Add check-in functionality for borrowed books

src/main/java/example/borrow/application/CirculationDesk.java

@@ -50,8 +50,32 @@ public HoldInformation checkout(Hold.Checkout command) {
 
         return HoldInformation.from(
                 hold.checkout(command)
-                        .then(holds::save)
-        );
+                        .then(holds::save));
+    }
+
+    public HoldInformation checkin(Hold.Checkin command) {
+        var hold = holds.findById(command.holdId())
+                .orElseThrow(() -> new IllegalArgumentException("Hold not found!"));
+
+        if (!hold.isCheckedOut()) {
+            throw new IllegalArgumentException("Book is not checked out");
+        }
+
+        if (!hold.isHeldBy(command.patronId())) {
+            throw new IllegalArgumentException("Hold belongs to a different patron");
+        }
+
+        return HoldInformation.from(
+                hold.checkin(command)
+                        .then(holds::save));
+    }
+
+    @ApplicationModuleListener
+    public void handle(Hold.BookCheckedIn event) {
+        books.findCheckedOutBook(new Book.Barcode(event.inventoryNumber()))
+                .map(Book::markAvailable)
+                .map(books::save)
+                .orElseThrow(() -> new IllegalArgumentException("Book not checked out?"));
     }
 
     @ApplicationModuleListener

src/main/java/example/borrow/application/HoldInformation.java

@@ -13,14 +13,16 @@ public class HoldInformation {
     private final String patronId;
     private final LocalDate dateOfHold;
     private final LocalDate dateOfCheckout;
+    private final LocalDate dateOfCheckin;
     private final Hold.HoldStatus holdStatus;
 
-    private HoldInformation(String id, String bookBarcode, String patronId, LocalDate dateOfHold, LocalDate dateOfCheckout, Hold.HoldStatus holdStatus) {
+    private HoldInformation(String id, String bookBarcode, String patronId, LocalDate dateOfHold, LocalDate dateOfCheckout, LocalDate dateOfCheckin, Hold.HoldStatus holdStatus) {
         this.id = id;
         this.bookBarcode = bookBarcode;
         this.patronId = patronId;
         this.dateOfHold = dateOfHold;
         this.dateOfCheckout = dateOfCheckout;
+        this.dateOfCheckin = dateOfCheckin;
         this.holdStatus = holdStatus;
     }
 
@@ -29,6 +31,9 @@ public static HoldInformation from(Hold hold) {
                 hold.getId().id().toString(),
                 hold.getOnBook().barcode(),
                 hold.getHeldBy().email(),
-                hold.getDateOfHold(), hold.getDateOfCheckout(), hold.getStatus());
+                hold.getDateOfHold(),
+                hold.getDateOfCheckout(),
+                hold.getDateOfCheckin(),
+                hold.getStatus());
     }
-}
+}

src/main/java/example/borrow/domain/Book.java

@@ -62,6 +62,11 @@ public Book markCheckedOut() {
         return this;
     }
 
+    public Book markAvailable() {
+        this.status = BookStatus.AVAILABLE;
+        return this;
+    }
+
     public record BookId(UUID id) implements Identifier {
     }
 
@@ -82,4 +87,4 @@ public enum BookStatus implements ValueObject {
     public record AddBook(Barcode barcode, String title, String isbn) {
     }
 
-}
+}

src/main/java/example/borrow/domain/BookRepository.java

@@ -23,4 +23,8 @@ public interface BookRepository extends CrudRepository<Book, Book.BookId> {
 
     Optional<Book> findByInventoryNumber(Book.Barcode inventoryNumber);
 
-}
+    @Query("""
+            SELECT b FROM Book b WHERE b.inventoryNumber = :inventoryNumber AND b.status = 'CHECKED_OUT'
+            """)
+    Optional<Book> findCheckedOutBook(Book.Barcode inventoryNumber);
+}

src/main/java/example/borrow/domain/Hold.java

@@ -5,6 +5,7 @@
 import org.springframework.data.domain.AbstractAggregateRoot;
 
 import java.time.LocalDate;
+import java.time.LocalDateTime;
 import java.util.UUID;
 import java.util.function.UnaryOperator;
 
@@ -43,6 +44,8 @@ public class Hold extends AbstractAggregateRoot<Hold> {
 
     private LocalDate dateOfCheckout;
 
+    private LocalDate dateOfCheckin;
+
     @Enumerated(EnumType.STRING)
     private HoldStatus status;
 
@@ -70,6 +73,12 @@ public Hold checkout(Checkout command) {
         return this;
     }
 
+    public Hold checkin(Checkin command) {
+        this.status = HoldStatus.RETURNED;
+        this.dateOfCheckin = command.dateOfCheckin();
+        return this;
+    }
+
     public Hold then(UnaryOperator<Hold> function) {
         return function.apply(this);
     }
@@ -78,11 +87,15 @@ public boolean isHeldBy(PatronId patronId) {
         return this.heldBy.equals(patronId);
     }
 
+    public boolean isCheckedOut() {
+        return status == HoldStatus.ACTIVE;
+    }
+
     public record HoldId(UUID id) implements Identifier {
     }
 
     public enum HoldStatus {
-        HOLDING, ACTIVE, COMPLETED
+        HOLDING, ACTIVE, RETURNED
     }
 
     ///
@@ -96,6 +109,8 @@ public record Checkout(HoldId holdId, LocalDate dateOfCheckout, PatronId patronI
 
     }
 
+    public record Checkin(HoldId holdId, LocalDate dateOfCheckin, PatronId patronId) {}
+
     ///
     // Events
     ///
@@ -111,4 +126,10 @@ public record BookPlacedOnHold(UUID holdId,
                                    String inventoryNumber,
                                    LocalDate dateOfHold) {
     }
+
+    @DomainEvent
+    public record BookCheckedIn(UUID holdId,
+                                String inventoryNumber,
+                                LocalDateTime dateOfCheckin) {
+    }
 }

src/main/java/example/borrow/infrastructure/CirculationDeskController.java

@@ -39,6 +39,13 @@ ResponseEntity<HoldInformation> checkoutBook(@PathVariable("id") UUID holdId, @A
         return ResponseEntity.ok(hold);
     }
 
+    @PostMapping("/borrow/holds/{id}/checkin")
+    ResponseEntity<HoldInformation> checkinBook(@PathVariable("id") UUID holdId, @Authenticated UserAccount userAccount) {
+        var command = new Hold.Checkin(new Hold.HoldId(holdId), LocalDate.now(), new PatronId(userAccount.email()));
+        var hold = circulationDesk.checkin(command);
+        return ResponseEntity.ok(hold);
+    }
+
     @GetMapping("/borrow/holds/{id}")
     ResponseEntity<HoldInformation> viewSingleHold(@PathVariable("id") UUID holdId) {
         return circulationDesk.locate(holdId)

src/test/java/example/borrow/CirculationDeskControllerIT.java

@@ -67,4 +67,16 @@ void checkoutBookRestCall() throws Exception {
                 .andExpect(jsonPath("$.dateOfCheckout").isNotEmpty())
                 .andExpect(jsonPath("$.holdStatus", equalTo("ACTIVE")));
     }
-}
+
+    @Test
+    void checkinBookRestCall() throws Exception {
+        mockMvc.perform(post("/borrow/holds/018dc74a-9c4e-743f-916f-e152f190d13e/checkin")
+                        .with(jwt().jwt(jwt -> jwt.claim("email", "[email protected]"))))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.id", equalTo("018dc74a-9c4e-743f-916f-e152f190d13e")))
+                .andExpect(jsonPath("$.bookBarcode", equalTo("55667788")))
+                .andExpect(jsonPath("$.patronId", equalTo("[email protected]")))
+                .andExpect(jsonPath("$.dateOfCheckin").isNotEmpty())
+                .andExpect(jsonPath("$.holdStatus", equalTo("RETURNED")));
+    }
+}

src/test/java/example/borrow/CirculationDeskTest.java

@@ -110,4 +110,45 @@ void bookStatusUpdatedWhenCheckoutBook() {
         // Assert
         assertThat(book.getStatus()).isEqualTo(ISSUED);
     }
+
+    @Test
+    void patronCanCheckinBook() {
+        // Arrange
+        var patronId = new PatronId("[email protected]");
+        var book = Book.addBook(new Book.AddBook(new Book.Barcode("12345"), "Test Book", "1234567890"));
+        var hold = Hold.placeHold(new Hold.PlaceHold(book.getInventoryNumber(), LocalDate.now(), patronId));
+        hold.checkout(new Hold.Checkout(hold.getId(), LocalDate.now(), patronId));
+
+        var checkinCommand = new Hold.Checkin(hold.getId(), LocalDate.now(), patronId);
+
+        when(holdRepository.findById(hold.getId())).thenReturn(Optional.of(hold));
+        when(holdRepository.save(any())).thenReturn(hold);
+
+        // Act
+        var holdInformation = circulationDesk.checkin(checkinCommand);
+
+        // Assert
+        assertThat(holdInformation.getId()).isEqualTo(hold.getId().id().toString());
+        assertThat(holdInformation.getDateOfCheckin()).isNotNull();
+        assertThat(hold.getStatus()).isEqualTo(Hold.HoldStatus.RETURNED);
+    }
+
+    @Test
+    void patronCannotCheckinBookHeldBySomeoneElse() {
+        // Arrange
+        var patronId = new PatronId("[email protected]");
+        var otherPatronId = new PatronId("[email protected]");
+        var book = Book.addBook(new Book.AddBook(new Book.Barcode("12345"), "Test Book", "1234567890"));
+        var hold = Hold.placeHold(new Hold.PlaceHold(book.getInventoryNumber(), LocalDate.now(), patronId));
+        hold.checkout(new Hold.Checkout(hold.getId(), LocalDate.now(), patronId));
+
+        var checkinCommand = new Hold.Checkin(hold.getId(), LocalDate.now(), otherPatronId);
+
+        when(holdRepository.findById(hold.getId())).thenReturn(Optional.of(hold));
+
+        // Act & Assert
+        assertThatIllegalArgumentException()
+                .isThrownBy(() -> circulationDesk.checkin(checkinCommand))
+                .withMessage("Hold belongs to a different patron");
+    }
 }

src/test/resources/borrow.sql

@@ -2,8 +2,10 @@ INSERT INTO borrow_books (id, version, title, barcode, isbn, status)
 VALUES ('018dc771-7b96-776b-980d-caf7c6b2c00b', 0, 'Sapiens', '13268510', '9780062316097', 'AVAILABLE'),
        ('018dc771-6e03-7f3b-adc1-0b9f9810bde4', 0, 'Moby-Dick', '64321704', '9780763630188', 'AVAILABLE'),
        ('018dc771-97e4-7e1e-921f-50d3397d6b32', 0, 'To Kill a Mockingbird', '49031878', '9780446310789', 'ON_HOLD'),
-       ('018dc771-bd5f-71c5-b481-e9b9e8268c6c', 0, '1984', '37040952', '9780451520500', 'ISSUED');
+       ('018dc771-bd5f-71c5-b481-e9b9e8268c6c', 0, '1984', '37040952', '9780451520500', 'ISSUED'),
+       ('018dc771-ce5a-7d2f-b591-fa9f98375c1d', 0, 'The Great Gatsby', '55667788', '9780743273565', 'ISSUED');
 
-INSERT INTO borrow_holds (id, version, book_barcode, patron_id, date_of_hold, status)
-VALUES ('018dc74a-4830-75cf-a194-5e9815727b02', 0, '49031878', '[email protected]', '2023-03-11', 'HOLDING'),
-       ('018dc74a-8b3d-732e-806f-d210f079c0cc', 0, '37040952', '[email protected]', '2023-03-24', 'ACTIVE');
+INSERT INTO borrow_holds (id, version, book_barcode, patron_id, date_of_hold, date_of_checkout, status)
+VALUES ('018dc74a-4830-75cf-a194-5e9815727b02', 0, '49031878', '[email protected]', '2023-03-11', null, 'HOLDING'),
+       ('018dc74a-8b3d-732e-806f-d210f079c0cc', 0, '37040952', '[email protected]', '2023-03-24', null, 'ACTIVE'),
+       ('018dc74a-9c4e-743f-916f-e152f190d13e', 0, '55667788', '[email protected]', '2023-03-24', '2023-03-25', 'ACTIVE');