1 files changed, 147 insertions, 0 deletions
diff --git a/bin/apt-why b/bin/apt-why
new file mode 100755
index 0000000..b9df057
--- /dev/null
+++ b/bin/apt-why
@@ -0,0 +1,147 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+use AptPkg::Cache;
+use Switch;
+
+my $cache = AptPkg::Cache->new;
+my $packagename = pop or dir("No packagename given");
+my $query = shift || '';
+my $package = $cache->{$packagename};
+
+unless($package) {
+	print STDERR "E: Package not found: $packagename\n";
+	exit(100);
+}
+
+sub revdeps {
+	my $rdepsref = shift;
+	my $depsref;
+	my $parent;
+
+	foreach(@$rdepsref) {
+		undef($parent);
+		$parent->{name} = $_->{ParentPkg}{Name};
+		$parent->{ver} = $_->{ParentVer}{VerStr};
+		$parent->{current_state} = $cache->{$_->{ParentPkg}{Name}}->{CurrentState};
+		$parent->{selected_state} = $cache->{$_->{ParentPkg}{Name}}->{SelectedState};
+		$parent->{deptype} = $_->{DepType};
+		$parent->{targetname} = $_->{TargetPkg}{Name};
+		if ($_->{TargetVer}) {
+			$parent->{depsign} = $_;
+			$parent->{depver} = $_;
+		}
+		$depsref->{$parent->{name}} = $parent;
+	}
+	return($depsref);
+}
+
+sub why {
+	my $revdeps = revdeps(shift);
+	my $why;
+	foreach(keys(%$revdeps)) {
+		if ($revdeps->{$_}->{current_state} eq 'Installed' and $revdeps->{$_}->{deptype} !~ /^(Conflicts|Replaces|Obsoletes)$/) {
+			$why->{$_} = $revdeps->{$_};
+		}
+	}
+	return($why);
+}
+
+sub why_not {
+	my $revdeps = revdeps(shift);
+	my $why_not;
+	foreach(keys(%$revdeps)) {
+		if ($revdeps->{$_}->{current_state} eq 'Installed' and $revdeps->{$_}->{deptype} =~ /^(Conflicts|Replaces|Obsoletes)$/) {
+			$why_not->{$_} = $revdeps->{$_};
+		}
+	}
+	return($why_not);
+}
+
+sub short_states {
+	my $pkg = shift;
+	my $state = '';
+	switch($pkg->{selected_state}) {
+		case('Unkwnon') {
+			$state .= ' ';
+		} case('Install') {
+			$state .= 'i';
+		} case('Hold') {
+			$state .= 'h';
+		} case('DeInstall') {
+			$state .= 'r';
+		} case('Purge') {
+			$state .= 'p';
+		}
+	}
+	switch($pkg->{current_state}) {
+		case('Installed') {
+			$state .= 'i';
+		} case('UnPacked') {
+			$state .= 'u';
+		} case('HalfConfigured') {
+			$state .= 'f';
+		} case('HalfInstalled') {
+			$state .= 'h';
+		} case('ConfigFiles') {
+			$state .= 'c';
+		} case('NotInstalled') {
+			$state .= ' ';
+		}
+	}
+	return($state);
+}
+
+
+sub print_deps {
+	my $deps = shift;
+	foreach(keys(%$deps)) {
+		printf "%-2s  %-30s %-15s %s\n", short_states($deps->{$_}), $deps->{$_}->{name}, $deps->{$_}->{deptype}, $deps->{$_}->{targetname};
+	}
+}
+
+if ($query eq 'not') {
+	print_deps(why_not($package->{RevDependsList}));
+} else {
+	print_deps(why($package->{RevDependsList}));
+}
+
+__END__
+
+=head1 NAME
+
+apt-perl - reverse dependency displayer using AptPkg::Cache
+
+=head1 SYNOPSIS
+
+B<apt-perl> I<command> I<package>
+
+=head1 DESCRIPTION
+
+B<apt-perl> displays various informations based on a I<package>s reverse
+dependencies
+
+The output is prefixed by two charactes, the former representing the desired
+package state, the latter the current state.
+
+The states are I<i>nstall, I<h>old, I<r>emove (deinstall), I<p>urge,
+I<u>npacked, halI<f> configured, I<h>alf installed, I<c>onfigfiles installed.
+An empty field means not installed.
+
+I<command> may be one of:
+
+=over
+
+=item why
+
+Show dependencies that justify the installation of a package
+
+=item why-not
+
+Show dependencies that prohibit the installation of a package
+
+=item rdeps
+
+Show all reverse dependencies of a package
+
+=back