semver.h

#include <compare> // IWYU pragma: keep -used for operator <=>, false positive
#include <cstdint>
#include <expected>
#include <string_view>

struct SemVer {
    uint8_t major;

    uint8_t minor;

    uint8_t patch;

    std::string_view pre_release{};
 
    // std::optional<std::string_view> build{};

    bool operator==(const SemVer&) const = default;

    std::strong_ordering operator<=>(const SemVer& other) const;

    class Parser {
    public:
        enum class Error {
            INVALID_NUMBER,

            WRONG_CHAR,

            END_OF_STREAM,
        };

        Parser(std::string_view input) : input_(input) {};

        std::expected<SemVer, Error> parse();
 
    private:
        std::string_view input_;
        size_t index_ = 0;

        std::expected<void, Error> expect(char expected);

        std::expected<SemVer, Error> parseVersionCore();

        std::expected<uint8_t, Error> parseNumericIdentifier();

        std::string_view parsePreRelease();
 
        // std::string_view parseBuild();
    };

    static std::expected<SemVer, Parser::Error> parse(std::string_view input) { return Parser{input}.parse(); }
};