using System;
using UnityEngine.Rendering;
using UnityEngine.XR.ARSubsystems;

using Object = UnityEngine.Object;

namespace UnityEngine.XR.ARFoundation
{
    /// <summary>
    /// A game object component to manage the reflection probe settings as the environment probe changes are applied.
    /// </summary>
    [RequireComponent(typeof(ReflectionProbe))]
    [DisallowMultipleComponent]
    [DefaultExecutionOrder(ARUpdateOrder.k_EnvironmentProbe)]
    [HelpURL("https://docs.unity3d.com/Packages/com.unity.xr.arfoundation@3.0/api/UnityEngine.XR.ARFoundation.AREnvironmentProbe.html")]
    public class AREnvironmentProbe : ARTrackable<XREnvironmentProbe, AREnvironmentProbe>
    {
        /// <summary>
        /// The reflection probe component attached to the game object.
        /// </summary>
        /// <value>
        /// The reflection probe component attached to the game object.
        /// </value>
        ReflectionProbe m_ReflectionProbe;

        /// <summary>
        /// The current environment texture data wrapping the reflection probe environment texture.
        /// </summary>
        /// <value>
        /// The current environment texture data wrapping the reflection probe environment texture.
        /// </value>
        XRTextureDescriptor m_CurrentTextureDescriptor;

        /// <summary>
        /// Specifies the texture filter mode to be used with the environment texture.
        /// </summary>
        /// <value>
        /// The texture filter mode to be used with the environment texture.
        /// </value>
        public FilterMode environmentTextureFilterMode
        {
            get { return m_EnvironmentTextureFilterMode; }
            set
            {
                m_EnvironmentTextureFilterMode = value;
                if ((m_ReflectionProbe != null) && (m_ReflectionProbe.customBakedTexture != null))
                {
                    m_ReflectionProbe.customBakedTexture.filterMode = m_EnvironmentTextureFilterMode;
                }
            }
        }

        FilterMode m_EnvironmentTextureFilterMode = FilterMode.Trilinear;

        /// <summary>
        /// The placement type (for example, manual or automatic). If manual, this probe was created by <see cref="AREnvironmentProbeManager.AddEnvironmentProbe(Pose, Vector3, Vector3)"/>.
        /// </summary>
        public AREnvironmentProbePlacementType placementType { get; internal set; }

        /// <summary>
        /// The size (dimensions) of the environment probe.
        /// </summary>
        public Vector3 size
        {
            get { return sessionRelativeData.size; }
        }

        /// <summary>
        /// The extents of the environment probe. This is always half the <see cref="size"/>.
        /// </summary>
        public Vector3 extents
        {
            get { return size * .5f; }
        }

        /// <summary>
        /// A native pointer associated with this environment probe.
        /// The data pointed to by this pointer is implementation defined.
        /// While the lifetime is also implementation defined, it should be valid at
        /// least until the next frame.
        /// </summary>
        public IntPtr nativePtr
        {
            get { return sessionRelativeData.nativePtr; }
        }

        /// <summary>
        /// The <c>XRTextureDescriptor</c> associated with this environment probe. This is used to generate the cubemap texture on the reflection probe component.
        /// </summary>
        public XRTextureDescriptor textureDescriptor
        {
            get { return m_CurrentTextureDescriptor; }
        }

        /// <summary>
        /// Initializes the game object transform and reflection probe component from the scene.
        /// </summary>
        void Awake()
        {
            m_ReflectionProbe = GetComponent<ReflectionProbe>();

            // Set the reflection probe mode to use a custom baked texture.
            m_ReflectionProbe.mode = ReflectionProbeMode.Custom;
        }

        internal protected override void OnAfterSetSessionRelativeData()
        {
            transform.localScale = sessionRelativeData.scale;

            // Update the environment texture if the environment texture is valid.
            if (sessionRelativeData.textureDescriptor.valid)
            {
                UpdateEnvironmentTexture(sessionRelativeData.textureDescriptor);
            }

            // Update the reflection probe box.
            m_ReflectionProbe.center = Vector3.zero;
            m_ReflectionProbe.size = sessionRelativeData.size;
            m_ReflectionProbe.boxProjection = !Single.IsInfinity(m_ReflectionProbe.size.x);

            // Manual placement is set by the manager. Unknown means it must have been added automatically.
            if (placementType == AREnvironmentProbePlacementType.Unknown)
            {
                placementType = AREnvironmentProbePlacementType.Automatic;
            }
        }

        /// <summary>
        /// Applies the texture data in the <c>XRTextureDescriptor</c> to the reflection probe settings.
        /// </summary>
        /// <param name="textureDescriptor">The environment texture data to apply to the reflection probe baked
        /// texture.</param>
        void UpdateEnvironmentTexture(XRTextureDescriptor textureDescriptor)
        {
            // If the current environment texture equals the given environment texture, the texture does not need to be
            // updated.
            if (m_CurrentTextureDescriptor.Equals(textureDescriptor))
            {
                return;
            }

            // Get the current baked texture as a cubemap, if any.
            Cubemap cubemapTexture = m_ReflectionProbe.customBakedTexture as Cubemap;

#if UNITY_2019_1_OR_NEWER
            const bool k_NoCubemapUpdate = false;
#else
            const bool k_NoCubemapUpdate = true;
#endif

            // If there is no current reflection probe texture or if the current environment texture data is not
            // identical to the given environment texture metadata, then we need to create a new environment texture
            // object.
            if (k_NoCubemapUpdate || (cubemapTexture == null) ||
                !m_CurrentTextureDescriptor.hasIdenticalTextureMetadata(textureDescriptor))
            {
                // Destroy any previous texture object.
                if (m_ReflectionProbe.customBakedTexture != null)
                {
                    Object.Destroy(m_ReflectionProbe.customBakedTexture);
                }

                // Create a new environment texture object.
                m_ReflectionProbe.customBakedTexture = CreateEnvironmentTexture(textureDescriptor);
            }
#if UNITY_2019_1_OR_NEWER
            else
            {
                // Else, we have a current texture object with identical metadata, we simply update the external
                // texture with the native texture.
                cubemapTexture.UpdateExternalTexture(textureDescriptor.nativeTexture);
            }
#endif

            // Update the current environment texture metadata.
            m_CurrentTextureDescriptor = textureDescriptor;
        }

        /// <summary>
        /// Create a new <c>Cubemap</c> texture object with the given native texture object.
        /// </summary>
        /// <param name="textureDescriptor">The <c>XRTextureDescriptor</c> wrapping a native texture object.
        /// </param>
        /// <returns>
        /// The <c>Cubemap</c> object created from the given native texture object.
        /// </returns>
        Cubemap CreateEnvironmentTexture(XRTextureDescriptor textureDescriptor)
        {
            Debug.Assert(textureDescriptor.valid,
                         "cannot create a cubemap with an invalid native texture object");

            Cubemap cubemap = Cubemap.CreateExternalTexture(textureDescriptor.width,
                                                            textureDescriptor.format,
                                                            (textureDescriptor.mipmapCount != 0),
                                                            textureDescriptor.nativeTexture);
            cubemap.filterMode = m_EnvironmentTextureFilterMode;

            return cubemap;
        }

        public override string ToString()
        {
            return string.Format("{0} [trackableId:{1}]", name, trackableId.ToString());
        }
    }
}