fix pagesize < 1

[perl/list-index.git] / lib / List / Index.pm

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index 483d1eb430104ad17cc4b6adf9e06b492da91796..e67e5ae730202bafb8bd4ff3640d35656b51c129 100644 (file)
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -22,39 +22,56 @@ sub ranges {
        my $length   = $options->{length  } || 4;
        my $pages    = $options->{pages   } || 1 + int $#$self / $pagesize;
 
-       $pagesize = @$self / $pages;
+       $pagesize = $pages >= $#$self ? 1 : @$self / $pages;
        my $offset = $pagesize + .5;
+       my $lookbehind = -$context;
+       my $lookahead  =  $context;
        my @links = ('');
        while ($offset < @$self) {
                my $link = substr $self->[$offset], 0, $length;
                if ($context) {
-                       {
-                               # take a value slightly before the current offset
-                               my $before = $offset > $context ? $self->[$offset - $context] : '.';
+                       my $penalty = 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 //, $self->[$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) {
+                                               $self->[$offset - $penalty] =~ /^\Q$link/ or last;
+                                               $penalty++;
+                                       }
+                               }
                        }
 
-                       if ($offset + $context < $#$self) {
-                               # take a value after the current offset
-                               my $after = $self->[$offset + $context];
+                       $lookbehind = -$context;
+
+                       # take a value after the current offset
+                       if ((my $after = $offset + $lookahead) < $#$self) {
                                # see how much of it matches the current link
                                my $trim = 1;
-                               for my $match (split //, $after) {
+                               for my $match (split //, $self->[$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;
+                                       $link = substr $self->[$after], 0, $trim;
+                                       # advance lookbehind offset on the next page
+                                       $penalty = 0;
+                                       for ($offset .. $after) {
+                                               last if $self->[$_] =~ /^\Q$link/;
+                                               $lookbehind++;
+                                       }
                                }
                        }
+
+                       $lookahead = $context - $penalty;
                }
 
                push @links, $link;
@@ -164,18 +181,18 @@ __END__
 
 =head1 NAME
 
-List::Index - Paginate alphabetic entries by finding minimal prefixes
+List::Index - Find and apply prefix ranges to paginate keywords
 
 =head1 SYNOPSIS
 
        use List::Index;
        my $index = List::Index->new(\@values);
        my @pages = $index->ranges({pagesize => 50});
-       printf '<a href="?q=%s-%s">%1$s</a> ', @$_ for @pages;
+       say "<a href='?q=$_'>$_</a>" for @pages;
 
        use List::Index 'rangematch';
-       my $limit = rangematch('b-bmq');  # matches prefix like 'baa'..'bmq'
-       @results = grep { $limit } @results;
+       my $limit = rangematch('b-bmq');  # ge 'b' && le 'bmq'
+       @request = grep { $limit } @values;
 
 =head1 DESCRIPTION