LibraryApp/LibraryApp.Domain/Entities/BookInstance.cs

namespace LibraryApp.Domain.Entities;

public enum BookInstanceStatus
{
    OnShelf,
    Lent,
    PutAside,
    Lost
}

public class BookInstance
{
    public BookInstanceId Id { get; private set; }
    public BookId BookId { get; private set; }
    public ShelfId ShelfId { get; private set; }
    public BookInstanceBarcode Barcode { get; private set; }
    public BookInstanceStatus Status { get; private set; }

    public BookInstance(BookId bookId, ShelfId shelfId, BookInstanceBarcode barcode)
        : this(new BookInstanceId(string.Empty), bookId, shelfId, barcode, BookInstanceStatus.OnShelf)
    { }

    public BookInstance(BookInstanceId id, BookId bookId, ShelfId shelfId, BookInstanceBarcode barcode, BookInstanceStatus status)
    {
        Id = id;
        BookId = bookId;
        ShelfId = shelfId;
        Barcode = barcode;
        Status = status;
    }

    public BookInstance MarkAsLent()
    {
        if (Status != BookInstanceStatus.OnShelf)
            throw new InvalidOperationException($"Cannot lend a book that is not on the shelf. Current status: {Status}.");
        Status = BookInstanceStatus.Lent;
        return this;
    }

    public BookInstance ReturnToShelf()
    {
        if (Status != BookInstanceStatus.Lent)
            throw new InvalidOperationException($"Cannot return a book that is not lent out. Current status: {Status}.");
        Status = BookInstanceStatus.OnShelf;
        return this;
    }

    public BookInstance MarkAsPutAside()
    {
        if (Status != BookInstanceStatus.OnShelf)
            throw new InvalidOperationException($"Cannot put aside a book that is not on the shelf. Current status: {Status}.");
        Status = BookInstanceStatus.PutAside;
        return this;
    }

    public BookInstance PlaceOnShelf(ShelfId shelfId)
    {
        if (Status != BookInstanceStatus.PutAside)
            throw new InvalidOperationException($"Cannot place on shelf a book that is not put aside. Current status: {Status}.");
        ShelfId = shelfId;
        Status = BookInstanceStatus.OnShelf;
        return this;
    }

    public BookInstance MarkAsLost()
    {
        if (Status != BookInstanceStatus.OnShelf)
            throw new InvalidOperationException($"Cannot mark as lost a book that is not on the shelf. Current status: {Status}.");
        Status = BookInstanceStatus.Lost;
        return this;
    }

    public BookInstance UnmarkAsLost()
    {
        if (Status != BookInstanceStatus.Lost)
            throw new InvalidOperationException($"Cannot unmark as lost a book that is not marked as lost. Current status: {Status}.");
        Status = BookInstanceStatus.OnShelf;
        return this;
    }
}

public record BookInstanceId : DbId
{
    public BookInstanceId(string id) : base(id) {}
}

public record BookInstanceBarcode
{
    public string Barcode { get; init; }

    public BookInstanceBarcode(string barcode)
    {
        if(string.IsNullOrWhiteSpace(barcode))
        {
            throw new ArgumentException("Barcode cannot be empty.");
        }
        Barcode = barcode;
    }
}