Create a search snippet.

gistfile1.pl

sub snippet {
	my ($text, $terms, $max, $tag_s, $tag_e) = @_;

	utf8::decode($text);

	if (length($text) < $max) {
		return $text;
	}

	if (! ref($terms)) {
		utf8::decode($terms);
		$terms = [ grep { $_ ne '' } split(/[\x00-\x2F\x3A-\x40\x5B-\x60\x7B-\x7F]+/, $terms) ];
	}

	my @idxes;
	foreach my $term (@{$terms}) {
		my $offset = -1;
		while (1) {
			$offset = index(lc $text, lc $term, $offset + 1);

			if ($offset >= 0) {
				push @idxes, $offset;
			} else {
				last;
			}
		}
	}

	my $idx_begin = 0;

	if (scalar(@idxes) > 0) {
		@idxes = sort { $a <=> $b } @idxes;

		my @idx_pairs;
		for (my $i = 0; $i < scalar(@idxes) - 1; $i++) {
			for (my $j = scalar(@idxes) -1; $j > $i; $j--) {
				if ($idxes[$j] - $idxes[$i] < $max) {
					push @idx_pairs, [ $idxes[$i], $idxes[$j], $j - $i ];
					last;
				}
			}
		}

		if (scalar(@idx_pairs) > 0) {
			@idx_pairs = sort { $b->[2] <=> $a->[2] || $a->[0] <=> $b->[0] } @idx_pairs;

			$idx_begin = (int(($idx_pairs[0]->[0] + $idx_pairs[0]->[1]) / 2 - $max / 2) > 0) ? int(($idx_pairs[0]->[0] + $idx_pairs[0]->[1]) / 2 - $max / 2) : 0;
		} else {
			$idx_begin = (int($idxes[0] - $max / 2) > 0) ? int($idxes[0] - $max / 2) : 0;
		}
	}

	if ($idx_begin + $max > length($text)) {
		$idx_begin = length($text) - $max;
	}

	my $snippet = substr($text, $idx_begin, $max);
	if ($idx_begin > 0) {
		$snippet = '... ' . $snippet;
	}
	if ($idx_begin + $max < length($text)) {
		$snippet = $snippet . ' ...';
	}

	if (defined $tag_s && defined $tag_e && scalar(@{$terms}) > 0) {
		my $re = join('|', @{$terms});

		$snippet =~ s/($re)/$tag_s$1$tag_e/ig;
	}

	return $snippet;
}