// ── Pin Definitions ──────────────────────────────
const int RED_PIN    = 2;
const int YELLOW_PIN = 3;
const int GREEN_PIN  = 4;
const int BLUE_PIN   = 5;  // Pedestrian LED

// ── Durations (ms) ───────────────────────────────
const unsigned long RED_DUR    = 5000;
const unsigned long YELLOW_DUR = 2000;
const unsigned long GREEN_DUR  = 5000;
const unsigned long PED_DUR    = 3000;
const unsigned long BLINK_SLOW = 500;
const unsigned long BLINK_FAST = 300;

// ── State Machine ────────────────────────────────
enum State {
  STATE_RED,
  STATE_YELLOW_RG,
  STATE_GREEN,
  STATE_YELLOW_GR,
  STATE_PEDESTRIAN
};

State currentState = STATE_RED;

// ── Timing Variables ─────────────────────────────
unsigned long stateStart = 0;
unsigned long lastBlink  = 0;
bool blinkOn = false;

// ── Helper ───────────────────────────────────────
void allOff() {
  digitalWrite(RED_PIN,    LOW);
  digitalWrite(YELLOW_PIN, LOW);
  digitalWrite(GREEN_PIN,  LOW);
  digitalWrite(BLUE_PIN,   LOW);
}

// ── Setup ────────────────────────────────────────
void setup() {
  pinMode(RED_PIN,    OUTPUT);
  pinMode(YELLOW_PIN, OUTPUT);
  pinMode(GREEN_PIN,  OUTPUT);
  pinMode(BLUE_PIN,   OUTPUT);

  Serial.begin(9600);
  Serial.println("=========================");
  Serial.println(" Traffic Light Started!");
  Serial.println("=========================");

  allOff();
  digitalWrite(RED_PIN, HIGH);
  stateStart = millis();
  Serial.println(">> State: RED");
}

// ── Loop ─────────────────────────────────────────
void loop() {
  unsigned long now     = millis();
  unsigned long elapsed = now - stateStart;

  switch (currentState) {

    case STATE_RED:
      // Blue pedestrian blinks slowly while RED
      if (now - lastBlink >= BLINK_SLOW) {
        lastBlink = now;
        blinkOn = !blinkOn;
        digitalWrite(BLUE_PIN, blinkOn);
      }
      if (elapsed >= RED_DUR) {
        allOff();
        digitalWrite(YELLOW_PIN, HIGH);
        currentState = STATE_YELLOW_RG;
        stateStart   = now;
        Serial.println(">> State: YELLOW (Red → Green)");
      }
      break;

    case STATE_YELLOW_RG:
      if (elapsed >= YELLOW_DUR) {
        allOff();
        digitalWrite(GREEN_PIN, HIGH);
        currentState = STATE_GREEN;
        stateStart   = now;
        Serial.println(">> State: GREEN");
      }
      break;

    case STATE_GREEN:
      if (elapsed >= GREEN_DUR) {
        allOff();
        digitalWrite(YELLOW_PIN, HIGH);
        currentState = STATE_YELLOW_GR;
        stateStart   = now;
        Serial.println(">> State: YELLOW (Green → Red)");
      }
      break;

    case STATE_YELLOW_GR:
      if (elapsed >= YELLOW_DUR) {
        allOff();
        digitalWrite(RED_PIN, HIGH);
        currentState = STATE_PEDESTRIAN;
        stateStart   = now;
        Serial.println(">> State: PEDESTRIAN CROSSING");
      }
      break;

    case STATE_PEDESTRIAN:
      // Blue pedestrian blinks FAST
      if (now - lastBlink >= BLINK_FAST) {
        lastBlink = now;
        blinkOn = !blinkOn;
        digitalWrite(BLUE_PIN, blinkOn);
      }
      if (elapsed >= PED_DUR) {
        allOff();
        digitalWrite(RED_PIN, HIGH);
        currentState = STATE_RED;
        stateStart   = now;
        Serial.println(">> State: RED");
      }
      break;
  }
}