// Lab Task 2 – UART Communication

// --- Pin definitions ---
const uint8_t LED_PIN          = 28;   // GP28 – external LED
const uint8_t POTI_PIN         = 26;   // GP26 – potentiometer (ADC0)
const uint8_t LED_BUILTIN_PIN  = 25;   // GP25 – onboard LED (heartbeat)

// --- State ---
bool     ledState      = false;
bool     blinkMode     = false;
uint16_t blinkInterval = 500;
uint32_t lastBlinkTime = 0;
bool     blinkLedState = false;

// --- Heartbeat ---
uint32_t       lastHeartbeatTime  = 0;
const uint16_t HEARTBEAT_INTERVAL = 500;

void setup() {
  Serial1.begin(115200);         // UART0 – matches Wokwi Serial Monitor
  Serial1.setTimeout(100);       // prevents blocking on readStringUntil

  pinMode(LED_PIN,         OUTPUT);
  pinMode(LED_BUILTIN_PIN, OUTPUT);
  // NOTE: no pinMode for POTI_PIN – ADC pins must not be set to INPUT

  digitalWrite(LED_PIN,         LOW);
  digitalWrite(LED_BUILTIN_PIN, LOW);

  Serial1.println("UART Command Protocol Ready");
  Serial1.println("Commands: ON, OFF, BLINK, NOBLINK, STATUS");
}

void loop() {
  updateHeartbeat();
  updateBlinkInterval();
  if (blinkMode) updateBlink();
  parseSerialCommands();
}

// --- Heartbeat ---
// Toggles onboard LED every 500 ms as a permanent sign of life
void updateHeartbeat() {
  uint32_t now = millis();
  if (now - lastHeartbeatTime >= HEARTBEAT_INTERVAL) {
    lastHeartbeatTime = now;
    digitalWrite(LED_BUILTIN_PIN, !digitalRead(LED_BUILTIN_PIN));
  }
}

// --- Potentiometer -> blink interval ---
void updateBlinkInterval() {
  static uint32_t lastRead = 0;
  uint32_t now = millis();
  if (now - lastRead < 100) return;
  lastRead = now;
  uint16_t potiValue = analogRead(POTI_PIN);
  blinkInterval = 50 + (potiValue * 950UL) / 4095;
}

// --- Non-blocking blink ---
// Toggles external LED at current blinkInterval when blink mode is active
void updateBlink() {
  uint32_t now = millis();
  if (now - lastBlinkTime >= blinkInterval) {
    lastBlinkTime  = now;
    blinkLedState  = !blinkLedState;
    digitalWrite(LED_PIN, blinkLedState ? HIGH : LOW);
    ledState = blinkLedState;
  }
}

// --- Serial command parser ---
// Reads line from Serial Monitor and executes matching command
void parseSerialCommands() {
  if (Serial1.available()) {
    String command = Serial1.readStringUntil('\n');
    command.trim();
    command.toUpperCase();

    if (command == "ON") {
      blinkMode = false;
      ledState  = true;
      digitalWrite(LED_PIN, HIGH);
      Serial1.println("ACK:ON");
    }
    else if (command == "OFF") {
      blinkMode = false;
      ledState  = false;
      digitalWrite(LED_PIN, LOW);
      Serial1.println("ACK:OFF");
    }
    else if (command == "BLINK") {
      blinkMode     = true;
      lastBlinkTime = millis();
      blinkLedState = false;
      Serial1.println("ACK:BLINK");
    }
    else if (command == "NOBLINK") {
      blinkMode = false;
      ledState  = false;
      digitalWrite(LED_PIN, LOW);
      Serial1.println("ACK:NOBLINK");
    }
    else if (command == "STATUS") {
      String status = "STATUS: LED=";
      status += (ledState ? "ON" : "OFF");
      if (blinkMode) {
        status += " BLINKING@";
        status += blinkInterval;
        status += "ms";
      }
      Serial1.println(status);
    }
    else {
      Serial1.print("ERROR: Unknown command '");
      Serial1.print(command);
      Serial1.println("'");
    }
  }
}