// sample-header-only.hpp: a header-only C++ library, guarded with #pragma once.
// Free sample from 99helpers.com/file-types/h
//
// "Header-only" means there is no .cpp file to compile or link: including
// this header is all it takes. sample-main.cpp uses it.

// #pragma once does the job of an include guard in one line. It isn't in the
// C or C++ standard, but GCC, Clang and MSVC all support it.
#pragma once

#include <cstddef>
#include <numeric>
#include <string>
#include <vector>

namespace sample {

// Templates live in headers: the compiler needs the full definition to
// generate code for each type it's used with.
template <typename T>
double average(const std::vector<T>& values)
{
    if (values.empty()) {
        return 0.0;
    }
    return static_cast<double>(std::accumulate(values.begin(), values.end(), T{})) /
           static_cast<double>(values.size());
}

// An ordinary function defined in a header must be marked inline. Without
// it, every .cpp file that includes the header defines its own copy and the
// linker reports "multiple definition".
inline std::string bar(double value, double max, std::size_t width = 20)
{
    if (max <= 0.0 || value <= 0.0) {
        return {};
    }
    auto filled = static_cast<std::size_t>(value / max * static_cast<double>(width) + 0.5);
    return std::string(filled > width ? width : filled, '#');
}

// inline variables (C++17) follow the same rule for constants and globals.
inline constexpr const char* library_name = "99helpers sample bars";

}  // namespace sample