From 56ba54e2d72c29a672fe10e0c4d96d387c82194b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Moritz=20B=C3=B6hme?= <mail@moritzboeh.me>
Date: Sat, 3 Aug 2024 10:14:19 +0200
Subject: [PATCH] feat!: add custom ServerProcess module

---
 todo_list.ex | 108 ++++++++++++++++++++++++---------------------------
 1 file changed, 51 insertions(+), 57 deletions(-)

diff --git a/todo_list.ex b/todo_list.ex
index 42c8642..8df4eb4 100644
--- a/todo_list.ex
+++ b/todo_list.ex
@@ -1,96 +1,90 @@
-defmodule TodoServer do
-  def start(entries \\ [], options \\ []) do
-    pid = spawn(fn -> loop(TodoList.new(entries)) end)
+defmodule ServerProcess do
+  def start(callback_module) do
+    spawn(fn ->
+      initial_state = callback_module.init()
+      loop(callback_module, initial_state)
+    end)
+  end
 
-    if Keyword.get(options, :local) do
-      Process.register(pid, :todo_list)
+  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
-
-    pid
   end
 
-  def from_list(todo_list) do
-    spawn(fn -> loop(todo_list) end)
+  def call(pid, message) do
+    send(pid, {:call, message, self()})
+
+    receive do
+      {:response, response} ->
+        response
+    end
   end
 
-  defp loop(todo_list) do
-    new_todo_list =
-      receive do
-        message ->
-          process_message(todo_list, message)
-      after
-        1000 -> todo_list
-      end
+  def cast(pid, message) do
+    send(pid, {:cast, message})
+    nil
+  end
+end
 
-    loop(new_todo_list)
+defmodule TodoServer do
+  def init(entries) do
+    TodoList.new(entries)
   end
 
-  defp process_message(todo_list, {:add, entry}) do
-    TodoList.add(todo_list, entry)
-  end
-
-  defp process_message(todo_list, {:entries, sender, date}) do
+  def handle_call({:entries, date}, todo_list) do
     entries = TodoList.entries(todo_list, date)
 
-    send(sender, {:entries, entries})
+    {entries, todo_list}
+  end
+
+  def handle_call(invalid_message, todo_list) do
+    IO.puts("Invalid message: #{IO.inspect(invalid_message)}")
 
     todo_list
   end
 
-  defp process_message(todo_list, {:update, id, update_fun}) do
+  def handle_cast({:add, entry}, todo_list) do
+    TodoList.add(todo_list, entry)
+  end
+
+  def handle_cast({:update, id, update_fun}, todo_list) do
     TodoList.update(todo_list, id, update_fun)
   end
 
-  defp process_message(todo_list, {:delete, id}) do
+  def handle_cast({:delete, id}, todo_list) do
     TodoList.delete(todo_list, id)
   end
 
-  defp process_message(todo_list, invalid_message) do
+  def handle_cast(invalid_message, todo_list) do
     IO.puts("Invalid message: #{IO.inspect(invalid_message)}")
 
     todo_list
   end
 
   def add(pid, entry) do
-    send(pid, {:add, entry})
-    nil
-  end
-
-  def add(entry) do
-    add(:todo_list, entry)
+    ServerProcess.cast(pid, {:add, entry})
   end
 
   def entries(pid, date) do
-    send(pid, {:entries, self(), date})
-
-    receive do
-      {:entries, value} ->
-        {:ok, value}
-    after
-      1000 -> {:error}
-    end
-  end
-
-  def entries(date) do
-    entries(:todo_list, date)
+    ServerProcess.call(pid, {:entries, date})
   end
 
   def update(pid, id, update_fun) do
-    send(pid, {:update, id, update_fun})
-    nil
-  end
-
-  def update(id, update_fun) do
-    update(:todo_list, id, update_fun)
+    ServerProcess.cast(pid, {:update, id, update_fun})
   end
 
   def delete(pid, id) do
-    send(pid, {:delete, id})
-    nil
-  end
-
-  def delete(id) do
-    delete(:todo_list, id)
+    ServerProcess.cast(pid, {:delete, id})
   end
 end