From 9cd3d57433fc18b2fb7f6758c8270862f67ea992 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sun, 25 Jan 2026 13:38:17 -0600
Subject: [PATCH] live reload yaml in dev

---
 lib/towerops/application.ex              | 13 +++++
 lib/towerops/profiles/profile_watcher.ex | 74 ++++++++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 lib/towerops/profiles/profile_watcher.ex

diff --git a/lib/towerops/application.ex b/lib/towerops/application.ex
index 78508179..de742134 100644
--- a/lib/towerops/application.ex
+++ b/lib/towerops/application.ex
@@ -34,6 +34,7 @@ defmodule Towerops.Application do
         SnmpKit.SnmpMgr.Config,
         SnmpKit.SnmpMgr.MIB
       ] ++
+        dev_only_workers() ++
         background_workers() ++
         [
           # Start to serve requests, typically the last entry
@@ -68,6 +69,18 @@ defmodule Towerops.Application do
     end
   end
 
+  # Configure dev-only workers - profile watcher for auto-reload
+  defp dev_only_workers do
+    if Application.get_env(:towerops, :env) == :dev do
+      [
+        # Watch YAML profiles for changes and auto-reload
+        Towerops.Profiles.ProfileWatcher
+      ]
+    else
+      []
+    end
+  end
+
   # Returns PubSub spec - uses Redis in production/clustered environments,
   # falls back to default PG2 adapter for Mix tasks and development
   defp pubsub_spec do
diff --git a/lib/towerops/profiles/profile_watcher.ex b/lib/towerops/profiles/profile_watcher.ex
new file mode 100644
index 00000000..a6a4eb18
--- /dev/null
+++ b/lib/towerops/profiles/profile_watcher.ex
@@ -0,0 +1,74 @@
+defmodule Towerops.Profiles.ProfileWatcher do
+  @moduledoc """
+  Watches YAML profile files for changes and automatically reloads them.
+
+  Uses FileSystem to monitor the priv/profiles directory for file changes.
+  When a .yaml or .yml file is created, modified, or deleted, triggers
+  a reload of all profiles via YamlProfiles.reload/0.
+  """
+  use GenServer
+
+  alias Towerops.Profiles.YamlProfiles
+
+  require Logger
+
+  @profiles_dir "priv/profiles"
+
+  def start_link(opts \\ []) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  @impl true
+  def init(_opts) do
+    # Get the absolute path to the profiles directory
+    profiles_path = Path.join(Application.app_dir(:towerops), @profiles_dir)
+
+    # Start watching the profiles directory for changes
+    {:ok, watcher_pid} = FileSystem.start_link(dirs: [profiles_path])
+    FileSystem.subscribe(watcher_pid)
+
+    Logger.info("ProfileWatcher: Started watching #{profiles_path}")
+
+    {:ok, %{watcher_pid: watcher_pid, profiles_path: profiles_path}}
+  end
+
+  @impl true
+  def handle_info({:file_event, _watcher_pid, {path, events}}, state) do
+    # Only reload if it's a YAML file change
+    if yaml_file?(path) and should_reload?(events) do
+      Logger.info("ProfileWatcher: Detected change in #{Path.relative_to_cwd(path)}, reloading profiles...")
+
+      case YamlProfiles.reload() do
+        {:ok, count} ->
+          Logger.info("ProfileWatcher: Successfully reloaded #{count} profiles")
+
+        {:error, reason} ->
+          Logger.error("ProfileWatcher: Failed to reload profiles: #{inspect(reason)}")
+      end
+    end
+
+    {:noreply, state}
+  end
+
+  @impl true
+  def handle_info({:file_event, _watcher_pid, :stop}, state) do
+    Logger.warning("ProfileWatcher: File watcher stopped")
+    {:noreply, state}
+  end
+
+  # Check if the file is a YAML profile file
+  defp yaml_file?(path) do
+    String.ends_with?(path, [".yaml", ".yml"])
+  end
+
+  # Check if the events indicate we should reload
+  # Reload on created, modified, or removed events
+  # Don't reload on :undefined or other metadata-only changes
+  defp should_reload?(events) when is_list(events) do
+    Enum.any?(events, fn event ->
+      event in [:created, :modified, :removed, :renamed]
+    end)
+  end
+
+  defp should_reload?(_), do: false
+end