public static void GiveBookToUser(BooksDataContext db, string bookArg, string authorArg)
{
int userId;
if (!int.TryParse(authorArg, out userId))
{
Console.WriteLine("Invalid user ID! Operation aborted!");
return;
}
int bookId;
if (!int.TryParse(bookArg, out bookId))
{
Console.WriteLine("Invalid book ID! Operation aborted!");
return;
}
var userToLendTo = (from user in db.Users
where user.UserID == userId
select user).SingleOrDefault();
if (userToLendTo == null)
{
Console.WriteLine("No such user! Operation aborted!");
return;
}
var bookToLend = (from book in db.Books
where book.BookID == bookId
select book).SingleOrDefault();
if (bookToLend == null)
{
Console.WriteLine("No such book! Operation aborted!");
return;
}
var userLoanings = from loanedBook in db.LoanedBooks
where loanedBook.UserID == userId
select loanedBook.Quantity;
int loanedBooksByUser = userLoanings.Any() ? userLoanings.Sum() : 0;
if (loanedBooksByUser == 5)
{
Console.WriteLine("User can't lend more than 5 books! Operation aborted!");
return;
}
var bookQuantities = (from book in db.LoanedBooks
where book.BookID == bookId
select book.Quantity);
int givenCopies = bookQuantities.Any() ? bookQuantities.Sum() : 0;
var availableCopies = bookToLend.Quantity - givenCopies;
if (availableCopies == 0)
{
Console.WriteLine("No more available copies of the book! Operation aborted!");
return;
}
var bookLoan = (from loanedBook in db.LoanedBooks
where loanedBook.BookID == bookId && loanedBook.UserID == userId
select loanedBook).SingleOrDefault();
if (bookLoan == null)
{
var newBookLoan = new LoanedBook();
newBookLoan.BookID = bookId;
newBookLoan.UserID = userId;
newBookLoan.Quantity = 1;
newBookLoan.LoanDate = DateTime.Now;
newBookLoan.ExpirationDate = DateTime.Now.AddMonths(1);
db.LoanedBooks.InsertOnSubmit(newBookLoan);
}
else
{
bookLoan.Quantity++;
bookLoan.LoanDate = DateTime.Now;
bookLoan.ExpirationDate = DateTime.Now.AddMonths(1);
}
try
{
db.SubmitChanges();
}
catch (ChangeConflictException ex)
{
Console.WriteLine("Cannot update info in database! Operation exited with message:");
Console.WriteLine(ex.Message);
return;
}
Console.WriteLine("Book loaned successfully!");
}
