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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2025                                                               *
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#include <modules/multiresvolume/rendering/histogrammanager.h>

#include <modules/multiresvolume/rendering/tsp.h>
#include <openspace/util/histogram.h>
#include <cstring>
#include <fstream>
#include <utility>

namespace openspace {

bool HistogramManager::buildHistograms(TSP* tsp, int numBins) {
    _numBins = numBins;

    std::ifstream& file = tsp->file();
    if (!file.is_open()) {
        return false;
    }
    _minBin = 0.f; // Should be calculated from tsp file
    _maxBin = 1.f; // Should be calculated from tsp file

    const int numTotalNodes = tsp->numTotalNodes();
    _histograms = std::vector<Histogram>(numTotalNodes);

    const bool success = buildHistogram(tsp, 0);
    return success;
}

Histogram* HistogramManager::histogram(unsigned int brickIndex) {
    return &_histograms[brickIndex];
}

bool HistogramManager::buildHistogram(TSP* tsp, unsigned int brickIndex) {
    Histogram histogram = Histogram(_minBin, _maxBin, _numBins);
    const bool isBstLeaf = tsp->isBstLeaf(brickIndex);
    const bool isOctreeLeaf = tsp->isOctreeLeaf(brickIndex);

    if (isBstLeaf && isOctreeLeaf) {
        // TSP leaf, read from file and build histogram
        std::vector<float> voxelValues = readValues(tsp, brickIndex);
        size_t numVoxels = voxelValues.size();

        for (size_t v = 0; v < numVoxels; v++) {
            histogram.add(voxelValues[v], 1.0);
        }
    }
    else {
        // Has children
        std::vector<unsigned int> children;

        if (!isBstLeaf) {
            // Push BST children
            children.push_back(tsp->bstLeft(brickIndex));
            children.push_back(tsp->bstRight(brickIndex));
        }
        if (!isOctreeLeaf) {
            // Push Octree children
            const unsigned int firstChild = tsp->firstOctreeChild(brickIndex);
            for (int c = 0; c < 8; c++) {
                children.push_back(firstChild + c);
            }
        }
        size_t numChildren = children.size();
        for (size_t c = 0; c < numChildren; c++) {
            // Visit child
            const unsigned int childIndex = children[c];
            if (_histograms[childIndex].isValid() || buildHistogram(tsp, childIndex)) {
                if (numChildren <= 8 || c < 2) {
                    // If node has both BST and Octree children, only add BST ones
                    histogram.add(_histograms[childIndex]);
                }
            }
            else {
                return false;
            }
        }
    }

    //histogram.normalize();
    _histograms[brickIndex] = std::move(histogram);

    return true;
}

std::vector<float> HistogramManager::readValues(TSP* tsp, unsigned int brickIndex) {
    const unsigned int paddedBrickDim = tsp->paddedBrickDim();
    const unsigned int numBrickVals = paddedBrickDim * paddedBrickDim * paddedBrickDim;
    std::vector<float> voxelValues(numBrickVals);

    std::streampos offset = tsp->dataPosition() +
                            static_cast<long long>(brickIndex*numBrickVals*sizeof(float));
    std::ifstream& file = tsp->file();
    file.seekg(offset);

    file.read(
        reinterpret_cast<char*>(voxelValues.data()),
        static_cast<size_t>(numBrickVals)*sizeof(float)
    );

    return voxelValues;
}

bool HistogramManager::loadFromFile(const std::filesystem::path& filename) {
    std::ifstream file = std::ifstream(filename, std::ios::in | std::ios::binary);
    if (!file.is_open()) {
        return false;
    }

    int numHistograms;
    file.read(reinterpret_cast<char*>(&numHistograms), sizeof(int));
    file.read(reinterpret_cast<char*>(&_numBins), sizeof(int));
    file.read(reinterpret_cast<char*>(&_minBin), sizeof(float));
    file.read(reinterpret_cast<char*>(&_maxBin), sizeof(float));

    int nFloats = numHistograms * _numBins;
    std::vector<float> histogramData(nFloats);
    file.read(reinterpret_cast<char*>(histogramData.data()), sizeof(float) * nFloats);

    _histograms = std::vector<Histogram>(numHistograms);

    for (int i = 0; i < numHistograms; i++) {
        int offset = i * _numBins;
        // No need to deallocate histogram data, since histograms take ownership.
        float* data = new float[_numBins];
        memcpy(data, &histogramData[offset], sizeof(float) * _numBins);
        _histograms[i] = Histogram(_minBin, _maxBin, _numBins, data);
    }

    return true;
}

bool HistogramManager::saveToFile(const std::filesystem::path& filename) {
    std::ofstream file = std::ofstream(filename, std::ios::out | std::ios::binary);
    if (!file.is_open()) {
        return false;
    }

    size_t numHistograms = _histograms.size();
    file.write(reinterpret_cast<char*>(&numHistograms), sizeof(int));
    file.write(reinterpret_cast<char*>(&_numBins), sizeof(int));
    file.write(reinterpret_cast<char*>(&_minBin), sizeof(float));
    file.write(reinterpret_cast<char*>(&_maxBin), sizeof(float));

    size_t nFloats = numHistograms * _numBins;
    std::vector<float> histogramData(nFloats);

    for (size_t i = 0; i < numHistograms; i++) {
        size_t offset = i*_numBins;
        memcpy(&histogramData[offset], _histograms[i].data(), sizeof(float) * _numBins);
    }

    file.write(reinterpret_cast<char*>(histogramData.data()), sizeof(float) * nFloats);

    return true;
}

} // namespace openspace