/*
 * Copyright (C) 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * 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.
 */

#ifndef GLTFIO_MORPHHELPER_H
#define GLTFIO_MORPHHELPER_H

#include "FFilamentAsset.h"
#include "FFilamentInstance.h"

#include <filament/MorphTargetBuffer.h>

#include <math/vec4.h>

#include <tsl/robin_map.h>

#include <vector>

struct cgltf_node;
struct cgltf_mesh;
struct cgltf_primitive;

namespace gltfio {

/**
 * Internal class that partitions lists of morph weights and maintains a cache of BufferObject
 * instances. This allows gltfio to support up to 255 morph targets.
 *
 * Each partition is associated with an unordered set of 4 (or fewer) morph target indices, which
 * we call the "primary indices" for that time slice.
 *
 * Animator has ownership over a single instance of MorphHelper, thus it is 1:1 with FilamentAsset.
 */
class MorphHelper {
public:
    using Entity = utils::Entity;
    MorphHelper(FFilamentAsset* asset, FFilamentInstance* inst);
    ~MorphHelper();

    void setWeights(Entity entity, float const* weights, int count) noexcept;
    int getTargetCount(Entity entity) const noexcept;

private:
    struct GltfPrimitive {
        filament::MorphTargetBuffer* targets;
    };

    struct TableEntry {
        std::vector<GltfPrimitive> primitives; // TODO: flatten this?
    };

    void addPrimitive(cgltf_mesh const* mesh, int primitiveIndex, Entity entity);

    tsl::robin_map<Entity, TableEntry> mMorphTable;
    const FFilamentAsset* mAsset;
    const FFilamentInstance* mInstance;
};

} // namespace gltfio

#endif // GLTFIO_MORPHHELPER_H