/*******************************************************************
  Palindrome.cc
  Author: Dana Vrsjitoru
  September 2020

  Function that inputs a line from the user and decides whether it
  represents a palindrome or not.
  Examples of palindromes: kaya, civic, mom, cc, h, Anna, deed,
  A man, a plan, a canal, Panama!  , step on no pets
*******************************************************************/

#include <iostream>
using namespace std;

#include <ctype.h>
#include <cstring>

// converts all the letters in the string to lowercase
void to_lowercase(char *text)
{
    if (! text)
        return;
    for (int i = 0; text[i] != '\0'; i++)
        if (isupper(text[i])) // convert all uppercase letters
            text[i] = tolower(text[i]);   // to lowercase
}

// copies the source to the destination by stripping all the
// characters that aren't letters
void strip_not_letters(char *source, char *dest)
{
    int i, j = 0;
    if (!source)
        return;
    for (int i = 0; source[i] != '\0'; i++)
        if (isalpha(source[i])) // copy only the letters into dest
        {
            dest[j] = source[i];
            j++;
        }
    dest[j] = '\0'; // finish the dest string properly
}

// checks if the text is a palindrome
bool is_palindrome(char *text)
{
    if (! text)
        return true;

    // clean up the text
    to_lowercase(text);
    int len = strlen(text);
    char *copy = new char[len+1];
    strip_not_letters(text, copy);

    // check for matching characters from the beginning and the end
    len = strlen(copy);
    for (int i = 0; i < len/2; i++)
        if (copy[i] != copy[len - i - 1])
            return false;
    return true;
}

int main()
{
    char text[50]; // hopefully it's big enough

    cout << "Enter a line to check if it's a palindrome" << endl;
    cin.getline(text, 50);

    if (is_palindrome(text))
        cout << "Yes, it's a palindrome" << endl;
    else
        cout << "No, it's not a palindrome" << endl;
}