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LibraryApp_Interactive/LibraryAppInteractive/LibraryApp/App.xaml.cs

@@ -2,13 +2,16 @@
 
 public partial class App : Application
 {
+    public static IServiceProvider ServiceProvider { get; private set; }
+
     public App()
     {
         InitializeComponent();
+        MainPage = new AppShell();
+    }
+    protected override void OnStart()
+    {
+        base.OnStart();
+        ServiceProvider = MauiProgram.CreateMauiApp().Services;
     }
-
-	protected override Window CreateWindow(IActivationState? activationState)
-	{
-		return new Window(new AppShell());
-	}
 }

LibraryApp_Interactive/LibraryAppInteractive/LibraryApp/Business Logic/AssetStatus.cs

@@ -0,0 +1,9 @@
+namespace LibraryAppInteractive.Business_Logic;
+
+public enum AssetStatus
+{
+    NotAvailable = 0,
+    Available = 1,
+    Loaned,
+    Reserved
+}

LibraryApp_Interactive/LibraryAppInteractive/LibraryApp/Business Logic/Book.cs

@@ -0,0 +1,164 @@
+namespace LibraryAppInteractive.Business_Logic;
+
+public class Book
+{
+    private string _bookName;
+    private string _bookISBN;
+    private List<string> _bookAuthorList;
+    private List<LibraryAsset> _libAssetList;
+    private BookType _bookType;
+
+    public string Name
+    {
+        get => _bookName;
+        set => _bookName = value;
+    }
+
+    public string ISBN
+    {
+        get => _bookISBN;
+        set => _bookISBN = value;
+    }
+
+    public List<string> Authors
+    {
+        get => _bookAuthorList;
+        set => _bookAuthorList = value;
+    }
+
+    public List<LibraryAsset> Assets
+    {
+        get => _libAssetList;
+        set => _libAssetList = value;
+    }
+
+    public BookType BookType
+    {
+        get => _bookType;
+        set => _bookType = value;
+    }
+
+    public Book(string bookName, string bookISBN, BookType bookType = BookType.Paper)
+    {
+        _bookName = bookName;
+        _bookISBN = bookISBN;
+        _bookType = bookType;
+        _bookAuthorList = new List<string>();
+        _libAssetList = new List<LibraryAsset>();
+    }
+
+    /// <summary>
+    /// Checks the availability of the book by checking if there are any library assets 
+    /// for this book that are available to borrow.
+    /// Returns:
+    ///     (true, null) - an asset is available and could be loaned
+    ///     (false, DateTime) - all assets are loaned or reserved. Returns the earliest available date.
+    /// </summary>
+    public (bool, DateTime?) CheckAvailability()
+    {
+        LibraryAsset nextAvailAsset = FindNextAvailableAsset();
+
+        if (nextAvailAsset?.Status == AssetStatus.Available)
+        {
+            return (true, null);
+        }
+        else
+        {
+            return (false, nextAvailAsset?.DueDate);
+        }
+    }
+
+    /// <summary>
+    /// Attempts to find an available asset and loans it to the user.
+    /// If no book asset is available, throws an exception.
+    /// </summary>
+    public virtual LibraryAsset BorrowBook()
+    {
+        LibraryAsset libraryAsset = FindNextAvailableAsset();
+
+        if (libraryAsset?.Status != AssetStatus.Available)
+        {
+            throw new InvalidOperationException("The requested book is not available. You can check for availability first and reserve it.");
+        }
+
+        libraryAsset.BorrowedOn = DateTime.Now;
+        libraryAsset.Status = AssetStatus.Loaned;
+
+        // Set default due date (14 days). Derived classes can override this.
+        libraryAsset.DueDate = DateTime.Now.AddDays(14);
+
+        return libraryAsset;
+    }
+
+    /// <summary>
+    /// Returns a borrowed asset back to the library using the ID of the library asset.
+    /// </summary>
+    public virtual (TimeSpan, int, decimal) ReturnBook(int libID)
+    {
+        LibraryAsset libraryAsset = FindLibraryAsset(libID);
+        libraryAsset.ReturnedOn = DateTime.Now;
+
+        TimeSpan loanDuration = libraryAsset.GetLoanDuration();
+        TimeSpan latePeriod = libraryAsset.GetLatePeriod();
+
+        libraryAsset.Status = AssetStatus.Available;
+
+        // Base method does not calculate late penalties. Derived classes must perform this.
+        return (loanDuration, latePeriod.Days, 0.0m);
+    }
+
+    /// <summary>
+    /// Finds and reserves the earliest available asset for this book.
+    /// </summary>
+    public LibraryAsset ReserveBook()
+    {
+        LibraryAsset nextAvailAsset = FindNextAvailableAsset();
+        nextAvailAsset.Status = AssetStatus.Reserved;
+        return nextAvailAsset;
+    }
+
+    /// <summary>
+    /// Finds the library asset with the given ID.
+    /// Throws an exception if no asset is found.
+    /// </summary>
+    private LibraryAsset FindLibraryAsset(int libID)
+    {
+        foreach (LibraryAsset asset in _libAssetList)
+        {
+            if (asset.LibId == libID)
+            {
+                return asset;
+            }
+        }
+
+        throw new InvalidOperationException($"An asset with ID = {libID} was not found for book {Name}");
+    }
+
+    /// <summary>
+    /// Finds the next available asset for this book.
+    /// If an asset is available immediately, it returns that one.
+    /// Otherwise, returns the asset with the earliest due date.
+    /// </summary>
+    private LibraryAsset FindNextAvailableAsset()
+    {
+        LibraryAsset nextAvailAsset = null;
+
+        foreach (LibraryAsset asset in _libAssetList)
+        {
+            // Check if asset is available immediately
+            if (asset.Status == AssetStatus.Available)
+            {
+                return asset;
+            }
+
+            // Find asset with the earliest due date
+            if (nextAvailAsset == null || 
+                (nextAvailAsset.DueDate > asset.DueDate && nextAvailAsset.Status != AssetStatus.Reserved))
+            {
+                nextAvailAsset = asset;
+            }
+        }
+
+        return nextAvailAsset;
+    }
+}

LibraryApp_Interactive/LibraryAppInteractive/LibraryApp/Business Logic/BookType.cs

@@ -0,0 +1,8 @@
+namespace LibraryAppInteractive.Business_Logic;
+
+public enum BookType
+{
+    Paper = 1,
+    Digital,
+    Audio
+}

LibraryApp_Interactive/LibraryAppInteractive/LibraryApp/Business Logic/DigitalBook.cs

@@ -0,0 +1,50 @@
+namespace LibraryAppInteractive.Business_Logic;
+
+public class DigitalBook : Book
+{
+    private int _maxBorrowDays;
+    private float _latePenaltyPerDay;
+    private Random _random = new Random();
+
+    public DigitalBook(string bookName, string bookISBN) : base(bookName, bookISBN, BookType.Digital)
+    {
+        _maxBorrowDays = 0;
+        _latePenaltyPerDay = 0.0f;
+
+        DetermineLoanLicense();
+    }
+
+    /// <summary>
+    /// Determine the values for maximum loan duration and late penalty according to license agreement using randomly generated values.
+    /// Maximum loan duration: 2-8 weeks (randomly)
+    /// Late penalty: 0.1 - 0.5 per day (randomly)
+    /// </summary>
+    private void DetermineLoanLicense()
+    {
+        _maxBorrowDays = _random.Next(2 * 7, 8 * 7 + 1); // 2-8 weeks in days
+        _latePenaltyPerDay = 0.1f + (float)_random.NextDouble() * 0.4f; // 0.1 to 0.5
+    }
+
+    /// <summary>
+    /// Overrides the base implementation to use the deadline for digital books.
+    /// </summary>
+    public override LibraryAsset BorrowBook()
+    {
+        LibraryAsset libAsset = base.BorrowBook();
+
+        // Adjust due date according to digital book policy
+        libAsset.DueDate = DateTime.Now.AddDays(_maxBorrowDays);
+
+        return libAsset;
+    }
+
+    /// <summary>
+    /// Returns a borrowed asset and calculates late fees according to digital book policy.
+    /// </summary>
+    public override (TimeSpan, int, decimal) ReturnBook(int libID)
+    {
+        (TimeSpan loanDuration, int daysLate, decimal lateFees) = base.ReturnBook(libID);
+
+        return (loanDuration, daysLate, (decimal)(daysLate * _latePenaltyPerDay));
+    }
+}