# Strange Markup Language processor 2 - iterator            17mar14waw

# Strange Markup Language (anyway, strange to me) processor 2.
# iterator generator version.
# refer to perlmonks node 1078356.

package SML2;

use warnings FATAL => 'all';
use strict;


sub Iterator (&) { return $_[0]; }  # syntactic sugar per mjd

my $nobrackets = qr{ [^{}]+ }xms;  # maybe use * quantifier??

use constant XLT => (  # basic translation mapping
    # captured tagged substrings represented by $ below
    # tag                 translates as
    '\textsuperscript' => ' startsuperscript $ endsuperscript ',
    '\textsubscript'   => ' startsubscript $ endsubscript'     ,
    '\textit'          => ' startitalic $ enditalic'           ,
    '\textcolor'       => ''                                   ,
    ''                 => '($)'                                ,
    );


my %xlate1 = XLT;

# tag will be in separate scalar.
# tagged string will be returned by anon. subroutine.

# convert strings (and placeholders) of %xlate1 to anon. subs.
for (values %xlate1) {  # convert:
    # placeholder to function parameter;
    s{ \$ }'$_[0]'xms;
    # value to anon. sub returning string w/interpolated param
    $_ = eval qq{ sub { \\ qq{$_} } };
    }


sub tag_converter {  # works -- iterator generator

    my (@tags,    # tags to process in order of processing
        ) = @_;

    # verify existence of tags before making iterator.
    exists $xlate1{$_} or die qq{unknown tag '$_'} for @tags;

    return Iterator {

        my $n = 0;  # total substitutions done for all tags

        for my $tag (@tags) {  # processes tags in order
            $n += $_[0] =~ s{ \Q$tag\E \{ ($nobrackets) \} }
                            {${ $xlate1{$tag}->($1)       }}xmsg;
            }

        return $n;

        }

    }


1;