Add remote serial log support for client and server

Introduces serial log buffering and transfer between client and server for remote debugging. The client now buffers serial logs and responds to server requests by sending logs via Notecard. The server tracks serial logs from itself and multiple clients, exposes new API endpoints for log retrieval and requests, and adds a web-based Serial Monitor UI for viewing and requesting logs from clients.

Author: dorkmo

TankAlarm-112025-Client-BluesOpta/TankAlarm-112025-Client-BluesOpta.ino

@@ -115,6 +115,18 @@ static size_t strlcpy(char *dst, const char *src, size_t size) {
 #define RELAY_CONTROL_FILE "relay.qi"
 #endif
 
+#ifndef SERIAL_LOG_FILE
+#define SERIAL_LOG_FILE "serial_log.qi"  // Send serial logs to server
+#endif
+
+#ifndef SERIAL_REQUEST_FILE
+#define SERIAL_REQUEST_FILE "serial_request.qi"  // Receive serial log requests
+#endif
+
+#ifndef CLIENT_SERIAL_BUFFER_SIZE
+#define CLIENT_SERIAL_BUFFER_SIZE 50  // Buffer up to 50 log messages
+#endif
+
 #ifndef NOTE_BUFFER_PATH
 #define NOTE_BUFFER_PATH "/pending_notes.log"
 #endif
@@ -308,6 +320,21 @@ static int gRpmLastPinState[MAX_TANKS];  // Initialized dynamically in setup()
 #define RPM_SAMPLE_DURATION_MS 3000
 #endif
 
+// Serial log buffer structure for client
+struct SerialLogEntry {
+  double timestamp;
+  char message[160];
+};
+
+struct ClientSerialLog {
+  SerialLogEntry entries[CLIENT_SERIAL_BUFFER_SIZE];
+  uint8_t writeIndex;
+  uint8_t count;
+};
+
+static ClientSerialLog gSerialLog;
+static unsigned long gLastSerialRequestCheckMillis = 0;
+
 // Forward declarations
 static void initializeStorage();
 static void ensureConfigLoaded();
@@ -345,6 +372,9 @@ static int getRelayPin(uint8_t relayIndex);
 static float readNotecardVinVoltage();
 static void checkRelayMomentaryTimeout(unsigned long now);
 static void resetRelayForTank(uint8_t idx);
+static void addSerialLog(const char *message);
+static void pollForSerialRequests();
+static void sendSerialLogs();
 
 void setup() {
   Serial.begin(115200);
@@ -355,6 +385,9 @@ void setup() {
   Serial.println();
   Serial.println(F("Tank Alarm Client 112025 starting"));
 
+  // Initialize serial log buffer
+  memset(&gSerialLog, 0, sizeof(ClientSerialLog));
+
   // Set analog resolution to 12-bit to match the /4095.0f divisor used in readTankSensor
   analogReadResolution(12);
 
@@ -434,6 +467,7 @@ void setup() {
   initializeRelays();
 
   Serial.println(F("Client setup complete"));
+  addSerialLog("Client started successfully");
 }
 
 void loop() {
@@ -472,6 +506,11 @@ void loop() {
     pollForRelayCommands();
   }
 
+  if (now - gLastSerialRequestCheckMillis >= 600000UL) {  // Check every 10 minutes
+    gLastSerialRequestCheckMillis = now;
+    pollForSerialRequests();
+  }
+
   // Check for momentary relay timeout (30 minutes)
   checkRelayMomentaryTimeout(now);
 
@@ -1205,6 +1244,7 @@ static void applyConfigUpdate(const JsonDocument &doc) {
   printHardwareRequirements(gConfig);
   scheduleNextDailyReport();
   Serial.println(F("Configuration updated from server"));
+  addSerialLog("Config updated from server");
 }
 
 static void persistConfigIfDirty() {
@@ -1703,6 +1743,10 @@ static void sendAlarm(uint8_t idx, const char *alarmType, float inches) {
     Serial.print(F(" type "));
     Serial.println(alarmType);
 
+    char logMsg[128];
+    snprintf(logMsg, sizeof(logMsg), "Alarm: %s - %s - %.1fin", cfg.name, alarmType, inches);
+    addSerialLog(logMsg);
+    
     // Handle relay control based on mode
     if (cfg.relayTargetClient[0] != '\0' && cfg.relayMask != 0) {
       bool shouldActivateRelay = false;
@@ -2485,6 +2529,129 @@ static void resetRelayForTank(uint8_t idx) {
   gRelayActivationTime[idx] = 0;
 }
 
+// ============================================================================
+// Serial Logging for Remote Debugging
+// ============================================================================
+
+static void addSerialLog(const char *message) {
+  if (!message || strlen(message) == 0) {
+    return;
+  }
+
+  SerialLogEntry &entry = gSerialLog.entries[gSerialLog.writeIndex];
+  entry.timestamp = currentEpoch();
+  
+  // Truncate if necessary
+  size_t len = strlen(message);
+  if (len >= sizeof(entry.message)) {
+    len = sizeof(entry.message) - 1;
+  }
+  memcpy(entry.message, message, len);
+  entry.message[len] = '\0';
+
+  gSerialLog.writeIndex = (gSerialLog.writeIndex + 1) % CLIENT_SERIAL_BUFFER_SIZE;
+  if (gSerialLog.count < CLIENT_SERIAL_BUFFER_SIZE) {
+    gSerialLog.count++;
+  }
+}
+
+static void pollForSerialRequests() {
+  // Check for serial log requests from server
+  while (true) {
+    J *req = notecard.newRequest("note.get");
+    if (!req) {
+      return;
+    }
+    
+    JAddStringToObject(req, "file", SERIAL_REQUEST_FILE);
+    JAddBoolToObject(req, "delete", true);
+    
+    J *rsp = notecard.requestAndResponse(req);
+    if (!rsp) {
+      return;
+    }
+
+    J *body = JGetObject(rsp, "body");
+    if (!body) {
+      notecard.deleteResponse(rsp);
+      break;
+    }
+
+    const char *request = JGetString(body, "request");
+    if (request && strcmp(request, "send_logs") == 0) {
+      DEBUG_PRINTLN(F("Serial log request received from server"));
+      addSerialLog("Serial log request received");
+      sendSerialLogs();
+    }
+
+    notecard.deleteResponse(rsp);
+  }
+}
+
+static void sendSerialLogs() {
+  if (gSerialLog.count == 0) {
+    DEBUG_PRINTLN(F("No serial logs to send"));
+    return;
+  }
+
+  // Create a note with an array of log entries
+  J *req = notecard.newRequest("note.add");
+  if (!req) {
+    return;
+  }
+
+  JAddStringToObject(req, "file", SERIAL_LOG_FILE);
+  JAddBoolToObject(req, "sync", true);
+
+  J *body = JCreateObject();
+  if (!body) {
+    return;
+  }
+
+  JAddStringToObject(body, "client", gDeviceUID);
+
+  J *logsArray = JCreateArray();
+  if (!logsArray) {
+    JDelete(body);
+    return;
+  }
+
+  // Add logs from oldest to newest (circular buffer)
+  uint8_t startIdx = (gSerialLog.count < CLIENT_SERIAL_BUFFER_SIZE) ? 0 : gSerialLog.writeIndex;
+  uint8_t sentCount = 0;
+  
+  for (uint8_t i = 0; i < gSerialLog.count && sentCount < 20; ++i) {  // Limit to 20 most recent logs
+    uint8_t idx = (startIdx + i) % CLIENT_SERIAL_BUFFER_SIZE;
+    SerialLogEntry &entry = gSerialLog.entries[idx];
+    
+    if (entry.message[0] == '\0') {
+      continue;
+    }
+
+    J *logEntry = JCreateObject();
+    if (!logEntry) {
+      break;
+    }
+
+    JAddNumberToObject(logEntry, "timestamp", entry.timestamp);
+    JAddStringToObject(logEntry, "message", entry.message);
+    JAddItemToArray(logsArray, logEntry);
+    sentCount++;
+  }
+
+  JAddItemToObject(body, "logs", logsArray);
+  JAddItemToObject(req, "body", body);
+
+  bool queued = notecard.sendRequest(req);
+  if (queued) {
+    DEBUG_PRINT(F("Sent "));
+    DEBUG_PRINT(sentCount);
+    DEBUG_PRINTLN(F(" serial logs to server"));
+  } else {
+    DEBUG_PRINTLN(F("Failed to queue serial logs"));
+  }
+}
+
 // ============================================================================
 // Notecard VIN Voltage Reading
 // ============================================================================