#include <iostream>
#include <sys/mman.h> // for mmap
#include <fcntl.h> // for O_RDWR
#include <unistd.h> // for close(fd)
using std::cout;
using std::endl;
using std::cin;
int validNumberToAdd()
{
    cout << "valid numbers are 0-10000" <<endl;
    int res;
    cin >> res;
    if(res <0 || res > 10000)
    {
        validNumberToAdd();
    }
    else
    {
        return res;
    }
}
int validIndex()
{
    cout << "What index do you want to look for 0-99? " << endl;
    int res;
    cin >> res;
    if(res < 0 || res > 99)
    {
        cout << "invalid selection pick between 0-99" << endl;
        validIndex();
    }
    else
    {
        return res;
    }
}
void readFile()
{
    const char * filePath = "num.txt";
    int index;
    index = validIndex();

    int fd = open(filePath,O_RDONLY );
    void *addr = mmap(nullptr,1000,PROT_READ, MAP_SHARED , fd,0);
    char *p = (char *)addr;
    cout << p[index] << endl;
    close(fd);
}
void writeFile()
{
    const char * filePath = "numbers.txt";
    int fd = open(filePath,O_RDWR);
    int index,numAdd;
    index = validIndex();
    numAdd = validNumberToAdd();
    void *addr = mmap(nullptr,1000,PROT_WRITE, MAP_SHARED| MAP_ANONYMOUS, fd,0);
    char *p = (char *)addr;
    p[index] = numAdd;
    cout << "wrote " << numAdd << endl;
    //munmap(addr,1000);
    close(fd);

}
void menu()
{
    cout << "Type 'r' to read" << endl;
    cout << "Type 'w' to write" << endl;
    cout << "Type 'q' to quit" << endl;
    char res;
    cin >> res;
    if(res != 'r' && res != 'w' && res != 'q')
    {
        cout << " Your selection was invalid " << res << " is not valid" << endl;
        menu();
    }
    if(res == 'r')
    {
        readFile();
        menu();
    }
    if(res == 'w')
    {
        writeFile();
        menu();
    }
    if(res == 'q')
    {
        cout << "Exiting program!" << endl;
        exit(1);
    }
}
int main()
{
    menu();
    return 0;
}