Grooming. Preparations for future features.

src/backends.cr

@@ -0,0 +1,61 @@
+require "./quadruplet.cr"
+
+abstract class RootFS::Backend
+	class_getter name : String = ""
+
+	def name : String
+		@@name
+	end
+
+	# FIXME: Remove @application once `def execute` is moved in the current
+	#        class.
+	def initialize(@directory : String, @application : ::RootFS::RootFS)
+	end
+
+	abstract def create!(architecture : String?, version : String?, variant : String?)
+	#abstract def add_package(name : String)
+	#abstract def remove_package(name : String)
+
+	class_property all = Array(::RootFS::Backend.class).new
+
+	macro register(name)
+		class ::RootFS::Backend::{{name.camelcase.id}} < ::RootFS::Backend
+			def self.name : String
+				{{name}}
+			end
+
+			{{yield}}
+		end
+
+		::RootFS::Backend.all << ::RootFS::Backend::{{name.camelcase.id}}
+	end
+end
+
+RootFS::Backend.register "debian" do
+	class_getter name : String = "debian"
+
+	def create!(architecture = nil, version = nil, variant = nil)
+		version      = version      || "buster"
+		architecture = architecture || "amd64"
+
+		@application.execute "debootstrap --arch '#{architecture}' '#{version}' '#{@directory}'"
+	end
+end
+
+RootFS::Backend.register "alpine" do
+	def create!(architecture = nil, version = nil, variant = nil)
+		version = version || "latest-stable"
+
+		if version == "latest"
+			version = "latest-stable"
+		elsif version == "latest-stable" || version == "edge"
+		else
+			version = "v" + version
+		end
+
+		arch = architecture || "x86_64"
+
+		@application.execute "apk --arch '#{arch}' -X http://dl-cdn.alpinelinux.org/alpine/#{version}/main/ -U --allow-untrusted --root '#{@directory}' --initdb add alpine-base"
+	end
+end
+

src/main.cr

@@ -2,6 +2,9 @@ require "colorize"
 require "option_parser"
 require "file_utils"
 
+require "./quadruplet.cr"
+require "./backends.cr"
+
 # Not currently used. Waiting for API updates.
 #require "baguette-crystal-base"
 
@@ -141,11 +144,7 @@ class RootFS::RootFS
 	end
 
 	protected def create!(template : String)
-		template_as_array = template.split /-/
-
-		template_name = template_as_array[0].downcase
-		template_version = template_as_array[1]?
-		template_architecture = template_as_array[2]?
+		quadruplet = Quadruplet.new template
 
 		is_btrfs = true # FIXME: do the actual detection
 
@@ -153,27 +152,17 @@ class RootFS::RootFS
 			raise "can only create rootfs in a btrfs filesystem"
 		end
 
+		unless backend = Backend.all.find &.name.==(quadruplet.name)
+			error "unrecognized quadruplet name: #{quadruplet.name}"
+			exit 2
+		end
+
 		execute "btrfs subvolume create '#{@directory}'"
 
-		if template_name == "debian"
-			version = template_version || "buster"
+		# FIXME: We should homogeneize quadruplet components.
+		backend.new(@directory, self).create! quadruplet.architecture, quadruplet.version, quadruplet.variant
 
-			execute "debootstrap --arch amd64 '#{version}' '#{@directory}'"
-		elsif template_name == "alpine"
-			version = template_version || "latest-stable"
-
-			if version == "latest"
-				version = "latest-stable"
-			elsif version == "latest-stable" || version == "edge"
-			else
-				version = "v" + version
-			end
-
-			# FIXME: We should homogeneize triplets.
-			arch = template_architecture || "x86_64"
-
-			execute "apk --arch '#{arch}' -X http://dl-cdn.alpinelinux.org/alpine/#{version}/main/ -U --allow-untrusted --root '#{@directory}' --initdb add alpine-base"
-		end
+		File.write template, "#{@directory}/rootfs"
 	end
 
 	def self.load(directory)

src/quadruplet.cr

@@ -0,0 +1,15 @@
+class RootFS::Quadruplet
+	getter name         : String
+	getter version      : String?
+	getter architecture : String?
+	getter variant      : String?
+
+	def initialize(template : String)
+		template_as_array = template.split /-/
+
+		@name         = template_as_array[0].downcase
+		@version      = template_as_array[1]?
+		@architecture = template_as_array[2]?
+		@variant      = template_as_array[3]?
+	end
+end