RainfallInterpolator.hpp

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// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2026 Caleb Buahin
//
// 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 OPENSWMM_ENGINE_2D_RAINFALL_INTERPOLATOR_HPP
#define OPENSWMM_ENGINE_2D_RAINFALL_INTERPOLATOR_HPP
 
#include <vector>
 
namespace openswmm::twoD {

class RainfallInterpolator {
public:
    enum class Method { NaturalNeighbour, NearestNeighbour };
    enum class CellMethod : signed char {
        NaturalNeighbour = 0, 
        InverseDistance = 1,  
        Nearest = 2           
    };
    struct Diagnostics {
        int unlocated = 0;
        int invalid = 0;
        int duplicates = 0;
        int idwCells = 0;
    };

    const Diagnostics& diagnostics() const noexcept { return diagnostics_; }
    void build(const std::vector<double>& cx, const std::vector<double>& cy,
               const std::vector<double>& gage_x, const std::vector<double>& gage_y, int n_gages,
               double gage_scale, Method method = Method::NaturalNeighbour);

    bool ready() const noexcept { return ready_; }

    void apply(const std::vector<double>& rain, std::vector<double>& out) const;

    CellMethod cellMethod(int i) const { return cell_method_[static_cast<std::size_t>(i)]; }
    void cellWeights(int i, std::vector<int>& gages, std::vector<double>& weights) const;
 
private:
    Diagnostics diagnostics_;
    std::vector<CellMethod> cell_method_;
    bool ready_ = false;
    int nt_ = 0;
 
    // CSR weight store: cell i owns weights [w_ptr_[i], w_ptr_[i+1]); each slot
    // pairs a global gage index (w_gage_) with a normalized weight (w_val_,
    // sums to 1 per cell).
    std::vector<int> w_ptr_;
    std::vector<int> w_gage_;
    std::vector<double> w_val_;
};
 
} // namespace openswmm::twoD
 
#endif // OPENSWMM_ENGINE_2D_RAINFALL_INTERPOLATOR_HPP