From d61e8685992586de85f6b7b58fee20f15c8111b0 Mon Sep 17 00:00:00 2001
From: Mischa POSLAWSKY <perl@shiar.org>
Date: Wed, 11 Nov 2009 03:42:05 +0100
Subject: [PATCH] XXX: rangematch()

---
 lib/List/Index.pm | 43 +++++++++++++++++++++++++++++++++++++++++++
 t/20-links.t      | 27 +++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 t/20-links.t

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index c799221..6a818bb 100644
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -4,7 +4,10 @@ use 5.010;
 use strict;
 use warnings;
 
+use Exporter 'import';
+
 our $VERSION = '1.00';
+our @EXPORT_OK = qw(rangematch);
 
 sub new {
 	my ($class, $values) = @_;
@@ -49,6 +52,46 @@ sub ranges {
 	return \@links;
 }
 
+sub rangematch {
+	my ($link) = @_;
+	my ($s1, $s2) = $link =~ /([^-]*) - ([^-]*)/x
+		or return qr/^\Q$link/i;
+	my @allow;
+
+	if (length $s1) {
+		my $prefix = '';
+		my $c1;
+		for my $i (0 .. length($s1) - 1) {
+			$c1 = substr $s1, $i, 1;
+			my $c2 = length $s2 <= $i ? undef : substr $s2, $i, 1;
+			my $next = $i + 1 >= length($s1) ? $c1 : chr( ord($c1) + 1 );
+			$next le $c2 or next if defined $c2;
+			my $last = defined $c2 && $i == 0 ? chr( ord($c2) - (length $s2 > 1) ) : 'z';
+			push @allow, $prefix."[$next-$last]";
+		}
+		continue {
+			$prefix .= $c1;
+		}
+	}
+
+	if (length $s2) {
+		my $prefix = '';
+		for my $i (0 .. length($s2) - 1) {
+			my $c1 = length $s1 <= $i ? undef : substr $s1, $i, 1;
+			my $c2 = substr $s2, $i, 1;
+			my $last = 'z';
+			push @allow, "$prefix(?![$c2-$last])"
+				if $i or $s1 eq '';
+			$prefix .= $c2;
+		}
+		push @allow, $prefix
+			unless length $s1 > length $s2 or length $s1 != 0 && length $s2 == 1; #TODO
+	}
+
+	my $match = sprintf @allow <= 1 ? '%s' : '(?:%s)', join('|', @allow);
+	return qr/^$match/i;
+}
+
 1;
 
 __END__
diff --git a/t/20-links.t b/t/20-links.t
new file mode 100644
index 0000000..89f5dee
--- /dev/null
+++ b/t/20-links.t
@@ -0,0 +1,27 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use Test::More tests => 13;
+use Test::NoWarnings;
+
+BEGIN { use_ok('List::Index' => 'rangematch'); }
+
+for (
+	[   q      => 'q'],
+	['#foo.!$' => '\#foo\.\!\$'],
+	[    -q    =>            '(?:(?![q-z])|q)'],
+	[    -qqq  =>            '(?:(?![q-z])|q(?![q-z])|qq(?![q-z])|qqq)'],
+	[  'q-'    =>    '[q-z]'],
+	['qqq-'    => '(?:[r-z]|q[r-z]|qq[q-z])'],
+	[  'q-x'   =>    '[q-x]'],
+	['qqq-xxx' => '(?:[r-w]|q[r-z]|qq[q-z]|x(?![x-z])|xx(?![x-z])|xxx)'],
+	['qqq-x'   => '(?:[r-x]|q[r-z]|qq[q-z])'],
+	['qqq-q'   =>       '(?:q[r-z]|qq[q-z])'],
+	[  'q-xxx' =>                '(?:[q-w]|x(?![x-z])|xx(?![x-z])|xxx)'],
+) {
+	my ($in, $out) = @$_;
+	is(eval { rangematch($in) }, "(?i-xsm:^$out)", $in);
+	diag($@) if $@;
+}
+
-- 
2.30.0