use base64::engine;

pub(crate) const BASE64: engine::GeneralPurpose = engine::GeneralPurpose::new(

    &base64::alphabet::STANDARD,

    engine::GeneralPurposeConfig::new()

        .with_decode_allow_trailing_bits(true)

        .with_decode_padding_mode(engine::DecodePaddingMode::Indifferent)

        .with_encode_padding(true),

);

const fn is_tchar(c: u8) -> bool {

    // See tchar values list in https://tools.ietf.org/html/rfc7230#section-3.2.6

    matches!(

        c,

        b'!' | b'#'

            | b'$'

            | b'%'

            | b'&'

            | b'\''

            | b'*'

            | b'+'

            | b'-'

            | b'.'

            | b'^'

            | b'_'

            | b'`'

            | b'|'

            | b'~'

    ) || c.is_ascii_alphanumeric()

}

pub(crate) const fn is_allowed_start_token_char(c: u8) -> bool {

    c.is_ascii_alphabetic() || c == b'*'

}

pub(crate) const fn is_allowed_inner_token_char(c: u8) -> bool {

    is_tchar(c) || c == b':' || c == b'/'

}

pub(crate) const fn is_allowed_start_key_char(c: u8) -> bool {

    c.is_ascii_lowercase() || c == b'*'

}

pub(crate) const fn is_allowed_inner_key_char(c: u8) -> bool {

    c.is_ascii_lowercase() || c.is_ascii_digit() || matches!(c, b'_' | b'-' | b'*' | b'.')

}