main.cpp

/**
 * Student Record Management System
 * Description: A console-based CRUD application built with C++ and MySQL.
 * Employs Object-Oriented Programming principles to manage student data.
 */

#include <iostream>
#include <string>
#include <iomanip>
#include <fstream> 
#include <mysql.h> 

using namespace std;

/**
 * @class Student
 * @brief Represents a single student entity. 
 * Encapsulates student data to ensure safe data transfer between the UI and database.
 */
class Student {
private:
    int id;
    string firstName;
    string lastName;
    string department;
    double cgpa;

public:
    // Constructor to initialize a new student record
    Student(string fName, string lName, string dept, double gpa) {
        firstName = fName;
        lastName = lName;
        department = dept;
        cgpa = gpa;
    }

    // Accessor methods (Getters)
    string getFirstName() { return firstName; }
    string getLastName() { return lastName; }
    string getDepartment() { return department; }
    double getCgpa() { return cgpa; }
};

/**
 * @class DatabaseManager
 * @brief Handles all interactions with the MySQL database.
 * Abstracts the C API to provide clean CRUD operations for the main application.
 */
class DatabaseManager {
private:
    MYSQL* conn; 

    /**
     * Reads database credentials from an external configuration file.
     * This prevents hardcoding sensitive passwords in the source code.
     * @return string Password read from db_config.txt
     */
    string getDatabasePassword() {
        ifstream file("db_config.txt");
        string password = "";
        if (file.is_open()) {
            getline(file, password);
            file.close();
        } else {
            cout << "\n[WARNING] Configuration file 'db_config.txt' missing. Connection may fail." << endl;
        }
        return password;
    }

public:
    // Initializes the MySQL connection using external credentials
    DatabaseManager() {
        conn = mysql_init(0);
        string dbPassword = getDatabasePassword();
        
        // Establish connection to the local database server
        conn = mysql_real_connect(conn, "127.0.0.1", "root", dbPassword.c_str(), "StudentRecordDB", 3306, NULL, 0);
        
        if (!conn) {
            cout << "\n[ERROR] Database Connection failed: " << mysql_error(conn) << endl;
        }
    }

    // Destructor ensures the database connection is gracefully closed
    ~DatabaseManager() {
        if (conn) {
            mysql_close(conn);
        }
    }

    /**
     * Inserts a new Student object into the database.
     * @param student The Student object containing the data to be inserted.
     */
    void addStudent(Student student) {
        string query = "INSERT INTO students(first_name, last_name, department, cgpa) VALUES ('" 
                     + student.getFirstName() + "', '" 
                     + student.getLastName() + "', '" 
                     + student.getDepartment() + "', " 
                     + to_string(student.getCgpa()) + ")";

        if (mysql_query(conn, query.c_str()) == 0) {
            cout << "\n[SUCCESS] Student record saved successfully." << endl;
        } else {
            cout << "\n[ERROR] Failed to save record: " << mysql_error(conn) << endl;
        }
    }

    /**
     * Retrieves and formats all student records from the database into a table.
     */
    void viewAllStudents() {
        if (mysql_query(conn, "SELECT * FROM students") == 0) {
            MYSQL_RES* res = mysql_store_result(conn);
            MYSQL_ROW row;

            cout << "\n=======================================================" << endl;
            cout << left << setw(5) << "ID" << setw(15) << "First Name" << setw(15) << "Last Name" << setw(20) << "Department" << "CGPA" << endl;
            cout << "=======================================================" << endl;

            while ((row = mysql_fetch_row(res))) {
                cout << left << setw(5) << row[0] 
                     << setw(15) << row[1] 
                     << setw(15) << row[2] 
                     << setw(20) << row[3] 
                     << row[4] << endl;
            }
            cout << "=======================================================\n" << endl;
            mysql_free_result(res);
        } else {
            cout << "\n[ERROR] Failed to retrieve records: " << mysql_error(conn) << endl;
        }
    }

    /**
     * Deletes a student record based on the primary key (ID).
     * @param studentId The ID of the student to delete.
     */
    void deleteStudent(int studentId) {
        string query = "DELETE FROM students WHERE id = " + to_string(studentId);
        
        if (mysql_query(conn, query.c_str()) == 0) {
            if (mysql_affected_rows(conn) > 0) {
                cout << "\n[SUCCESS] Student ID " << studentId << " has been deleted." << endl;
            } else {
                cout << "\n[ERROR] Student ID not found in the database." << endl;
            }
        } else {
            cout << "\n[ERROR] Failed to delete record: " << mysql_error(conn) << endl;
        }
    }
};

/**
 * Entry point of the application. 
 * Manages the main event loop and user interaction via CLI.
 */
int main() {
    DatabaseManager db;
    int choice;

    while (true) {
        cout << "\n=== STUDENT RECORD MANAGEMENT SYSTEM ===" << endl;
        cout << "1. Add New Student" << endl;
        cout << "2. View All Students" << endl;
        cout << "3. Delete a Student" << endl;
        cout << "4. Exit" << endl;
        cout << "Enter your choice: ";
        cin >> choice;

        if (choice == 1) {
            string fName, lName, dept;
            double gpa;
            
            cout << "Enter First Name: ";
            cin >> fName;
            cout << "Enter Last Name: ";
            cin >> lName;
            cin.ignore();
            cout << "Enter Department (e.g., CS, IT): ";
            getline(cin, dept);
            cout << "Enter CGPA: ";
            cin >> gpa;

            Student newStudent(fName, lName, dept, gpa);
            db.addStudent(newStudent);

        } else if (choice == 2) {
            db.viewAllStudents();
            
        } else if (choice == 3) {
            int id;
            cout << "Enter Student ID to delete: ";
            cin >> id;
            db.deleteStudent(id);
            
        } else if (choice == 4) {
            cout << "Exiting system. Goodbye!" << endl;
            break;
            
        } else {
            cout << "Invalid choice. Please try again." << endl;
        }
    }
    return 0;
}