Fix dashboard MQTT connection and remove simulation code

- Replace SimpleMqtt simulation with real MqttSubscriber
- Fix String.split bug when handling MQTT topic parsing
- Use hostname-based client ID to avoid MQTT client conflicts
- Add process management tools (hivemind, just) to development environment

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

dashboard/lib/dashboard/application.ex

@@ -13,8 +13,8 @@ defmodule Dashboard.Application do
       {Phoenix.PubSub, name: Dashboard.PubSub},
       # Start the Finch HTTP client for sending emails
       {Finch, name: Dashboard.Finch},
-      # Start simple MQTT subscriber
-      Dashboard.SimpleMqtt,
+      # Start real MQTT subscriber
+      Dashboard.MqttSubscriber,
       # Start to serve requests, typically the last entry
       DashboardWeb.Endpoint
     ]

dashboard/lib/dashboard/mqtt_subscriber.ex

@@ -19,17 +19,27 @@ defmodule Dashboard.MqttSubscriber do
 
   @impl true
   def init(_opts) do
-    # Start MQTT connection in a supervised way
-    {:ok, _pid} = Tortoise.Supervisor.start_child(
-      :dashboard_mqtt,
-      client_id: :dashboard_mqtt,
+    # Start MQTT connection directly with hostname-based client ID to avoid conflicts
+    {:ok, hostname} = :inet.gethostname()
+    client_id = "systant-dashboard-#{hostname}"
+    connection_opts = [
+      client_id: client_id,
       server: {Tortoise.Transport.Tcp, host: "mqtt.home", port: 1883},
       handler: {__MODULE__, []},
       subscriptions: [{"systant/+/stats", 0}]
-    )
+    ]
 
-    Logger.info("Dashboard MQTT subscriber started")
-    {:ok, %{hosts: %{}}}
+    case Tortoise.Connection.start_link(connection_opts) do
+      {:ok, _pid} ->
+        Logger.info("Dashboard MQTT subscriber connected successfully")
+        {:ok, %{hosts: %{}}}
+      {:error, {:already_started, _pid}} ->
+        Logger.info("Dashboard MQTT connection already exists, reusing")
+        {:ok, %{hosts: %{}}}
+      {:error, reason} ->
+        Logger.error("Failed to connect to MQTT broker: #{inspect(reason)}")
+        {:stop, reason}
+    end
   end
 
   @impl true
@@ -43,11 +53,19 @@ defmodule Dashboard.MqttSubscriber do
   end
 
   # Tortoise handler callbacks
-  def connection(_status, _state), do: []
-  def subscription(_status, _topic, _state), do: []
+  def connection(status, state) do
+    Logger.info("MQTT connection status: #{status}")
+    {:ok, state}
+  end
+  
+  def subscription(status, topic, state) do
+    Logger.info("MQTT subscription status for #{topic}: #{status}")
+    {:ok, state}
+  end
   
   def handle_message(topic, payload, _state) do
-    case String.split(topic, "/") do
+    topic_parts = if is_binary(topic), do: String.split(topic, "/"), else: topic
+    case topic_parts do
       ["systant", hostname, "stats"] ->
         case Jason.decode(payload) do
           {:ok, data} ->
@@ -74,5 +92,6 @@ defmodule Dashboard.MqttSubscriber do
     {:noreply, %{state | hosts: updated_hosts}}
   end
 
+  @impl true
   def terminate(_reason, _state), do: []
 end

dashboard/lib/dashboard/simple_mqtt.ex

@@ -1,42 +0,0 @@
-defmodule Dashboard.SimpleMqtt do
-  @moduledoc """
-  Simple GenServer that polls for MQTT data instead of complex subscriptions.
-  """
-  use GenServer
-  require Logger
-
-  alias Phoenix.PubSub
-
-  def start_link(_opts) do
-    GenServer.start_link(__MODULE__, [], name: __MODULE__)
-  end
-
-  @impl true
-  def init(_) do
-    # Start a timer that simulates receiving MQTT data
-    # In a real implementation, you'd use a proper MQTT client here
-    Logger.info("Starting simple MQTT poller")
-    
-    # For now, just generate fake data that matches what systant publishes
-    :timer.send_interval(5000, self(), :simulate_mqtt)
-    
-    {:ok, %{}}
-  end
-
-  @impl true
-  def handle_info(:simulate_mqtt, state) do
-    # Simulate receiving an MQTT message from orion
-    hostname = "orion"
-    host_data = %{
-      "message" => "Hello from systant",
-      "hostname" => hostname,
-      "timestamp" => DateTime.utc_now() |> DateTime.to_iso8601(),
-      "last_seen" => DateTime.utc_now()
-    }
-    
-    Logger.info("Simulating MQTT message from #{hostname}")
-    PubSub.broadcast(Dashboard.PubSub, "systant:hosts", {:host_update, hostname, host_data})
-    
-    {:noreply, state}
-  end
-end

flake.nix

@@ -27,13 +27,20 @@
             elixir
             erlang
 
+            # File watching for Phoenix live reload
+            inotifyTools
+
+            # Process management and task running
+            hivemind
+            just
+
             # AI/Development tools
             claude-code
             aider-chat
 
             # Node.js for Phoenix assets
             nodejs_20
-            npm
+            nodePackages.npm
 
             # Database for development
             postgresql
@@ -69,7 +76,8 @@
           };
         };
       }
-    ) // {
+    )
+    // {
       nixosModules.default = import ./nix/nixos-module.nix;
     };
 }