fix: register NIF compiler, add Nix shell NIF build, make NIF optional at boot

- Register :towerops_nif compiler in mix.exs so mix compile/test builds the C NIF
- Add 'make -C c_src' to nix devShell shellHook so NIF is pre-built
- Extract init_mib_resolution/0 from Application.start/2 (reduces CC)
- Wrap NIF calls in try/rescue ErlangError for graceful fallback
- Wrap test_helper.exs NIF calls in try/rescue ErlangError
- Add .nix-postgres-version to .gitignore

.gitignore

@@ -5,6 +5,7 @@
 .nix-mix/
 .nix-hex/
 .nix-postgres/
+.nix-postgres-version
 .nix-redis/
 .nix-services-started
 

lib/towerops/application.ex

@@ -41,46 +41,8 @@ defmodule Towerops.Application do
         Towerops.Release.migrate()
       end
 
-    # Configure MIB directories for NIF resolution (before supervisor starts)
-    Logger.info("Configuring MIB directories for NIF resolution...")
-    mib_dir = Application.app_dir(:towerops, "priv/mibs")
-
-    # Build list of all MIB directories (including subdirectories for vendor MIBs)
-    mib_dirs =
-      if File.dir?(mib_dir) do
-        # Get main directory plus all subdirectories
-        subdirs =
-          mib_dir
-          |> File.ls!()
-          |> Enum.map(&Path.join(mib_dir, &1))
-          |> Enum.filter(&File.dir?/1)
-
-        [mib_dir | subdirs]
-      else
-        [mib_dir]
-      end
-
-    # Set MIBDIRS environment variable for net-snmp (must be set BEFORE init)
-    # Join with colon for Unix-style path list
-    mibdirs_env = Enum.join(mib_dirs, ":")
-    System.put_env("MIBDIRS", mibdirs_env)
-    System.put_env("MIBS", "ALL")
-
-    Logger.info("MIB directories configured: #{length(mib_dirs)} directories")
-
-    # Add each directory to net-snmp's search path
-    Enum.each(mib_dirs, fn dir ->
-      :ok = ToweropsNative.load_mib_directory(dir)
-    end)
-
-    # Initialize the MIB library (loads all MIBs into memory)
-    case ToweropsNative.init_mib_library() do
-      result when result in ["initialized", "already_initialized"] ->
-        Logger.info("MIB library initialized: #{result}")
-
-      other ->
-        Logger.warning("Unexpected MIB library init result: #{inspect(other)}")
-    end
+    # Initialize MIB resolution via C NIF
+    init_mib_resolution()
 
     # Load antenna pattern registry (priv/antennas/*.ant) into :persistent_term
     Antenna.load_registry()
@@ -152,6 +114,48 @@ defmodule Towerops.Application do
     result
   end
 
+  # Configure MIB resolution via C NIF. Handles missing NIF gracefully.
+  defp init_mib_resolution do
+    Logger.info("Configuring MIB directories for NIF resolution...")
+    mib_dir = Application.app_dir(:towerops, "priv/mibs")
+
+    mib_dirs =
+      if File.dir?(mib_dir) do
+        subdirs =
+          mib_dir
+          |> File.ls!()
+          |> Enum.map(&Path.join(mib_dir, &1))
+          |> Enum.filter(&File.dir?/1)
+
+        [mib_dir | subdirs]
+      else
+        [mib_dir]
+      end
+
+    mibdirs_env = Enum.join(mib_dirs, ":")
+    System.put_env("MIBDIRS", mibdirs_env)
+    System.put_env("MIBS", "ALL")
+
+    Logger.info("MIB directories configured: #{length(mib_dirs)} directories")
+
+    try do
+      Enum.each(mib_dirs, fn dir ->
+        :ok = ToweropsNative.load_mib_directory(dir)
+      end)
+
+      case ToweropsNative.init_mib_library() do
+        result when result in ["initialized", "already_initialized"] ->
+          Logger.info("MIB library initialized: #{result}")
+
+        other ->
+          Logger.warning("Unexpected MIB library init result: #{inspect(other)}")
+      end
+    rescue
+      _e in ErlangError ->
+        Logger.warning("ToweropsNative NIF not loaded — MIB resolution unavailable")
+    end
+  end
+
   # Post-startup work runs only when the supervisor came up cleanly. The Task
   # supervisor call is wrapped in try/catch so a transient noproc (the named
   # supervisor may not be ready or may already be dying) cannot exit the boot

mix.exs

@@ -10,7 +10,7 @@ defmodule Towerops.MixProject do
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
       deps: deps(),
-      compilers: [:phoenix_live_view] ++ Mix.compilers(),
+      compilers: [:towerops_nif, :phoenix_live_view] ++ Mix.compilers(),
       prune_code_paths: false,
       listeners: [Phoenix.CodeReloader],
       dialyzer: dialyzer(),

nix/shell.nix

@@ -326,6 +326,12 @@ mkShell {
       mix local.hex --force --if-missing > /dev/null 2>&1
       mix local.rebar --force --if-missing > /dev/null 2>&1
 
+      # Compile C NIF if not already built (uses Nix-provided gcc/make/net-snmp)
+      if [ ! -f "priv/towerops_nif.so" ]; then
+        echo "🔧 Building C NIF..."
+        make -C c_src
+      fi
+
       # Auto-start services on first shell entry.
       # Run in a detached subshell to prevent nix develop from waiting
       # on daemonized PostgreSQL/Redis child processes.

test/test_helper.exs

@@ -18,22 +18,27 @@ if File.dir?(mib_dir) do
   System.put_env("MIBDIRS", mibdirs_env)
   System.put_env("MIBS", "ALL")
 
-  # Add each directory to net-snmp's search path
-  Enum.each(mib_dirs, fn dir ->
-    case ToweropsNative.load_mib_directory(dir) do
-      :ok -> :ok
-      # Ignore errors in test environment
-      {:error, _reason} -> :ok
+  # Add each directory to net-snmp's search path (NIF may not be loaded)
+  try do
+    Enum.each(mib_dirs, fn dir ->
+      case ToweropsNative.load_mib_directory(dir) do
+        :ok -> :ok
+        # Ignore errors in test environment
+        {:error, _reason} -> :ok
+      end
+    end)
+
+    # Explicitly initialize the MIB library with correct environment variables
+    case ToweropsNative.init_mib_library() do
+      result when result in ["initialized", "already_initialized"] ->
+        IO.puts("Test MIB library initialized: #{result}")
+
+      other ->
+        IO.puts("Warning: Unexpected MIB library init result: #{inspect(other)}")
     end
-  end)
-
-  # Explicitly initialize the MIB library with correct environment variables
-  case ToweropsNative.init_mib_library() do
-    result when result in ["initialized", "already_initialized"] ->
-      IO.puts("Test MIB library initialized: #{result}")
-
-    other ->
-      IO.puts("Warning: Unexpected MIB library init result: #{inspect(other)}")
+  rescue
+    _e in ErlangError ->
+      IO.puts("ToweropsNative NIF not available — MIB resolution disabled in tests")
   end
 end