#
# Check if a email is valid
# Tests aplied: there must not be space chars on the mail, there must be only one @ char, there must be a mail user
#               there must be a mail domain and a domain prefix
#               optionally it can also restrict a email into a given list of domain prefixes (com,pt,org,etc)
# Will Return 0 ; 1
# 0 email is valid ; 1 email is not valid
sub check_email {

    my $email = $_[0]; # email to test
    my $global_config_p = $_[1]; # configuration pointer
    print "Running the check_email() function\n" if ( defined $$global_config_p{debug_level} and ($$global_config_p{debug_level} eq "half" or $$global_config_p{debug_level} eq "full") ); # print message if the debug level requires it
    my $alllowed_domain_prefixes = $_[2]; # optional value where you can say what email prefixes (.pt .com .org etc) are allowed 
                                          # the list should be passed without the . char and separated by the , char example (pt,com,org,es)

    my $error_flag = 1; # by default the email is invalid

    $email =~ s/^\s+//;  # Delete leading whitespace ^ is the first caracter  \s is space then // replace with nothing if there was /a/ then replace with a
    $email =~ s/\s+$//;  # Delete trailing whitespace same thing kind of but $ represents end of line.

    if ( length($email) >= 5 and ($email =~ tr/@//) == 1 and ($email =~ tr/ //) == 0 ) { # email must have at least 5 chars ( a@a.c) and one @ char and no SPACE CHARS

        my ( $mail_user, $mail_domain ) = split (/@/, $email );
        # find the last occurence of .
        my $mail_domain_pref_pos = rindex($mail_domain,".");
        my $mail_domain_prefix = ""; # .pt .org etc
        if ( $mail_domain_pref_pos >= 0 ) {
            $mail_domain_prefix = substr($mail_domain,$mail_domain_pref_pos+1,length($mail_domain)); # get the domain prefix
        }

        # if mail user exists (exanmple miguel) and if the mail domain exists (mail.pt) and if the mail domain prefix exists (pt)
        if ( defined $mail_user and defined $mail_domain and defined $mail_domain_prefix and length($mail_user) > 0 and length($mail_domain) > 0 and length($mail_domain_prefix) > 0 ) {
            my $allowed_prefix = "";
            if ( defined $alllowed_domain_prefixes and length($alllowed_domain_prefixes) > 0 ) { # check the allowed prefixed if required (pt com org etc)
                my @alllowed_domain_prefixes = split(/,/, $alllowed_domain_prefixes);
                $allowed_prefix = "no";
                foreach my $allowed_prefix_record (@alllowed_domain_prefixes) {
                    if ( $mail_domain_prefix eq $allowed_prefix_record ) {
                        $allowed_prefix = "yes";
                        last;
                    }
                }
            }
            if ( $allowed_prefix ne "no" ) { # check if the prefix is not allowed
                $error_flag = 0; # mail is valid
            }
        }
    }

    print "Function check_email() exit value is [ $error_flag ]\n" if ( defined $$global_config_p{debug_level} and $$global_config_p{debug_level} eq "full" ); # print message if the debug level requires it
    return $error_flag;
}