Update: Finished persistable todo server

chapter7/todo/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

chapter7/todo/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+todo-*.tar
+

chapter7/todo/README.md

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+# Todo
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `todo` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:todo, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at [https://hexdocs.pm/todo](https://hexdocs.pm/todo).
+

chapter7/todo/lib/todo/list.ex

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+defmodule Todo.List do
+  defstruct auto_id: 1, entries: %{}
+
+  def new(), do: %Todo.List{}
+
+  def add_entry(todo_list, entry) do
+    entry = Map.put(entry, :id, todo_list.auto_id)
+
+    new_entries =
+      Map.put(
+        todo_list.entries,
+        todo_list.auto_id,
+        entry
+      )
+
+    %Todo.List{todo_list | entries: new_entries, auto_id: todo_list.auto_id + 1}
+  end
+
+  def entries(todo_list, date) do
+    todo_list.entries
+    |> Stream.filter(fn {_, entry} -> entry.date == date end)
+    |> Enum.map(fn {_, entry} -> entry end)
+  end
+
+  def update_entry(todo_list, %{} = new_entry) do
+    update_entry(todo_list, new_entry.id, fn _ -> new_entry end)
+  end
+
+  def update_entry(todo_list, entry_id, updater_fun) do
+    case Map.fetch(todo_list.entries, entry_id) do
+      :error ->
+        todo_list
+
+      {:ok, old_entry} ->
+        old_entry_id = old_entry.id
+        # Make sure that the result of the updater is a map and the
+        # id remains unchanged.
+        new_entry = %{id: ^old_entry_id} = updater_fun.(old_entry)
+        new_entries = Map.put(todo_list.entries, new_entry.id, new_entry)
+        %Todo.List{todo_list | entries: new_entries}
+    end
+  end
+
+  def delete_entry(todo_list, entry_id) do
+    %Todo.List{todo_list | entries: Map.delete(todo_list.entries, entry_id)}
+  end
+end

chapter7/todo/lib/todo/server.ex

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+defmodule Todo.Server do
+  use GenServer
+
+  def start do
+    GenServer.start(__MODULE__, nil)
+  end
+
+  def add_entry(pid, entry) do
+    GenServer.cast(pid, {:add_entry, entry})
+  end
+
+  def delete_entry(pid, entry_id) do
+    GenServer.cast(pid, {:delete_entry, entry_id})
+  end
+
+  def update_entry(pid, entry_id, updater_fun) do
+    GenServer.cast(pid, {:update_entry, entry_id, updater_fun})
+  end
+
+  def entries(pid, date) do
+    GenServer.call(pid, {:entries, date})
+  end
+
+  @impl true
+  def init(_) do
+    {:ok, Todo.List.new()}
+  end
+
+  @impl true
+  def handle_cast({:add_entry, entry}, state) do
+    {:noreply, Todo.List.add_entry(state, entry)}
+  end
+
+  @impl true
+  def handle_cast({:delete_entry, entry_id}, state) do
+    {:noreply, Todo.List.delete_entry(state, entry_id)}
+  end
+
+  @impl true
+  def handle_cast({:update_entry, entry_id, updater_fun}, state) do
+    {:noreply, Todo.List.update_entry(state, entry_id, updater_fun)}
+  end
+
+  @impl true
+  def handle_call({:entries, date}, _, state) do
+    {:reply, Todo.List.entries(state, date), state}
+  end
+end

chapter7/todo/mix.exs

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+defmodule Todo.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :todo,
+      version: "0.1.0",
+      elixir: "~> 1.10",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

chapter7/todo/test/test_helper.exs

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+ExUnit.start()