#include <iostream> // cin, cout
#include <fstream>  // ifstream, ofstream

const int LINE_BUFFER_SIZE = 1024;
const int MAX_STUDENT_PROP_SIZE = 2048;

bool strNotEqual(const char* a, const char* b) {
	for (int i = 0; a[i] != '\0' || b[i] != '\0'; i++)
		if (a[i] != b[i]) return true;
	return false;
}

/* Student */

struct Student {
	char FirstName[MAX_STUDENT_PROP_SIZE];
	char LastName[MAX_STUDENT_PROP_SIZE];
	char Email[MAX_STUDENT_PROP_SIZE];
	char FN[MAX_STUDENT_PROP_SIZE];
};

void printStudent(Student st) {
	std::cout << "Name = " << st.FirstName << " " << st.LastName << ", Email: " << st.Email << ", FN: " << st.FN << std::endl; 
}

Student parseStudent(const char* str) {
	Student toRet = {};
	char* prop = toRet.FirstName;

	for (int i = 0, j = 0; str[i] != '\0'; i++) {
		if (str[i] == ',') {
			if (prop == toRet.FirstName) prop = toRet.LastName;
			else if (prop == toRet.LastName) prop = toRet.Email;
			else if (prop == toRet.Email) prop = toRet.FN;
			j = 0;
		}
		else prop[j++] = str[i];
	}
	return toRet;
}

/* StudentsList */

struct StudentsList {
	Student* students;
	int count;
	int length;
};

bool resizeStudentsList(StudentsList& sl, int newSize) {
	if (newSize < sl.count) return false; // We cant fit all of the old students in the new students array

	Student* temp = new Student[newSize];
	for (int i = 0; i < sl.count; i++)
		temp[i] = sl.students[i];

	delete[] sl.students;
	sl.students = temp;

	return true;
}

void addStudents(StudentsList& sl, Student st) {
	if (sl.count == sl.length) {
		sl.length = (!sl.length) ? 2 : sl.length << 1;
		resizeStudentsList(sl, sl.length);
	}

	sl.students[sl.count++] = st;
}

int findStudentIndByFN(const StudentsList& sl, const char* FN) {
	for (int i = 0; i < sl.count; i++)
		if (strNotEqual(sl.students[i].FN, FN)) return i;

	std::cout << "Error: No student with FN of " << FN << "!" << std::endl;
	return -1;
}

StudentsList getStudentsListFromFile(const char* fileName) {
	std::ifstream inFile(fileName);
	if (!inFile.is_open()) {
		std::cout << "Error: Could not open file!" << std::endl;
		return {};
	}

	StudentsList sl = {};

	char buffer[LINE_BUFFER_SIZE];
	while (!inFile.eof()) {
		inFile.getline(buffer, LINE_BUFFER_SIZE);
		if (buffer[0] != '\0')
			addStudents(sl, parseStudent(buffer));
	}
	return sl;
}

/* Commands */

bool isCommand(const char* inputBuffer, const char* command) { // The buffer could get dirty with leftover data, so we check only if the beginning matches
	for (int i = 0; command[i] != '\0'; i++)
		if (inputBuffer[i] != command[i]) return false;

	return true;
}

void printStudentByFN(const StudentsList& sl, const char* FN) {
	int stInd = findStudentIndByFN(sl, FN);
	if (stInd >= 0) printStudent(sl.students[stInd]);
}

void replaceStudentEmail(const StudentsList& sl, const char* FN, const char* newEmail) {
	int stdInd = findStudentIndByFN(sl, FN);
	if (stdInd < 0) return;

	Student& st = sl.students[stdInd];
	for (int i = 0; st.Email[i] != '\0' || newEmail[i] != '\0'; i++)
		st.Email[i] = (newEmail[i] == '\0') ? '\0' : newEmail[i];
}

void saveToFile(const StudentsList& sl, const char* newFileName) {
	std::ofstream newFile(newFileName);
	if (!newFile.is_open()) {
		std::cout << "Error: File could not be opened!" << std::endl;
		return;
	}

	for (int i = 0; i < sl.count; i++) {
		Student st = sl.students[i];
		newFile << st.FirstName << "," << st.LastName << "," << st.Email << "," << st.FN << std::endl;
	}

	newFile.close();
}

/* Main */

int main() {
	char inputBuffer[LINE_BUFFER_SIZE];
	std::cout << "Open file:" << std::endl << ">";
	std::cin >> inputBuffer;

	StudentsList readSL = getStudentsListFromFile(inputBuffer);
	if (readSL.students == nullptr)
		return -1;

	do {
		std::cout << ">";
		std::cin >> inputBuffer;

		if (isCommand(inputBuffer, "print")) {
			std::cin >> inputBuffer;
			printStudentByFN(readSL, inputBuffer);
		}
		else if (isCommand(inputBuffer, "edit")) {
			char tempFNBuffer[LINE_BUFFER_SIZE];
			std::cin >> tempFNBuffer >> inputBuffer;
			replaceStudentEmail(readSL, tempFNBuffer, inputBuffer);
		}
		else if (isCommand(inputBuffer, "save")) {
			std::cin >> inputBuffer;
			saveToFile(readSL, inputBuffer);
		}
	} while (!isCommand(inputBuffer, "end"));

	delete[] readSL.students;
}