# Copyright © 2005, 2007 Frank Lichtenheld <frank@lichtenheld.de>
# Copyright © 2009       Raphaël Hertzog <hertzog@debian.org>
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

=head1 NAME

Dpkg::Changelog::Parse - generic changelog parser for dpkg-parsechangelog

=head1 DESCRIPTION

This module provides a single function changelog_parse() which reproduces
all the features of dpkg-parsechangelog.

=head2 Functions

=cut

package Dpkg::Changelog::Parse;

#use strict;
#use warnings;

use Dpkg; # for $dpkglibdir
use Dpkg::Gettext;
use Dpkg::ErrorHandling;
use Dpkg::Control::Changelog;

use base qw(Exporter);
our @EXPORT = qw(changelog_parse);

=head3 my $fields = changelog_parse(%opt)

This function will parse a changelog. In list context, it return as many
Dpkg::Control object as the parser did output. In scalar context, it will
return only the first one. If the parser didn't return any data, it will
return an empty in list context or undef on scalar context. If the parser
failed, it will die.

The parsing itself is done by an external program (searched in the
following list of directories: $opt{libdir},
/usr/local/lib/dpkg/parsechangelog, /usr/lib/dpkg/parsechangelog) That
program is named according to the format that it's able to parse. By
default it's either "debian" or the format name lookep up in the 40 last
lines of the changelog itself (extracted with this perl regular expression
"\schangelog-format:\s+([0-9a-z]+)\W"). But it can be overriden
with $opt{changelogformat}. The program expects the content of the
changelog file on its standard input.

The changelog file that is parsed is debian/changelog by default but it
can be overriden with $opt{file}.

All the other keys in %opt are forwarded as parameter to the external
parser. If the key starts with "-", it's passed as is. If not, it's passed
as "--<key>". If the value of the corresponding hash entry is defined, then
it's passed as the parameter that follows.

=cut

sub changelog_parse {
    my (%options) = @_;
    my @parserpath = ("/usr/local/lib/dpkg/parsechangelog",
                      "$dpkglibdir/parsechangelog",
                      "/usr/lib/dpkg/parsechangelog");
    my $format = "debian";
    my $changelogfile = "debian/changelog";
    my $force = 0;

    # Extract and remove options that do not concern the changelog parser
    # itself (and that we shouldn't forward)
    if (exists $options{"libdir"}) {
	unshift @parserpath, $options{"libdir"};
	delete $options{"libdir"};
    }
    if (exists $options{"file"}) {
	$changelogfile = $options{"file"};
	delete $options{"file"};
    }
    if (exists $options{"changelogformat"}) {
	$format = $options{"changelogformat"};
	delete $options{"changelogformat"};
	$force = 1;
    }

    # Extract the format from the changelog file if possible
    unless($force or ($changelogfile eq "-")) {
	open(P, "-|", "tail", "-n", "40", $changelogfile);
	while(<P>) {
	    $format = $1 if m/\schangelog-format:\s+([0-9a-z]+)\W/;
	}
	close(P) or subprocerr(_g("tail of %s"), $changelogfile);
    }

    # Find the right changelog parser
    my $parser;
    foreach my $dir (@parserpath) {
        my $candidate = "$dir/$format";
	next if not -e $candidate;
	if (-x _) {
	    $parser = $candidate;
	    last;
	} else {
	    warning(_g("format parser %s not executable"), $candidate);
	}
    }
    error(_g("changelog format %s is unknown"), $format) if not defined $parser;

    # Create the arguments for the changelog parser
    my @exec = ($parser, "-l$changelogfile");
    foreach (keys %options) {
	if (m/^-/) {
	    # Options passed untouched
	    push @exec, $_;
	} else {
	    # Non-options are mapped to long options
	    push @exec, "--$_";
	}
	push @exec, $options{$_} if defined($options{$_});
    }

    # Fork and call the parser
    my $pid = open(P, "-|");
    syserr(_g("fork for %s"), $parser) unless defined $pid;
    if (not $pid) {
	if ($changelogfile ne "-") {
	    open(STDIN, "<", $changelogfile) or
		syserr(_g("cannot open %s"), $changelogfile);
	}
	exec(@exec) || syserr(_g("cannot exec format parser: %s"), $parser);
    }

    # Get the output into several Dpkg::Control objects
    my (@res, $fields);
    while (1) {
        $fields = Dpkg::Control::Changelog->new();
        last unless $fields->parse_fh(\*P, _g("output of changelog parser"));
	push @res, $fields;
    }
    close(P) or subprocerr(_g("changelog parser %s"), $parser);
    if (wantarray) {
	return @res;
    } else {
	return $res[0] if (@res);
	return undef;
    }
}

1;
