From 323d35cad2d804249b18222f8a8abb7c8aac9129 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Moritz=20B=C3=B6hme?= <mail@moritzboeh.me>
Date: Sat, 3 Aug 2024 22:21:55 +0200
Subject: [PATCH] feat: use GenServer

---
 todo_list.ex | 94 ++++++++++++++++++++--------------------------------
 1 file changed, 36 insertions(+), 58 deletions(-)

diff --git a/todo_list.ex b/todo_list.ex
index 8df4eb4..becfb53 100644
--- a/todo_list.ex
+++ b/todo_list.ex
@@ -1,90 +1,68 @@
-defmodule ServerProcess do
-  def start(callback_module) do
-    spawn(fn ->
-      initial_state = callback_module.init()
-      loop(callback_module, initial_state)
-    end)
-  end
-
-  defp loop(callback_module, current_state) do
-    receive do
-      {:call, request, caller} ->
-        {response, new_state} = callback_module.handle_call(request, current_state)
-
-        send(caller, {:response, response})
-
-        loop(callback_module, new_state)
-
-      {:cast, request} ->
-        new_state = callback_module.handle_cast(request, current_state)
-        loop(callback_module, new_state)
-    end
-  end
-
-  def call(pid, message) do
-    send(pid, {:call, message, self()})
-
-    receive do
-      {:response, response} ->
-        response
-    end
-  end
-
-  def cast(pid, message) do
-    send(pid, {:cast, message})
-    nil
-  end
-end
-
 defmodule TodoServer do
-  def init(entries) do
-    TodoList.new(entries)
+  use GenServer
+
+  @impl GenServer
+  def init(%_{} = todo_list) do
+    {:ok, todo_list}
   end
 
-  def handle_call({:entries, date}, todo_list) do
+  @impl GenServer
+  def init(entries) do
+    {:ok, TodoList.new(entries)}
+  end
+
+  @impl GenServer
+  def handle_call({:entries, date}, _from, todo_list) do
     entries = TodoList.entries(todo_list, date)
 
-    {entries, todo_list}
-  end
-
-  def handle_call(invalid_message, todo_list) do
-    IO.puts("Invalid message: #{IO.inspect(invalid_message)}")
-
-    todo_list
+    {:reply, entries, todo_list}
   end
 
+  @impl GenServer
   def handle_cast({:add, entry}, todo_list) do
-    TodoList.add(todo_list, entry)
+    new_todo_list = TodoList.add(todo_list, entry)
+
+    {:no_reply, new_todo_list}
   end
 
+  @impl GenServer
   def handle_cast({:update, id, update_fun}, todo_list) do
-    TodoList.update(todo_list, id, update_fun)
+    new_todo_list = TodoList.update(todo_list, id, update_fun)
+
+    {:no_reply, new_todo_list}
   end
 
+  @impl GenServer
   def handle_cast({:delete, id}, todo_list) do
-    TodoList.delete(todo_list, id)
+    new_todo_list = TodoList.delete(todo_list, id)
+
+    {:no_reply, new_todo_list}
   end
 
-  def handle_cast(invalid_message, todo_list) do
-    IO.puts("Invalid message: #{IO.inspect(invalid_message)}")
+  def start(entries \\ [])
 
-    todo_list
+  def start(%_{} = todo_list) do
+    GenServer.start(__MODULE__, todo_list)
+  end
+
+  def start(entries) do
+    GenServer.start(__MODULE__, entries)
   end
 
   def add(pid, entry) do
-    ServerProcess.cast(pid, {:add, entry})
+    GenServer.cast(pid, {:add, entry})
   end
 
   def entries(pid, date) do
-    ServerProcess.call(pid, {:entries, date})
+    GenServer.call(pid, {:entries, date})
   end
 
   def update(pid, id, update_fun) do
-    ServerProcess.cast(pid, {:update, id, update_fun})
+    GenServer.cast(pid, {:update, id, update_fun})
   end
 
   def delete(pid, id) do
-    ServerProcess.cast(pid, {:delete, id})
+    GenServer.cast(pid, {:delete, id})
   end
 end