Refactor to delegate pattern

Vagrantfile

@@ -14,7 +14,7 @@ Vagrant.configure('2') do |config| # rubocop:disable Metrics/BlockLength
     dev.vm.network 'private_network', ip: '192.168.50.11'
 
     dev.vm.provider 'virtualbox' do |vb|
-      vb.memory = '2048'
+      vb.memory = '4096'
       vb.cpus = 4
     end
 
@@ -131,7 +131,7 @@ Vagrant.configure('2') do |config| # rubocop:disable Metrics/BlockLength
     prod.vm.network 'private_network', ip: '192.168.50.10'
 
     prod.vm.provider 'virtualbox' do |vb|
-      vb.memory = '2048'
+      vb.memory = '4096'
       vb.cpus = 4
     end
 

lib/shortnr/url.ex

@@ -4,6 +4,7 @@ defmodule Shortnr.URL do
   domain service.
   """
   alias Shortnr.Transport
+  alias Shortnr.URL.Repo
 
   defstruct id: "",
             created_at: DateTime.utc_now(),
@@ -17,37 +18,39 @@ defmodule Shortnr.URL do
           url: URI.t()
         }
 
-  @spec create(String.t(), module()) :: {:ok, String.t()} | Transport.error()
-  def create(url, repo) do
+  @spec create(String.t()) :: {:ok, String.t()} | Transport.error()
+  def create(url) when is_binary(url) do
     url_struct = %__MODULE__{id: generate_id(), url: URI.parse(url)}
 
-    {:ok, extant_url} = repo.get(url_struct.id)
-
-    if extant_url do
-      create(url, repo)
-    else
-      :ok = repo.put(url_struct)
-      {:ok, url_struct.id}
-    end
+    url_struct.id
+    |> Repo.get()
+    |> create_if_no_collision(url_struct, url)
   end
 
-  @spec get(String.t(), module()) :: {:ok, t()} | Transport.error()
-  def get(key, repo) do
-    case repo.get(key) do
-      {:ok, nil} -> {:error, {:not_found, "url could not be found with the given id"}}
-      {:ok, url} -> {:ok, url}
-    end
+  defp create_if_no_collision({:ok, nil}, %__MODULE__{id: id} = url, _url) do
+    :ok = Repo.put(url)
+    {:ok, id}
   end
 
-  @spec list(module()) :: {:ok, list(t())} | Transport.error()
-  def list(repo) do
-    {:ok, _} = repo.list
+  defp create_if_no_collision({:ok, _}, _url_struct, url) when is_binary(url), do: create(url)
+
+  @spec get(String.t()) :: {:ok, t()} | Transport.error()
+  def get(key) do
+    key
+    |> Repo.get()
+    |> handle_errors
   end
 
-  @spec delete(String.t(), module()) :: {:ok, String.t()} | Transport.error()
-  def delete(key, repo) do
-    :ok = repo.delete(key)
-    {:ok, "Success"}
+  @spec list() :: {:ok, list(t())}
+  def list do
+    handle_errors(Repo.list())
+  end
+
+  @spec delete(String.t()) :: {:ok, String.t()}
+  def delete(key) do
+    key
+    |> Repo.delete()
+    |> handle_errors
   end
 
   @id_chars String.codepoints("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXWYZ0123456789")
@@ -58,6 +61,13 @@ defmodule Shortnr.URL do
         do: Enum.random(@id_chars)
   end
 
+  defp handle_errors({:ok, nil}),
+    do: {:error, {:not_found, "url could not be found with the given id"}}
+
+  defp handle_errors({:ok, _} = response), do: response
+
+  defp handle_errors(:ok), do: {:ok, "Success"}
+
   defimpl Transport.Text.Encodable do
     alias Shortnr.URL
     @spec encode(URL.t()) :: String.t()

lib/shortnr/url/endpoints.ex

@@ -8,7 +8,7 @@ defmodule Shortnr.URL.Endpoints do
   def list(conn) do
     conn
     |> HTTP.wrap()
-    |> HTTP.handle(fn -> URL.list(URL.Repo.ETS) end)
+    |> HTTP.handle(&URL.list/0)
     |> Text.encode()
     |> HTTP.send(:ok)
   end
@@ -16,7 +16,7 @@ defmodule Shortnr.URL.Endpoints do
   def create(conn, url) do
     conn
     |> HTTP.wrap(url)
-    |> HTTP.handle(&URL.create(&1, URL.Repo.ETS))
+    |> HTTP.handle(&URL.create(&1))
     |> Text.encode()
     |> HTTP.send(:created)
   end
@@ -24,7 +24,7 @@ defmodule Shortnr.URL.Endpoints do
   def get(conn, id) do
     conn
     |> HTTP.wrap(id)
-    |> HTTP.handle(&URL.get(&1, URL.Repo.ETS))
+    |> HTTP.handle(&URL.get(&1))
     |> Text.encode()
     |> HTTP.send(:found)
   end
@@ -32,7 +32,7 @@ defmodule Shortnr.URL.Endpoints do
   def delete(conn, id) do
     conn
     |> HTTP.wrap(id)
-    |> HTTP.handle(&URL.delete(&1, URL.Repo.ETS))
+    |> HTTP.handle(&URL.delete(&1))
     |> Text.encode()
     |> HTTP.send(:ok)
   end

lib/shortnr/url/repo.ex

@@ -7,9 +7,18 @@ defmodule Shortnr.URL.Repo do
   alias Shortnr.Transport
   alias Shortnr.URL
 
-  @callback put(URL.t()) :: :ok | Transport.error()
-  @callback get(String.t()) :: {:ok, URL.t()} | Transport.error()
-  @callback delete(String.t()) :: :ok | Transport.error()
-  @callback list() :: {:ok, list(URL.t())} | Transport.error()
-  @callback reset() :: :ok | Transport.error()
+  @spec put(URL.t()) :: :ok | Transport.error()
+  defdelegate put(url), to: Shortnr.URL.Repo.ETS
+
+  @spec get(String.t()) :: {:ok, URL.t() | nil} | Transport.error()
+  defdelegate get(url), to: Shortnr.URL.Repo.ETS
+
+  @spec delete(String.t()) :: :ok | Transport.error()
+  defdelegate delete(url), to: Shortnr.URL.Repo.ETS
+
+  @spec list() :: {:ok, list(URL.t())} | Transport.error()
+  defdelegate list(), to: Shortnr.URL.Repo.ETS
+
+  @spec reset() :: :ok | Transport.error()
+  defdelegate reset(), to: Shortnr.URL.Repo.ETS
 end

lib/shortnr/url/repo/ets.ex

@@ -2,11 +2,7 @@ defmodule Shortnr.URL.Repo.ETS do
   @moduledoc """
   This module is an implemention of the Repo behaviour using the Erlang ETS library.
   """
-  alias Shortnr.URL.Repo
 
-  @behaviour Repo
-
-  @impl true
   def get(key) do
     case ets().lookup(:urls, key) |> List.first() do
       {_, url} -> {:ok, url}
@@ -14,25 +10,21 @@ defmodule Shortnr.URL.Repo.ETS do
     end
   end
 
-  @impl true
   def put(url) do
     :ok = ets().insert(:urls, {url.id, url})
     :ok
   end
 
-  @impl true
   def list do
     resp = ets().select(:urls, [{:"$1", [], [:"$1"]}])
     {:ok, resp |> Enum.map(&elem(&1, 1))}
   end
 
-  @impl true
   def delete(key) do
     :ok = ets().delete(:urls, key)
     :ok
   end
 
-  @impl true
   def reset do
     :ok = ets().delete_all_objects(:urls)
   end