/* This program demonstrates c-strings
 * a c-string is an array of chars.
 * chars are still integer types. When we store a character in a variable or as an array
 * element, it stores the equivalent ASCII value of that character, as an integer
 * So, we can do math with characters, since they are internally numbers.
 *
 * This program shows us the 4 main functions for c-string
 * 1. Finding the length of a string: strlen
 * 2. Copying strings: strcpy
 * 3. concatenating strings: strcat
 * 4. Comparing strings: strcmp
 *
 * We also implement strcpy ourselves, to understand how it works
 */
#include<iostream>
#include<cstring>

using namespace std;

void stringCopy(char st1[], char st2[]);
int main()
{
    char str[200];
    char copy[200];

    cout<<"Enter a string: ";
    cin.getline(str, 200, '#');

    cout<<"Enter another string: ";
    cin.getline(copy, 200);

    cout<<"You entered: "<<copy<<endl;

    stringCopy(copy, str);
    cout<<"Copy is now: "<<copy<<"\nstr is now "<<str<<endl;

    cout<<"\nString concatenation:\n";
    cout<<"Enter 2 string: ";
    cin.getline(str, 200);
    cin.getline(copy, 200);

    /* Concatenation is the process of attaching one string at the end of another string
    * The cstring library contains the strcat function that will concatenate strings
    * strcat(target string, source string)
    * The source string is attache dto the end of the target string. The source
    * string is left unchanged. We need to make sure the target string has enough
    * room for both strings. C++ does not do this check for us.
    * We cannot concatenate multiple strings at one go. strcat only takes 2 parameters.
    * If we need multiple concatenations, we should do it one at a time.
    */

    strcat(str, copy);      // attaches the contents of the second string to the end of the first
    // second string left unchanged

    cout<<"str: "<<str<<"\ncopy: "<<copy<<endl;

    /* Lexicographic ordering:
     * space < numeral (0-9) < uppercase letters (A-Z) < lowercase letters (a-z)
     * Spongebob, Patrick -> Patrick is "first" P < S
     * Spongebob , patirck -> Spongebob is "first", S < p
     * Spongebob, 4atrick -> 4atrick is "first", numeral < letters
     * Spongebob, Sqiudward -> Spongebob is "first" S==S, p<q
     * Squid, Square -> Square is first, first 3 letters are the same, a < i
     * Squid, Squidward -> Squid is "first", all letters matched until "Squid" ran out of letters
     * Squid Squid -> strings are equal
     */

    cout<<"Demonstrating strcmp for string comparison:\n";
    char str2[100];
    cout<<"Enter a string to compare: ";
    cin.getline(str2,100);
    int diff = strcmp(str, str2);
    if (diff < 0)
        cout<<str<< " was first"<<endl;
    else if (diff > 0)
        cout<<str2<<" was first"<<endl;
    else cout<<"The two strings were equal"<<endl;
    return 0;
}

/* function stringCopy
 * parameters: 2 - 2 strings (c-style)
 * returns nothing
 *
 * algorithm: iterate through the second string, copy out individual characters
 * into the same position on the first string
 * Note- remember to terminate the string
 */
void stringCopy(char st1[], char st2[])
{
    int i;
    for( i=0; i<strlen(st2); i++)
    {
        st1[i] = st2[i];
    }
    st1[i] = '\0';      // string termination

}