From 97ad9105d8d151db26839e59c465ea39b9fb59a6 Mon Sep 17 00:00:00 2001
From: Felipe Sere <felipesere@gmail.com>
Date: Tue, 1 Jan 2019 16:30:51 +0000
Subject: [PATCH] WIP: Stab at refactoring watcher for testability

---
 lib/watcher.ex        | 21 +++++++++++++--------
 mix.exs               |  7 +++++--
 mix.lock              |  5 ++++-
 test/watcher_test.exs | 13 +++++++++++++
 4 files changed, 35 insertions(+), 11 deletions(-)
 create mode 100644 test/watcher_test.exs

diff --git a/lib/watcher.ex b/lib/watcher.ex
index 6839b55a..4a7591cd 100644
--- a/lib/watcher.ex
+++ b/lib/watcher.ex
@@ -1,26 +1,31 @@
 defmodule Watcher do
   use GenServer
 
-  def start_link() do
-    GenServer.start_link(__MODULE__, dirs: ["lib/koans"])
+  @default_arguments %{folder_to_watch: "lib/koans", handler: &Watcher.reload/1}
+
+  def start_link(args \\ %{}) do
+    state = Map.merge(@default_arguments, args)
+    GenServer.start_link(__MODULE__, state)
   end
 
-  def init(args) do
-    {:ok, watcher_pid} = FileSystem.start_link(args)
+  def init(%{folder_to_watch: dirs} = args) do
+    {:ok, watcher_pid} = FileSystem.start_link([dirs: [dirs]])
     FileSystem.subscribe(watcher_pid)
-    {:ok, %{watcher_pid: watcher_pid}}
+    IO.inspect(args)
+    {:ok, Map.merge(args, %{watcher_pid: watcher_pid})}
   end
 
-  def handle_info({:file_event, watcher_pid, {path, events}}, %{watcher_pid: watcher_pid} = state) do
+  def handle_info({:file_event, watcher_pid, {path, events}}, %{watcher_pid: watcher_pid, handler: file_handler} = state) do
+    IO.inspect path, events
     # respond to renamed as well due to that some editors use temporary files for atomic writes (ex: TextMate)
     if Enum.member?(events, :modified) || Enum.member?(events, :renamed) do
-      path |> normalize |> reload
+      path |> normalize |> file_handler.()
     end
 
     {:noreply, state}
   end
 
-  defp reload(file) do
+  def reload(file) do
     if Path.extname(file) == ".ex" do
       try do
         file
diff --git a/mix.exs b/mix.exs
index ac553bb0..df249183 100644
--- a/mix.exs
+++ b/mix.exs
@@ -11,11 +11,14 @@ defmodule Koans.Mixfile do
 
   def application do
     [mod: {ElixirKoans, []},
-     applications: [:file_system, :logger]]
+     applications: [:file_system, :logger, :briefly]]
   end
 
   defp deps do
-    [{:file_system, "~> 0.2"}]
+    [
+      {:file_system, "~> 0.2"},
+      {:briefly, "~> 0.3"}
+    ]
   end
 
   defp elixirc_path(:test), do: ["lib/", "test/support"]
diff --git a/mix.lock b/mix.lock
index d7a007ee..eabfd519 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1 +1,4 @@
-%{"file_system": {:hex, :file_system, "0.2.2", "7f1e9de4746f4eb8a4ca8f2fbab582d84a4e40fa394cce7bfcb068b988625b06", [], [], "hexpm"}}
+%{
+  "briefly": {:hex, :briefly, "0.3.0", "16e6b76d2070ebc9cbd025fa85cf5dbaf52368c4bd896fb482b5a6b95a540c2f", [:mix], [], "hexpm"},
+  "file_system": {:hex, :file_system, "0.2.2", "7f1e9de4746f4eb8a4ca8f2fbab582d84a4e40fa394cce7bfcb068b988625b06", [], [], "hexpm"},
+}
diff --git a/test/watcher_test.exs b/test/watcher_test.exs
new file mode 100644
index 00000000..67244696
--- /dev/null
+++ b/test/watcher_test.exs
@@ -0,0 +1,13 @@
+defmodule WatcherTest do
+  use ExUnit.Case
+
+  test "watches for changes" do
+    parent = self()
+    {:ok, path} = Briefly.create(directory: true)
+    {:ok, pid} = Watcher.start_link(%{folder_to_watch: path, handler: fn(file) -> send parent, {:file, file} end})
+
+    File.write!(Path.join(path, "test.exs"), "Some Text")
+
+    assert_receive {:file, "foo"}, 1_000
+  end
+end