Algorithms.h

// SPDX-FileCopyrightText: 2024 Linus Jahn <lnj@kaidan.im>
//
// SPDX-License-Identifier: LGPL-2.1-or-later
 
#ifndef ALGORITHMS_H
#define ALGORITHMS_H
 
#include <algorithm>
#include <functional>
#include <optional>
 
namespace QXmpp::Private {
 
template<typename T>
constexpr bool HasShrinkToFit = requires(const T &t) {
    t.shrink_to_fit();
};
 
template<typename T>
constexpr bool HasSqueeze = requires(const T &t) {
    t.squeeze();
};
 
template<typename OutputVector, typename InputVector, typename Converter>
auto transform(const InputVector &input, Converter convert)
{
    OutputVector output;
    if constexpr (std::ranges::sized_range<InputVector>) {
        output.reserve(input.size());
    }
    for (const auto &value : input) {
        output.push_back(std::invoke(convert, value));
    }
    return output;
}
 
template<typename OutputVector, typename InputVector, typename Converter>
auto transformFilter(const InputVector &input, Converter convert)
{
    OutputVector output;
    if constexpr (std::ranges::sized_range<InputVector>) {
        output.reserve(input.size());
    }
    for (const auto &value : input) {
        if (const std::optional<std::decay_t<decltype(value)>> result = std::invoke(convert, value)) {
            output.push_back(*result);
        }
    }
    if constexpr (HasShrinkToFit<InputVector>) {
        output.shrink_to_fit();
    } else if constexpr (HasSqueeze<InputVector>) {
        output.squeeze();
    }
    return output;
}
 
template<typename Vec, typename T>
auto contains(const Vec &vec, const T &value)
{
    return std::find(std::begin(vec), std::end(vec), value) != std::end(vec);
}
 
template<typename T, typename Function>
auto map(Function mapValue, std::optional<T> &&optValue) -> std::optional<std::invoke_result_t<Function, T &&>>
{
    if (optValue) {
        return mapValue(std::move(*optValue));
    }
    return {};
}
 
template<typename To, typename From>
auto into(std::optional<From> &&value) -> std::optional<To>
{
    if (value) {
        return To { *value };
    }
    return {};
}
 
}  // namespace QXmpp::Private
 
#endif  // ALGORITHMS_H