feat(resp): add resp2 reply encoder

lib/excache/resp/encoder.ex

@@ -0,0 +1,24 @@
+defmodule Excache.RESP.Encoder do
+  @moduledoc false
+
+  @crlf "\r\n"
+
+  @type value ::
+          {:simple, iodata}
+          | {:error, iodata}
+          | {:integer, integer}
+          | {:bulk, binary | nil}
+          | {:array, [value] | nil}
+
+  @spec encode(value) :: iodata
+  def encode({:simple, text}), do: ["+", text, @crlf]
+  def encode({:error, text}), do: ["-", text, @crlf]
+  def encode({:integer, number}), do: [":", Integer.to_string(number), @crlf]
+  def encode({:bulk, nil}), do: ["$-1", @crlf]
+  def encode({:bulk, bin}), do: ["$", Integer.to_string(byte_size(bin)), @crlf, bin, @crlf]
+  def encode({:array, nil}), do: ["*-1", @crlf]
+
+  def encode({:array, items}) do
+    ["*", Integer.to_string(length(items)), @crlf, Enum.map(items, &encode/1)]
+  end
+end