Start implementing a Dockerfile parser

Build/Docker.pm

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+################################################################
+#
+# Copyright (c) 2017 SUSE Linux Products GmbH
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or 3 as
+# published by the Free Software Foundation.
+#
+# 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 (see the file COPYING); if not, write to the
+# Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+#
+################################################################
+
+# TODO:
+# - parse Dockerfile and extract dependecies
+# - start docker daemon
+# - import base image to the docker daemon
+# - setup the dependencies directory
+# - setup a zypper repository that will serve the dependecies directory
+# - inject this repository as and ARG in the Dockerfile
+# - build the Dockerfile
+# - export the image tarball [OPTIONAL]
+
+package Build::Dockerimage;
+
+use strict;
+
+sub parse {
+  my ($cf, $fn) = @_;
+
+  # Perl slurp mode
+  local $/=undef;
+  open DOCKERFILE, $fn or die "Couldn't open Dockefile";
+  my $dockerfile_data = <DOCKERFILE>;
+  close DOCKERFILE;
+
+  # Remove all whitespace from end of lines to make parsing easier
+  $dockerfile_data =~ s/[^\S\n\r]+$//gm;
+
+  my @deps = ();
+  my $pkg_string;
+
+  # Match from start of line until an end of line which doesn't have a backslash
+  # as the last character (Negative lookbehind).
+  # That would mean, continue to the next line. E.g.
+  # RUN obs_install package1 package2 \
+  #   package3
+  while ($dockerfile_data =~ /^\s*RUN\s+obs_install\s+((.|\n|\r)*?)(?<!\\)$/gm) {
+    $pkg_string = $1;
+
+    # Remove the Dockerfile escape character and merge multiple lines in one
+    $pkg_string =~ s/\\(\n|\r)*//gm;
+
+    # Make sure we only match obs_install arguments and not any commands that
+    # follow. E.g.
+    # RUN obs_install vim && do_something_else
+    $pkg_string =~ s/(.*?)[;&].*/$1/;
+
+    my @packages = split(/\s+/, $pkg_string);
+    if (0+@packages != 0) { push @deps, @packages; }
+  }
+
+  print STDERR "Dependencies: @deps \n";
+
+  my $ret = {};
+  $ret->{'deps'} = \@deps;
+
+  return $ret;
+}
+
+1;