#include <iostream>
#include <iomanip>
#include <ctime>
#include <fstream>

using namespace std;

// Structure to represent student details
struct Student {
    int studentID;
    string name;
    string contactInfo;
};

// Structure to represent course enrollment details
struct Enrollment {
    int courseID;
    string enrollmentDate;
};

// Function prototypes
void displayMenu();
void addStudent(Student students[], int& studentCount);
void displayAllStudents(Student students[], int studentCount);
void enrollInCourse(Student students[], int studentCount, Enrollment enrollments[], int& enrollmentCount);
void displayAllEnrollments(Student students[], int studentCount, Enrollment enrollments[], int enrollmentCount);
void calculateFine(Enrollment enrollments[], int enrollmentCount);
void displayAllFines(Student students[], int studentCount, Enrollment enrollments[], int enrollmentCount);
void saveData(Student students[], int studentCount, Enrollment enrollments[], int enrollmentCount);
void loadData(Student students[], int& studentCount, Enrollment enrollments[], int& enrollmentCount);

int main() {
    const int MAX_STUDENTS = 100;
    const int MAX_ENROLLMENTS = 500;

    Student students[MAX_STUDENTS];
    Enrollment enrollments[MAX_ENROLLMENTS];

    int studentCount = 0;
    int enrollmentCount = 0;

    loadData(students, studentCount, enrollments, enrollmentCount);

    int choice;

    do {
        displayMenu();
        cout << "Enter your choice: ";
        cin >> choice;

        switch (choice) {
            case 1:
                addStudent(students, studentCount);
                break;
            case 2:
                displayAllStudents(students, studentCount);
                break;
            case 3:
                enrollInCourse(students, studentCount, enrollments, enrollmentCount);
                break;
            case 4:
                displayAllEnrollments(students, studentCount, enrollments, enrollmentCount);
                break;
            case 5:
                calculateFine(enrollments, enrollmentCount);
                break;
            case 6:
                displayAllFines(students, studentCount, enrollments, enrollmentCount);
                break;
            case 7:
                saveData(students, studentCount, enrollments, enrollmentCount);
                cout << "Data saved successfully.\n";
                break;
            case 8:
                loadData(students, studentCount, enrollments, enrollmentCount);
                cout << "Data loaded successfully.\n";
                break;
            case 9:
                cout << "Exiting the program. Thank you!\n";
                break;
            default:
                cout << "Invalid choice. Please try again.\n";
        }
    } while (choice != 9);

    return 0;
}

void displayMenu() {
    cout << "\n===== Student Registration System Menu =====\n";
    cout << "1. Add new student\n";
    cout << "2. Display all students\n";
    cout << "3. Enroll in a course\n";
    cout << "4. Display all enrollments\n";
    cout << "5. Calculate fine for late registration\n";
    cout << "6. Display all fines\n";
    cout << "7. Save data to file\n";
    cout << "8. Load data from file\n";
    cout << "9. Exit\n";
}

void addStudent(Student students[], int& studentCount) {
    cout << "Enter student ID: ";
    cin >> students[studentCount].studentID;

    cout << "Enter student name: ";
    cin.ignore();
    getline(cin, students[studentCount].name);

    cout << "Enter contact information: ";
    getline(cin, students[studentCount].contactInfo);

    cout << "Student added successfully.\n";

    // Increment student count
    studentCount++;
}

void displayAllStudents(Student students[], int studentCount) {
    if (studentCount == 0) {
        cout << "No students registered yet.\n";
    } else {
        cout << "\n===== List of Registered Students =====\n";
        cout << setw(10) << "Student ID" << setw(20) << "Name" << setw(30) << "Contact Information\n";
        for (int i = 0; i < studentCount; ++i) {
            cout << setw(10) << students[i].studentID << setw(20) << students[i].name << setw(30) << students[i].contactInfo << endl;
        }
    }
}

void enrollInCourse(Student students[], int studentCount, Enrollment enrollments[], int& enrollmentCount) {
    int studentID;
    int courseID;

    cout << "Enter student ID: ";
    cin >> studentID;

    // Validate student ID
    int studentIndex = -1;
    for (int i = 0; i < studentCount; ++i) {
        if (students[i].studentID == studentID) {
            studentIndex = i;
            break;
        }
    }

    if (studentIndex == -1) {
        cout << "Student not found. Please register the student first.\n";
        return;
    }

    cout << "Enter course ID: ";
    cin >> courseID;

    // Validate course ID

    // Assuming a course ID validation mechanism is implemented

    // Enroll the student in the course
    enrollments[enrollmentCount].courseID = courseID;

    // Get current date and time
    time_t currentTime = time(0);
    enrollments[enrollmentCount].enrollmentDate = ctime(&currentTime);

    cout << "Enrollment successful.\n";

    // Increment enrollment count
    enrollmentCount++;
}

void displayAllEnrollments(Student students[], int studentCount, Enrollment enrollments[], int enrollmentCount) {
    if (enrollmentCount == 0) {
        cout << "No enrollments yet.\n";
    } else {
        cout << "\n===== List of Enrollments =====\n";
        cout << setw(10) << "Student ID" << setw(15) << "Course ID" << setw(30) << "Enrollment Date\n";
        for (int i = 0; i < enrollmentCount; ++i) {
            cout << setw(10) << students[i].studentID << setw(15) << enrollments[i].courseID << setw(30) << enrollments[i].enrollmentDate;
        }
    }
}

void calculateFine(Enrollment enrollments[], int enrollmentCount) {
    const double FINE_RATE_PER_DAY = 0.5; // Example fine rate per day

    for (int i = 0; i < enrollmentCount; ++i) {
        // Assuming today's date for simplicity
        time_t currentTime = time(0);
        string currentDate = ctime(&currentTime);

        // Convert enrollment date to time_t
        struct tm enrollmentTime = {};
        strptime(enrollments[i].enrollmentDate.c_str(), "%a %b %d %H:%M:%S %Y", &enrollmentTime);
        time_t enrollmentDate = mktime(&enrollmentTime);

        // Calculate days difference
        double daysDifference = difftime(currentTime, enrollmentDate) / (60 * 60 * 24);

        // Calculate fine
        double fine = max(0.0, daysDifference) * FINE_RATE_PER_DAY;

        cout << "Fine for enrollment " << i + 1 << ": $" << fixed << setprecision(2) << fine << endl;
    }
}

void displayAllFines(Student students[], int studentCount, Enrollment enrollments[], int enrollmentCount) {
    cout << "\n===== List of Fines =====\n";
    calculateFine(enrollments, enrollmentCount);
}

void saveData(Student students[], int studentCount, Enrollment enrollments[], int enrollmentCount) {
    ofstream outFile("student_data.txt");

    // Save student data
    outFile << studentCount << endl;
    for (int i = 0; i < studentCount; ++i) {
        outFile << students[i].studentID << " " << students[i].name << " " << students[i].contactInfo << endl;
    }

    // Save enrollment data
    outFile << enrollmentCount << endl;
    for (int i = 0; i < enrollmentCount; ++i) {
        outFile << enrollments[i].courseID << " " << enrollments[i].enrollmentDate;
    }

    outFile.close();
}

void loadData(Student students[], int& studentCount, Enrollment enrollments[], int& enrollmentCount) {
    ifstream inFile("student_data.txt");

    if (!inFile) {
        cout << "No previous data found.\n";
        return;
    }

    // Load student data
    inFile >> studentCount;
    for (int i = 0; i < studentCount; ++i) {
        inFile >> students[i].studentID;
        inFile.ignore();
        getline(inFile, students[i].name);
        getline(inFile, students[i].contactInfo);
    }

    // Load enrollment data
    inFile >> enrollmentCount;
    for (int i = 0; i < enrollmentCount; ++i) {
        inFile >> enrollments[i].courseID;
        inFile.ignore();
        getline(inFile, enrollments[i].enrollmentDate);
    }

    inFile.close();
}