Join.hpp

// SPDX-FileCopyrightText: 2025 Vincent Leroy
// SPDX-License-Identifier: MIT
//
// This file is part of dfx.
//
// Licensed under the MIT License. See the LICENSE file in the project root
// for full license information.
 
#pragma once
 
// Standard includes
#include <format>
#include <ranges>
#include <string_view>
 
namespace dfx::Utils
{
template <std::ranges::forward_range Range>
class JoinedView
{
public:
    constexpr JoinedView(Range range, std::string_view delimiter) noexcept
        : _range     { range }
        , _delimiter { delimiter }
    {}

    constexpr Range const & range() const noexcept        { return _range; }

    constexpr std::string_view delimiter() const noexcept { return _delimiter; }
 
private:
    Range            _range;
    std::string_view _delimiter;
};

template <std::ranges::forward_range Range>
constexpr JoinedView<Range> join(Range const & range, std::string_view delimiter) noexcept
{
    return JoinedView<Range>(range, delimiter);
}

template <typename It, typename Sent>
requires std::forward_iterator<It> && std::sentinel_for<Sent, It>
constexpr auto join(It first, Sent last, std::string_view delimiter) noexcept
{
    auto sub = std::ranges::subrange(first, last);
    return join(sub, delimiter);
}
} // !namespace dfx::Utils

template <typename Range, typename CharT>
struct std::formatter<dfx::Utils::JoinedView<Range>, CharT> : std::formatter<std::basic_string<CharT>, CharT>
{
    template <typename FormatContext>
    auto format(dfx::Utils::JoinedView<Range> const & joined, FormatContext & ctx) const
    {
        std::basic_string<CharT> result;
 
        auto it = std::ranges::begin(joined.range());
        auto end = std::ranges::end(joined.range());
 
        if (it != end)
        {
            result += std::format("{}", *it);
            ++it;
            for (; it != end; ++it)
            {
                result += joined.delimiter();
                result += std::format("{}", *it);
            }
        }
 
        return std::formatter<std::basic_string<CharT>, CharT>::format(result, ctx);
    }
};