#include <iostream>
#include <string_view>
#include <string>
#include <cstring>

using namespace std ;



//Problem when std::string is passed
void print_view_char_array( const char* ptr  )
{
	//need to recalculate string length
    std::cout << ptr << " (Length: " << strlen( ptr ) << ")\n";
}

//New memory allocation if c style string is passed
void print_view_standard_string( const std::string& str  )
{
    std::cout << str << " (Length: " << str.length() << ")\n";
}

// Best Practice: Pass by value, not by reference
//Can take both c style and std::string without any new
//memory allocation
void print_view(std::string_view sv)
{
    std::cout << sv << " (Length: " << sv.length() << ")\n";
}



int main()
{
	std::string str = "Modern C++";

	//pass std string to old style c string.
    print_view_char_array ( str.c_str() ) ;

    //c style to std string&
    //new memory is allocated on the heap for the string
    print_view_standard_string( "Hello World!"  ) ;

    // 1. Implicit conversion from literal (Zero allocation)
    print_view("Hello World")   ;

    // 2. Implicit conversion from std::string (Zero allocation)
    print_view(str);



     // 3. Cheap substringing
    std::string_view full_view{"Data Science"};
    std::string_view sub_view = full_view.substr(0, 4); // "Data"
    print_view(sub_view);

    cout << "full_view[0]" << full_view[0] << endl ;
    //No bounds checking but undefined behaviour
    //With g++ program aborts
    //cout << "full_view[20]" << full_view[20] << endl ;
    try
     {
        cout << "full_view.at(20)" << full_view.at(20) << endl ;
	 }
	catch( out_of_range& obj1 )
	 {
		 cout << "Exception." <<
		 obj1.what() << endl ;

	 }
    cout << "full_view.back():  " << full_view.back() << endl ;

    //Not guranteed to be null terminated. string_view always keeps the
    //size information.
    cout << "full_view.data():  " << full_view.data() << endl ;
    //begin() end()
    cout << "full_view.size():  " << full_view.size() << endl ;
    cout << "full_view.length():  " << full_view.length() << endl ;

    //Internal data string is not modified. Instead the pointer is moved
    full_view.remove_prefix(4) ;
    cout << "full_view:  " << full_view << endl ;

    char arr1[10] ;
    full_view.copy( arr1, 4 )  ;
    cout << "arr1: " << arr1 << endl ;

    //Searching functions are similar to the std::string search functions
    size_t index =  full_view.find("c") ;
    if ( index != string_view::npos )
        cout << "index: " << index << endl ;

    index =  full_view.find("d") ;
    if ( index != string_view::npos )
        cout << "index: " << index << endl ;

}