#include <iostream>
#include <stdlib.h>

using namespace std;

//mystring class stores the string in the character pointer
class mystring {
	// attributes of class
	int mLength;
	char *mData;

public:
	mystring();
	mystring(const char cstring[]);
	mystring(const mystring &rhs);
	~mystring();
	void append(char c);
	void append(const mystring &rhs);
	void pop();
	void clear();
	int length() const;
	char at(int index) const;
	const char *c_str() const;
};

// default constructor of class
mystring::mystring() {
	// set length to 0
	mLength = 0;

	// set data to null pointer
	mData = NULL;
}

// parameterized constructor of class with character array
mystring::mystring(const char cstring[]) {
	// set length to 0
	mLength = 0;

	// determine the length of cstring
	while (cstring[mLength] != '\0') {
		mLength++;
	}

	// dynamically allocate character array of length mLength + 1
	mData = new char[mLength + 1];

	// copy data from cstring to mData
	for (int i = 0; i < mLength; i++) {
		mData[i] = cstring[i];
	}
	// store null pointer at mLength index
	mData[mLength] = '\0';
}

// copy constructor of class
mystring::mystring(const mystring &rhs) {
	// copy length of rhs to mLength
	mLength = rhs.mLength;

	// dynamically allocate memory
	mData = new char[mLength + 1];

	// copy data of rhs to mData
	for (int i = 0; i < mLength + 1; i++) {
		mData[i] = rhs.mData[i];
	}
}

// destructor of class
mystring::~mystring() {
	// deallocate memory if any exist
	if (mData != NULL)
		delete[] mData;
	// set mLength to 0
	mLength = 0;
}

// This function is used to append character to the character array
void mystring::append(char c) {
	//  copy mData to temp
	char *temp = mData;

	// create a new memeory with increased length
	mData = new char[mLength + 2];
	// copy each character in temp to mData
	for (int i = 0; i < mLength; i++) {
		mData[i] = temp[i];
	}
	// add character to end and add null character
	mData[mLength] = c;
	mData[mLength + 1] = '\0';

	// increment length of string by 1
	mLength += 1;

	// deallocate old memory
	if (temp != NULL)
		delete[] temp;

}

// This function is used append data in another mystring to this string
void mystring::append(const mystring &rhs) {
	//  copy mData to temp
	char *temp = mData;

	// create a new memeory with increased length
	mData = new char[mLength + rhs.length() + 1];

	// copy each character in temp to mData
	for (int i = 0; i < mLength; i++) {
		mData[i] = temp[i];
	}

	// copy each character in rhs data to mData
	for (int i = mLength; i<(mLength + rhs.length()); i++) {
		mData[i] = rhs.at(i - mLength);
	}
	// add null character at end
	mData[mLength + rhs.length()] = '\0';

	// increment mLength by rhs's mLength
	mLength += rhs.length();

	// deallocate old memory
	if (temp != NULL)
		delete[] temp;
}

// This function is used to remove last character from  data
void mystring::pop() {
	//  copy mData to temp
	char *temp = mData;

	// create a new memeory with decreased length
	mData = new char[1];

	// add null character at end
	mData[0] = '\0';

	// set length to 0
	mLength = 0;

	// deallocate old memory
	if (temp != NULL)
		delete[] temp;
}

// This function is used to clear the data in mystring
void mystring::clear() {
	// deallocate memory if any exist
	if (mData != NULL) {
		delete[] mData;
		mData = NULL;
	}
	// set mLength to 0
	mLength = 0;
}

// This function is used to return length of string
int mystring::length() const {
	return mLength;
}

// This function is used to return character at specific index
char mystring::at(int index) const {
	// return null if index is out of range
	if (index<0 || index >= mLength)
		return '\0';
	// return character at index if in range
	return mData[index];
}

// This function is used to return data
const char *mystring::c_str() const {
	return mData;
}

int main() {
	cout << "Creating mystring1 with empty constructor" << endl;
	mystring mystring1;
	cout << "Length of mystring1 is " << mystring1.length() << endl;
	cout << "Accessing character at 2 of mystring1 returns " << mystring1.at(2) << endl;
	cout << "Appending character A to mystring1" << endl;
	mystring1.append('A');
	cout << "Length of mystring1 is " << mystring1.length() << endl;
	cout << "Data of mystring1 is " << mystring1.c_str() << endl;
	cout << "Accessing character at 0 of mystring1 returns " << mystring1.at(0) << endl;
	cout << "Accessing character at 2 of mystring1 returns " << mystring1.at(2) << endl;


	cout << "\nCreating mystring2 with character array" << endl;
	char data[] = "Hello";
	mystring mystring2(data);
	cout << "Length of mystring2 is " << mystring2.length() << endl;
	cout << "Data of mystring2 is " << mystring2.c_str() << endl;
	cout << "Accessing character at 2 of mystring2 returns " << mystring2.at(2) << endl;
	cout << "Appending character ! to mystring2" << endl;
	mystring2.append('!');
	cout << "Length of mystring2 is " << mystring2.length() << endl;
	cout << "Data of mystring2 is " << mystring2.c_str() << endl;
	cout << "Accessing character at 5 of mystring2 returns " << mystring2.at(5) << endl;
	cout << "Popping character from mystring2" << endl;
	mystring2.pop();
	cout << "Length of mystring2 is " << mystring2.length() << endl;
	cout << "Data of mystring2 is " << mystring2.c_str() << endl;
	cout << "Appending mystring1 to mystring2" << endl;
	mystring2.append(mystring1);
	cout << "Length of mystring2 is " << mystring2.length() << endl;
	cout << "Data of mystring2 is " << mystring2.c_str() << endl;

	cout << "\nCreating mystring3 with mystring2" << endl;
	mystring mystring3(mystring2);
	cout << "Length of mystring3 is " << mystring3.length() << endl;
	cout << "Data of mystring3 is " << mystring3.c_str() << endl;
	cout << "Appending string 'll!' to mystring3" << endl;
	mystring3.append("ll!");
	cout << "Length of mystring3 is " << mystring3.length() << endl;
	cout << "Data of mystring3 is " << mystring3.c_str() << endl;
	cout << "Clearing character from mystring3" << endl;
	mystring3.clear();
	cout << "Length of mystring3 is " << mystring3.length() << endl;

	system("pause");

	return 0;
}