            };
        }

        public FeatureStateProvider<FingerFeature, string> GetStateProvider(HandFinger finger)
        {
            return _fingerState[(int)finger].StateProvider;
        }
    }

    public interface IFingerFeatureStateProvider
    {
        bool GetCurrentState(HandFinger finger, FingerFeature fingerFeature, out string currentState);
        bool IsStateActive(HandFinger finger, FingerFeature feature, FeatureStateActiveMode mode, string stateId);
    }

    /// <summary>
    /// Interprets finger feature values using <see cref="FingerShapes"/> and uses
    /// the given <see cref="FingerFeatureStateThresholds"/> to quantize these values into states.
    /// To avoid rapid fluctuations at the edges of two states, this class uses the calculated
    /// feature state from the previous frame and the given state thresholds to apply a buffer
    /// between state transition edges.
    /// </summary>
    public class FingerFeatureStateProvider : MonoBehaviour, IFingerFeatureStateProvider
    {
        [SerializeField, Interface(typeof(IHand))]
        private MonoBehaviour _hand;
        public IHand Hand { get; private set; }

        [Serializable]
        public struct FingerStateThresholds
        {
            public HandFinger Finger;
            public FingerFeatureStateThresholds StateThresholds;
        }

        [SerializeField]
        private List<FingerStateThresholds> _fingerStateThresholds;

        [Header("Advanced Settings")]
        [SerializeField]
        [Tooltip("If true, disables proactive evaluation of any FingerFeature that has been " +
                 "queried at least once. This will force lazy-evaluation of state within calls " +
                 "to IsStateActive, which means you must do so each frame to avoid missing " +
                 "transitions between states.")]
        private bool _disableProactiveEvaluation;

        protected bool _started = false;

        private FingerFeatureStateDictionary _state;
        Func<float> _timeProvider;

        public static FingerShapes DefaultFingerShapes { get; } = new FingerShapes();
        private FingerShapes _fingerShapes = DefaultFingerShapes;
        private ReadOnlyHandJointPoses _handJointPoses;

        #region Unity Lifecycle Methods

        protected virtual void Awake()
        {
            Hand = _hand as IHand;

            _state = new FingerFeatureStateDictionary();
            _handJointPoses = ReadOnlyHandJointPoses.Empty;
        }

        protected virtual void Start()
        {
            this.BeginStart(ref _started);
            Assert.IsNotNull(Hand);
            if (_timeProvider == null)
            {
                _timeProvider = () => Time.time;
            }
            this.EndStart(ref _started);
        }

        protected virtual void OnEnable()
        {
            if (_started)
            {
                Hand.HandUpdated += HandDataAvailable;
                ReadStateThresholds();
            }
        }

        protected virtual void OnDisable()
        {
            if (_started)
            {
                Hand.HandUpdated -= HandDataAvailable;
                _handJointPoses = ReadOnlyHandJointPoses.Empty;
            }
        }

        #endregion

        private void ReadStateThresholds()
        {
            Assert.IsNotNull(_fingerStateThresholds);
            Assert.IsNotNull(_timeProvider);
            Assert.AreEqual(Constants.NUM_FINGERS, _fingerStateThresholds.Count);

            HandFingerFlags seenFingers = HandFingerFlags.None;
            foreach (FingerStateThresholds fingerStateThresholds in _fingerStateThresholds)
            {
                seenFingers |= HandFingerUtils.ToFlags(fingerStateThresholds.Finger);
                HandFinger finger = fingerStateThresholds.Finger;

                var featureStateProvider = _state.GetStateProvider(finger);
                if (featureStateProvider == null)
                {
                    featureStateProvider =
                        new FeatureStateProvider<FingerFeature, string>(
                            feature => GetFeatureValue(finger, feature),
                            feature => (int)feature,
                            _timeProvider);

                    _state.InitializeFinger(fingerStateThresholds.Finger,
                        featureStateProvider);
                }

                featureStateProvider.InitializeThresholds(fingerStateThresholds.StateThresholds);
            }
            Assert.AreEqual(seenFingers, HandFingerFlags.All);
        }

        private void HandDataAvailable()
        {
            int frameId = Hand.CurrentDataVersion;

            if (!Hand.GetJointPosesFromWrist(out _handJointPoses))
            {
                return;
            }

            // Update the frameId of all state providers to mark data as dirty. If
            // proactiveEvaluation is enabled, also read the state of any feature that has been
            // touched, which will force it to evaluate.
            if (!_disableProactiveEvaluation)
            {
                for (var fingerIdx = 0; fingerIdx < Constants.NUM_FINGERS; ++fingerIdx)
                {
                    var featureStateProvider = _state.GetStateProvider((HandFinger)fingerIdx);
                    featureStateProvider.LastUpdatedFrameId = frameId;
                    featureStateProvider.ReadTouchedFeatureStates();
                }
            }
            else
            {
                for (var fingerIdx = 0; fingerIdx < Constants.NUM_FINGERS; ++fingerIdx)
                {
                    _state.GetStateProvider((HandFinger)fingerIdx).LastUpdatedFrameId =
                        frameId;
                }
            }
        }

        public bool GetCurrentState(HandFinger finger, FingerFeature fingerFeature, out string currentState)
        {
            if (!IsDataValid())
            {
                currentState = default;
                return false;
            }
            else
            {
                currentState = GetCurrentFingerFeatureState(finger, fingerFeature);
                return currentState != default;
            }
        }

        private string GetCurrentFingerFeatureState(HandFinger finger, FingerFeature fingerFeature)
        {
            return _state.GetStateProvider(finger).GetCurrentFeatureState(fingerFeature);
        }

        /// <summary>
        /// Returns the current value of the feature. If the finger joints are not populated with
        /// valid data (for instance, due to a disconnected hand), the method will return NaN.
        /// </summary>
        public float? GetFeatureValue(HandFinger finger, FingerFeature fingerFeature)
        {
            if (!IsDataValid())
            {
                return null;
            }

            return _fingerShapes.GetValue(finger, fingerFeature, Hand);
        }

        private bool IsDataValid()
        {
            return _handJointPoses.Count > 0;
        }

        public FingerShapes GetValueProvider(HandFinger finger)
        {
            return _fingerShapes;
        }

        public bool IsStateActive(HandFinger finger, FingerFeature feature, FeatureStateActiveMode mode, string stateId)
        {
            var currentState = GetCurrentFingerFeatureState(finger, feature);
            switch (mode)
            {
                case FeatureStateActiveMode.Is:
                    return currentState == stateId;
                case FeatureStateActiveMode.IsNot:
                    return currentState != stateId;
                default:
                    return false;
            }
        }

        #region Inject
        public void InjectAllFingerFeatureStateProvider(IHand hand, List<FingerStateThresholds> fingerStateThresholds, FingerShapes fingerShapes,
            bool disableProactiveEvaluation)
        {
            InjectHand(hand);
            InjectFingerStateThresholds(fingerStateThresholds);
            InjectFingerShapes(fingerShapes);
            InjectDisableProactiveEvaluation(disableProactiveEvaluation);
        }

        public void InjectHand(IHand hand)
        {
            _hand = hand as MonoBehaviour;
            Hand = hand;
        }

        public void InjectFingerStateThresholds(List<FingerStateThresholds> fingerStateThresholds)
        {
            _fingerStateThresholds = fingerStateThresholds;
        }

        public void InjectFingerShapes(FingerShapes fingerShapes)
        {
            _fingerShapes = fingerShapes;
        }

        public void InjectDisableProactiveEvaluation(bool disableProactiveEvaluation)
        {
            _disableProactiveEvaluation = disableProactiveEvaluation;
        }

        public void InjectOptionalTimeProvider(Func<float> timeProvider)
        {
            _timeProvider = timeProvider;
        }
        #endregion
    }
}