#define BUTTON_PIN 2

String email = "";
String message = "";

bool emailEntered = false;
bool messageEntered = false;
bool emailSent = false;

unsigned long lastDebounceTime = 0;
unsigned long debounceDelay = 200;
 
// -------- Email Validation --------
bool isValidEmail(String e) {
  e.trim();

  if (e.length() < 6) return false;
  if (e.indexOf(' ') != -1) return false;

  int atPos = e.indexOf('@');
  int dotPos = e.lastIndexOf('.');

  if (atPos <= 0) return false;
  if (dotPos <= atPos + 1) return false;
  if (dotPos >= e.length() - 1) return false;

  return true;
}

// -------- Reset Function --------
void resetProgram() {
  email = "";
  message = "";
  emailEntered = false;
  messageEntered = false;
  emailSent = false;

  Serial.println("\nEnter your email:");
}

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  Serial.begin(115200);
  Serial.println("===== Email Sender System =====");
  Serial.println("Enter your email:");
}

void loop() {

  // -------- Serial Input Handling --------
  if (Serial.available()) {
    String input = Serial.readStringUntil('\n');
    input.trim();

    if (!emailEntered) {
      if (isValidEmail(input)) {
        email = input;
        emailEntered = true;
        Serial.println(" Valid email accepted.");
        Serial.println("Enter your message:");
      } else {
        Serial.println(" Invalid email! Try again:");
      }
    }
    else if (!messageEntered) {
      message = input;
      messageEntered = true;
      Serial.println(" Message saved.");
      Serial.println("Press the button to send the email...");
    }
  }

  // -------- Button Handling with Debounce --------
  if (emailEntered && messageEntered && !emailSent) {

    if (digitalRead(BUTTON_PIN) == LOW) {

      if ((millis() - lastDebounceTime) > debounceDelay) {

        Serial.println("\n📨 Sending Email...");
        Serial.println("To      : " + email);
        Serial.println("Message : " + message);
        delay(1000);

        Serial.println(" Email sent successfully!");

        emailSent = true;
        lastDebounceTime = millis();

        delay(1000);
        resetProgram();
      }
    }
  }
}