/* This program demonstrates
 * 1. Writing functions that work with c-strings
 * 2. Using the query an conversion functions in the cctype library.
 * 3. Copying strings: strcpy
 * 4. Concatenating Strings: strcat
 *
 * The cctype library contains a variety of functions that answer questions about individual characters.
 * They can be used in conjunction with c-strings to et some statistics about the string. 
 * 
 * c-strings are still arrays. The need to be deep-copied. 
 *
 * We also implement strcpy ourselves, to understand how it works
 */

#include<iostream>
#include<cctype> // for query functions
#include<cstring> // for string length

using namespace std;

//function declarations
int sentenceCount(char st[]);
int numeralCount(char st[]);
void convert(char st[]);


int main()
{
    //Declare a C-string and read it in
    char str[200];
    cin.getline(str, 100, '#');      //read until #
    char c;
    cin>>c;                                 // read in a single character
    
	/* We can print the length of a string using the strlen function fromt he cstring library */
    cout<<"Length of st is "<< strlen(st)<<endl;
    
    /* The query functions in the cctype library only work on individual characters */
    cout<<"Is the first character of st uppercase? "<< isupper(st[0])<<endl;
	
    char copy[200];
    cin.getline(copy, 100);             // no delimiter, uses '\n'

    cout<<"str now "<<str<<endl;
    cout<<"c is "<< c<<endl;
    cout<<"copy is "<<copy<<endl;

    /* string copy
     * We cannot copy strings using the = operator like we did for numeric variables.
     * This is because, C-strings are essentially arrays and we've seen that we
     * cannot copy arrays using the = operator. We used a loop to do that.
     * For strings, we have a function in the cstring library for copying strings.
     * strcpy(target_string, source_string)
     * the source string is copied on to the target string. the source string is
     * left unchanged. The target string is erased and the source string is
     * copied on to it.
     * If the target string has fewer characters available than the source string,
     * the strcpy function might overwrite some other data. C++ does not check
     * bound on this. We have to do it ourselves.
     */

    strcpy(copy, str);  // second string is copied on to the first

    cout<<"Copy is now "<< copy<<endl;

    /* copy function only cuts off the target at the length of the source is the source is
     * shorter than the target. However, the cutting-off is done with the '\0' character. 
     * The rest of the array (After the length of the source) still has the old data */
    for(int i=0; i<100; i++)
        cout<< copy[i]<<" ";
    cout<<endl;

    //We can pass a c-sting into a function, just like a regular array. Call the functions we wrote

    cout<<"number of sentences: "<< sentenceCount(str)<<endl;
    cout<<"Number of numeral characters: "<< numeralCount(str)<< endl;

    convert(str);
    cout<<"Converted string: "<< str<<endl;
	
	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;

    return 0;
}

/* function senenteceCount
 * parameters - 1, c-style string
 * returns - int, number of sentences
 * bunch of characters that end with ., ?, !
 *Examine the string character by character. We define a sentence as a piece of text that
 * ends with a period, question mark or exclamation mark.
 * So, every time we see one of those characters, we determine that a sentence has ended,
 * and we increment the counter.
 * Assumption: Proper punctuation, no stray punctuation
 */
int sentenceCount(char st[])
{
    int count = 0;
    for(int i=0; i< strlen(st); i++)
    {
        if( st[i] =='.' || st[i] =='?' || st[i] =='!')
            count++;
    }
    return count;
}

/* function numeralCount
 * parameters - 1, the c-string
 * returns- int, the number of numeral characters
 *
 * Examine the string character by character. Every time we see a digit character,
 * character, we determine that a sentence has ended,
 * we increment the counter.
 * Instead of writing a compound condition with 10 or-separated parts, wu use the
 * isdigit function from the cctype library.
 */
int numeralCount(char st[]) {
    int count = 0;
    for (int i = 0; i < strlen(st); i++)
    {
        if(isdigit(st[i]))
            count++;
    }
    return count;
}

/* function convert
 * parameters - 1, the c-string
 * returns nothing
 * Go through the string one character at a time. To convert the characters, use the
 * toupper() conversion function in the cctype library
 * The toupper() function takes 1 char as parameter, converts a character to uppercase
 * if it is a lowercase character, and returns it. IF it is not a lowercase character,
 * it returns the unchanged character.
 * Since chars pass by value, we would have to replace the current character with the
 * converted character.
 */
void convert(char st[])
{
    for(int i=0; i<strlen(st); i++)
    {
        st[i] = toupper(st[i]);
    }
}

/* 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

}