#!/usr/bin/perl

=head1 NAME

dh_link - create symlinks in package build directories

=cut

use strict;
use warnings;
use File::Find;
use Debian::Debhelper::Dh_Lib;

=head1 SYNOPSIS

B<dh_link> [S<I<debhelper options>>] [B<-A>] [B<-X>I<item>] [S<I<source destination> ...>]

=head1 DESCRIPTION

B<dh_link> is a debhelper program that creates symlinks in package build
directories.

B<dh_link> accepts a list of pairs of source and destination
files. The source files are the already existing files that will be
symlinked from (called B<target> by L<ln(1)>). The destination files
are the symlinks that will be created (called B<link name> by
L<ln(1)>). There B<must> be an equal number of source and destination
files specified.

Be sure you B<do> specify the absolute path to both the source and
destination files (unlike you would do if you were using something
like L<ln(1)>).  Please note that the leading slash is optional.

B<dh_link> will generate symlinks that comply with Debian policy - absolute
when policy says they should be absolute, and relative links with as short
a path as possible. It will also create any subdirectories it needs to put
the symlinks in.

Any pre-existing destination files will be replaced with symlinks.

B<dh_link> also scans the package build tree for existing symlinks which do not
conform to Debian policy, and corrects them (v4 or later).

=head1 FILES

=over 4

=item debian/I<package>.links

Lists pairs of source and destination files to be symlinked. Each pair
should be put on its own line, with the source and destination separated by
whitespace.

In each pair the source file (called B<target> by L<ln(1)>) comes
first and is followed by the destination file (called B<link name> by
L<ln(1)>). Thus the pairs of source and destination files in each line
are give in the same order as they would be given to L<ln(1)>.

In contrast to L<ln(1)>, source and destination paths must be absolute
(the leading slash is optional).

=back

=head1 OPTIONS

=over 4

=item B<-A>, B<--all>

Create any links specified by command line parameters in ALL packages
acted on, not just the first.

=item B<-X>I<item>, B<--exclude=>I<item>

Exclude symlinks that contain I<item> anywhere in their filename from
being corrected to comply with Debian policy.

=item I<source destination> ...

Create a file named I<destination> as a link to a file named I<source>. Do
this in the package build directory of the first package acted on.
(Or in all packages if B<-A> is specified.)

=back

=head1 EXAMPLES

 dh_link usr/share/man/man1/foo.1 usr/share/man/man1/bar.1

Make F<bar.1> be a symlink to F<foo.1>

 dh_link var/lib/foo usr/lib/foo \
   usr/share/man/man1/foo.1 usr/share/man/man1/bar.1

Make F</usr/lib/foo/> be a link to F</var/lib/foo/>, and F<bar.1> be a symlink to
the F<foo.1>

 var/lib/foo usr/lib/foo
 usr/share/man/man1/foo.1 usr/share/man/man1/bar.1

Same as above but as content for a debian/I<package>.links file.

=cut

init();

foreach my $package (@{$dh{DOPACKAGES}}) {
	my $tmp=tmpdir($package);
	my $file=pkgfile($package,"links");

	my @links;
	if ($file) {
		@links=filearray($file);
	}

	# Make sure it has pairs of symlinks and destinations. If it
	# doesn't, $#links will be _odd_ (not even, -- it's zero-based).
	if (int($#links/2) eq $#links/2) {
		error("$file lists a link without a destination.");
	}

	if (($package eq $dh{FIRSTPACKAGE} || $dh{PARAMS_ALL}) && @ARGV) {
		push @links, @ARGV;
	}

	# Same test as above, including arguments this time.
	if (int($#links/2) eq $#links/2) {
		error("parameters list a link without a destination.");
	}

	# If there is a temp dir already
	if (-e $tmp) {
		# Scan for existing links and add them to @links, so they
		# are recreated policy conformant.
		find(
			sub {
				return unless -l;
				return if excludefile($_);
				my $dir=$File::Find::dir;
				$dir=~s/^\Q$tmp\E//;
				my $target = readlink($_);
				if ($target=~/^\//) {
					push @links, $target;
				}
				else {
					push @links, "$dir/$target";
				}
				push @links, "$dir/$_";
				
			},
			$tmp);
	}
	
	while (@links) {
		my $dest=pop @links;
		my $src=pop @links;
		make_symlink($dest, $src, $tmp);
	}
}

=head1 SEE ALSO

L<debhelper(7)>

This program is a part of debhelper.

=head1 AUTHOR

Joey Hess <joeyh@debian.org>

=cut