// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using Microsoft.MixedReality.Toolkit.Utilities;
using System;
using System.Collections.Generic;
using UnityEngine;

namespace Microsoft.MixedReality.Toolkit.Input
{
    /// <summary>
    /// Snapshot of simulated hand data.
    /// </summary>
    [Serializable]
    public class SimulatedHandData
    {
        [SerializeField]
        private bool isTracked = false;

        /// <summary>
        /// Whether the hand is currently being tracked
        /// </summary>
        public bool IsTracked => isTracked;

        [SerializeField]
        private MixedRealityPose[] joints = new MixedRealityPose[ArticulatedHandPose.JointCount];

        /// <summary>
        /// Array storing the joints of the hand
        /// </summary>
        public MixedRealityPose[] Joints => joints;

        [SerializeField]
        private bool isPinching = false;

        /// <summary>
        /// Whether the hand is pinching
        /// </summary>
        public bool IsPinching => isPinching;

        /// <summary>
        /// Generator function producing joint positions and rotations
        /// </summary>
        public delegate void HandJointDataGenerator(MixedRealityPose[] jointPoses);

        public void Copy(SimulatedHandData other)
        {
            isTracked = other.isTracked;
            isPinching = other.isPinching;
            for (int i = 0; i < ArticulatedHandPose.JointCount; ++i)
            {
                joints[i] = other.joints[i];
            }
        }

        /// <summary>
        /// Replace the hand data with the given values.
        /// </summary>
        /// <returns>True if the hand data has been changed.</returns>
        /// <param name="isTrackedNew">True if the hand is currently tracked.</param>
        /// <param name="isPinchingNew">True if the hand is in a pinching pose that causes a "Select" action.</param>
        /// <param name="generator">Generator function that produces joint positions and rotations. The joint data generator is only used when the hand is tracked.</param>
        /// <remarks>The timestamp of the hand data will be the current time, see [DateTime.UtcNow](https://docs.microsoft.com/dotnet/api/system.datetime.utcnow?view=netframework-4.8).</remarks>
        public bool Update(bool isTrackedNew, bool isPinchingNew, HandJointDataGenerator generator)
        {
            bool handDataChanged = false;

            if (isTracked != isTrackedNew || isPinching != isPinchingNew)
            {
                isTracked = isTrackedNew;
                isPinching = isPinchingNew;
                handDataChanged = true;
            }

            if (isTracked)
            {
                generator?.Invoke(Joints);
                handDataChanged = true;
            }

            return handDataChanged;
        }
    }

    public abstract class SimulatedHand : BaseHand
    {
        public abstract ControllerSimulationMode SimulationMode { get; }

        protected readonly Dictionary<TrackedHandJoint, MixedRealityPose> jointPoses = new Dictionary<TrackedHandJoint, MixedRealityPose>();

        /// <summary>
        /// Constructor.
        /// </summary>
        protected SimulatedHand(
            TrackingState trackingState,
            Handedness controllerHandedness,
            IMixedRealityInputSource inputSource = null,
            MixedRealityInteractionMapping[] interactions = null,
            IMixedRealityInputSourceDefinition definition = null)
            : base(trackingState, controllerHandedness, inputSource, interactions, definition)
        { }

        /// <inheritdoc />
        public override bool TryGetJoint(TrackedHandJoint joint, out MixedRealityPose pose) => jointPoses.TryGetValue(joint, out pose);

        public void UpdateState(SimulatedHandData handData)
        {
            UpdateHandJoints(handData);
            UpdateVelocity();

            UpdateInteractions(handData);
        }

        /// <summary>
        /// Updates the positions and orientations of the hand joints of the simulated hand
        /// </summary>
        /// <param name="handData">hand data provided by the simulation</param>
        protected abstract void UpdateHandJoints(SimulatedHandData handData);

        /// <summary>
        /// Updates the interactions raised by the simulated hand
        /// </summary>
        /// <param name="handData">hand data provided by the simulation</param>
        protected abstract void UpdateInteractions(SimulatedHandData handData);
    }
}