feat(command): add Excache.Command.Introspection and commandNames

lib/excache/command/introspection.ex

@@ -0,0 +1,91 @@
+defmodule Excache.Command.Introspection do
+  @moduledoc false
+
+  alias Excache.Command.Introspection.Catalog
+  alias Excache.Command.Introspection.Client
+  alias Excache.Command.Introspection.Info
+
+  @names ~w(INFO CLIENT COMMAND)
+
+  def commandNames, do: @names
+
+  def dispatch("INFO", args, state), do: {[{:bulk, Info.render(args)}], state}
+
+  def dispatch("CLIENT", [subcommand | rest], state),
+    do: Client.dispatch(String.upcase(subcommand), rest, state)
+
+  def dispatch("CLIENT", [], state), do: {[wrongArity("client")], state}
+
+  def dispatch("COMMAND", [], state), do: {[fullTable()], state}
+
+  def dispatch("COMMAND", [subcommand | rest], state),
+    do: command(String.upcase(subcommand), rest, state)
+
+  defp command("COUNT", [], state), do: {[{:integer, Catalog.count()}], state}
+
+  defp command("LIST", [], state) do
+    {[{:array, Enum.map(Catalog.names(), fn name -> {:bulk, String.downcase(name)} end)}], state}
+  end
+
+  defp command("INFO", [], state), do: {[fullTable()], state}
+
+  defp command("INFO", names, state) do
+    {[{:array, Enum.map(names, fn name -> Catalog.infoTerm(String.upcase(name)) end)}], state}
+  end
+
+  defp command("DOCS", [], state) do
+    {[{:array, Enum.flat_map(Catalog.names(), &docsEntry/1)}], state}
+  end
+
+  defp command("DOCS", names, state) do
+    entries =
+      names
+      |> Enum.map(&String.upcase/1)
+      |> Enum.filter(&Catalog.known?/1)
+      |> Enum.flat_map(&docsEntry/1)
+
+    {[{:array, entries}], state}
+  end
+
+  defp command("GETKEYS", [name | args], state) do
+    {[getkeys(String.upcase(name), args)], state}
+  end
+
+  defp command("GETKEYS", [], state), do: {[wrongArity("command|getkeys")], state}
+
+  defp command(subcommand, _args, state) do
+    {[
+       {:error,
+        "ERR Unknown subcommand or wrong number of arguments for '#{subcommand}'. " <>
+          "Try COMMAND HELP."}
+     ], state}
+  end
+
+  defp fullTable, do: {:array, Enum.map(Catalog.names(), &Catalog.infoTerm/1)}
+
+  defp docsEntry(name), do: [{:bulk, String.downcase(name)}, Catalog.docsTerm(name)]
+
+  defp getkeys(name, args) do
+    cond do
+      not Catalog.known?(name) ->
+        {:error, "ERR Invalid command specified"}
+
+      not Catalog.arityOk?(name, length(args) + 1) ->
+        {:error, "ERR Invalid number of arguments specified for command"}
+
+      true ->
+        extractKeys(name, args)
+    end
+  end
+
+  defp extractKeys(name, args) do
+    case Catalog.keysFor(name, args) do
+      {:ok, []} -> {:error, "ERR The command has no key arguments"}
+      {:ok, keys} -> {:array, Enum.map(keys, fn key -> {:bulk, key} end)}
+      :error -> {:error, "ERR Invalid arguments specified for command"}
+    end
+  end
+
+  defp wrongArity(name),
+    do: {:error, "ERR wrong number of arguments for '#{name}' command"}
+end