/***************************************************************************
Program:	A2Q3.cpp

Purpose:	This program will tests the three functions sort(), strcmp(),
			palindrome().
****************************************************************************/

#include <iostream>

using namespace std;

// Function Prototypes
char* getStr();
void sort(char *s, char *d);
int strcmp(char *s1, char *s2);
bool palindrome(char *s);

int main(){
    char *string1, *string2;
	int choice, comp;
	bool ispal;

	string1 = new char;
	string2 = new char;

	// menu - loop while user option != 4
	do{
        cout << "\nWhat would you like to do?\n"
            << "1. Sort a string in increasing order.\n"
			<< "2. Compare two strings.\n"
			<< "3. Check if a word is a palindrome.\n"
			<< "4. Exit program.\n\n";
		cin >> choice;  // get user option

		switch(choice){
			case 1:  // sort a given string
				string1 = getStr();  // get string from user
				sort(string1, string2); //call sort function
				break;
			case 2:  // compare two given strings
				string1 = getStr();  // get 1st string
				string2 = getStr();  // get 2nd string
				comp = strcmp(string1,string2); // call strcmp
				if (comp == 1)  // string 1 > string 2
					cout << "\nString 1 is GREATER THAN String 2\n";
				else if (comp == 0) // string 1 == string 2
					cout << "\nString 1 is EQUALS String 2\n";
				else  // string 1 < string 2
					cout << "\nString 1 is LESS THAN String 2\n";
				break;
			case 3:  // check if a given word is a palindrome
				string1 = getStr();  // get string
				ispal = palindrome(string1);  // call palindrome
				if (ispal == true)  // is a palindrome
					cout << "\nThis is a palindrome\n";
				else  // is not a palindrome
					cout << "\nThis is NOT a palindrome\n";
				break;
			default: // exit switch
                if (choice != 4)  // default - invalid option
                    cout << "That is not a valid choice. Please choose again.\n\n";
		}
	}while(choice!=4); // exit program

	return 0;
}

/****************************************************************************
Function:		getStr
Purpose:		This function will prompt the user to enter a string
Parameters:		NONE
Return Value:	char pointer to string
****************************************************************************/

char* getStr(){
	char *str;

	str = new char;
	if(str == NULL){
		cout << "\nERROR - Insufficient memory\n";
		exit(1);
	}

	// get string from user
	cout << "Please enter a string: \n";
    cin >> str;

	return str;
}

/****************************************************************************
Function:		sort
Purpose:		This function will sort a given string in ascending order
				and return the sorted string
Parameters:		char pointer to original string
Return Value:	char pointer to sorted string
****************************************************************************/
void sort(char *s, char *d){
	size_t len = strlen(s);

	// copy string s to string d
	strcpy(d,s);
	
	// sort string d
	for(size_t i = 0; i < len-1; i++)
        for(size_t j = len-1; j > i; --j){
            if(d[j] < d[j-1]){
                char temp;
                temp = d[j];
                d[j] = d[j-1];
                d[j-1] = temp;
			}
		}
		cout << "\nOriginal string s is: " << s 
			<< "\nSorted string d is: "<< d << endl;
}

/****************************************************************************
Function:		strcmp
Purpose:		This function will compare two given strings and return
				1, if S1 > S2
				0, if S1 == S2
				-1, if S1 < S2
Parameters:		Two char pointers
Return Value:	int
****************************************************************************/
int strcmp(char *s1, char *s2){
	short *asc1, *asc2;
	int cmp = 0;
	size_t len;

	size_t len1 = strlen(s1); // get length of 1st string
	size_t len2 = strlen(s2); // get length of 2nd string
	
	asc1 = new short;
	if(asc1 == NULL){
		cout << "\nERROR - Insufficient memory\n";
		exit(1);
	}
	asc2 = new short;
	if(asc2 == NULL){
		cout << "\nERROR - Insufficient memory\n";
		exit(1);
	}

	// get shortest length of two strings
	if (len1<=len2)
		len = len1;
	else
		len = len2;

	// convert both strings to ascii strings
	for (size_t i = 0; i<len1; i++)
		asc1[i] = s1[i];
    
	asc1[i] = '\0';  // add NULL character to end
    
	for (size_t i = 0; i<len2; i++)
		asc2[i] = s2[i];

	asc2[i] = '\0';  // add NULL character to end
	
	i = 0;
	// compare each ascii code
	// loop while ascii codes are EQUAL OR NOT end of string 
	// if ascii code not equal, assign appropriate value to cmp
	// and exit loop.
	do{
		if (asc1[i] > asc2[i]) //S1 is greater than S2
            cmp = 1;		
		else if (asc1[i] < asc2[i]) //S1 is less than S2
			cmp = (-1);
		else
			cmp = 0;
		i++;
	}while((asc1[i] == asc2[i] || i <= len) && cmp == 0);

	// all ascii codes are equal up to shortest length
	// check to see if the lengths are the same or not and
	// return appropriate value
	if (cmp == 0){
		if (len1>len2)
			cmp = 1;
		else if (len1<len2)
			cmp = (-1);
		else
			cmp = 0;
	}
	return cmp;
}

/****************************************************************************
Function:		palindrome
Purpose:		This function will test if a word is a palindrome and return
				true, if the word is a palindrome
				false, if the word is not a palidrome
Parameters:		char pointer to string to be tested
Return Value:	boolean value
****************************************************************************/
bool palindrome(char *s){
	char *reverse;
	int len = strlen(s); // get length of string s
	int i = 0;
	int j = 0;
	bool pal;
	
	reverse = new char;
	if(reverse == NULL){
		cout << "\nERROR - Insufficient memory\n";
		exit(1);
	}
	
	// get reverse of string s
    for(i = len-1; i >= 0; --i){
		reverse[j] = s[i];
		j++;
	}    
	reverse[j] = '\0'; // add NULL charcter to reversed string
	cout << "\nThe original string is: " << s 
		<< "\nThe reverse string is: " << reverse << endl;

	// check if s is a palindrome
	// if string s is equal to reverse, then s is a palindrome
    for (i = 0; i<len; i++){
        if (reverse[i] != s[i])  // not a palindrome
            return(pal = false);
		else // is a palindrome
			pal = true;
	}

	return pal;
}