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'.')
}