// Week 4 - XIAO RP2040
// Modified version: stable button (INPUT_PULLUP), press-event trigger, no delay (millis), LED array

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
const unsigned long STEP_MS = 250;      // speed of the animation
const int CYCLES_TO_RUN = 7;            // how many times the pattern repeats

// Debounce
int lastReading = HIGH;
int stableState = HIGH;
unsigned long lastDebounceTime = 0;
const unsigned long DEBOUNCE_MS = 30;

// Sequence state machine
bool running = false;
int cycleCount = 0;
int stepIndex = 0;                      // 0..(2*NLEDS - 1)
unsigned long lastStepTime = 0;

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

void setup() {
  Serial.begin(9600);

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

  allOff();
  Serial.println("RP2040 ready. Press the button to run the LED sequence.");
}

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

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

  unsigned long now = millis();
  if (now - lastStepTime < STEP_MS) return;
  lastStepTime = 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 >= CYCLES_TO_RUN) {
      running = false;
      allOff();
      Serial.println("Sequence finished.");
    }
  }
}

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

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

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

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

  // ----- Run the LED animation without blocking -----
  updateSequence();
}