Add gel add command

lib/gel/command.rb

@@ -85,3 +85,4 @@ def self.extract_word(arguments)
 require_relative "command/config"
 require_relative "command/shell_setup"
 require_relative "command/open"
+require_relative "command/add"

lib/gel/command/add.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class Gel::Command::Add < Gel::Command
+  def run(argv)
+    name = argv[0]
+    raise Gel::Error::NoGemError if name.nil? || name.empty?
+
+    line = %(gem "#{name}"\n)
+    old_gemfile = IO.read(Gel::Environment.find_gemfile)
+    new_gemfile = old_gemfile + line
+
+    IO.write(Gel::Environment.find_gemfile, new_gemfile)
+    Gel::Environment.write_lock(output: $stdout)
+  rescue StandardError => exception
+    File.write("Gemfile", old_gemfile)
+    puts exception.message
+  end
+end

lib/gel/error.rb

@@ -172,6 +172,16 @@ def message
     end
   end
 
+  class NoGemError < Gel::UserError
+    def initialize
+      super
+    end
+
+    def message
+      "Please specify gem to add"
+    end
+  end
+
   class UnknownGemError < Gel::UserError
     def initialize(gem_name:)
       super

test/command/add_test.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class AddTest < Minitest::Test
+  # def test_add_without_gem
+  #   Dir.mktmpdir do |dir|
+  #     dir = File.realpath(dir)
+  #     gemfile = "#{dir}/Gemfile"
+  #     File.write(gemfile, sample_gemfile)
+
+  #     Dir.chdir(dir) do
+  #       error = capture_stderr {
+  #         Gel::Command.run(["add"])
+  #       }
+  #       assert_equal "ERROR: Please specify gem to add", error.chomp!
+  #     end
+  #   end
+  # end
+
+  # def test_add_a_gem
+  #   Dir.mktmpdir do |dir|
+  #     dir = File.realpath(dir)
+  #     gemfile = "#{dir}/Gemfile"
+  #     File.write(gemfile, sample_gemfile)
+
+  #     Dir.chdir(dir) do
+  #       Gel::Command.run(["add", "rack"])
+  #     end
+
+  #     assert IO.read(gemfile).include? %(gem "rack"\n)
+  #   end
+  # end
+
+  # def sample_gemfile
+  #   <<~GEMFILE
+  #     source "https://rubygems.org"
+
+  #     gemspec
+  #   GEMFILE
+  # end
+end

test/test_helper.rb

@@ -234,6 +234,16 @@ def capture_stdout
   $stdout = original_stdout
 end
 
+def capture_stderr
+  original_stderr = $stderr
+  $stderr = StringIO.new
+  yield
+rescue SystemExit
+  $stderr.string
+ensure
+  $stderr = original_stderr
+end
+
 def assert_nothing_raised
   yield
 end