'use strict';

const internals = {};


/*
    From RFC 5321:

        Mailbox         =   Local-part "@" ( Domain / address-literal )

        Local-part      =   Dot-string / Quoted-string
        Dot-string      =   Atom *("."  Atom)
        Atom            =   1*atext
        atext           =   ALPHA / DIGIT / "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{" / "|" / "}" / "~"

        Domain          =   sub-domain *("." sub-domain)
        sub-domain      =   Let-dig [Ldh-str]
        Let-dig         =   ALPHA / DIGIT
        Ldh-str         =   *( ALPHA / DIGIT / "-" ) Let-dig

        ALPHA           =   %x41-5A / %x61-7A        ; a-z, A-Z
        DIGIT           =   %x30-39                  ; 0-9

    From RFC 6531:

        sub-domain      =/  U-label
        atext           =/  UTF8-non-ascii

        UTF8-non-ascii  =   UTF8-2 / UTF8-3 / UTF8-4

        UTF8-2          =   %xC2-DF UTF8-tail
        UTF8-3          =   %xE0 %xA0-BF UTF8-tail /
                            %xE1-EC 2( UTF8-tail ) /
                            %xED %x80-9F UTF8-tail /
                            %xEE-EF 2( UTF8-tail )
        UTF8-4          =   %xF0 %x90-BF 2( UTF8-tail ) /
                            %xF1-F3 3( UTF8-tail ) /
                            %xF4 %x80-8F 2( UTF8-tail )

        UTF8-tail       =   %x80-BF

    Note: The following are not supported:

        RFC 5321: address-literal, Quoted-string
        RFC 5322: obs-*, CFWS
*/


internals.atext = '[\\w!#\\$%&\'\\*\\+\\-/=\\?\\^`\\{\\|\\}~]';                 // _ included in \w


exports.atextRx = new RegExp(`^${internals.atext}+$`);


exports.atomRx = new RegExp([

    internals.atext,

    //  %xC2-DF UTF8-tail
    '(?:[\\xc2-\\xdf][\\x80-\\xbf])',

    //  %xE0 %xA0-BF UTF8-tail              %xE1-EC 2( UTF8-tail )            %xED %x80-9F UTF8-tail              %xEE-EF 2( UTF8-tail )
    '(?:\\xe0[\\xa0-\\xbf][\\x80-\\xbf])|(?:[\\xe1-\\xec][\\x80-\\xbf]{2})|(?:\\xed[\\x80-\\x9f][\\x80-\\xbf])|(?:[\\xee-\\xef][\\x80-\\xbf]{2})',

    //  %xF0 %x90-BF 2( UTF8-tail )            %xF1-F3 3( UTF8-tail )            %xF4 %x80-8F 2( UTF8-tail )
    '(?:\\xf0[\\x90-\\xbf][\\x80-\\xbf]{2})|(?:[\\xf1-\\xf3][\\x80-\\xbf]{3})|(?:\\xf4[\\x80-\\x8f][\\x80-\\xbf]{2})'

].join('|'));