Add Debian RFC822 parser

app/services/packages/debian/parse_debian822_service.rb

+# frozen_string_literal: true
+
+module Packages
+  module Debian
+    # Parse String as Debian RFC822 control data format
+    # https://manpages.debian.org/unstable/dpkg-dev/deb822.5
+    class ParseDebian822Service
+      InvalidDebian822Error = Class.new(StandardError)
+
+      def initialize(input)
+        @input = input
+      end
+
+      def execute
+        output = {}
+        @input.each_line('', chomp: true) do |block|
+          section = {}
+          section_name, field = nil
+          block.each_line(chomp: true) do |line|
+            next if comment_line?(line)
+
+            if continuation_line?(line)
+              raise InvalidDebian822Error, "Parse error. Unexpected continuation line" if field.nil?
+
+              section[field] += "\n"
+              section[field] += line[1..] unless paragraph_separator?(line)
+            elsif match = match_section_line(line)
+              section_name = match[:name] if section_name.nil?
+              field = match[:field].to_sym
+
+              raise InvalidDebian822Error, "Duplicate field '#{field}' in section '#{section_name}'" if section.include?(field)
+
+              section[field] = match[:value]
+            else
+              raise InvalidDebian822Error, "Parse error on line #{line}"
+            end
+          end
+
+          raise InvalidDebian822Error, "Duplicate section '#{section_name}'" if output[section_name]
+
+          output[section_name] = section
+        end
+
+        output
+      end
+
+      private
+
+      def comment_line?(line)
+        line.match?(/^#/)
+      end
+
+      def continuation_line?(line)
+        line.match?(/^ /)
+      end
+
+      def paragraph_separator?(line)
+        line == ' .'
+      end
+
+      def match_section_line(line)
+        line.match(/(?<name>(?<field>^\S+):\s*(?<value>.*))/)
+      end
+    end
+  end
+end

spec/services/packages/debian/parse_debian822_service_spec.rb

+# frozen_string_literal: true
+require 'spec_helper'
+
+RSpec.describe Packages::Debian::ParseDebian822Service do
+  subject { described_class.new(input) }
+
+  context 'with dpkg-deb --field output' do
+    let(:input) do
+      <<~HEREDOC
+        Package: libsample0
+        Source: sample
+        Version: 1.2.3~alpha2
+        Architecture: amd64
+        Maintainer: John Doe <john.doe@example.com>
+        Installed-Size: 9
+        Section: libs
+        Priority: optional
+        Multi-Arch: same
+        Homepage: https://gitlab.com/
+        Description: Some mostly empty lib
+         Used in GitLab tests.
+         .
+         Testing another paragraph.
+      HEREDOC
+    end
+
+    it 'return as expected, preserving order' do
+      expected = {
+        'Package: libsample0' => {
+          'Package': 'libsample0',
+          'Source': 'sample',
+          'Version': '1.2.3~alpha2',
+          'Architecture': 'amd64',
+          'Maintainer': 'John Doe <john.doe@example.com>',
+          'Installed-Size': '9',
+          'Section': 'libs',
+          'Priority': 'optional',
+          'Multi-Arch': 'same',
+          'Homepage': 'https://gitlab.com/',
+          'Description': "Some mostly empty lib\nUsed in GitLab tests.\n\nTesting another paragraph."
+        }
+      }
+
+      expect(subject.execute.to_s).to eq(expected.to_s)
+    end
+  end
+
+  context 'with control file' do
+    let(:input) { fixture_file('packages/debian/sample/debian/control') }
+
+    it 'return as expected, preserving order' do
+      expected = {
+        'Source: sample' => {
+          'Source': 'sample',
+          'Priority': 'optional',
+          'Maintainer': 'John Doe <john.doe@example.com>',
+          'Build-Depends': 'debhelper-compat (= 13)',
+          'Standards-Version': '4.5.0',
+          'Section': 'libs',
+          'Homepage': 'https://gitlab.com/',
+          # 'Vcs-Browser': 'https://salsa.debian.org/debian/sample-1.2.3',
+          # '#Vcs-Git': 'https://salsa.debian.org/debian/sample-1.2.3.git',
+          'Rules-Requires-Root': 'no'
+        },
+        'Package: sample-dev' => {
+          'Package': 'sample-dev',
+          'Section': 'libdevel',
+          'Architecture': 'any',
+          'Multi-Arch': 'same',
+          'Depends': 'libsample0 (= ${binary:Version}), ${misc:Depends}',
+          'Description': "Some mostly empty developpement files\nUsed in GitLab tests.\n\nTesting another paragraph."
+        },
+        'Package: libsample0' => {
+          'Package': 'libsample0',
+          'Architecture': 'any',
+          'Multi-Arch': 'same',
+          'Depends': '${shlibs:Depends}, ${misc:Depends}',
+          'Description': "Some mostly empty lib\nUsed in GitLab tests.\n\nTesting another paragraph."
+         },
+         'Package: sample-udeb' => {
+           'Package': 'sample-udeb',
+           'Package-Type': 'udeb',
+           'Architecture': 'any',
+           'Depends': 'installed-base',
+           'Description': 'Some mostly empty udeb'
+         }
+      }
+
+      expect(subject.execute.to_s).to eq(expected.to_s)
+    end
+  end
+
+  context 'with empty input' do
+    let(:input) { '' }
+
+    it 'return a empty hash' do
+      expect(subject.execute).to eq({})
+    end
+  end
+
+  context 'with unexpected continuation line' do
+    let(:input) { ' continuation' }
+
+    it 'raise error' do
+      expect {subject.execute}.to raise_error(described_class::InvalidDebian822Error, 'Parse error. Unexpected continuation line')
+    end
+  end
+
+  context 'with duplicate field' do
+    let(:input) do
+      <<~HEREDOC
+        Package: libsample0
+        Source: sample
+        Source: sample
+      HEREDOC
+    end
+
+    it 'raise error' do
+      expect {subject.execute}.to raise_error(described_class::InvalidDebian822Error, "Duplicate field 'Source' in section 'Package: libsample0'")
+    end
+  end
+
+  context 'with incorrect input' do
+    let(:input) do
+      <<~HEREDOC
+        Hello
+      HEREDOC
+    end
+
+    it 'raise error' do
+      expect {subject.execute}.to raise_error(described_class::InvalidDebian822Error, 'Parse error on line Hello')
+    end
+  end
+
+  context 'with duplicate section' do
+    let(:input) do
+      <<~HEREDOC
+        Package: libsample0
+
+        Package: libsample0
+      HEREDOC
+    end
+
+    it 'raise error' do
+      expect {subject.execute}.to raise_error(described_class::InvalidDebian822Error, "Duplicate section 'Package: libsample0'")
+    end
+  end
+end