X-Git-Url: http://git.shiar.nl/perl/list-index.git/blobdiff_plain/e5fa8cd7b5cc84943c5f7c32c4f34974613a235b..e2a186365224032ff37caac824d50c9b43130952:/lib/List/Index.pm

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index 339bd7d..35f0549 100644
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -6,75 +6,92 @@ use warnings;
 
 use Exporter 'import';
 
-our $VERSION = '1.01';
+our $VERSION = '1.02';
 our @EXPORT_OK = qw(rangematch);
 
 sub new {
-	my ($class, $values) = @_;
-	bless [sort map { s/[^a-z]/./g; $_ } @$values], $class;
+	my ($class, $options) = @_;
+	$options ||= {};
+	bless $options, $class;
 }
 
 sub ranges {
 	my $self = shift;
+	my @rows = sort map { s/[^a-z]/./g; $_ } @{ shift() };
 	my $options = shift || {};
+	$options->{$_} //= $self->{$_} for keys %$self;
+
 	my $pagesize = $options->{pagesize} || 50;
 	my $context  = $options->{context } // 1 + ($pagesize >> 4);
 	my $length   = $options->{length  } || 4;
-	my $pages    = $options->{pages   } || 1 + int $#$self / $pagesize;
+	my $pages    = $options->{pages   } || 1 + int($#rows / $pagesize);
+
+	$pagesize = $pages >= @rows ? 1 : @rows / $pages;
+	my $shrunk = 0;
+	my $enlarged = 0;
 
-	$pagesize = @$self / $pages;
-	my $offset = $pagesize + .5;
-	my $penalty = 0;
 	my @links = ('');
-	while ($offset < @$self) {
-		my $link = substr $self->[$offset], 0, $length;
+	for (my $offset = $pagesize + .5; $offset < @rows; $offset += $pagesize) {
+		my $link = substr $rows[$offset], 0, $length;
 		if ($context) {
-			if ($offset > $context - 1 + $penalty) {
-				# take a value slightly before the current offset
-				my $before = $self->[$offset - $context - 1 + $penalty];
+			my $lookbehind = -$context + $shrunk;
+			my $lookahead  =  $context - $enlarged;
+			$shrunk = $enlarged = 0;
+
+			# take a value slightly before the current offset
+			if ((my $before = $offset + $lookbehind) > 0) {
 				# see how much of it matches the current link
 				my $trim = 1;
-				for my $match (split //, $before) {
+				for my $match (split //, $rows[$before - 1]) {
 					scalar $link =~ /\G\Q$match/g or last;
 					$trim++;
 				}
 				# truncate link upto where the earlier value starts to differ
-				substr($link, $trim) = '' unless $trim > length $link;
+				if ($trim < length $link) {
+					substr($link, $trim) = '';
+					for (reverse $before .. $offset - 1) {
+						$rows[$_] =~ /^\Q$link/ or last;
+						$enlarged++;
+					}
+				}
 			}
 
-			$penalty = 0;
-			if ($offset + $context < $#$self) {
-				# take a value after the current offset
-				my $after = $self->[$offset + $context];
+			# take a value after the current offset
+			if ((my $after = $offset + $lookahead) < $#rows) {
 				# see how much of it matches the current link
 				my $trim = 1;
-				for my $match (split //, $after) {
+				pos $link = 0;
+				for my $match (split //, $rows[$after]) {
 					scalar $link =~ /\G\Q$match/g or last;
 					$trim++;
 				}
 				# use this link if it's shorter
 				if ($trim < length $link) {
-					$link = substr $after, 0, $trim;
-					for ($offset .. $#$self) {
-						last if $self->[$offset + $penalty] =~ /^\Q$link/;
-						$penalty++;
+					$enlarged = 0;
+					for ($offset + 1 .. $after) {
+						my $prefix = substr $rows[$_], 0, $trim;
+						# advance lookbehind offset on the next page
+						$shrunk++;
+						next if $link =~ /^\Q$prefix/;
+						$link = $prefix;
+						last;
 					}
 				}
 			}
 		}
 
-		push @links, $link;
-		$offset += $pagesize;
+		push @links, $link unless $links[-1] eq $link;
 	}
 
-	use List::MoreUtils 'uniq';
-	@links = uniq @links;
+	# add range end to each link
 	for my $i (0 .. $#links - 1) {
-		my ($link, $lastchar) = $links[$i + 1] =~ /(.*)(.)/;
-		$link .= $lastchar le 'a' ? '.' : chr( ord($lastchar) - 1 );
-		next if $link eq $links[$i] and $i;
-		$links[$i] .= '-'.$link;
+		# end at start of next value with the last character decremented
+		my $next = $links[$i + 1];
+		$next =~ s{(.)$}{ $1 le 'a' ? '.' : chr( ord($1) - 1 ) }e;
+		# amend range if it's ahead
+		$links[$i] .= '-'.$next unless $next eq $links[$i];
 	}
+	# final value takes the rest
 	$links[-1] .= '-';
 
 	return \@links;
@@ -175,8 +192,8 @@ List::Index - Find and apply prefix ranges to paginate keywords
 =head1 SYNOPSIS
 
 	use List::Index;
-	my $index = List::Index->new(\@values);
-	my @pages = $index->ranges({pagesize => 50});
+	my $index = List::Index->new({ pagesize => 50 });
+	my @pages = $index->ranges(\@values);
 	say "<a href='?q=$_'>$_</a>" for @pages;
 
 	use List::Index 'rangematch';