init: inital commit

lib/localiser/mqtt/router.ex

@@ -0,0 +1,83 @@
+defmodule Localiser.MQTT.Router do
+  @moduledoc """
+  Module responsible for routing incoming MQTT messages to the appropriate handlers.
+  """
+
+  use GenServer
+  require Logger
+
+  alias Localiser.Domain.Sensors
+
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  def route(topic, payload) do
+    GenServer.cast(__MODULE__, {:route, topic, payload})
+  end
+
+  # GenServer Callbacks
+
+  @impl true
+  def init(_opts) do
+    {:ok, %{}}
+  end
+
+  @impl true
+  def handle_cast({:route, topic, payload}, state) do
+    case parse_topic(topic) do
+      {:rssi, sensor_id} ->
+        handle_rssi(sensor_id, payload)
+
+      {:announce, sensor_id} ->
+        handle_announce(sensor_id)
+
+      {:error, :invalid_topic} ->
+        Logger.debug("[MQTT.Router] Received message with invalid topic: #{topic}")
+    end
+
+    {:noreply, state}
+  end
+
+  # Private helper functions
+
+  defp parse_topic(topic) do
+    # Example topic: "localiser/sensor/device123/rssi"
+    case String.split(topic, "/") do
+      ["localiser", "sensor", sensor_id, "rssi"] -> {:rssi, sensor_id}
+      ["localiser", "sensor", sensor_id, "announce"] -> {:announce, sensor_id}
+      _ -> {:error, :invalid_topic}
+    end
+  end
+
+  defp handle_rssi(sensor_id, payload) do
+    with {:ok, %{"tag_id" => tag_id, "rssi" => rssi}} <-
+           Jason.decode(payload) do
+
+      reading = %{
+        sensor_id: sensor_id,
+        tag_id: tag_id,
+        rssi: rssi,
+        timestamp: DateTime.utc_now()
+      }
+
+      Localiser.MQTT.Telemetry.count_reading()
+      Localiser.RSSI.Buffer.push(reading)
+
+    else
+      {:error, reason} ->
+        Logger.error("[MQTT.Router] Bad payload from #{sensor_id}: #{inspect(reason)}")
+        Localiser.MQTT.Telemetry.count_error()
+    end
+  end
+
+  defp handle_announce(sensor_id) do
+    case Sensors.upsert_announced(sensor_id) do
+      {:ok, _sensor} ->
+        Logger.info("[MQTT.Router] Sensor announced: #{sensor_id}")
+
+      {:error, reason} ->
+        Logger.error("[MQTT.Router] Failed to register announced sensor #{sensor_id}: #{inspect(reason)}")
+    end
+  end
+end