copied some more stuff - still no idea what im doing

src/main.cpp

@@ -75,10 +75,40 @@ void reconnect()
   }
 }
 
+#define RELAY_ACTIVATION_PIN D6
+#define REED_ACTIVATION_PIN D5
+
+void callback(char *topic, byte *payload, unsigned int length)
+{
+  StaticJsonDocument<256> doc;
+  deserializeJson(doc, payload, length);
+
+  Serial.print("Message arrived [");
+  Serial.print(topic);
+  Serial.print("] ");
+  for (int i = 0; i < length; i++)
+  {
+    Serial.print((char)payload[i]);
+  }
+  Serial.println();
+
+  if (doc["deviceId"] == deviceId && doc["lock"] == true)
+  {
+    digitalWrite(RELAY_ACTIVATION_PIN, HIGH); // Turn the relay on
+  }
+  else
+  {
+    digitalWrite(RELAY_ACTIVATION_PIN, LOW); // Turn the relay off
+  }
+}
+
 void setup()
 {
   Serial.begin(115200);
 
+  pinMode(RELAY_ACTIVATION_PIN, OUTPUT);
+  pinMode(REED_ACTIVATION_PIN, INPUT);
+
   lcd.init();
   lcd.backlight();
   pinMode(buzzerPin, OUTPUT);
@@ -102,14 +132,34 @@ void isArmed()
   lcd.clear();
 }
 
+bool lastReed = 0;
+
 void loop()
 {
-  client.loop();
-
   if (!client.connected())
   {
     reconnect();
   }
-  
-  isArmed();
+
+  bool reed = !digitalRead(REED_ACTIVATION_PIN);
+    
+    if (reed != lastReed)
+    {
+        Serial.print("Reed has changed to: ");
+        Serial.println(reed);
+        
+
+        DynamicJsonDocument doc(1024);
+
+        doc["deviceId"] = deviceId;
+        doc["open"] = reed;
+
+        char buffer[1024];
+        size_t n = serializeJson(doc, buffer);
+        
+        client.publish("door/status", buffer, n);
+        lastReed = reed;
+    }
+
+  client.loop();
 }