using System.Runtime.InteropServices;
using Unity.Collections;
using Unity.Collections.LowLevel.Unsafe;
using UnityEngine.Scripting;
using UnityEngine.XR.ARSubsystems;

namespace UnityEngine.XR.ARKit
{
    /// <summary>
    /// This subsystem provides implementing functionality for the <c>XRHumanBodySubsystem</c> class.
    /// </summary>
    [Preserve]
    public sealed class ARKitHumanBodySubsystem : XRHumanBodySubsystem
    {
        /// <summary>
        /// Register the ARKit human body subsystem if iOS and not the editor.
        /// </summary>
        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
        static void Register()
        {
            if (!Api.AtLeast13_0())
                return;

            const string k_SubsystemId = "ARKit-HumanBody";

            var humanBodySubsystemCinfo = new XRHumanBodySubsystemDescriptor.Cinfo()
            {
                id = k_SubsystemId,
                providerType = typeof(ARKitHumanBodySubsystem.ARKitProvider),
                subsystemTypeOverride = typeof(ARKitHumanBodySubsystem),
                supportsHumanBody2D = NativeApi.UnityARKit_HumanBodyProvider_DoesSupportBodyPose2DEstimation(),
                supportsHumanBody3D = NativeApi.UnityARKit_HumanBodyProvider_DoesSupportBodyPose3DEstimation(),
                supportsHumanBody3DScaleEstimation = NativeApi.UnityARKit_HumanBodyProvider_DoesSupportBodyPose3DScaleEstimation(),
            };

            XRHumanBodySubsystemDescriptor.Register(humanBodySubsystemCinfo);
        }

        /// <summary>
        /// The implementation provider class.
        /// </summary>
        class ARKitProvider : Provider
        {
            /// <summary>
            /// Construct the implementation provider.
            /// </summary>
            public ARKitProvider() => NativeApi.UnityARKit_HumanBodyProvider_Construct();

            /// <summary>
            /// Start the provider.
            /// </summary>
            public override void Start() => NativeApi.UnityARKit_HumanBodyProvider_Start();

            /// <summary>
            /// Stop the provider.
            /// </summary>
            public override void Stop() => NativeApi.UnityARKit_HumanBodyProvider_Stop();

            /// <summary>
            /// Destroy the human body subsystem by first ensuring that the subsystem has been stopped and then
            /// destroying the provider.
            /// </summary>
            public override void Destroy() => NativeApi.UnityARKit_HumanBodyProvider_Destruct();

            /// <summary>
            /// Sets whether human body pose 2D estimation is enabled.
            /// </summary>
            /// <param name="enabled">Whether the human body pose 2D estimation should be enabled.
            /// </param>
            /// <returns>
            /// <c>true</c> if the human body pose 2D estimation is set to the given value. Otherwise, <c>false</c>.
            /// </returns>
            /// <remarks>
            /// Current restrictions limit either human body pose estimation to be enabled or human segmentation images
            /// to be enabled. At this time, these features are mutually exclusive.
            /// </remarks>
            public override bool pose2DRequested
            {
                get => Api.GetRequestedFeatures().All(Feature.Body2D);
                set => Api.SetFeatureRequested(Feature.Body2D, value);
            }

            /// <summary>
            /// Tests whether 2D body tracking is enabled.
            /// </summary>
            public override bool pose2DEnabled => NativeApi.UnityARKit_HumanBodyProvider_GetHumanBodyPose2DEstimationEnabled();

            /// <summary>
            /// Sets whether human body pose 3D estimation is enabled.
            /// </summary>
            /// <param name="enabled">Whether the human body pose 3D estimation should be enabled.
            /// </param>
            /// <returns>
            /// <c>true</c> if the human body pose 3D estimation is set to the given value. Otherwise, <c>false</c>.
            /// </returns>
            /// <remarks>
            /// Current restrictions limit either human body pose estimation to be enabled or human segmentation images
            /// to be enabled. At this time, these features are mutually exclusive.
            /// </remarks>
            public override bool pose3DRequested
            {
                get => Api.GetRequestedFeatures().All(Feature.Body3D);
                set => Api.SetFeatureRequested(Feature.Body3D, value);
            }

            /// <summary>
            /// Tests whether 3D body tracking is enabled.
            /// </summary>
            public override bool pose3DEnabled => NativeApi.UnityARKit_HumanBodyProvider_GetHumanBodyPose3DEstimationEnabled();

            public override bool pose3DScaleEstimationRequested
            {
                get => Api.GetRequestedFeatures().All(Feature.Body3DScaleEstimation);
                set => Api.SetFeatureRequested(Feature.Body3DScaleEstimation, value);
            }

            public override bool pose3DScaleEstimationEnabled => NativeApi.UnityARKit_HumanBodyProvider_GetHumanBodyPose3DScaleEstimationEnabled();

            /// <summary>
            /// Queries for the set of human body changes.
            /// </summary>
            /// <param name="defaultHumanBody">The default human body.</param>
            /// <param name="allocator">The memory allocator to use for the returns trackable changes.</param>
            /// <returns>
            /// The set of human body changes.
            /// </returns>
            public override unsafe TrackableChanges<XRHumanBody> GetChanges(XRHumanBody defaultHumanBody, Allocator allocator)
            {
                var context = NativeApi.UnityARKit_HumanBodyProvider_AcquireChanges(
                    out var numAddedHumanBodies, out var addedHumanBodiesPointer,
                    out var numUpdatedHumanBodies, out var updatedHumanBodiesPointer,
                    out var numRemovedHumanBodyIds, out var removedHumanBodyIdsPointer,
                    out var stride);

                try
                {
                    // Wrap the navite pointers into a native array and then copy them into a separate native array enabled
                    // with temporary allocations.
                    return new TrackableChanges<XRHumanBody>(
                        addedHumanBodiesPointer, numAddedHumanBodies,
                        updatedHumanBodiesPointer, numUpdatedHumanBodies,
                        removedHumanBodyIdsPointer, numRemovedHumanBodyIds,
                        defaultHumanBody, stride,
                        allocator);
                }
                finally
                {
                    NativeApi.UnityARKit_HumanBodyProvider_ReleaseChanges(context);
                }
            }

            /// <summary>
            /// Get the skeleton joints for the requested trackable identifier.
            /// </summary>
            /// <param name="trackableId">The human body trackable identifier for which to query.</param>
            /// <param name="allocator">The memory allocator to use for the returned arrays.</param>
            /// <param name="skeleton">The array of skeleton joints to update and return.</param>
            public override unsafe void GetSkeleton(TrackableId trackableId, Allocator allocator, ref NativeArray<XRHumanBodyJoint> skeleton)
            {
                int numJoints;
                void* joints = NativeApi.UnityARKit_HumanBodyProvider_AcquireJoints(trackableId, out numJoints);

                try
                {
                    if (joints == null)
                    {
                        numJoints = 0;
                    }

                    if (!skeleton.IsCreated || (skeleton.Length != numJoints))
                    {
                        if (skeleton.IsCreated)
                        {
                            skeleton.Dispose();
                        }
                        skeleton = new NativeArray<XRHumanBodyJoint>(numJoints, allocator);
                    }

                    if (joints != null)
                    {
                        var tmp = NativeArrayUnsafeUtility.ConvertExistingDataToNativeArray<XRHumanBodyJoint>(
                            joints,
                            numJoints,
                            Allocator.None);

                        skeleton.CopyFrom(tmp);
                    }
                }
                finally
                {
                    NativeApi.UnityARKit_HumanBodyProvider_ReleaseJoints(joints);
                }
            }

            /// <summary>
            /// Gets the human body pose 2D joints for the current frame.
            /// </summary>
            /// <param name="defaultHumanBodyPose2DJoint">The default value for the body pose 2D joint.</param>
            /// <param name="screenWidth">The width of the screen, in pixels.</param>
            /// <param name="screenHeight">The height of the screen, in pixels.</param>
            /// <param name="screenOrientation">The orientation of the device so that the joint positions can be
            /// adjusted as required.</param>
            /// <param name="allocator">The allocator to use for the returned array memory.</param>
            /// <returns>
            /// The array of body pose 2D joints.
            /// </returns>
            /// <remarks>
            /// The returned array can be empty if the system does not detect a human in the camera image.
            /// </remarks>
            public override unsafe NativeArray<XRHumanBodyPose2DJoint> GetHumanBodyPose2DJoints(
                XRHumanBodyPose2DJoint defaultHumanBodyPose2DJoint,
                int screenWidth,
                int screenHeight,
                ScreenOrientation screenOrientation,
                Allocator allocator)
            {
                var joints = NativeApi.UnityARKit_HumanBodyProvider_AcquireHumanBodyPose2DJoints(
                    screenWidth,
                    screenHeight,
                    screenOrientation,
                    out var length,
                    out var elementSize);

                try
                {
                    var returnJoints = NativeCopyUtility.PtrToNativeArrayWithDefault(
                        defaultHumanBodyPose2DJoint,
                        joints,
                        elementSize,
                        length,
                        allocator);

                    return returnJoints;
                }
                finally
                {
                    NativeApi.UnityARKit_HumanBodyProvider_ReleaseHumanBodyPose2DJoints(joints);
                }
            }
        }

        /// <summary>
        /// Container to wrap the native ARKit human body APIs.
        /// </summary>
        static class NativeApi
        {
#if UNITY_XR_ARKIT_LOADER_ENABLED
            [DllImport("__Internal")]
            public static extern void UnityARKit_HumanBodyProvider_Construct();

            [DllImport("__Internal")]
            public static extern void UnityARKit_HumanBodyProvider_Start();

            [DllImport("__Internal")]
            public static extern void UnityARKit_HumanBodyProvider_Stop();

            [DllImport("__Internal")]
            public static extern void UnityARKit_HumanBodyProvider_Destruct();

            [DllImport("__Internal")]
            public static extern unsafe void* UnityARKit_HumanBodyProvider_AcquireChanges(
                out int numAddedHumanBodies, out void* addedBodys,
                out int numUpdatedHumanBodies, out void* updatedBodys,
                out int numRemovedHumanBodyIds, out void* removedBodyIds,
                out int stride);

            [DllImport("__Internal")]
            public static extern unsafe void UnityARKit_HumanBodyProvider_ReleaseChanges(void* context);

            [DllImport("__Internal")]
            public static extern unsafe void* UnityARKit_HumanBodyProvider_AcquireJoints(TrackableId trackableId, out int numJoints);

            [DllImport("__Internal")]
            public static extern unsafe void UnityARKit_HumanBodyProvider_ReleaseJoints(void* joints);

            [DllImport("__Internal")]
            public static unsafe extern void* UnityARKit_HumanBodyProvider_AcquireHumanBodyPose2DJoints(
                int screenWidth,
                int screenHeight,
                ScreenOrientation screenOrientation,
                out int length,
                out int elementSize);

            [DllImport("__Internal")]
            public static unsafe extern void UnityARKit_HumanBodyProvider_ReleaseHumanBodyPose2DJoints(void* joints);

            [DllImport("__Internal")]
            public static extern bool UnityARKit_HumanBodyProvider_GetHumanBodyPose2DEstimationEnabled();

            [DllImport("__Internal")]
            public static extern bool UnityARKit_HumanBodyProvider_GetHumanBodyPose3DEstimationEnabled();

            [DllImport("__Internal")]
            public static extern bool UnityARKit_HumanBodyProvider_GetHumanBodyPose3DScaleEstimationEnabled();

            [DllImport("__Internal")]
            public static extern bool UnityARKit_HumanBodyProvider_DoesSupportBodyPose2DEstimation();

            [DllImport("__Internal")]
            public static extern bool UnityARKit_HumanBodyProvider_DoesSupportBodyPose3DEstimation();

            [DllImport("__Internal")]
            public static extern bool UnityARKit_HumanBodyProvider_DoesSupportBodyPose3DScaleEstimation();
#else
            static readonly string k_ExceptionMsg = "Apple ARKit XR Plug-in Provider not enabled in project settings.";

            public static void UnityARKit_HumanBodyProvider_Construct()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static void UnityARKit_HumanBodyProvider_Start()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static void UnityARKit_HumanBodyProvider_Stop()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static void UnityARKit_HumanBodyProvider_Destruct()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static unsafe void* UnityARKit_HumanBodyProvider_AcquireChanges(
                out int numAddedHumanBodies, out void* addedBodys,
                out int numUpdatedHumanBodies, out void* updatedBodys,
                out int numRemovedHumanBodyIds, out void* removedBodyIds,
                out int stride)
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static unsafe void UnityARKit_HumanBodyProvider_ReleaseChanges(void* context)
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static unsafe void* UnityARKit_HumanBodyProvider_AcquireJoints(TrackableId trackableId, out int numJoints)
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static unsafe void UnityARKit_HumanBodyProvider_ReleaseJoints(void* joints)
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static unsafe void* UnityARKit_HumanBodyProvider_AcquireHumanBodyPose2DJoints(
                int screenWidth,
                int screenHeight,
                ScreenOrientation screenOrientation,
                out int length,
                out int elementSize)
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static unsafe void UnityARKit_HumanBodyProvider_ReleaseHumanBodyPose2DJoints(void* joints)
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static bool UnityARKit_HumanBodyProvider_GetHumanBodyPose2DEstimationEnabled()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static bool UnityARKit_HumanBodyProvider_GetHumanBodyPose3DEstimationEnabled()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static bool UnityARKit_HumanBodyProvider_GetHumanBodyPose3DScaleEstimationEnabled()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static bool UnityARKit_HumanBodyProvider_DoesSupportBodyPose2DEstimation()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static bool UnityARKit_HumanBodyProvider_DoesSupportBodyPose3DEstimation()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }

            public static bool UnityARKit_HumanBodyProvider_DoesSupportBodyPose3DScaleEstimation()
            {
                throw new System.NotImplementedException(k_ExceptionMsg);
            }
#endif
        }
    }
}