import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class BonusExercises {

    public boolean validateEmail(String email) {
        String regex = "^[a-zA-Z0-9]+[a-zA-Z0-9._]*@[a-zA-Z0-9]+[a-zA-Z0-9-]*(\\.[a-zA-Z]+)+$";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(email);

        return matcher.matches();
    }

    public String findDate(String string) {
        if (string == null) {return null;}
        String regex = "\\b(\\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])|\\d{4}/(0[1-9]|1[0-2])/(0[1-9]|[12][0-9]|3[01])|(0[1-9]|[12][0-9]|3[01])/(0[1-9]|1[0-2])/\\d{4})\\b";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(string);
        if (matcher.find()) {
            return matcher.group();
        }
        return null;
    }


    public int findValidPasswords(String string) {
        String regex = "^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[^A-Za-z0-9])\\S{8,}$";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(string);
        String[] passwords = string.split(" ");
        int count = 0;
        for (String pass: passwords){
            if (pattern.matcher(pass).matches()){
                count++;
            }
        }
        return count;
    }
    
    public List<String> findPalindromes(String string) {
        List<String> list = new ArrayList<>();
        String regex = "\\b[a-zA-Z]{3,}\\b";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(string);
        while (matcher.find()) {
            if (CheckPalindrome(matcher.group())) {
                list.add(matcher.group());
            }
        }
        return list;
    }

    private boolean CheckPalindrome(String str) {
        str = str.toLowerCase();
        int i = 0;
        int j = str.length() - 1;
        while (i < str.length() / 2 ) {
            if (str.charAt(i) != str.charAt(j)) {
                return false;
            }
            i++;
            j--;

        }
        return true;
    }

    public static void main(String[] args) {
        // you can test your code here
    }
}