Features/loan

src/main/java/org/example/Book.java

@@ -64,6 +64,15 @@ public void setTitle(String title) {
     public Long getId() {
         return bookId;
     }
+
+    public Loan getLoan() {
+        return loan;
+    }
+
+    public void setLoan(Loan loan) {
+        this.loan = loan;
+    }
+
     @ManyToMany
     @JoinTable(name = "book_author",
         joinColumns = @JoinColumn(name = "bookId"))

src/main/java/org/example/Loan.java

@@ -1,11 +1,7 @@
 package org.example;
 
 import jakarta.persistence.*;
-
 import java.time.ZonedDateTime;
-import java.util.ArrayList;
-import java.util.Date;
-import java.util.List;
 
 @Entity
 public class Loan {
@@ -16,27 +12,24 @@ public class Loan {
 
     private ZonedDateTime loanDate;
     private ZonedDateTime returnDate;
-    private Long userId;
-    private Long bookId;
 
     public Loan(){
     }
 
-
-    public Long getBookId() {
-        return bookId;
+    public User getUser() {
+        return user;
     }
 
-    public void setBookId(Long bookId) {
-        this.bookId = bookId;
+    public void setUser(User user){
+        this.user = user;
     }
 
-    public Long getUserId() {
-        return userId;
+    public Book getBook() {
+        return book;
     }
 
-    public void setUserId(Long userId) {
-        this.userId = userId;
+    public void setBook(Book book){
+        this.book = book;
     }
 
     public ZonedDateTime getReturnDate() {

src/main/java/org/example/LoanServices.java

@@ -0,0 +1,76 @@
+package org.example;
+
+import jakarta.persistence.EntityManager;
+import java.time.ZonedDateTime;
+import java.util.List;
+
+public class LoanServices {
+
+    final private EntityManager em;
+
+    public LoanServices(EntityManager em) {
+        this.em = em;
+    }
+
+    // Kolla om en bok är utlånad
+    public boolean isBookLoaned(Long bookId) {
+
+        List<Loan> loans = em.createQuery(
+            "SELECT l FROM Loan l WHERE l.book.bookId = :bookId AND l.returnDate IS NULL",
+            Loan.class
+        )
+        .setParameter("bookId", bookId)
+            .getResultList();
+
+        if (loans.isEmpty()) {
+            return false;
+        } else {
+            return true;
+        }
+    }
+
+    // Låna en bok
+    public boolean loanBook(Long bookId, Long userId) {
+
+        if (isBookLoaned(bookId)) {
+            return false;
+        }
+
+        User user = em.find(User.class, userId);
+        Book book = em.find(Book.class, bookId);
+
+        Loan loan = new Loan();
+
+        loan.setUser(user);
+        loan.setBook(book);
+        loan.setLoanDate(ZonedDateTime.now());
+        loan.setReturnDate(null);
+        em.persist(loan);
+        return true;
+    }
+
+    // Lämna tillbak en bok
+    public boolean returnBook(User user, Book book) {
+
+        Loan loan = em.createQuery(
+            "SELECT l FROM Loan l WHERE l.user = :user AND l.book = :book AND l.returnDate IS NULL",
+            Loan.class
+        )
+            .setParameter("user", user)
+            .setParameter("book", book)
+            .getResultStream()
+            .findFirst()
+            .orElse(null);
+
+        if (loan == null) {
+            return false;
+        }
+
+        em.getTransaction().begin();
+
+        loan.setReturnDate(ZonedDateTime.now());
+        book.setLoan(null);
+        em.getTransaction().commit();
+        return true;
+    }
+}