#!/usr/bin/perl
#
# Copyright (C) 2007-2008 Canonical, Ltd.,
#               2011,     Stefano Rivera <stefanor@ubuntu.com>
# Author: Kees Cook <kees@ubuntu.com>
#
# ##################################################################
#
# 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 3
# 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.
#
# See file /usr/share/common-licenses/GPL for more details.
#
# ##################################################################
#
# This script is used to repeat a change log into an older release.  It
# expects that --build-tree is laid out with each Ubuntu release as a
# separate directory ("feisty", "edgy", etc).
#
# For example, if gimp had a security update prepared for Feisty in
# $TREE/feisty/gimp-2.2.13, running "dch-repeat" in
# $TREE/edgy/gimp-2.2.13 would pull in the latest changelog from the Feisty
# build.

use strict;
use warnings;
use Getopt::Long;
use Cwd;
use File::Glob ':glob';

sub Usage
{
    print <<EOM;
Usage: $0 [OPTIONS]
 --build-tree PATH             Base of build trees
 -s, --source-release RELEASE  Which release to snag a changelog from
 --target-release RELEASE      Which release to build into
 --devel-release RELEASE       Which release is the devel release
 --pocket POCKET               Which pocket to use
EOM
    exit(0);
}

my @releases = undef;
our $devel_release = undef;

#Getopt::Long::Configure("bundling", "no_ignore_case");
our $opt_build_tree = "/scratch/ubuntu/build";
our $opt_pocket = undef;
our $opt_package = undef;
our $opt_source_release = undef;
our $opt_target_release = undef;

our $opt_help = undef;
our $opt_verbose = undef;

Usage() unless (GetOptions(
    "build-tree=s",
    "source-release|s=s",
    "target-release=s",
    "package|p=s",
    "help|h",
    "verbose|v",
));
Usage() if ($opt_help);

@releases = split(/\s+/, `ubuntu-distro-info --supported`);
$devel_release = `ubuntu-distro-info --devel`;
chomp($devel_release);

sub get_changelog($)
{
    my ($path) = @_;

    open(LOG,"<$path/debian/changelog") || die "Cannot find changelog for '$path'\n";
    my $log="";
    my $line="";
    # Skip to package name
    $line = <LOG>;
    # Collect changelog
    while ($line=<LOG>) {
        last if ($line=~/^\S/); # Stop on next changelog entry
        $log.=$line;
    }
    close(LOG);
    return $log;
}

sub replace_changelog($)
{
    my ($log) = @_;
    open(LOG,"<debian/changelog") || die "Cannot find changelog\n";
    open(NEWLOG,">debian/changelog.new") || die "Cannot write changelog\n";
    my $line;
    while ($line=<LOG>) {
        last if ($line =~ /^\s*$/);
        print NEWLOG $line || die "Changelog write failed: $!\n";
    }
    print NEWLOG $log || die "Changelog write failed: $!\n";
    # Skip log items
    while ($line=<LOG>) {
        last if ($line =~ /^\S/);
    }
    print NEWLOG $line || die "Changelog write failed: $!\n";
    while ($line=<LOG>) {
        print NEWLOG $line || die "Changelog write failed: $!\n";
    }
    close(LOG);
    close(NEWLOG) || die "Changelog close failed: $!\n";
    rename("debian/changelog.new","debian/changelog") || die "Changelog rename failed: $!\n";
}

# By default examine Cwd for target release
if (!defined($opt_target_release)) {
    my $dir = getcwd;
    if ($dir =~ m#^$opt_build_tree/([^/]+)/[^/]+$#) {
        $opt_target_release = $1;
    }
    else {
        die "No --target-release used, or current directory '$dir' outside of --build-tree of '$opt_build_tree'\n";
    }
}
warn "target-release: '$opt_target_release'\n" if ($opt_verbose);

# By default, examine changelog for package
if (!defined($opt_package)) {
    chomp($opt_package=`dpkg-parsechangelog | grep ^"Source: " | cut -d" " -f2`);
    if ($opt_package eq "") {
        die "Cannot figure out package name from changelog\n";
    }
}
warn "package: '$opt_package\n" if ($opt_verbose);

# By default, take changelog from newer release
if (!defined($opt_source_release)) {
    if ($opt_target_release eq $devel_release) {
        die "No more recent release than '$devel_release' to take changelog from\n";
    }
    foreach my $i (0 .. $#releases) {
        if ($releases[$i] eq $opt_target_release) {
            $opt_source_release = $releases[$i+1];
        }
    }
    if (!defined($opt_source_release)) {
        die "Could not locate a newer release than '$releases[$#releases]'";
    }
}
warn "source-release: '$opt_source_release\n" if ($opt_verbose);
warn "devel-release: '$devel_release\n" if ($opt_verbose);

# By default, use "security" pocket for non-devel releases
if (!defined($opt_pocket)) {
    if ($opt_target_release eq $devel_release) {
        $opt_pocket = "";
    }
    else {
        $opt_pocket = "security";
    }
}
warn "pocket: '$opt_pocket'\n" if ($opt_verbose);

# Source location
my @dirs = grep((-d $_),bsd_glob("$opt_build_tree/$opt_source_release/$opt_package-*"));
if (scalar(@dirs)==0) {
    die "Cannot find '$opt_build_tree/$opt_source_release/$opt_package-*'\n";
}
elsif (scalar(@dirs)>1) {
    warn "Multiple possible source dirs, using '$dirs[0]'\n";
}
warn "source dir: '$dirs[0]'\n" if ($opt_verbose);
my $log = get_changelog($dirs[0]);
my $args = "";
if ($opt_pocket ne "") {
    $args = "-s -D $opt_target_release-$opt_pocket";
}
else {
    $args = "-i";
}
system("dch $args auto-changelog")==0 || die "dch failed: $!\n";
replace_changelog($log);

# Report!
system("dpkg-parsechangelog");

exit(0);