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* Copyright (c) 2016, Hobu Inc. (info@hobu.co)
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#include <math.h>
#include <memory>
#include <string>
#include <vector>
#include <stdexcept>

namespace pdal
{

class GDALGrid
{
public:
    static const int statCount = 1;
    static const int statMin = 2;
    static const int statMax = 4;
    static const int statMean = 8;
    static const int statStdDev = 16;
    static const int statIdw = 32;

    struct error : public std::runtime_error
    {
        error(const std::string& err) : std::runtime_error(err)
        {}
    };

    GDALGrid(size_t width, size_t height, double edgeLength, double radius,
        int outputTypes, size_t windowSize);

    void expand(size_t width, size_t height, size_t xshift, size_t yshift);

    // Get the number of bands represented by this grid.
    int numBands() const;

    // Return a pointer to the data in a raster band, row-major ordered.
    double *data(const std::string& name);

    // Add a point to the raster grid.
    void addPoint(double x, double y, double z);

    // Compute final values after all points have been added.
    void finalize();

    size_t width() const
        { return m_width; }

    size_t height() const
        { return m_height; }

private:
    size_t m_width;
    size_t m_height;
    size_t m_windowSize;
    double m_edgeLength;
    double m_radius;

    typedef std::vector<double> DataVec;
    typedef std::unique_ptr<DataVec> DataPtr;
    DataPtr m_count;
    DataPtr m_min;
    DataPtr m_max;
    DataPtr m_mean;
    DataPtr m_stdDev;
    DataPtr m_idw;
    DataPtr m_idwDist;

    int m_outputTypes;

    // Find an index into the actual storage given a grid coordinate.
    size_t index(size_t i, size_t j)
        { return (j * m_width) + i; }

    // Determine if a cell i, j has no associated points.
    bool empty(size_t i, size_t j)
        { return empty(index(i, j)); }

    // Determine if a cell with index \c idx has no associated points.
    bool empty(size_t idx)
        { return ((*m_count)[idx] <= 0); }

    // Convert an absolute X position to a horizontal cell index.
    int horizontalIndex(double x)
        { return (int)(x / m_edgeLength); }

    // Convert an absolute Y position to a vertical cell index.
    int verticalIndex(double y)
        { return (int)(m_height - (y / m_edgeLength) - 1); }

    // Return the absolute horizontal position of the center of a cell given
    // the cell i index.
    double horizontalPos(size_t i)
        { return (i + .5) * m_edgeLength; }

    // Return the absolute vertical position of the center of a cell given
    // the cell j index.
    double verticalPos(size_t j)
        { return (m_height - (j + .5)) * m_edgeLength; }

    // Determine the distance from the center of cell at coordinate i, j to
    // a point at absolute coordinate x, y.
    double distance(size_t i, size_t j, double x, double y)
    {
        double x1 = horizontalPos(i);
        double y1 = verticalPos(j);
        return sqrt(pow(x1 - x, 2) + pow(y1 - y, 2));
    }

    // Update cell at i, j with value at a distance.
    void update(size_t i, size_t j, double val, double dist);

    // Fill cell at index \c i with the nondata value.
    void fillNodata(size_t i);

    // Fill an empty cell with a value inverse-distance averaged from
    // surrounding cells.
    void windowFill()
    {
        for (size_t i = 0; i < width(); ++i)
            for (size_t j = 0; j < height(); ++j)
                if (empty(i, j))
                    windowFill(i, j);
    }

    // Fill empty cell at dstI, dstJ with inverse-distance weighted values
    // from neighboring cells.
    void windowFill(size_t dstI, size_t dstJ);

    // Cumulate data from a source cell to a destination cell when doing
    // a window fill.
    void windowFillCell(size_t srcIdx, size_t dstIdx, double distance);
};
typedef std::unique_ptr<GDALGrid> GDALGridPtr;

} //namespace pdal
