Program.cs

using System;
using System.Linq;

class Program
{
    private static readonly MemberCollection members = new MemberCollection();
    private static readonly MovieCollection movies = new MovieCollection();

    private const string StaffUsername = "staff";
    private const string StaffPassword = "today123";

    static void Main()
    {
        SeedTestData();

        while (true)
        {
            Console.Clear();
            DisplayMainMenu();

            string input = Console.ReadLine()?.Trim();

            if (input == "0") break;

            if (input == "1")
            {
                if (StaffLogin())
                    StaffMenu();
            }
            else if (input == "2")
            {
                Member member = MemberLogin();
                if (member != null)
                    MemberMenu(member);
            }
            else
            {
                Console.WriteLine("Invalid choice. Press any key...");
                Console.ReadKey();
            }
        }
    }

    static void DisplayMainMenu()
    {
        Console.WriteLine("=============================================================");
        Console.WriteLine("COMMUNITY LIBRARY MOVIE DVD MANAGEMENT SYSTEM");
        Console.WriteLine("=============================================================");
        Console.WriteLine();
        Console.WriteLine("Main Menu");
        Console.WriteLine("-------------------------------------------------------------");
        Console.WriteLine("Select from the following:");
        Console.WriteLine();
        Console.WriteLine("1. Staff");
        Console.WriteLine("2. Member");
        Console.WriteLine("0. End the program");
        Console.WriteLine();
        Console.Write("Enter your choice => ");
    }

    static bool StaffLogin()
    {
        Console.Clear();
        Console.WriteLine("Staff Login");
        Console.WriteLine("---------------------");
        Console.Write("Username: ");
        string username = Console.ReadLine()?.Trim();
        Console.Write("Password: ");
        string password = Console.ReadLine()?.Trim();

        if (username == StaffUsername && password == StaffPassword)
            return true;

        Console.WriteLine("Invalid staff credentials. Press any key...");
        Console.ReadKey();
        return false;
    }

    static Member MemberLogin()
    {
        Console.Clear();
        Console.WriteLine("Member Login");
        Console.WriteLine("---------------------");
        Console.Write("First name: ");
        string first = Console.ReadLine()?.Trim();
        Console.Write("Last name: ");
        string last = Console.ReadLine()?.Trim();
        Console.Write("Password (4 digits): ");
        string pass = Console.ReadLine()?.Trim();

        string fullName = $"{first} {last}";
        Member member = members.Search(fullName);

        if (member != null && member.Password == pass)
            return member;

        Console.WriteLine("Login failed. Press any key...");
        Console.ReadKey();
        return null;
    }

    static void StaffMenu()
    {
        while (true)
        {
            Console.Clear();
            Console.WriteLine("Staff Menu");
            Console.WriteLine("-------------------------------------------------------------");
            Console.WriteLine("1. Add DVDs of a new movie to the system");
            Console.WriteLine("2. Add new DVDs of an existing movie to the system");
            Console.WriteLine("3. Remove a DVD from the system");
            Console.WriteLine("4. Register a new member to the system");
            Console.WriteLine("5. Remove a registered member from the system");
            Console.WriteLine("6. Find a member's contact phone number, given the member's name");
            Console.WriteLine("7. Find members who are currently renting a particular movie");
            Console.WriteLine("0. Return to main menu");
            Console.WriteLine();
            Console.Write("Enter your choice => ");

            string choice = Console.ReadLine()?.Trim();

            if (choice == "0") break;

            switch (choice)
            {
                case "1": AddNewMovie(); break;
                case "2": AddCopiesToExistingMovie(); break;
                case "3": RemoveDVD(); break;
                case "4": RegisterMember(); break;
                case "5": RemoveMember(); break;
                case "6": FindMemberPhone(); break;
                case "7": FindRentersOfMovie(); break;
                default:
                    Console.WriteLine("Invalid choice. Press any key...");
                    Console.ReadKey();
                    break;
            }
        }
    }

    static void MemberMenu(Member member)
    {
        while (true)
        {
            Console.Clear();
            Console.WriteLine($"Member Menu - Welcome, {member.FullName}");
            Console.WriteLine("-------------------------------------------------------------");
            Console.WriteLine("1. Browse all the movies");
            Console.WriteLine("2. Display all the information about a movie, given the title");
            Console.WriteLine("3. Borrow a movie DVD");
            Console.WriteLine("4. Return a movie DVD");
            Console.WriteLine("5. List current borrowing movies");
            Console.WriteLine("6. Display the top 3 movies rented by the members");
            Console.WriteLine("0. Return to main menu");
            Console.WriteLine();
            Console.Write("Enter your choice => ");

            string choice = Console.ReadLine()?.Trim();

            if (choice == "0") break;

            switch (choice)
            {
                case "1": BrowseAllMovies(); break;
                case "2": DisplayMovieInfo(); break;
                case "3": BorrowMovie(member); break;
                case "4": ReturnMovie(member); break;
                case "5": ListMyMovies(member); break;
                case "6": DisplayTop3(); break;
                default:
                    Console.WriteLine("Invalid choice. Press any key...");
                    Console.ReadKey();
                    break;
            }
        }
    }

    // ──────────────────────────────────────────────────────────────
    // All functional requirements implemented below
    // ──────────────────────────────────────────────────────────────
    static void SeedTestData()
    {
        movies.Add(new Movie("Inception", "Sci-Fi", "M15+", 148, 3));
        movies.Add(new Movie("The Matrix", "Action", "M15+", 136, 2));
        movies.Add(new Movie("Interstellar", "Sci-Fi", "PG", 169, 1));
        movies.Add(new Movie("The Godfather", "Drama", "M15+", 175, 2));

        var alice = new Member("Alice", "Johnson", "0412345678");
        alice.SetPassword("1234");
        members.Add(alice);

        var bob = new Member("Bob", "Smith", "0412987654");
        bob.SetPassword("5678");
        members.Add(bob);
    }

    static void AddNewMovie()
    {
        Console.Clear();
        Console.WriteLine("Add DVDs of a new movie");
        Console.Write("Title: ");
        string title = Console.ReadLine()?.Trim();
        Console.Write("Genre: ");
        string genre = Console.ReadLine()?.Trim();
        Console.Write("Classification: ");
        string classification = Console.ReadLine()?.Trim();
        Console.Write("Duration (minutes): ");
        if (!int.TryParse(Console.ReadLine(), out int duration) || duration <= 0)
        {
            Console.WriteLine("Invalid duration. Press any key...");
            Console.ReadKey();
            return;
        }
        Console.Write("Number of DVDs: ");
        if (!int.TryParse(Console.ReadLine(), out int copies) || copies <= 0)
        {
            Console.WriteLine("Invalid number of copies. Press any key...");
            Console.ReadKey();
            return;
        }

        Movie movie = new Movie(title, genre, classification, duration, copies);
        if (movies.Add(movie))
            Console.WriteLine("Movie added successfully.");
        else
            Console.WriteLine("Movie title already exists.");

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void AddCopiesToExistingMovie()
    {
        Console.Clear();
        Console.WriteLine("Add new DVDs of an existing movie");
        Console.Write("Movie title: ");
        string title = Console.ReadLine()?.Trim();
        Console.Write("Number of additional DVDs: ");
        if (!int.TryParse(Console.ReadLine(), out int copies) || copies <= 0)
        {
            Console.WriteLine("Invalid number. Press any key...");
            Console.ReadKey();
            return;
        }

        Movie movie = movies.Search(title);
        if (movie == null)
            Console.WriteLine("Movie not found.");
        else
        {
            movie.AddCopies(copies);
            Console.WriteLine($"Added {copies} copies. Total now: {movie.TotalCopies}");
        }

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void RemoveDVD()
    {
        Console.Clear();
        Console.WriteLine("Remove a DVD from the system");
        Console.Write("Movie title: ");
        string title = Console.ReadLine()?.Trim();

        Movie movie = movies.Search(title);
        if (movie == null)
        {
            Console.WriteLine("Movie not found.");
        }
        else if (movie.AvailableCopies > 0)
        {
            movie.DecreaseAvailableCopy();
            movie.DecreaseTotalCopy();

            Console.WriteLine($"Removed one copy. Available now: {movie.AvailableCopies}/{movie.TotalCopies}");

            if (movie.TotalCopies == 0)
            {
                movies.Remove(title);
                Console.WriteLine("Last copy removed – movie deleted from system.");
            }
        }
        else
        {
            Console.WriteLine("No available copies to remove.");
        }

        Console.WriteLine("\nPress any key...");
        Console.ReadKey();
    }

    static void RegisterMember()
    {
        Console.Clear();
        Console.WriteLine("Register a new member");
        Console.Write("First name: ");
        string first = Console.ReadLine()?.Trim();
        Console.Write("Last name: ");
        string last = Console.ReadLine()?.Trim();
        Console.Write("Phone number: ");
        string phone = Console.ReadLine()?.Trim();

        if (string.IsNullOrWhiteSpace(first) || string.IsNullOrWhiteSpace(last) || string.IsNullOrWhiteSpace(phone))
        {
            Console.WriteLine("All fields required.");
            Console.ReadKey();
            return;
        }

        Console.Write("Set 4-digit password: ");
        string pass = Console.ReadLine()?.Trim();
        if (pass?.Length != 4 || !int.TryParse(pass, out _))
        {
            Console.WriteLine("Password must be exactly 4 digits.");
            Console.ReadKey();
            return;
        }

        Member member = new Member(first, last, phone);
        member.SetPassword(pass);

        if (members.Add(member))
            Console.WriteLine("Member registered successfully.");
        else
            Console.WriteLine("Member collection full or name already exists.");

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void RemoveMember()
    {
        Console.Clear();
        Console.WriteLine("Remove a registered member");
        Console.Write("Full name: ");
        string fullName = Console.ReadLine()?.Trim();

        if (members.Remove(fullName))
            Console.WriteLine("Member removed.");
        else
            Console.WriteLine("Member not found.");

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void FindMemberPhone()
    {
        Console.Clear();
        Console.WriteLine("Find member's phone number");
        Console.Write("Full name: ");
        string fullName = Console.ReadLine()?.Trim();

        Member member = members.Search(fullName);
        if (member != null)
            Console.WriteLine($"Phone: {member.PhoneNumber}");
        else
            Console.WriteLine("Member not found.");

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void FindRentersOfMovie()
    {
        Console.Clear();
        Console.WriteLine("Find members renting a particular movie");
        Console.Write("Movie title: ");
        string title = Console.ReadLine()?.Trim();

        Movie movie = movies.Search(title);
        if (movie == null)
        {
            Console.WriteLine("Movie not found.");
            Console.ReadKey();
            return;
        }

        bool found = false;
        foreach (var member in members.ToArray())
        {
            if (member.GetBorrowedTitles().Contains(title, StringComparer.OrdinalIgnoreCase))
            {
                Console.WriteLine($"{member.FullName} ({member.PhoneNumber})");
                found = true;
            }
        }

        if (!found)
            Console.WriteLine("No one is currently renting this movie.");

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void BrowseAllMovies()
    {
        Console.Clear();
        Console.WriteLine("All movies (alphabetical order)");
        Console.WriteLine("-------------------------------------------------------------");

        var list = movies.ToArray();
        if (list.Length == 0)
        {
            Console.WriteLine("No movies in the system.");
        }
        else
        {
            foreach (var m in list)
                Console.WriteLine($"{m.Title} - {m.AvailableCopies}/{m.TotalCopies} available");
        }

        Console.WriteLine("\nPress any key...");
        Console.ReadKey();
    }

    static void DisplayMovieInfo()
    {
        Console.Clear();
        Console.WriteLine("Display movie information");
        Console.Write("Title: ");
        string title = Console.ReadLine()?.Trim();

        Movie movie = movies.Search(title);
        if (movie == null)
            Console.WriteLine("Movie not found.");
        else
            Console.WriteLine(movie.ToString());

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void BorrowMovie(Member member)
    {
        Console.Clear();
        Console.WriteLine("Borrow a movie DVD");
        Console.Write("Title: ");
        string title = Console.ReadLine()?.Trim();

        Movie movie = movies.Search(title);
        if (movie == null)
        {
            Console.WriteLine("Movie not found.");
        }
        else if (!member.CanBorrowMore())
        {
            Console.WriteLine("You have reached the maximum borrowing limit (5).");
        }
        else if (member.GetBorrowedTitles().Contains(title, StringComparer.OrdinalIgnoreCase))
        {
            Console.WriteLine("You already have this movie.");
        }
        else if (movie.BorrowCopy())
        {
            member.BorrowMovie(title);
            Console.WriteLine("Movie borrowed successfully.");
        }
        else
        {
            Console.WriteLine("No copies available.");
        }

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void ReturnMovie(Member member)
    {
        Console.Clear();
        Console.WriteLine("Return a movie DVD");
        Console.Write("Title: ");
        string title = Console.ReadLine()?.Trim();

        if (member.ReturnMovie(title))
        {
            Movie movie = movies.Search(title);
            if (movie != null)
                movie.ReturnCopy();
            Console.WriteLine("Movie returned successfully.");
        }
        else
        {
            Console.WriteLine("You are not currently borrowing this movie.");
        }

        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }

    static void ListMyMovies(Member member)
    {
        Console.Clear();
        Console.WriteLine("Your current borrowings");
        Console.WriteLine("-------------------------------------------------------------");

        var titles = member.GetBorrowedTitles();
        if (titles.Length == 0)
        {
            Console.WriteLine("You have no movies borrowed.");
        }
        else
        {
            foreach (var title in titles)
                Console.WriteLine(title);
        }

        Console.WriteLine("\nPress any key...");
        Console.ReadKey();
    }

    static void DisplayTop3()
    {
        Console.Clear();
        Console.WriteLine("Top 3 most frequently borrowed movies");
        Console.WriteLine("-------------------------------------------------------------");

        var top3 = movies.GetTop3Borrowed();
        if (top3.Length == 0)
        {
            Console.WriteLine("No movies have been borrowed yet.");
        }
        else
        {
            for (int i = 0; i < top3.Length; i++)
                Console.WriteLine($"{i + 1}. {top3[i].Title} – Borrowed {top3[i].TimesBorrowed} times");
        }

        Console.WriteLine("\nPress any key...");
        Console.ReadKey();
    }
}