#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <EEPROM.h>
#include <Keypad.h>
#include <WiFi.h>
#include <HTTPClient.h>

// ---------------- LCD & PINS ----------------
LiquidCrystal_I2C lcd(0x27, 16, 2);
#define SENSOR_PIN 34
#define RELAY_PIN 5
#define TAMPER_PIN 15
#define BUZZER_PIN 18

// ---------------- KEYPAD ----------------
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {13, 12, 14, 27};
byte colPins[COLS] = {26, 25, 33, 32};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// ---------------- VARIABLES ----------------
float voltage = 230.0, current = 0, power = 0, energy = 0;
float balance = 0.0, cost_per_unit = 100.0;

byte tamperFlag = 0;
unsigned long lastTime = 0, lastCloudUpdate = 0, lastEepromWrite = 0;

bool pinVerified = false, enteringAmount = false;
bool lowBalanceAlertSent = false;

String input = "";
String enteredPIN = "";
String correctPIN = "1234";

const char* ssid = "Wokwi-GUEST";
const char* password = "";
String apiKey = "RY1OBK9W52Y7LARL";

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

  pinMode(RELAY_PIN, OUTPUT);
  pinMode(TAMPER_PIN, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);

  digitalWrite(RELAY_PIN, HIGH);

  Wire.begin(21, 22);
  lcd.init();
  lcd.backlight();

  EEPROM.begin(512);

  EEPROM.get(10, tamperFlag);
  if (tamperFlag == 1) {
    lcd.print("LOCKED");
    while (true) delay(100);
  }

  EEPROM.get(0, balance);
  if (isnan(balance) || balance < 0) {
    balance = 50;
    EEPROM.put(0, balance);
    EEPROM.commit();
  }

  lcd.print("Enter PIN");

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(300);
  }
}

// ---------------- HELPERS ----------------
void beep(int d) {
  digitalWrite(BUZZER_PIN, HIGH);
  delay(d);
  digitalWrite(BUZZER_PIN, LOW);
}

void sendToCloud(int statusFlag) {
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;

    char url[200];
    snprintf(url, sizeof(url),
      "http://api.thingspeak.com/update?api_key=%s&field1=%.2f&field2=%.2f&field3=%.2f&field4=%d",
      apiKey.c_str(), balance, energy, power, statusFlag);

    http.begin(url);
    http.setTimeout(2000);
    http.GET();
    http.end();
  }
}

// ---------------- MODULES ----------------
void handleTamper() {
  if (digitalRead(TAMPER_PIN) == LOW) {
    tamperFlag = 1;
    EEPROM.put(10, tamperFlag);
    EEPROM.commit();

    digitalWrite(RELAY_PIN, LOW);
    lcd.clear();
    lcd.print("TAMPER!");

    while (true) delay(100);
  }
}

void handleKeypad() {
  char key = keypad.getKey();
  if (!key) return;

  if (key == '*') {
    input = "";
    enteredPIN = "";
    lcd.clear();
    lcd.print("Enter PIN");
  }
  else if (key == '#') {
    if (!pinVerified) {
      if (enteredPIN == correctPIN) {
        pinVerified = true;
        enteringAmount = true;
        lcd.clear();
        lcd.print("Enter Amt");
      } else {
        lcd.clear();
        lcd.print("Wrong PIN");
        beep(300);
        enteredPIN = "";
      }
    }
    else {
      float recharge = input.toFloat();
      if (recharge > 0) {
        balance += recharge;
        EEPROM.put(0, balance);
        EEPROM.commit();
        beep(100);
      }
      input = "";
      enteredPIN = "";
      pinVerified = false;
      enteringAmount = false;
      lcd.clear();
      lcd.print("Enter PIN");
    }
  }
  else {
    if (!pinVerified) {
      enteredPIN += key;
      lcd.setCursor(0,1);
      lcd.print(enteredPIN);
    } else {
      input += key;
      lcd.setCursor(0,1);
      lcd.print(input);
    }
  }
}

void updateEnergy() {
  if (millis() - lastTime < 1000) return;
  lastTime = millis();

  int sensorValue = analogRead(SENSOR_PIN);
  current = (sensorValue / 4095.0) * 5.0;
  power = voltage * current;

  float delta = (power / 1000.0) / 3600.0;
  energy += delta;
  balance -= delta * cost_per_unit;

  if (balance < 0) balance = 0;

  if (millis() - lastEepromWrite > 60000) {
    EEPROM.put(0, balance);
    EEPROM.commit();
    lastEepromWrite = millis();
  }
}

void updateRelay() {
  digitalWrite(RELAY_PIN, balance > 0 ? HIGH : LOW);
}

void updateDisplay() {
  lcd.setCursor(0,0);
  lcd.print("E:");
  lcd.print(energy,2);

  lcd.setCursor(0,1);
  lcd.print("Bal:");
  lcd.print(balance,1);
}

void handleCloud() {
  if (millis() - lastCloudUpdate > 20000) {
    sendToCloud(0);
    lastCloudUpdate = millis();
  }
}

// ---------------- LOOP ----------------
void loop() {
  handleTamper();
  handleKeypad();
  updateEnergy();
  updateRelay();
  updateDisplay();
  handleCloud();

  delay(10); // IMPORTANT
}