format_string_impl.h

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#pragma once
 
#include "di/assert/assert_bool.h"
#include "di/container/string/string_view_impl.h"
#include "di/format/concepts/formattable.h"
#include "di/format/format_parse_context.h"
#include "di/meta/constexpr.h"
#include "di/meta/util.h"
#include "di/util/source_location.h"
 
namespace di::format {
namespace detail {
    template<concepts::Encoding Enc, concepts::Formattable... Args>
    class FormatStringImpl {
    private:
        using StringView = container::string::StringViewImpl<Enc>;
 
    public:
        consteval FormatStringImpl(StringView view) : m_view(view) {
            auto parse_context = format::FormatParseContext<Enc> { view, sizeof...(Args) };
            for (auto part : parse_context) {
                if (!part) {
                    util::compile_time_fail<FixedString { "Invalid format string." }>();
                } else if (part->index() == 0) {
                    continue;
                }
 
                if constexpr (sizeof...(Args) > 0) {
                    auto arg_index = util::get<1>(*part).index;
                    function::index_dispatch<void, sizeof...(Args)>(arg_index, [&]<size_t index>(Constexpr<index>) {
                        auto formatter = format::formatter<meta::At<meta::List<Args...>, index>>(parse_context);
                        if (!formatter) {
                            util::compile_time_fail<FixedString { "Invalid format string argument format." }>();
                        }
                    });
                }
            }
        }
 
        constexpr operator StringView() const { return m_view; }
 
        constexpr auto encoding() const { return m_view.encoding(); }
 
    private:
        StringView m_view;
    };
 
    template<concepts::Encoding Enc, concepts::Formattable... Args>
    class FormatStringWithLocationImpl {
    private:
        using StringView = container::string::StringViewImpl<Enc>;
 
    public:
        consteval FormatStringWithLocationImpl(StringView view,
                                               util::SourceLocation location = util::SourceLocation::current())
            : m_base(view), m_location(location) {}
 
        constexpr operator StringView() const { return m_base; }
 
        constexpr auto encoding() const { return m_base.encoding(); }
        constexpr auto location() const { return m_location; }
 
    private:
        FormatStringImpl<Enc, Args...> m_base;
        util::SourceLocation m_location;
    };
}
 
template<concepts::Encoding Enc, concepts::Formattable... Args>
using FormatStringImpl = detail::FormatStringImpl<Enc, meta::TypeIdentity<Args>...>;
 
template<concepts::Encoding Enc, concepts::Formattable... Args>
using FormatStringWithLocationImpl = detail::FormatStringWithLocationImpl<Enc, meta::TypeIdentity<Args>...>;
}
 
namespace di {
using format::FormatStringImpl;
}