// XIAO RP2040 - Week 4 (Fab Academy)
// Interaction: Button starts LED sequence (input)
// Output: 3 LEDs blink in a pattern (output)
// Communication: USB Serial PC <-> XIAO (commands + logs)
//
// Pins used (change if needed):
// LEDs: D0, D6, D7
// Button: D1 to GND (INPUT_PULLUP)

const uint8_t LEDS[] = {D0, D6, D7};
const uint8_t NLEDS = sizeof(LEDS) / sizeof(LEDS[0]);
const uint8_t BUTTON_PIN = D1;          // button to GND

// Sequence parameters
bool running = false;
int cyclesToRun = 7;
int cycleCount = 0;
int stepIndex = 0;                       // 0..(2*NLEDS-1)
unsigned long lastStep = 0;
unsigned long stepMs = 250;              // animation speed

// Button debounce / press-event
int lastReading = HIGH;
int stableState = HIGH;
unsigned long lastDebounceTime = 0;
const unsigned long DEBOUNCE_MS = 30;

// Serial input buffer
String cmd = "";

// ---------- helpers ----------
void allOff() {
  for (uint8_t i = 0; i < NLEDS; i++) digitalWrite(LEDS[i], LOW);
}

void allOn() {
  for (uint8_t i = 0; i < NLEDS; i++) digitalWrite(LEDS[i], HIGH);
}

// ---------- sequence ----------
void startSequence() {
  running = true;
  cycleCount = 0;
  stepIndex = 0;
  lastStep = millis();
  allOff();
  Serial.println("Button pressed -> sequence start");
}

void updateSequence() {
  if (!running) return;

  unsigned long now = millis();
  if (now - lastStep < stepMs) return;
  lastStep = now;

  // Pattern: turn ON LEDs forward, then turn OFF LEDs backward
  if (stepIndex < NLEDS) {
    digitalWrite(LEDS[stepIndex], HIGH);
  } else {
    int offIdx = (2 * NLEDS - 1) - stepIndex;
    digitalWrite(LEDS[offIdx], LOW);
  }

  stepIndex++;

  // End of one full cycle
  if (stepIndex >= 2 * NLEDS) {
    stepIndex = 0;
    cycleCount++;
    Serial.print("Cycle: ");
    Serial.println(cycleCount);

    if (cycleCount >= cyclesToRun) {
      running = false;
      allOff();
      Serial.println("Sequence finished.");
    }
  }
}

// ---------- serial commands ----------
void handleCommand(String s) {
  // Debug: show what arrived
  Serial.print("RX: ");
  Serial.println(s);

  s.trim();
  s.toLowerCase();

  if (s == "on") {
    running = false;
    allOn();
    Serial.println("OK: LEDs ON");
    return;
  }

  if (s == "off") {
    running = false;
    allOff();
    Serial.println("OK: LEDs OFF");
    return;
  }

  if (s == "start") {
    if (!running) startSequence();
    Serial.println("OK: start");
    return;
  }

  if (s == "status") {
    Serial.print("running=");
    Serial.print(running ? "true" : "false");
    Serial.print(" stepMs=");
    Serial.print(stepMs);
    Serial.print(" cyclesToRun=");
    Serial.println(cyclesToRun);
    return;
  }

  if (s.startsWith("blink ")) {
    int v = s.substring(6).toInt();
    if (v < 50) v = 50;
    stepMs = (unsigned long)v;
    Serial.print("OK: stepMs=");
    Serial.println(stepMs);
    return;
  }

  Serial.println("ERR: try: on | off | start | status | blink 300");
}

// ---------- setup / loop ----------
void setup() {
  Serial.begin(115200);
  delay(1200); // helps to see the first messages after reset

  for (uint8_t i = 0; i < NLEDS; i++) pinMode(LEDS[i], OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);

  allOff();

  Serial.println("XIAO RP2040 ready.");
  Serial.println("Commands: on | off | start | status | blink <ms>");
  Serial.println("Press the button to start the LED sequence.");
}

void loop() {
  // ---- Debounced button press event ----
  int reading = digitalRead(BUTTON_PIN);

  if (reading != lastReading) {
    lastDebounceTime = millis();
    lastReading = reading;
  }

  if (millis() - lastDebounceTime > DEBOUNCE_MS) {
    if (reading != stableState) {
      stableState = reading;

      // INPUT_PULLUP => pressed = LOW
      if (stableState == LOW) {
        if (!running) startSequence();
        else Serial.println("Sequence already running...");
      }
    }
  }

  // ---- Read serial command line (PC -> XIAO) ----
  if (Serial.available()) {
    String line = Serial.readStringUntil('\n');
    line.trim(); // removes \r
    if (line.length() > 0) handleCommand(line);
  }

  // ---- Run LED sequence (non-blocking) ----
  updateSequence();
}