#include <iostream>
#include <optional>
#include <string>
#include <map>

using namespace std ;


// username with id
map<string, int> students_db =
{
    {"John Kerr", 12501 },
    {"Fred Louis", 32502 },
    {"David Marlowe", 42503 }
};


optional<int> get_student_id(  const string& name )
{
    auto it = students_db.find( name )   ;
    if (  it != students_db.end())
    {
		return optional<int>(it->second)  ;
    }
    return nullopt; // Explicitly returns "nothing"
}

optional<int> get_student_id1(  const string& name )
{
    auto it = students_db.find( name )   ;
    if (  it != students_db.end())
    {
		return it->second  ;
    }
    return {} ; // Explicitly returns "nothing"
}





int main()
{

    string student_name  = "John Kerr" ;
    optional<int> id = get_student_id( student_name )  ;

    // 1. Check if the optional contains a value using contextual bool conversion
    //optional can be used as a condition and will produce true if
    //it contains a valid value
    if ( id )
    {
        // 2. Access the value safely using the * operator
        cout << student_name << "'s id is: " << *id << endl;
    }
    else
    {
        cout << student_name << " was not found." << endl;
    }

    //Another way
    if ( id.has_value() )
    {
        // 2. Access the value safely using the * operator
        cout << student_name << "'s id is : " << id.value() << endl;
    }
    else
    {
        cout << student_name << " was not found." << endl;
    }

     student_name  = "Charles Bronson" ;
     //Use the second function.
     id = get_student_id1( student_name )  ;

     cout << student_name << " id is: " <<
      id.value_or(0) << endl;



}