Implement basic CLI usage help

lib/uh/wm/cli.rb

@@ -1,13 +1,56 @@
 module Uh
   module WM
     class CLI
+      ArgumentError = Class.new(ArgumentError)
+
+      USAGE = "Usage: #{File.basename $0} [options]".freeze
+
+      EX_USAGE = 64
+
       class << self
-        def run! arguments
-          $stdout.sync = true
-          @display = Display.new
-          @display.open
-          puts "Connected to X server on `#{display}'"
-          sleep 8
+        def run arguments, **options
+          cli = new arguments, **options
+          cli.parse_arguments!
+          cli.run
+        rescue ArgumentError => e
+          $stderr.puts e
+          exit EX_USAGE
+        end
+      end
+
+      def initialize args, stdin: $stdin, stdout: $stdout, stderr: $stderr
+        @arguments  = args
+        @stdin      = stdin
+        @stdout     = stdout
+        @stderr     = stderr
+      end
+
+      def parse_arguments!
+        option_parser.parse! @arguments
+      rescue OptionParser::InvalidOption => e
+        fail ArgumentError, option_parser
+      end
+
+      def run
+        @stdout.sync = true
+        @display = Display.new
+        @display.open
+        @stdout.puts "Connected to X server on `#{@display}'"
+      end
+
+
+      private
+
+      def option_parser
+        OptionParser.new do |opts|
+          opts.banner = USAGE
+          opts.separator ''
+          opts.separator 'options:'
+
+          opts.on '-h', '--help', 'print this message' do
+            @stdout.print opts
+            exit
+          end
         end
       end
     end