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

// ===== LCD I2C =====
LiquidCrystal_I2C lcd(0x27, 20, 4);

// ===== Pin Setup =====
#define TRIG_FRONT 13
#define ECHO_FRONT 12
#define TRIG_BACK 14
#define ECHO_BACK 27

#define BUZZER 19
#define BTN_ENGINE 18
#define BTN_SENSOR 5

#define LED_ENGINE 2
#define LED_LOCK 4

#define RELAY_BRAKE 15
#define LED_BRAKE 16

#define HEADLIGHT 17
#define LDR_PIN 34
#define LDR_THRESHOLD 1000 // ปรับตามความสว่าง

// ===== Auto-lock settings =====
const unsigned long AUTO_LOCK_DELAY_MS = 5000UL;  // 5 วินาที หลังสตาร์ทรถ
const unsigned long AUTO_LOCK_AFTER_OFF_MS = 15000UL; // 15 วินาที หลังดับรถ

// ===== State Variables =====
bool engineOn = false;
bool sensorOn = false;

// button prev state for edge detect
int prevBtnEngine = HIGH;
int prevBtnSensor = HIGH;

// auto-lock timer
bool autoLockPending = false;
unsigned long autoLockStartMillis = 0;
unsigned long autoLockDelayMS = 0;

// ===== Function วัดระยะ Ultrasonic =====
long readDistanceCM(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  long duration = pulseIn(echoPin, HIGH, 30000); // timeout 30ms
  long distance = duration * 0.034 / 2;
  return distance;
}

// ===== Lock Door =====
void lockDoorNow() {
  digitalWrite(LED_LOCK, HIGH); // lock
  lcd.setCursor(0,2);
  lcd.print("Door: Locked     ");
  autoLockPending = false;
  Serial.println("Door auto-locked.");
}

void cancelAutoLock() {
  if (autoLockPending) {
    autoLockPending = false;
    Serial.println("Auto-lock canceled.");
  }
}

void setup() {
  Serial.begin(115200);
  lcd.init();
  lcd.backlight();

  // Pin modes
  pinMode(TRIG_FRONT, OUTPUT);
  pinMode(ECHO_FRONT, INPUT);
  pinMode(TRIG_BACK, OUTPUT);
  pinMode(ECHO_BACK, INPUT);

  pinMode(BUZZER, OUTPUT);
  pinMode(LED_ENGINE, OUTPUT);
  pinMode(LED_LOCK, OUTPUT);

  pinMode(BTN_ENGINE, INPUT_PULLUP);
  pinMode(BTN_SENSOR, INPUT_PULLUP);

  pinMode(RELAY_BRAKE, OUTPUT);
  pinMode(LED_BRAKE, OUTPUT);

  pinMode(HEADLIGHT, OUTPUT);

  // Initial Display
  lcd.setCursor(0,0); lcd.print(" Smart Parking Sys ");
  lcd.setCursor(0,1); lcd.print("Engine: OFF ");
  lcd.setCursor(0,2); lcd.print("Door: Locked ");
  lcd.setCursor(0,3); lcd.print("Sensor: OFF ");
  digitalWrite(LED_LOCK, HIGH);   // Locked by default
  digitalWrite(LED_ENGINE, LOW);
  digitalWrite(RELAY_BRAKE, LOW);
  digitalWrite(LED_BRAKE, LOW);
  digitalWrite(HEADLIGHT, LOW);

  // init prev button states
  prevBtnEngine = digitalRead(BTN_ENGINE);
  prevBtnSensor = digitalRead(BTN_SENSOR);
}

void loop() {
  // ===== Read buttons with edge detection =====
  int curBtnEngine = digitalRead(BTN_ENGINE);
  if (prevBtnEngine == HIGH && curBtnEngine == LOW) { // falling edge = pressed
    engineOn = !engineOn;
    if (engineOn) {
      digitalWrite(LED_ENGINE, HIGH);
      digitalWrite(LED_LOCK, LOW); // unlock
      lcd.setCursor(0,1); lcd.print("Engine: ON       ");
      lcd.setCursor(0,2); lcd.print("Door: Unlocked   ");
      cancelAutoLock();

      // Start auto-lock countdown for 5s
      autoLockPending = true;
      autoLockStartMillis = millis();
      autoLockDelayMS = AUTO_LOCK_DELAY_MS;

    } else {
      digitalWrite(LED_ENGINE, LOW);
      sensorOn = false;
      lcd.setCursor(0,1); lcd.print("Engine: OFF      ");
      lcd.setCursor(0,3); lcd.print("Sensor: OFF      ");

      // Start auto-lock countdown for 15s if door unlocked
      if (digitalRead(LED_LOCK) == LOW) { // unlocked
        autoLockPending = true;
        autoLockStartMillis = millis();
        autoLockDelayMS = AUTO_LOCK_AFTER_OFF_MS;
        lcd.setCursor(0,2); lcd.print("Door: Unlocked   ");
      } else {
        digitalWrite(LED_LOCK, HIGH);
        lcd.setCursor(0,2); lcd.print("Door: Locked     ");
      }

      digitalWrite(RELAY_BRAKE, LOW);
      digitalWrite(LED_BRAKE, LOW);
      digitalWrite(HEADLIGHT, LOW);
    }
    delay(150); // debounce
  }
  prevBtnEngine = curBtnEngine;

  int curBtnSensor = digitalRead(BTN_SENSOR);
  if (engineOn && prevBtnSensor == HIGH && curBtnSensor == LOW) {
    sensorOn = !sensorOn;
    lcd.setCursor(0,3);
    lcd.print(sensorOn ? "Sensor: ON       " : "Sensor: OFF      ");
    delay(150);
  }
  prevBtnSensor = curBtnSensor;

  // ===== Auto-lock handling =====
  if (autoLockPending) {
    unsigned long now = millis();
    if (engineOn && autoLockDelayMS == AUTO_LOCK_AFTER_OFF_MS) {
      cancelAutoLock(); // cancel exit lock if engine turned on
    } else if (now - autoLockStartMillis >= autoLockDelayMS) {
      lockDoorNow();
    } else {
      unsigned long remain = (autoLockDelayMS - (now - autoLockStartMillis)) / 1000;
      lcd.setCursor(12,2);
      if (remain < 10) lcd.print("0");
      lcd.print(remain);
      lcd.print("s");
    }
  } else {
    lcd.setCursor(12,2); lcd.print("    ");
  }

  // ===== Sensor / Brake logic =====
  if (engineOn && sensorOn) {
    long front = readDistanceCM(TRIG_FRONT, ECHO_FRONT);
    long back = readDistanceCM(TRIG_BACK, ECHO_BACK);

    lcd.setCursor(0,3);
    lcd.print("F:");
    if (front < 0 || front > 400) lcd.print("---");
    else lcd.print(front);
    lcd.print("cm B:");
    if (back < 0 || back > 400) lcd.print("---");
    else lcd.print(back);
    lcd.print("cm   ");

    if (front <= 40 || back <= 40) {
      tone(BUZZER, 1000);
      digitalWrite(RELAY_BRAKE, HIGH);
      digitalWrite(LED_BRAKE, HIGH);
    } else {
      noTone(BUZZER);
      digitalWrite(RELAY_BRAKE, LOW);
      digitalWrite(LED_BRAKE, LOW);
    }
  } else {
    noTone(BUZZER);
    digitalWrite(RELAY_BRAKE, LOW);
    digitalWrite(LED_BRAKE, LOW);
    if (!sensorOn) {
      lcd.setCursor(0,3);
      lcd.print("Sensor: OFF      ");
    }
  }

  // ===== Headlight (LDR) =====
  int ldrValue = analogRead(LDR_PIN);
  if (engineOn) {
    if (ldrValue < LDR_THRESHOLD) {
      digitalWrite(HEADLIGHT, HIGH);
      lcd.setCursor(0,1); lcd.print("Headlight: ON   ");
    } else {
      digitalWrite(HEADLIGHT, LOW);
      lcd.setCursor(0,1); lcd.print("Headlight: OFF  ");
    }
  } else {
    digitalWrite(HEADLIGHT, LOW);
  }

  delay(150);
}