Suggest commands by Levenshtein distance

deps/rabbitmq_cli/lib/rabbitmq/cli/core/parser.ex

@@ -16,7 +16,8 @@
 alias RabbitMQ.CLI.Core.CommandModules, as: CommandModules
 
 defmodule RabbitMQ.CLI.Core.Parser do
-  alias RabbitMQ.CLI.Core.Helpers, as: Helpers
+
+  @levenshtein_distance_limit 5
 
   @spec parse(String.t) :: {command :: :no_command | atom(),
                             command_name :: String.t,
@@ -33,6 +34,8 @@ defmodule RabbitMQ.CLI.Core.Parser do
     case command_module do
       nil ->
         {:no_command, command_name, arguments, options, invalid};
+      {:suggest, _} = suggest ->
+        {suggest, command_name, arguments, options, invalid};
       command_module when is_atom(command_module) ->
         {[^command_name | cmd_arguments], cmd_options, cmd_invalid} =
           parse_command_specific(input, command_module)
@@ -43,12 +46,35 @@ defmodule RabbitMQ.CLI.Core.Parser do
   defp look_up_command(parsed_args) do
     case parsed_args do
       [cmd_name | arguments] ->
-        {cmd_name, CommandModules.module_map[cmd_name], arguments}
+        module_map = CommandModules.module_map
+        command = case module_map[cmd_name] do
+          nil     -> closest_similar_command(cmd_name, module_map)
+          command -> command
+        end
+        {cmd_name, command, arguments}
       [] ->
         {"", nil, []}
     end
   end
 
+  defp closest_similar_command(_cmd_name, empty) when empty == %{} do
+    nil
+  end
+  defp closest_similar_command(cmd_name, module_map) do
+    suggestion = module_map
+                 |> Map.keys
+                 |> Enum.map(fn(cmd) ->
+                      {cmd, Simetric.Levenshtein.compare(cmd, cmd_name)}
+                    end)
+                 |> Enum.min_by(fn({_,distance}) -> distance end)
+    case suggestion do
+      {cmd, distance} when distance < @levenshtein_distance_limit ->
+        {:suggest, cmd};
+      _ ->
+        nil
+    end
+  end
+
   def parse_command_specific(input, command) do
     switches = build_switches(default_switches(), command)
     aliases = build_aliases(default_aliases(), command)

deps/rabbitmq_cli/lib/rabbitmqctl.ex

@@ -36,11 +36,14 @@ defmodule RabbitMQCtl do
   end
   def main(unparsed_command) do
     {command, command_name, arguments, parsed_options, invalid} = parse(unparsed_command)
-
     case {command, invalid} do
       {:no_command, _} ->
         usage_string = HelpCommand.all_usage()
         {:error, ExitCodes.exit_usage, usage_string};
+      {{:suggest, suggested}, _} ->
+        suggest_message = "Command '#{command_name}' not found."<>
+                          " Did you mean '#{suggested}'?"
+        {:error, ExitCodes.exit_usage, suggest_message};
       {_, [_|_]} ->
         validation_error({:bad_option, invalid}, command_name, unparsed_command);
       _ ->
@@ -225,10 +228,6 @@ defmodule RabbitMQCtl do
   end
   defp format_validation_error(err, _), do: inspect err
 
-  defp command_flags(command) do
-    apply_if_exported(command, :switches, [], []) |> Keyword.keys
-  end
-
   defp exit_program(code) do
     :net_kernel.stop
     exit({:shutdown, code})

deps/rabbitmq_cli/mix.exs

@@ -110,16 +110,10 @@ defmodule RabbitMQCtl.MixfileBase do
         compile: make,
         override: true
       },
-      {
-        :amqp, "~> 0.1.5",
-        only: :test
-      },
-      {
-        :json, "~> 1.0.0"
-      },
-      {
-        :csv, "~> 1.4.2"
-      }
+      {:amqp, "~> 0.1.5", only: :test},
+      {:json, "~> 1.0.0"},
+      {:csv, "~> 1.4.2"},
+      {:simetric, "~> 0.1.0"}
     ]
   end