#define HEARTBEAT_LED  LED_BUILTIN   // GP25
#define BLINK_LED      15            // LED (GP28)
#define POT_PIN        26            // ADC0

const unsigned long HEARTBEAT_INTERVAL = 500;   

bool blinkEnabled  = false;  // Toggled by Serial command
bool blinkLedState = false;

unsigned long lastHeartbeatTime = 0;
unsigned long lastBlinkTime     = 0;

bool heartbeatState = false;   // Current heartbeat state

unsigned long lastPrintTime = 0;
const unsigned long PRINT_INTERVAL = 200;

// Serial command buffer
char serialBuffer[128];
int bufferIndex = 0;

void setup() {
  pinMode(HEARTBEAT_LED, OUTPUT);
  pinMode(BLINK_LED, OUTPUT);
  pinMode(POT_PIN, INPUT);

  digitalWrite(HEARTBEAT_LED, LOW);
  digitalWrite(BLINK_LED, LOW);

  Serial1.begin(115200);
  delay(100);
  Serial1.println("UART Communication");
  Serial1.println("========================================");

}

void loop() {
  unsigned long now = millis();

  // ===== HEARTBEAT (onboard LED) =====
  if (now - lastHeartbeatTime >= HEARTBEAT_INTERVAL) {
    lastHeartbeatTime = now;
    heartbeatState = !heartbeatState;
    digitalWrite(HEARTBEAT_LED, heartbeatState ? HIGH : LOW);
  }

  // ===== READ POTENTIOMETER =====
  int potRaw = analogRead(POT_PIN);       // 0–4095
  unsigned long blinkInterval = map(potRaw, 0, 4095, 50, 1000);

  // ===== BLINK CONTROL =====
  if (blinkEnabled) {
    if (now - lastBlinkTime >= blinkInterval) {
      lastBlinkTime = now;
      blinkLedState = !blinkLedState;
      digitalWrite(BLINK_LED, blinkLedState ? HIGH : LOW);
    }
  } else {
    digitalWrite(BLINK_LED, LOW);
    blinkLedState = false;
  }

  // ===== PRINT STATUS =====
  if (now - lastPrintTime >= PRINT_INTERVAL) {
    lastPrintTime = now;

    Serial1.print("Blink: ");
    Serial1.print(blinkEnabled ? "ON" : "OFF");
    Serial1.print(" | POT raw: ");
    Serial1.print(potRaw);
    Serial1.print(" | Interval (ms): ");
    Serial1.print(blinkInterval);
    Serial1.print(" | LED: ");
    Serial1.println(blinkLedState ? "HIGH" : "LOW");
  }

  // ===== HANDLE SERIAL INPUT =====
  handleSerialInput();
}


/**
 * Read and process Serial commands
 */
void handleSerialInput() {
  while (Serial1.available()) {
    char c = Serial1.read();

    // If newline or carriage return, process command
    if (c == '\n' || c == '\r') {
      if (bufferIndex > 0) {
        serialBuffer[bufferIndex] = '\0';
        processCommand(serialBuffer);
        bufferIndex = 0;
      }
    }
    // Add character to buffer
    else if (bufferIndex < sizeof(serialBuffer) - 1) {
      serialBuffer[bufferIndex++] = c;
    }
  }
}


/**
 * Process UART commands
 * Commands: ON, OFF, BLINK, NOBLINK, STATUS
 */
void processCommand(char *cmd) {
  // Trim whitespace
  trimString(cmd);
  
  // Convert to uppercase
  toUpperCase(cmd);

  if (strlen(cmd) == 0) {
    return;  // Empty command
  }

  Serial1.print("CMD: ");
  Serial1.println(cmd);

  if (strcmp(cmd, "ON") == 0) {
    blinkEnabled = true;
    blinkLedState = true;
    digitalWrite(BLINK_LED, HIGH);
    Serial1.println("ACK:ON - Blink enabled");
  }
  else if (strcmp(cmd, "OFF") == 0) {
    blinkEnabled = false;
    digitalWrite(BLINK_LED, LOW);
    blinkLedState = false;
    Serial1.println("ACK:OFF - Blink disabled");
  }
  else if (strcmp(cmd, "BLINK") == 0) {
    blinkEnabled = true;
    Serial1.println("ACK:BLINK - Blink started");
  }
  else if (strcmp(cmd, "NOBLINK") == 0) {
    blinkEnabled = false;
    digitalWrite(BLINK_LED, LOW);
    blinkLedState = false;
    Serial1.println("ACK:NOBLINK - Blink stopped");
  }
  else if (strcmp(cmd, "STATUS") == 0) {
    int potRaw = analogRead(POT_PIN);
    unsigned long blinkInterval = map(potRaw, 0, 4095, 50, 1000);
    
    Serial1.print("STATUS: Blink=");
    Serial1.print(blinkEnabled ? "ON" : "OFF");
    Serial1.print(", LED=");
    Serial1.print(blinkLedState ? "HIGH" : "LOW");
    Serial1.print(", Interval=");
    Serial1.print(blinkInterval);
    Serial1.println("ms");
    Serial1.println("ACK:STATUS");
  }
  else {
    Serial1.print("NACK:UNKNOWN_COMMAND [");
    Serial1.print(cmd);
    Serial1.println("]");
  }
}


/**
 * Trim leading and trailing whitespace
 */
void trimString(char *str) {
  int start = 0;
  int end = strlen(str) - 1;
  
  // Find first non-whitespace
  while (start <= end && isspace(str[start])) {
    start++;
  }
  
  // Find last non-whitespace
  while (end >= start && isspace(str[end])) {
    end--;
  }
  
  // Shift string
  int i = 0;
  while (start <= end) {
    str[i++] = str[start++];
  }
  str[i] = '\0';
}


/**
 * Convert string to uppercase
 */
void toUpperCase(char *str) {
  while (*str) {
    if (*str >= 'a' && *str <= 'z') {
      *str = *str - 32;
    }
    str++;
  }
}