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

// ==================================================
// LCD I2C
// ==================================================
LiquidCrystal_I2C lcd(0x27, 16, 2);   // kalau tak jalan cuba 0x3F

// ==================================================
// INPUT
// ==================================================
const int PIR_PIN  = 34;
const int POT_PIN  = 32;
const int TRIG_PIN = 25;
const int ECHO_PIN = 26;

// ==================================================
// OUTPUT
// ==================================================
const int GREEN_LED = 18;
const int RED_LED   = 19;
const int BUZZER    = 27;

// ==================================================
// LCD I2C PINS
// ==================================================
const int SDA_PIN = 21;
const int SCL_PIN = 22;

// ==================================================
// SETTINGS
// ==================================================
const int SOAP_LOW_THRESHOLD = 1200;
const int DISTANCE_ALERT_CM  = 10;

// dispense control
bool dispensing = false;
bool pirLatched = false;
unsigned long dispenseStart = 0;
const unsigned long DISPENSE_DURATION = 1500; // 1.5 saat

// ultrasonic alert timer
unsigned long lastBeepTime = 0;
const unsigned long BEEP_INTERVAL = 400;

// LCD refresh timer
unsigned long lastLCDUpdate = 0;
const unsigned long LCD_INTERVAL = 500; // lebih slow, kurang flicker

// ==================================================
// SETUP
// ==================================================
void setup() {
  Serial.begin(115200);

  // Input
  pinMode(PIR_PIN, INPUT);
  pinMode(POT_PIN, INPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  // Output
  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(BUZZER, OUTPUT);

  digitalWrite(GREEN_LED, LOW);
  digitalWrite(RED_LED, LOW);
  digitalWrite(BUZZER, LOW);

  // LCD setup
  Wire.begin(SDA_PIN, SCL_PIN);
  lcd.init();
  lcd.backlight();

  lcd.setCursor(0, 0);
  lcd.print("SMART SINK");
  lcd.setCursor(0, 1);
  lcd.print("System Start");
  delay(2000);

  lcd.setCursor(0, 0);
  lcd.print("SYSTEM READY    ");
  lcd.setCursor(0, 1);
  lcd.print("P:0 D:-- S:OK   ");

  Serial.println("SMART SINK SIMULATOR START");
  Serial.println("System Ready...");
}

// ==================================================
// LOOP
// ==================================================
void loop() {
  int pirState = digitalRead(PIR_PIN);
  int potValue = analogRead(POT_PIN);
  float distance = readDistanceCM();

  bool soapLow = (potValue < SOAP_LOW_THRESHOLD);
  bool distanceAlert = (distance > 0 && distance < DISTANCE_ALERT_CM);

  // -----------------------------
  // SERIAL MONITOR STATUS
  // -----------------------------
  Serial.print("PIR: ");
  Serial.print(pirState);
  Serial.print(" | POT: ");
  Serial.print(potValue);
  Serial.print(" | DIST: ");
  Serial.print(distance);
  Serial.print(" cm");
  Serial.print(" | SOAP LOW: ");
  Serial.print(soapLow ? "YES" : "NO");
  Serial.print(" | ALERT: ");
  Serial.println(distanceAlert ? "YES" : "NO");

  // -----------------------------
  // 1. SOAP LOW WARNING
  // -----------------------------
  if (soapLow) {
    digitalWrite(RED_LED, HIGH);
    digitalWrite(BUZZER, HIGH);
  } else {
    digitalWrite(RED_LED, LOW);
    digitalWrite(BUZZER, LOW);
  }

  // -----------------------------
  // 2. DISPENSE SOAP (PIR)
  // -----------------------------
  if (pirState == HIGH && !soapLow && !dispensing && !pirLatched) {
    dispensing = true;
    pirLatched = true;
    dispenseStart = millis();
    digitalWrite(GREEN_LED, HIGH);
    Serial.println("HAND DETECTED -> DISPENSING SOAP");
  }

  if (dispensing && millis() - dispenseStart >= DISPENSE_DURATION) {
    dispensing = false;
    digitalWrite(GREEN_LED, LOW);
    Serial.println("DISPENSE DONE");
  }

  if (pirState == LOW) {
    pirLatched = false;
  }

  // -----------------------------
  // 3. ULTRASONIC ALERT
  // -----------------------------
  if (distanceAlert && !soapLow) {
    if (millis() - lastBeepTime >= BEEP_INTERVAL) {
      lastBeepTime = millis();
      digitalWrite(BUZZER, HIGH);
      delay(80);
      digitalWrite(BUZZER, LOW);
      Serial.println("DISTANCE ALERT TRIGGERED");
    }
  }

  // -----------------------------
  // 4. LCD DISPLAY
  // -----------------------------
  if (millis() - lastLCDUpdate >= LCD_INTERVAL) {
    lastLCDUpdate = millis();
    updateLCD(pirState, distance, soapLow, distanceAlert);
  }

  delay(150);
}

// ==================================================
// FUNCTION: READ DISTANCE FROM HC-SR04
// ==================================================
float readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 30000);

  if (duration <= 0) {
    return -1;
  }

  float distance = duration * 0.0343 / 2.0;
  return distance;
}

// ==================================================
// FUNCTION: UPDATE LCD (NO FLICKER)
// ==================================================
void updateLCD(int pirState, float distance, bool soapLow, bool distanceAlert) {
  static String lastLine1 = "";
  static String lastLine2 = "";

  String line1 = "";
  String line2 = "";

  // Line 1 status utama
  if (soapLow) {
    line1 = "SOAP LOW!";
  }
  else if (dispensing) {
    line1 = "DISPENSING...";
  }
  else if (distanceAlert) {
    line1 = "OBJ TOO CLOSE";
  }
  else {
    line1 = "SYSTEM READY";
  }

  // Line 2 info sensor
  line2 = "P:";
  line2 += String(pirState);
  line2 += " D:";

  if (distance < 0) {
    line2 += "--";
  } else {
    line2 += String((int)distance);
  }

  line2 += " S:";
  line2 += (soapLow ? "LOW" : "OK");

  // Pastikan 16 char penuh
  while (line1.length() < 16) line1 += " ";
  while (line2.length() < 16) line2 += " ";

  // Update hanya bila berubah
  if (line1 != lastLine1) {
    lcd.setCursor(0, 0);
    lcd.print(line1);
    lastLine1 = line1;
  }

  if (line2 != lastLine2) {
    lcd.setCursor(0, 1);
    lcd.print(line2);
    lastLine2 = line2;
  }
}