#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// ===== LCD =====
LiquidCrystal_I2C lcd(0x27, 16, 2);

// ===== Pins (adjust if needed) =====
// RGB LED (common cathode)
const int rgbRedPin   = 14;
const int rgbGreenPin = 12;
const int rgbBluePin  = 13;

const int pirPin = 33;          // PIR motion sensor OUT
const int buttonPin = 19;       // button to GND (INPUT_PULLUP)
const int buzzerPin = 32;       // active/passive buzzer (tone works on ESP32)

// ===== States =====
enum State { IDLE, MOTION, REGISTERED };
State state = IDLE;

// ===== Timing =====
unsigned long tStateStart = 0;

// Variables for MOTION cycle steps
unsigned long tStep = 0;
int motionStep = 0;

// Button debounce
int lastButtonReading = HIGH;
int stableButtonState = HIGH;
unsigned long tLastDebounce = 0;
const unsigned long debounceMs = 30;

// ===== RGB helpers =====
void rgbWrite(bool r, bool g, bool b) {
  digitalWrite(rgbRedPin,   r ? HIGH : LOW);
  digitalWrite(rgbGreenPin, g ? HIGH : LOW);
  digitalWrite(rgbBluePin,  b ? HIGH : LOW);
}

void rgbOff()  { rgbWrite(false, false, false); }
void rgbBlue() { rgbWrite(false, false, true);  }
void rgbGreen(){ rgbWrite(false, true,  false); }

// ===== LCD helpers =====
void lcdShow(const char* line1, const char* line2) {
  lcd.setCursor(0, 0);
  lcd.print("                ");
  lcd.setCursor(0, 1);
  lcd.print("                ");
  lcd.setCursor(0, 0);
  lcd.print(line1);
  lcd.setCursor(0, 1);
  lcd.print(line2);
}

// ===== Friendly sound (mini jingle) =====
void friendlyBeep() {
  tone(buzzerPin, 880);
  delay(80);

  tone(buzzerPin, 1300);
  delay(100);

  tone(buzzerPin, 0);  // stop
}


// ===== Button read with debounce (returns true on press edge) =====
bool buttonPressedEdge() {
  int reading = digitalRead(buttonPin);

  if (reading != lastButtonReading) {
    tLastDebounce = millis();
    lastButtonReading = reading;
  }

  if ((millis() - tLastDebounce) > debounceMs) {
    if (reading != stableButtonState) {
      stableButtonState = reading;

      // Using INPUT_PULLUP → pressed = LOW
      if (stableButtonState == LOW) return true;
    }
  }
  return false;
}

// ===== Change system state =====
void setState(State s) {
  state = s;
  tStateStart = millis();

  if (state == IDLE) {
    rgbBlue();
    lcdShow("Welcome", "");
  }

  if (state == MOTION) {
    // Initialize motion cycle
    motionStep = 0;
    tStep = millis();
  }

  if (state == REGISTERED) {
    rgbGreen();
    lcdShow("Thank you :)", "");
  }
}

void setup() {
  Serial.begin(115200);

  pinMode(rgbRedPin, OUTPUT);
  pinMode(rgbGreenPin, OUTPUT);
  pinMode(rgbBluePin, OUTPUT);

  pinMode(pirPin, INPUT_PULLDOWN);
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(buzzerPin, OUTPUT);

  lcd.init();
  lcd.backlight();

  setState(IDLE);
}

void loop() {
  const bool motion = (digitalRead(pirPin) == HIGH);

  // If button is pressed in any state → register action
  if (buttonPressedEdge()) {
    setState(REGISTERED);
  }

  // Motion-based transitions
  if (state == IDLE) {
    if (motion) setState(MOTION);
  } 
  else if (state == MOTION) {
    if (!motion) setState(IDLE);
  }

  // ===== State logic =====
  if (state == IDLE) {
    // Maintain idle state
    return;
  }

  if (state == REGISTERED) {
    // Keep green LED for 1 second
    if (millis() - tStateStart >= 1000) {
      // After 2 seconds total → return to idle
      if (millis() - tStateStart >= 2000) {
        setState(IDLE);
      }
    }
    return;
  }

  if (state == MOTION) {

    // Repeat while motion is detected:
    // - Blink LED 3 times
    // - Play friendly sound
    // - Alternate LCD messages
    // - Wait 2s between repetitions

    const unsigned long blinkOn  = 150;
    const unsigned long blinkOff = 150;
    const unsigned long msgHold  = 1000;
    const unsigned long gapBetweenReps = 2000;

    unsigned long now = millis();

    switch (motionStep) {

      case 0: 
        rgbBlue(); 
        friendlyBeep(); 
        tStep = now; 
        motionStep = 1; 
        break;

      case 1: 
        if (now - tStep >= blinkOn)  { rgbOff(); tStep = now; motionStep = 2; } 
        break;

      case 2: 
        if (now - tStep >= blinkOff) { rgbBlue(); tStep = now; motionStep = 3; } 
        break;

      case 3: 
        if (now - tStep >= blinkOn)  { rgbOff(); tStep = now; motionStep = 4; } 
        break;

      case 4: 
        if (now - tStep >= blinkOff) { rgbBlue(); tStep = now; motionStep = 5; } 
        break;

      case 5: 
        if (now - tStep >= blinkOn)  { rgbOff(); tStep = now; motionStep = 6; } 
        break;

      case 6: 
        if (now - tStep >= blinkOff) {
          rgbBlue();
          lcdShow("Hello there!", "");
          tStep = now;
          motionStep = 7;
        } 
        break;

      case 7: 
        if (now - tStep >= msgHold) {
          lcdShow("Register here", "");
          tStep = now;
          motionStep = 8;
        } 
        break;

      case 8: 
        if (now - tStep >= msgHold) {
          tStep = now;
          motionStep = 9;
        } 
        break;

      case 9: 
        if (now - tStep >= gapBetweenReps) {
          if (digitalRead(pirPin) == HIGH) {
            motionStep = 0;
          } else {
            setState(IDLE);
          }
        } 
        break;
    }
  }
}