#pragma once
#include "FluidSim/Fluid.hpp"
#include <span>

namespace fluidsim::port {
struct PipeSection {
    float length, inlet_diameter, outlet_diameter;
};
inline int profile_section_cells(float length,float maximum_cell_length) {
    const double count=double(length)/maximum_cell_length;
    return std::max(1,static_cast<int>(std::ceil(count-1e-6*std::max(1.,count))));
}

// Linear diameter within each section. Cell area is the exact frustum-volume
// average, so refining the mesh preserves the specified chamber volume.
inline Pipe1D make_profiled_pipe(std::span<const PipeSection> sections, float maximum_cell_length = .01f) {
    if (!std::isfinite(maximum_cell_length) || maximum_cell_length <= 0 || sections.empty())
        throw std::invalid_argument("invalid pipe profile mesh");
    std::vector<float> areas, lengths;
    float previous_diameter = sections.front().inlet_diameter;
    for (const auto& section : sections) {
        if (!std::isfinite(section.length) || !std::isfinite(section.inlet_diameter) ||
            !std::isfinite(section.outlet_diameter) || section.length <= 0 ||
            section.inlet_diameter <= 0 || section.outlet_diameter <= 0 ||
            std::abs(section.inlet_diameter - previous_diameter) > 1e-6f)
            throw std::invalid_argument("invalid/discontinuous pipe profile");
        const int count = profile_section_cells(section.length,maximum_cell_length);
        for (int i = 0; i < count; ++i) {
            const float d0 = std::lerp(section.inlet_diameter, section.outlet_diameter, float(i) / count);
            const float d1 = std::lerp(section.inlet_diameter, section.outlet_diameter, float(i + 1) / count);
            areas.push_back(pi / 12 * (d0*d0 + d0*d1 + d1*d1));
            lengths.push_back(section.length / count);
        }
        previous_diameter = section.outlet_diameter;
    }
    return Pipe1D(std::move(areas), std::move(lengths));
}
} // namespace fluidsim::port