+++: first link (prefill, keep dot references)

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

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index 50e48a5eb30f71d6b3abaefe77bcbd2a09b9cfa7..bf4e04db592dabcf488ab9a2dfd5386bbd3a4668 100644 (file)
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -23,18 +23,38 @@ sub ranges {
        my $pages    = $options->{pages   } || 1 + int $#$self / $pagesize;
 
        $pagesize = @$self / $pages;
-       my $offset = 0;
-       my @links;
+       my $offset = $pagesize;
+       my @links = (['']);
        while ($offset < @$self) {
                my $link = substr $self->[$offset], 0, $length;
                if ($context) {
-                       my $trim = 1;
-                       my $before = $offset > $context ? $self->[$offset - $context] : '.';
-                       for my $match (split //, $before) {
-                               scalar $link =~ /\G\Q$match/g or last;
-                               $trim++;
+                       {
+                               # take a value slightly before the current offset
+                               my $before = $offset > $context ? $self->[$offset - $context] : '.';
+                               # see how much of it matches the current link
+                               my $trim = 1;
+                               for my $match (split //, $before) {
+                                       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 $link;
+                       }
+
+                       if ($offset + $context < $#$self) {
+                               # take a value after the current offset
+                               my $after = $self->[$offset + $context];
+                               # see how much of it matches the current link
+                               my $trim = 1;
+                               for my $match (split //, $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, $trim;
+                               }
                        }
-                       substr($link, $trim) = '' unless $trim > length $link;
                }
 
                push @links, [$link];
@@ -43,8 +63,8 @@ sub ranges {
 
        for my $i (0 .. $#links - 1) {
                my ($link, $lastchar) = $links[$i + 1]->[0] =~ /(.*)(.)/;
-               $link .= $lastchar eq 'a' ? '.' : chr( ord($lastchar) - 1 )
-                       unless $lastchar eq '.';
+               $link .= $lastchar le 'a' ? '.' : chr( ord($lastchar) - 1 );
+               next if $link eq $links[$i]->[0] and $i;
                $links[$i]->[1] = $link;
        }
        $links[-1]->[1] = '';