Persist MQTT settings when disabling MQTT

src/main.cpp

@@ -13,6 +13,9 @@
 #define PWM_RES 10
 #define MQTT_MANUFACTURER "Baumann Enkataleiptics"
 #define AUTH_USERNAME "admin"
+#define MQTT_PROBE_TIMEOUT_MS 400  // keep short: blocks loop()/handleClient() per reconnect attempt
+#define MQTT_PAYLOAD_AVAILABLE "online"
+#define MQTT_PAYLOAD_NOT_AVAILABLE "offline"
 
 struct MeterConfig {
   int pin;
@@ -138,12 +141,29 @@ static void saveConfig() {
 // PWM helpers
 // ---------------------------------------------------------------------------
 
+// Tracks the GPIO currently bound to each PWM channel so channels that get
+// freed (meter count shrinks, or a pin is changed/cleared) are detached
+// instead of being left driving PWM on their old pin.
+static int8_t attachedPin[8] = { -1, -1, -1, -1, -1, -1, -1, -1 };
+
 static void attachMeters() {
-  for (int i = 0; i < meterCount && i < 8; i++) {
-    if (meters[i].pin > 0) {
+  for (int i = 0; i < 8; i++) {
+    int pin = (i < meterCount && meters[i].pin > 0) ? meters[i].pin : -1;
+
+    // Release the channel if it's no longer used or its pin changed.
+    if (attachedPin[i] != -1 && attachedPin[i] != pin) {
+      ledcDetachPin(attachedPin[i]);
+      pinMode(attachedPin[i], OUTPUT);
+      digitalWrite(attachedPin[i], LOW);  // drive freed pin low so the meter reads zero
+      Serial.printf("[PWM] detach ch%d pin%d\n", i, attachedPin[i]);
+      attachedPin[i] = -1;
+    }
+
+    if (pin > 0 && attachedPin[i] != pin) {
       ledcSetup(i, PWM_FREQ, PWM_RES);
-      ledcAttachPin(meters[i].pin, i);
-      Serial.printf("[PWM] attach ch%d pin%d\n", i, meters[i].pin);
+      ledcAttachPin(pin, i);
+      attachedPin[i] = pin;
+      Serial.printf("[PWM] attach ch%d pin%d\n", i, pin);
     }
   }
 }
@@ -238,6 +258,10 @@ static void mqttPublishDiscovery() {
     doc["name"]              = name;
     doc["state_topic"]       = stat;
     doc["command_topic"]     = stat + "/set";
+    doc["retain"]                = true;  // HA publishes commands retained so values survive restarts
+    doc["availability_topic"]    = String(mqttCfg.prefix) + "/status";
+    doc["payload_available"]     = MQTT_PAYLOAD_AVAILABLE;
+    doc["payload_not_available"] = MQTT_PAYLOAD_NOT_AVAILABLE;
     doc["min"]               = meters[i].rangeMin;
     doc["max"]               = meters[i].rangeMax;
     doc["step"]              = 0.1;
@@ -250,11 +274,21 @@ static void mqttPublishDiscovery() {
 
     char topic[128];
     snprintf(topic, sizeof(topic), "homeassistant/number/%s/config", objId.c_str());
-    char payload[512];
+    char payload[768];
     serializeJson(doc, payload, sizeof(payload));
     bool pubOk = mqttClient.publish(topic, payload, true);
     Serial.printf("[MQTT] discovery %s -> %s (ok=%d)\n", topic, payload, pubOk);
   }
+
+  // Clear retained discovery for slots no longer in use (meters removed) so
+  // Home Assistant drops the stale entities instead of keeping them forever.
+  for (int i = meterCount; i < MAX_METERS; i++) {
+    String objId = String(devId) + "_meter_" + String(i) + "_current";
+    char topic[128];
+    snprintf(topic, sizeof(topic), "homeassistant/number/%s/config", objId.c_str());
+    mqttClient.publish(topic, "", true);
+    Serial.printf("[MQTT] discovery clear %s\n", topic);
+  }
 }
 
 static void mqttSubscribe() {
@@ -268,9 +302,9 @@ static void mqttSubscribe() {
 }
 
 static bool mqttConnect() {
-  if (!mqttCfg.enabled || strlen(mqttCfg.host) == 0 || strlen(mqttCfg.user) == 0 || strlen(mqttCfg.pass) == 0) {
-    Serial.printf("[MQTT] connect skipped en=%d host=%d user=%d pass=%d\n",
-      mqttCfg.enabled, strlen(mqttCfg.host) > 0, strlen(mqttCfg.user) > 0, strlen(mqttCfg.pass) > 0);
+  if (!mqttCfg.enabled || strlen(mqttCfg.host) == 0) {
+    Serial.printf("[MQTT] connect skipped en=%d host=%d\n",
+      mqttCfg.enabled, strlen(mqttCfg.host) > 0);
     return false;
   }
 
@@ -288,13 +322,18 @@ static bool mqttConnect() {
   mqttClient.setCallback(mqttCallback);
   mqttClient.setBufferSize(1024);
 
+  // Pass NULL for empty credentials so the broker treats it as an anonymous
+  // connection rather than an empty-string login (which some brokers reject).
+  const char* user = strlen(mqttCfg.user) > 0 ? mqttCfg.user : nullptr;
+  const char* pass = strlen(mqttCfg.pass) > 0 ? mqttCfg.pass : nullptr;
+
   Serial.printf("[MQTT] connecting to %s:%d as %s\n", mqttCfg.host, mqttCfg.port, clientId);
-  bool ok = mqttClient.connect(clientId, mqttCfg.user, mqttCfg.pass,
-                               statusTopic, 0, true, "online: false");
+  bool ok = mqttClient.connect(clientId, user, pass,
+                               statusTopic, 0, true, MQTT_PAYLOAD_NOT_AVAILABLE);
 
   if (ok) {
     Serial.printf("[MQTT] connected to %s:%d\n", mqttCfg.host, mqttCfg.port);
-    mqttClient.publish(statusTopic, "online: true", true);
+    mqttClient.publish(statusTopic, MQTT_PAYLOAD_AVAILABLE, true);
     mqttSubscribe();
     mqttPublishDiscovery();
     for (int i = 0; i < meterCount; i++)
@@ -306,14 +345,14 @@ static bool mqttConnect() {
 }
 
 static void mqttLoop() {
-  if (!mqttCfg.enabled || strlen(mqttCfg.host) == 0 || strlen(mqttCfg.user) == 0 || strlen(mqttCfg.pass) == 0) return;
+  if (!mqttCfg.enabled || strlen(mqttCfg.host) == 0) return;
 
   if (!mqttClient.connected()) {
     unsigned long now = millis();
     if (now > mqttReconnectAt) {
       Serial.printf("[MQTT] probing %s:%d\n", mqttCfg.host, mqttCfg.port);
       WiFiClient probe;
-      bool reachable = probe.connect(mqttCfg.host, mqttCfg.port, 1500);
+      bool reachable = probe.connect(mqttCfg.host, mqttCfg.port, MQTT_PROBE_TIMEOUT_MS);
       probe.stop();
 
       if (reachable) {
@@ -353,6 +392,8 @@ static String escHtml(const String& s) {
     char c = s.charAt(i);
     switch (c) {
       case '&':  out += "&amp;";  break;
+      case '<':  out += "&lt;";   break;
+      case '>':  out += "&gt;";   break;
       case '\'': out += "&#39;";  break;
       case '"':  out += "&quot;"; break;
       default:   out += c;
@@ -516,8 +557,8 @@ static void handleConfig() {
       val.toCharArray(hostname, sizeof(hostname));
   }
 
-  if (server.hasArg("mqtt_en")) {
-    mqttCfg.enabled = true;
+  // Persist the connection fields regardless of the enable checkbox so edits
+  // made while disabling MQTT aren't discarded.
   if (server.hasArg("mqtt_host"))
     strlcpy(mqttCfg.host, server.arg("mqtt_host").c_str(), sizeof(mqttCfg.host));
   if (server.hasArg("mqtt_port"))
@@ -528,12 +569,10 @@ static void handleConfig() {
     strlcpy(mqttCfg.pass, server.arg("mqtt_pass").c_str(), sizeof(mqttCfg.pass));
   if (server.hasArg("mqtt_prefix"))
     strlcpy(mqttCfg.prefix, server.arg("mqtt_prefix").c_str(), sizeof(mqttCfg.prefix));
-    Serial.printf("[HTTP] mqtt enabled host=%s port=%u user=%s prefix=%s\n",
-      mqttCfg.host, mqttCfg.port, mqttCfg.user, mqttCfg.prefix);
-  } else {
-    mqttCfg.enabled = false;
-    Serial.println("[HTTP] mqtt disabled");
-  }
+
+  mqttCfg.enabled = server.hasArg("mqtt_en");
+  Serial.printf("[HTTP] mqtt enabled=%d host=%s port=%u user=%s prefix=%s\n",
+    mqttCfg.enabled, mqttCfg.host, mqttCfg.port, mqttCfg.user, mqttCfg.prefix);
 
   if (server.hasArg("auth_en")) {
     if (server.hasArg("auth_pass") && server.arg("auth_pass").length() > 0)