/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * Licensed under the Oculus SDK License Agreement (the "License");
 * you may not use the Oculus SDK except in compliance with the License,
 * which is provided at the time of installation or download, or which
 * otherwise accompanies this software in either electronic or hard copy form.
 *
 * You may obtain a copy of the License at
 *
 * https://developer.oculus.com/licenses/oculussdk/
 *
 * Unless required by applicable law or agreed to in writing, the Oculus 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 System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System;
using UnityEngine;

/// <summary>
/// Helper class that loads KTX2 textures contained within GLTF (GL Transmission Format) models. This requires that the GLTF model supports the KHR_texture_basisu extension.
/// Check the [KHR_texture_basisu](https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_texture_basisu/README.md) extension page for more details.
/// </summary>
[HelpURL("https://developer.oculus.com/documentation/unity/unity-runtime-controller/#use-apis-in-customized-scripts")]
public class OVRKtxTexture
{
    private const uint KTX_TTF_BC7_RGBA = 6;
    private const uint KTX_TTF_ASTC_4x4_RGBA = 10;

    /// <summary>
    /// Loads the given KTX2 texture data, as well as metadata, into a given <see cref="OVRTextureData"/> struct.
    /// </summary>
    /// <param name="data">Binary data that represents the KTX2 texture.</param>
    /// <param name="ktxData">Output data for the KTX2 texture.</param>
    /// <returns>True if the loading of the KTX2 texture was successful, otherwise false.</returns>
    public static bool Load(byte[] data, ref OVRTextureData ktxData)
    {
        int unmanagedSize = Marshal.SizeOf(data[0]) * data.Length;
        IntPtr dataPtr = Marshal.AllocHGlobal(unmanagedSize);

        Marshal.Copy(data, 0, dataPtr, data.Length);
        IntPtr ktxTexturePtr = OVRPlugin.Ktx.LoadKtxFromMemory(dataPtr, (uint)data.Length);
        Marshal.FreeHGlobal(dataPtr);

        ktxData.width = (int)OVRPlugin.Ktx.GetKtxTextureWidth(ktxTexturePtr);
        ktxData.height = (int)OVRPlugin.Ktx.GetKtxTextureHeight(ktxTexturePtr);

        bool transcodeResult = false;
#if UNITY_ANDROID && !UNITY_EDITOR
        transcodeResult = OVRPlugin.Ktx.TranscodeKtxTexture(ktxTexturePtr, KTX_TTF_ASTC_4x4_RGBA);
        ktxData.transcodedFormat = TextureFormat.ASTC_4x4;
#else
        transcodeResult = OVRPlugin.Ktx.TranscodeKtxTexture(ktxTexturePtr, KTX_TTF_BC7_RGBA);
        ktxData.transcodedFormat = TextureFormat.BC7;
#endif
        if (!transcodeResult)
        {
            Debug.LogError("Failed to transcode KTX texture.");
            return false;
        }

        uint textureSize = OVRPlugin.Ktx.GetKtxTextureSize(ktxTexturePtr);
        IntPtr textureDataPtr = Marshal.AllocHGlobal(sizeof(byte) * (int)textureSize);
        if (!OVRPlugin.Ktx.GetKtxTextureData(ktxTexturePtr, textureDataPtr, textureSize))
        {
            Debug.LogError("Failed to get texture data from Ktx texture reference");
            return false;
        }

        byte[] textureData = new byte[textureSize];
        Marshal.Copy(textureDataPtr, textureData, 0, textureData.Length);
        Marshal.FreeHGlobal(textureDataPtr);
        ktxData.data = textureData;

        OVRPlugin.Ktx.DestroyKtxTexture(ktxTexturePtr);

        return true;
    }
}