Project1

#include <iostream> // header file for c++ and it gives me service of input and output
#include <string> //This is a string library that lets me use string in the program and any string related functions*/
using namespace std;

class Email {               // here you are declaring or defining a class called email
public:
 void inputEmail(); //prompts user to enter a string (email).
 void caseInput();  //convert capital letters to small-case letters.
 void parseInput(); // divide the string into substrings (token).
 void validate(); // verify if the user-entered string is correct form of an email address.
private:
 string email; //user-entered string
 string username;
 string domain;
};

/* this is end of declaring class and i put my functions in public so i can use it in main function and
switch it around because things that are in private can not be changed outside the class declaring part.*/

void Email::inputEmail() {
 cout << "Enter an Email Address: ";
 getline(cin, email);
}

void Email::caseInput() {
 for (int i = 0; i < email.length(); i++) {
  if ((email.at(i) <= 'Z') && (email.at(i) >= 'A')) {
   email.at(i) += 32;
  }
 }
}

void Email::parseInput() {
 for (int i = 0; i < email.length(); i++) {
  if (email.at(i) == '@') {
   //everything before '@' goes into string username.
   username = email.substr(0, i);
   //everything after '@' goes into string domain
   domain = email.substr(i + 1);
  }
 }
}

void Email::validate() {
 bool isAtPresent = true;  // is '@' in the user-entered string?
 bool isUserValid = true; //is username in valid form?
 bool isDomainValid = true;   // is domain in valid form?
 int at = 0; //works as a counter to find the number of '@'
 int period = 0; // works as a counter to find the number of '.' period

 for (int i = 0; i < email.length(); i++) {       //reason for doing this is to count number of '@' when '@' shows up for the first time, at= at+1 so at becomes 2
  if (email.at(i) == '@') {                       // and then if it detects second '@', then again it goes at= at + 1, since there was already one '@', we can 
   at++;
  }
  // know that at = 1+1 = 2. If there's more '@' showing up, this counting process continues.
 }

 if ((at == 0)) {
  isAtPresent = false; // means that there is no '@' in the user-entered string.
 }

 //now we are validating username

 for (int i = 0; i < username.length(); i++) {
  if ((username.at(i) == ' ') || (username.at(i) == '@')) {
   isUserValid = false;
  }
 }


 // now validate domain
 for (int i = 0; i < domain.length(); i++) {
  if ((domain.at(i) < 'a') && (domain.at(i) > 'z') && (domain.at(i) != '.')) {
   isDomainValid = false; // if there is any chracters other than a-z or '.', domain is not valid.
  }
  if (domain.at(i) == '.') {
   period++;
  }
 }

 if (period == 0) {
  isDomainValid = false; // if there is no '.' at all, then the domain is not valid
 }
 if ((isUserValid == false) || (isDomainValid == false) || (isAtPresent == false)) {
  cout << "*****I N V A L I D*****" << endl;
 }
 else {
  cout << "******VALID*******" << endl;
 }
}

int main() { //main function
 Email E;

 E.inputEmail();
 E.caseInput();
 E.parseInput();
 E.validate();

 cin.get(); 
 return 0;
}