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 Copyright (c) 2021-2023 Xiamen Yaji Software Co., Ltd.

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#include "scene/LODGroup.h"
#include <cmath>
#include "core/scene-graph/Node.h"
#include "scene/Camera.h"

namespace cc {
namespace scene {

void LODData::eraseModel(Model *model) {
    auto iter = std::find(_vecModels.begin(), _vecModels.end(), model);
    if (iter != _vecModels.end()) {
        _vecModels.erase(iter);
    }
}

LODGroup::LODGroup() = default;

LODGroup::~LODGroup() = default;

int8_t LODGroup::getVisibleLODLevel(const Camera *camera) const {
    float screenUsagePercentage = getScreenUsagePercentage(camera);

    int8_t lodIndex = -1;
    for (auto i = 0; i < _vecLODData.size(); ++i) {
        const auto &lod = _vecLODData[i];
        if (screenUsagePercentage >= lod->getScreenUsagePercentage()) {
            lodIndex = i;
            break;
        }
    }
    return lodIndex;
}

float LODGroup::getScreenUsagePercentage(const Camera *camera) const {
    if (!_node.get()) {
        return 0;
    }

    auto distance = 0;
    if (camera->getProjectionType() == CameraProjection::PERSPECTIVE) {
        Vec3 tmp{_localBoundaryCenter};
        tmp.transformMat4(_node->getWorldMatrix());
        tmp.subtract(camera->getNode()->getWorldPosition());
        distance = tmp.length();
    }

    return distanceToScreenUsagePercentage(camera, distance, getWorldSpaceSize());
}

float LODGroup::distanceToScreenUsagePercentage(const Camera *camera, float distance, float size) {
    if (camera->getProjectionType() == CameraProjection::PERSPECTIVE) {
        return static_cast<float>((size * fabs(camera->getMatProj().m[5])) / (distance * 2.0)); // note: matProj.m11 is 1 / tan(fov / 2.0)
    }
    return static_cast<float>(size * fabs(camera->getMatProj().m[5]) * 0.5);
}

float LODGroup::getWorldSpaceSize() const {
    auto scale = _node->getScale();
    auto maxScale = fmaxf(fabs(scale.x), fabs(scale.y));
    maxScale = fmaxf(maxScale, fabs(scale.z));
    return maxScale * _objectSize;
}

void LODGroup::lockLODLevels(ccstd::vector<int> &levels) {
    if (levels.size() != _vecLockedLevels.size()) {
        _isLockLevelChanged = true;
    } else {
        auto size = levels.size();
        for (int index = 0; index < size; index++) {
            if (levels[index] != _vecLockedLevels[index]) {
                _isLockLevelChanged = true;
                break;
            }
        }
    }
    _vecLockedLevels.clear();
    _vecLockedLevels.insert(_vecLockedLevels.begin(), levels.begin(), levels.end());
}

void LODGroup::insertLOD(uint8_t index, LODData *data) {
    if (index >= _vecLODData.size()) {
        _vecLODData.emplace_back(data);
    } else {
        _vecLODData.insert(_vecLODData.begin() + index, data);
    }
}

void LODGroup::updateLOD(uint8_t index, LODData *data) {
    if (index >= _vecLODData.size()) {
        CC_LOG_WARNING("LODGroup updateLOD error, index out of range.");
        return;
    }
    _vecLODData[index] = data;
}

void LODGroup::eraseLOD(uint8_t index) {
    if (index >= _vecLODData.size()) {
        CC_LOG_WARNING("LODGroup eraseLOD error, index out of range.");
        return;
    }
    _vecLODData.erase(_vecLODData.begin() + index);
}

} // namespace scene
} // namespace cc