1 files changed, 75 insertions, 0 deletions
diff --git a/lib/irb/command/help.rb b/lib/irb/command/help.rb
new file mode 100644
index 0000000000..1ed7a7707c
--- /dev/null
+++ b/lib/irb/command/help.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+module IRB
+  module Command
+    class Help < Base
+      category "Help"
+      description "List all available commands. Use `help <command>` to get information about a specific command."
+
+      def execute(command_name)
+        content =
+          if command_name.empty?
+            help_message
+          else
+            if command_class = Command.load_command(command_name)
+              command_class.help_message || command_class.description
+            else
+              "Can't find command `#{command_name}`. Please check the command name and try again.\n\n"
+            end
+          end
+        Pager.page_content(content)
+      end
+
+      private
+
+      def help_message
+        commands_info = IRB::Command.all_commands_info
+        helper_methods_info = IRB::HelperMethod.all_helper_methods_info
+        commands_grouped_by_categories = commands_info.group_by { |cmd| cmd[:category] }
+        commands_grouped_by_categories["Helper methods"] = helper_methods_info
+
+        user_aliases = irb_context.instance_variable_get(:@user_aliases)
+
+        commands_grouped_by_categories["Aliases"] = user_aliases.map do |alias_name, target|
+          { display_name: alias_name, description: "Alias for `#{target}`" }
+        end
+
+        if irb_context.with_debugger
+          # Remove the original "Debugging" category
+          commands_grouped_by_categories.delete("Debugging")
+          # Add an empty "Debugging (from debug.gem)" category at the end
+          commands_grouped_by_categories["Debugging (from debug.gem)"] = []
+        end
+
+        longest_cmd_name_length = commands_info.map { |c| c[:display_name].length }.max
+
+        output = StringIO.new
+
+        help_cmds = commands_grouped_by_categories.delete("Help")
+
+        add_category_to_output("Help", help_cmds, output, longest_cmd_name_length)
+
+        commands_grouped_by_categories.each do |category, cmds|
+          add_category_to_output(category, cmds, output, longest_cmd_name_length)
+        end
+
+        # Append the debugger help at the end
+        if irb_context.with_debugger
+          output.puts DEBUGGER__.help
+        end
+
+        output.string
+      end
+
+      def add_category_to_output(category, cmds, output, longest_cmd_name_length)
+        output.puts Color.colorize(category, [:BOLD])
+
+        cmds.each do |cmd|
+          output.puts "  #{cmd[:display_name].to_s.ljust(longest_cmd_name_length)}    #{cmd[:description]}"
+        end
+
+        output.puts
+      end
+    end
+  end
+end