feat: add TodoServer

todo_list.ex

@@ -1,3 +1,77 @@
+defmodule TodoServer do
+  def start(entries \\ []) do
+    spawn(fn -> loop(TodoList.new(entries)) end)
+  end
+
+  def from_list(todo_list) do
+    spawn(fn -> loop(todo_list) end)
+  end
+
+  defp loop(todo_list) do
+    new_todo_list =
+      receive do
+        message ->
+          process_message(todo_list, message)
+      after
+        1000 -> todo_list
+      end
+
+    loop(new_todo_list)
+  end
+
+  defp process_message(todo_list, {:add, entry}) do
+    TodoList.add(todo_list, entry)
+  end
+
+  defp process_message(todo_list, {:entries, sender, date}) do
+    entries = TodoList.entries(todo_list, date)
+
+    send(sender, {:entries, entries})
+
+    todo_list
+  end
+
+  defp process_message(todo_list, {:update, id, update_fun}) do
+    TodoList.update(todo_list, id, update_fun)
+  end
+
+  defp process_message(todo_list, {:delete, id}) do
+    TodoList.delete(todo_list, id)
+  end
+
+  defp process_message(todo_list, invalid_message) do
+    IO.puts("Invalid message: #{IO.inspect(invalid_message)}")
+
+    todo_list
+  end
+
+  def add(pid, entry) do
+    send(pid, {:add, entry})
+    nil
+  end
+
+  def entries(pid, date) do
+    send(pid, {:entries, self(), date})
+
+    receive do
+      {:entries, value} ->
+        {:ok, value}
+    after
+      1000 -> {:error}
+    end
+  end
+
+  def update(pid, id, update_fun) do
+    send(pid, {:update, id, update_fun})
+    nil
+  end
+
+  def delete(pid, id) do
+    send(pid, {:delete, id})
+    nil
+  end
+end
+
 defmodule TodoList do
   defstruct entries: %{}, next_id: 1
 
@@ -16,8 +90,8 @@ defmodule TodoList do
     %__MODULE__{todo_list | entries: new_entries, next_id: next_id + 1}
   end
 
-  def entries(%__MODULE__{entries: entries}, date) do
-    entries
+  def entries(%__MODULE__{} = todo_list, date) do
+    todo_list.entries
     |> Map.filter(fn {_, entry} -> entry.date == date end)
     |> Map.values()
   end