From d8754165cc584ee81141cbafea4635161c80d606 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Tue, 22 Jul 2025 15:18:53 +0100
Subject: [PATCH 01/21] Clean up comments

---
 app/datastore/mongo_db.py     | 4 ++--
 app/datastore/mongo_helper.py | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/app/datastore/mongo_db.py b/app/datastore/mongo_db.py
index 8d400eb..0fcb3ca 100644
--- a/app/datastore/mongo_db.py
+++ b/app/datastore/mongo_db.py
@@ -14,10 +14,10 @@ def get_book_collection():
         client = MongoClient(
             current_app.config["MONGO_URI"], serverSelectionTimeoutMS=5000
         )
-        # Check the status of the server, will fail if server is down
+
         db = client[current_app.config["DB_NAME"]]
         books_collection = db[current_app.config["COLLECTION_NAME"]]
         return books_collection
     except ConnectionFailure as e:
-        # Handle the connection error and return error information
+
         raise ConnectionFailure(f"Could not connect to MongoDB: {str(e)}") from e
diff --git a/app/datastore/mongo_helper.py b/app/datastore/mongo_helper.py
index 72956d9..9538ce9 100644
--- a/app/datastore/mongo_helper.py
+++ b/app/datastore/mongo_helper.py
@@ -24,7 +24,7 @@ def insert_book_to_mongo(book_data, collection):
     #      - "If you DON'T find a document, INSERT the new data as a new document."
     result = collection.replace_one(query_filter, book_data, upsert=True)
 
-    # 3. Check the result for logging/feedback.
+    # Check the result for logging/feedback.
     if result.upserted_id:
         print(f"✅ INSERTED new book with id: {result.upserted_id}")
     elif result.modified_count > 0:

From 13c783c9ddc05560c65f2c42a94c38121b6985c6 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 13:47:45 +0100
Subject: [PATCH 02/21] Format file with make format

---
 tests/test_api_security.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/test_api_security.py b/tests/test_api_security.py
index 694eeb9..eb34c29 100644
--- a/tests/test_api_security.py
+++ b/tests/test_api_security.py
@@ -55,7 +55,6 @@ def test_add_book_fails_with_missing_key(client, monkeypatch):
     )
     monkeypatch.setattr("app.routes.append_hostname", lambda book, host: book)
 
-
     # Hit the endpoint without Authorization header
     response = client.post("/books", json=DUMMY_PAYLOAD)
 
@@ -114,7 +113,6 @@ def test_update_book_succeeds_with_valid_api_key(monkeypatch, client):
     # 2. Patch append_hostname to just return the book
     monkeypatch.setattr("app.routes.append_hostname", lambda book, host: book)
 
-
     # 3. Call the endpoint with request details
     response = client.put("/books/abc123", json=DUMMY_PAYLOAD, headers=HEADERS["VALID"])
 
@@ -137,7 +135,9 @@ def test_update_book_fails_with_missing_api_key(monkeypatch, client):
 def test_update_book_fails_with_invalid_api_key(client, monkeypatch):
     monkeypatch.setattr("app.routes.books", [])
 
-    response = client.put("/books/abc123", json=DUMMY_PAYLOAD, headers=HEADERS["INVALID"])
+    response = client.put(
+        "/books/abc123", json=DUMMY_PAYLOAD, headers=HEADERS["INVALID"]
+    )
     # ASSERT: Verify the server rejected the request as expected.
     assert response.status_code == 401
     assert "Invalid API key." in response.json["error"]["message"]

From ecbcc76aabf2161c6a32375d56ca5b444763ab18 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 14:11:17 +0100
Subject: [PATCH 03/21] Create book_service.py with fetch_active_books_cursor
 function

---
 app/services/book_service.py | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 app/services/book_service.py

diff --git a/app/services/book_service.py b/app/services/book_service.py
new file mode 100644
index 0000000..7ffc59a
--- /dev/null
+++ b/app/services/book_service.py
@@ -0,0 +1,10 @@
+from app.datastore.mongo_db import get_book_collection
+from app.datastore.mongo_helper import find_books
+
+def fetch_active_books_cursor():
+    """Fetches a cursor for all non-deleted books from the database."""
+
+    collection = get_book_collection()
+    query_filter = {"state": {"ne": "deleted"}}  # Only non-deleted books
+
+    return find_books(collection, query_filter=query_filter)

From f8e3c3c5375fd2f29c3c9b959c256f4e67e93420 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 14:20:58 +0100
Subject: [PATCH 04/21] Add find_books() to wrap collection.find and return a
 cursor

---
 app/datastore/mongo_helper.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/app/datastore/mongo_helper.py b/app/datastore/mongo_helper.py
index 9538ce9..140ddb0 100644
--- a/app/datastore/mongo_helper.py
+++ b/app/datastore/mongo_helper.py
@@ -1,5 +1,7 @@
 """Module containing pymongo helper functions."""
 
+from pymongo.cursor import Cursor
+
 
 def insert_book_to_mongo(book_data, collection):
     """
@@ -31,3 +33,22 @@ def insert_book_to_mongo(book_data, collection):
         print(f"✅ REPLACED existing book with id: {book_data['id']}")
 
     return result
+
+
+def find_books(collection, query_filter=None, projection=None, limit=None) -> Cursor:
+    """This acts as a wrapper around pymongo's collection.find() method.
+
+    Args:
+        collection: The pymongo collection object.
+        filter: The MongoDB query filter. Defaults to None (find all).
+        projection: The fields to include/exclude. Defaults to None (all fields).
+        limit: The maximum number of results to return. Defaults to None.
+
+    Returns:
+        A pymongo Cursor for the query results. 
+    """
+    query_filter = query_filter or {}
+    cursor = collection.find(query_filter, projection)
+    if limit is not None and limit > 0:
+        cursor = cursor.limit(limit)
+    return cursor

From 71fb70acf8ce864fde6a19803a647e781d99ac1f Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 15:09:41 +0100
Subject: [PATCH 05/21] Add API formatter for books fetched from MongoDB

---
 app/services/book_service.py | 54 ++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/app/services/book_service.py b/app/services/book_service.py
index 7ffc59a..d27af90 100644
--- a/app/services/book_service.py
+++ b/app/services/book_service.py
@@ -1,3 +1,6 @@
+"""Service layer for handling book-related operations."""
+
+from app.utils.helper import append_hostname
 from app.datastore.mongo_db import get_book_collection
 from app.datastore.mongo_helper import find_books
 
@@ -8,3 +11,54 @@ def fetch_active_books_cursor():
     query_filter = {"state": {"ne": "deleted"}}  # Only non-deleted books
 
     return find_books(collection, query_filter=query_filter)
+
+
+def format_books_for_api(books_cursor, host_url):
+    """
+    Validate and format a list or cursor of raw book dicts for API response.
+
+    Returns:
+        tuple: (formatted_list, None) on success,
+               (None, msg_lines) on validation failure.
+    """
+
+    required_fields = ["id", "title", "synopsis", "author", "links"]
+    missing_fields_info = []
+
+    # 1) Collect all validation errors
+    for raw in books_cursor:
+        missing = [f for f in required_fields if f not in raw]
+        if missing:
+            missing_fields_info.append(
+                {"book": raw, "missing_fields": missing}
+            )
+
+    # 2) If any errors, build error message and return
+    if missing_fields_info:
+        msg_lines_list = ["Missing required fields:"]
+
+        # In a loop, add new strings to the list
+        for info in missing_fields_info:
+            fields = ", ".join(info["missing_fields"])
+            msg_lines_list.append(f"- {fields} in book: {info['book']}")
+
+            # Join all the strings in the list ONCE at the end
+            error_message = "\n".join(msg_lines_list)
+
+            # 4. Return the final string
+            return None, error_message
+
+
+
+    # FORMAT: Remove fields not meant for the public API
+    formatted_list = []
+    for raw in books_cursor:
+        book = raw.copy()
+        book.pop("_id", None)
+        book.pop("state", None)
+
+        # Call the helper with the host_url it needs
+        book_with_hostname = append_hostname(book, host_url)
+        formatted_list.append(book_with_hostname)
+
+    return formatted_list

From daa48bd820e9ff9e48146fbe0a7b83d3066eb3ee Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 15:17:11 +0100
Subject: [PATCH 06/21] Refactor GET /books to use service layer helpers;
 format code

---
 app/routes.py | 60 ++++++++++++++++-----------------------------------
 1 file changed, 19 insertions(+), 41 deletions(-)

diff --git a/app/routes.py b/app/routes.py
index 112bfa0..df64f77 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -8,6 +8,8 @@
 
 from app.datastore.mongo_db import get_book_collection
 from app.datastore.mongo_helper import insert_book_to_mongo
+from app.services.book_service import (fetch_active_books_cursor,
+                                       format_books_for_api)
 from app.utils.api_security import require_api_key
 from app.utils.helper import append_hostname
 from data import books
@@ -26,7 +28,7 @@ def register_routes(app):  # pylint: disable=too-many-statements
     @require_api_key
     def add_book():
         """Function to add a new book to the collection."""
-        # check if request is json
+
         if not request.is_json:
             return jsonify({"error": "Request must be JSON"}), 415
 
@@ -65,9 +67,9 @@ def add_book():
             if not isinstance(new_book[field], expected_type):
                 return {"error": f"Field {field} is not of type {expected_type}"}, 400
 
-        # use helper function
+        # establish connection to mongoDB
         books_collection = get_book_collection()
-        # check if mongoDB connected??
+        # use mongoDB helper to insert/replace new book
         insert_book_to_mongo(new_book, books_collection)
 
         # Get the host from the request headers
@@ -89,45 +91,28 @@ def get_all_books():
         return them in a JSON response
         including the total count.
         """
-        if not books:
+        raw_books = fetch_active_books_cursor()  # pylint: disable=redefined-outer-name
+
+        if not raw_books:
             return jsonify({"error": "No books found"}), 404
 
-        all_books = []
         # extract host from the request
         host = request.host_url
 
-        for book in books:
-            # check if the book has the "deleted" state
-            if book.get("state") != "deleted":
-                # Remove state unless it's "deleted", then append
-                book_copy = copy.deepcopy(book)
-                book_copy.pop("state", None)
-                book_with_hostname = append_hostname(book_copy, host)
-                all_books.append(book_with_hostname)
-
-        # validation
-        required_fields = ["id", "title", "synopsis", "author", "links"]
-        missing_fields_info = []
-
-        for book in all_books:
-            missing_fields = [field for field in required_fields if field not in book]
-            if missing_fields:
-                missing_fields_info.append(
-                    {"book": book, "missing_fields": missing_fields}
-                )
+        all_formatted_books, error = format_books_for_api(raw_books, host)
 
-        if missing_fields_info:
-            error_message = "Missing required fields:\n"
-            for info in missing_fields_info:
-                error_message += f"Missing fields: {', '.join(info['missing_fields'])} in {info['book']}. \n"  # pylint: disable=line-too-long
+        if error:
+            # Return HTTP error in controller layer
+            return jsonify({"error": error}), 500
 
-            print(error_message)
-            return jsonify({"error": error_message}), 500
+        if not all_formatted_books:
+            return jsonify({"error": "No books found"}), 404
 
-        count_books = len(all_books)
-        response_data = {"total_count": count_books, "items": all_books}
+        return jsonify({
+            "total_count": len(all_formatted_books),
+            "items": all_formatted_books
+        }), 200
 
-        return jsonify(response_data), 200
 
     @app.route("/books/<string:book_id>", methods=["GET"])
     def get_book(book_id):
@@ -219,7 +204,6 @@ def update_book(book_id):
 
         return jsonify({"error": "Book not found"}), 404
 
-
     # ----------- CUSTOM ERROR HANDLERS ------------------
 
     @app.errorhandler(NotFound)
@@ -234,13 +218,7 @@ def handle_http_exception(e):
         """
         # e.code is the HTTP status code (e.g. 401)
         # e.description is the text you passed to abort()
-        response = {
-            "error": {
-                "code": e.code,
-                "name": e.name,
-                "message": e.description
-            }
-        }
+        response = {"error": {"code": e.code, "name": e.name, "message": e.description}}
         return jsonify(response), e.code
 
     @app.errorhandler(Exception)

From ce9c2b1ae4bf2483aa2ca156f025a70807d01815 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 16:17:13 +0100
Subject: [PATCH 07/21] Refactor fetch_active_books to return list; update
 callers

---
 app/routes.py                |  9 +++------
 app/services/book_service.py | 16 +++++++++-------
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/app/routes.py b/app/routes.py
index df64f77..953e703 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -8,7 +8,7 @@
 
 from app.datastore.mongo_db import get_book_collection
 from app.datastore.mongo_helper import insert_book_to_mongo
-from app.services.book_service import (fetch_active_books_cursor,
+from app.services.book_service import (fetch_active_books,
                                        format_books_for_api)
 from app.utils.api_security import require_api_key
 from app.utils.helper import append_hostname
@@ -91,13 +91,13 @@ def get_all_books():
         return them in a JSON response
         including the total count.
         """
-        raw_books = fetch_active_books_cursor()  # pylint: disable=redefined-outer-name
+        raw_books = fetch_active_books()
 
         if not raw_books:
             return jsonify({"error": "No books found"}), 404
 
         # extract host from the request
-        host = request.host_url
+        host = request.host_url.rstrip("/")
 
         all_formatted_books, error = format_books_for_api(raw_books, host)
 
@@ -105,9 +105,6 @@ def get_all_books():
             # Return HTTP error in controller layer
             return jsonify({"error": error}), 500
 
-        if not all_formatted_books:
-            return jsonify({"error": "No books found"}), 404
-
         return jsonify({
             "total_count": len(all_formatted_books),
             "items": all_formatted_books
diff --git a/app/services/book_service.py b/app/services/book_service.py
index d27af90..45b13df 100644
--- a/app/services/book_service.py
+++ b/app/services/book_service.py
@@ -4,16 +4,19 @@
 from app.datastore.mongo_db import get_book_collection
 from app.datastore.mongo_helper import find_books
 
-def fetch_active_books_cursor():
-    """Fetches a cursor for all non-deleted books from the database."""
+def fetch_active_books():
+    """
+    Fetches a cursor for all non-deleted books from the database.
+    Returns a Python list.
+    """
 
     collection = get_book_collection()
     query_filter = {"state": {"ne": "deleted"}}  # Only non-deleted books
 
-    return find_books(collection, query_filter=query_filter)
+    return list(find_books(collection, query_filter=query_filter))
 
 
-def format_books_for_api(books_cursor, host_url):
+def format_books_for_api(books, host_url):
     """
     Validate and format a list or cursor of raw book dicts for API response.
 
@@ -26,7 +29,7 @@ def format_books_for_api(books_cursor, host_url):
     missing_fields_info = []
 
     # 1) Collect all validation errors
-    for raw in books_cursor:
+    for raw in books:
         missing = [f for f in required_fields if f not in raw]
         if missing:
             missing_fields_info.append(
@@ -49,10 +52,9 @@ def format_books_for_api(books_cursor, host_url):
             return None, error_message
 
 
-
     # FORMAT: Remove fields not meant for the public API
     formatted_list = []
-    for raw in books_cursor:
+    for raw in books:
         book = raw.copy()
         book.pop("_id", None)
         book.pop("state", None)

From f2a41818170b54af457998e1f904dd1eb119d633 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 16:58:49 +0100
Subject: [PATCH 08/21] Update test to mock new service layer functions

---
 tests/test_app.py | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/tests/test_app.py b/tests/test_app.py
index e9c1d07..8b29eae 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -1,6 +1,6 @@
 # pylint: disable=missing-docstring
 
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 from pymongo.errors import ServerSelectionTimeoutError
@@ -152,25 +152,46 @@ def test_500_response_is_json(client):
 
 
 # ------------------------ Tests for GET --------------------------------------------
-def test_get_all_books_returns_all_books(client):
+
+@patch("app.routes.format_books_for_api")
+@patch("app.routes.fetch_active_books")
+def test_get_all_books_returns_all_books(mock_fetch, mock_format, client):
+
+    mock_books_list = MagicMock()
+    mock_fetch.return_value = mock_books_list
+
+    mock_formatted_data = [
+        {"id": "1", "title": "A", "synopsis": "x", "author": "y", "links": {}},
+        {"id": "2", "title": "B", "synopsis": "z", "author": "w", "links": {}},
+    ]
+
+    mock_format.return_value = (mock_formatted_data, None)
+
     response = client.get("/books")
 
+    # Assert HTTP properties
     assert response.status_code == 200
     assert response.headers["content-type"] == "application/json"
+
+    # Assert the repsonse body
     response_data = response.get_json()
     assert isinstance(response_data, dict)
-    assert "total_count" in response_data
-    assert "items" in response_data
+    assert response_data["total_count"] == 2
+    assert response_data["items"] == mock_formatted_data
+
+    # Assert that mocks were called correctly
+    mock_fetch.assert_called_once()
+    mock_format.assert_called_once_with(mock_books_list, "http://localhost")
 
 
-def test_return_error_404_when_list_is_empty(client):
+def test_get_all_books_returns_error_404_when_list_is_empty(client):
     with patch("app.routes.books", []):
         response = client.get("/books")
         assert response.status_code == 404
         assert "No books found" in response.get_json()["error"]
 
 
-def test_get_books_returns_404_when_books_is_none(client):
+def test_get_book_returns_404_when_books_is_none(client):
     with patch("app.routes.books", None):
         response = client.get("/books")
         assert response.status_code == 404

From 993eace080a66ad76490a6070971f575ba27a4ef Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 17:13:37 +0100
Subject: [PATCH 09/21] Fix indent to correctly aggregate validation errors

---
 app/services/book_service.py | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/app/services/book_service.py b/app/services/book_service.py
index 45b13df..f985a60 100644
--- a/app/services/book_service.py
+++ b/app/services/book_service.py
@@ -1,8 +1,9 @@
 """Service layer for handling book-related operations."""
 
-from app.utils.helper import append_hostname
 from app.datastore.mongo_db import get_book_collection
 from app.datastore.mongo_helper import find_books
+from app.utils.helper import append_hostname
+
 
 def fetch_active_books():
     """
@@ -32,9 +33,7 @@ def format_books_for_api(books, host_url):
     for raw in books:
         missing = [f for f in required_fields if f not in raw]
         if missing:
-            missing_fields_info.append(
-                {"book": raw, "missing_fields": missing}
-            )
+            missing_fields_info.append({"book": raw, "missing_fields": missing})
 
     # 2) If any errors, build error message and return
     if missing_fields_info:
@@ -45,12 +44,11 @@ def format_books_for_api(books, host_url):
             fields = ", ".join(info["missing_fields"])
             msg_lines_list.append(f"- {fields} in book: {info['book']}")
 
-            # Join all the strings in the list ONCE at the end
-            error_message = "\n".join(msg_lines_list)
-
-            # 4. Return the final string
-            return None, error_message
+        # Join all the strings in the list ONCE at the end
+        error_message = "\n".join(msg_lines_list)
 
+        # 4. Return the final string
+        return None, error_message
 
     # FORMAT: Remove fields not meant for the public API
     formatted_list = []

From 2ee43fa4e234afd9d95a74756bbbccebdf156348 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Wed, 23 Jul 2025 17:17:53 +0100
Subject: [PATCH 10/21] Align book endpoint tests with service layer

---
 tests/test_app.py | 51 ++++++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/tests/test_app.py b/tests/test_app.py
index 8b29eae..af7b2f9 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -153,6 +153,7 @@ def test_500_response_is_json(client):
 
 # ------------------------ Tests for GET --------------------------------------------
 
+
 @patch("app.routes.format_books_for_api")
 @patch("app.routes.fetch_active_books")
 def test_get_all_books_returns_all_books(mock_fetch, mock_format, client):
@@ -184,6 +185,33 @@ def test_get_all_books_returns_all_books(mock_fetch, mock_format, client):
     mock_format.assert_called_once_with(mock_books_list, "http://localhost")
 
 
+@patch("app.routes.fetch_active_books")
+def test_missing_fields_in_book_object_returned_by_database(mock_fetch, client):
+
+    bad_raw_data = [
+        {"id": "1", "synopsis": "x", "author": "y", "links": {}},  # Missing 'title'
+        {"id": "2", "title": "B", "author": "w", "links": {}},  # Missing 'synopsis'
+    ]
+    mock_fetch.return_value = bad_raw_data
+
+    expected_error_message = (
+        "Missing required fields:\n"
+        f"- title in book: {bad_raw_data[0]}\n"
+        f"- synopsis in book: {bad_raw_data[1]}"
+    )
+
+    # --- ACT ---
+    response = client.get("/books")
+
+    # --- ASSERT ---
+    assert response.status_code == 500
+
+    response_data = response.get_json()
+    assert "error" in response_data
+    assert response_data["error"] == expected_error_message
+    mock_fetch.assert_called_once()
+
+
 def test_get_all_books_returns_error_404_when_list_is_empty(client):
     with patch("app.routes.books", []):
         response = client.get("/books")
@@ -198,29 +226,6 @@ def test_get_book_returns_404_when_books_is_none(client):
         assert "No books found" in response.get_json()["error"]
 
 
-def test_missing_fields_in_book_object_returned_by_database(client):
-    with patch(
-        "app.routes.books",
-        [
-            {
-                "id": "1",
-                "title": "The Great Adventure",
-                "synopsis": "A thrilling adventure through the jungles of South America.",
-                "author": "Jane Doe",
-            },
-            {"id": "2", "title": "Mystery of the Old Manor"},
-            {
-                "id": "3",
-                "title": "The Science of Everything",
-                "synopsis": "An in-depth look at the scientific principles that govern our world.",
-            },
-        ],
-    ):
-        response = client.get("/books")
-        assert response.status_code == 500
-        assert "Missing fields" in response.get_json()["error"]
-
-
 # -------- Tests for filter GET /books by delete ----------------
 
 

From 3ee22686ad916366b5788dcff46ffc4cd8a70559 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 10:00:58 +0100
Subject: [PATCH 11/21] Fix $ MongoDB syntax; return None for consistency

---
 app/services/book_service.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/app/services/book_service.py b/app/services/book_service.py
index f985a60..e55ff9e 100644
--- a/app/services/book_service.py
+++ b/app/services/book_service.py
@@ -12,9 +12,10 @@ def fetch_active_books():
     """
 
     collection = get_book_collection()
-    query_filter = {"state": {"ne": "deleted"}}  # Only non-deleted books
+    query_filter = {"state": {"$ne": "deleted"}}  # Only non-deleted books
 
-    return list(find_books(collection, query_filter=query_filter))
+    cursor = find_books(collection, query_filter=query_filter)
+    return list(cursor)
 
 
 def format_books_for_api(books, host_url):
@@ -61,4 +62,4 @@ def format_books_for_api(books, host_url):
         book_with_hostname = append_hostname(book, host_url)
         formatted_list.append(book_with_hostname)
 
-    return formatted_list
+    return formatted_list, None

From 41f92a425889c820cd7533f17332fcd7d124e626 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 13:07:31 +0100
Subject: [PATCH 12/21] Fix format_books_for_api order: create id before
 validation

---
 app/services/book_service.py | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/app/services/book_service.py b/app/services/book_service.py
index e55ff9e..0d6e473 100644
--- a/app/services/book_service.py
+++ b/app/services/book_service.py
@@ -20,23 +20,27 @@ def fetch_active_books():
 
 def format_books_for_api(books, host_url):
     """
-    Validate and format a list or cursor of raw book dicts for API response.
-
-    Returns:
-        tuple: (formatted_list, None) on success,
-               (None, msg_lines) on validation failure.
+    Process, validate, and format a list of raw book dicts for API response.
     """
+    # 1) PRE-PROCESS: Create a new list with the fields we will validate.
+    processed_books = []
+    for raw in books:
+        book = raw.copy()
+        # Create the 'id' field from '_id' for consistent validation.
+        if "_id" in book:
+            book["id"] = str(book["_id"])
+        processed_books.append(book)
 
     required_fields = ["id", "title", "synopsis", "author", "links"]
     missing_fields_info = []
 
-    # 1) Collect all validation errors
-    for raw in books:
+    # 2) Collect all validation errors
+    for raw in processed_books:
         missing = [f for f in required_fields if f not in raw]
         if missing:
             missing_fields_info.append({"book": raw, "missing_fields": missing})
 
-    # 2) If any errors, build error message and return
+    # 3) If any errors, build error message and return
     if missing_fields_info:
         msg_lines_list = ["Missing required fields:"]
 
@@ -53,8 +57,7 @@ def format_books_for_api(books, host_url):
 
     # FORMAT: Remove fields not meant for the public API
     formatted_list = []
-    for raw in books:
-        book = raw.copy()
+    for book in processed_books:
         book.pop("_id", None)
         book.pop("state", None)
 

From 47cdfc7cd26202c734846fd05598f701b61fcae7 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 13:13:46 +0100
Subject: [PATCH 13/21] Replace in-memory GET books test with find_books mock
 and format check

---
 tests/test_app.py | 154 ++++++++++++++++++++++++++--------------------
 1 file changed, 87 insertions(+), 67 deletions(-)

diff --git a/tests/test_app.py b/tests/test_app.py
index af7b2f9..2bc8cda 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -1,6 +1,6 @@
 # pylint: disable=missing-docstring
 
-from unittest.mock import MagicMock, patch
+from unittest.mock import ANY, MagicMock, patch
 
 import pytest
 from pymongo.errors import ServerSelectionTimeoutError
@@ -212,79 +212,99 @@ def test_missing_fields_in_book_object_returned_by_database(mock_fetch, client):
     mock_fetch.assert_called_once()
 
 
-def test_get_all_books_returns_error_404_when_list_is_empty(client):
-    with patch("app.routes.books", []):
-        response = client.get("/books")
-        assert response.status_code == 404
-        assert "No books found" in response.get_json()["error"]
+@patch("app.routes.fetch_active_books")
+def test_get_all_books_returns_error_404_when_list_is_empty(mock_fetch, client):
+    empty_data = []
+    mock_fetch.return_value = empty_data
+    response = client.get("/books")
+    assert response.status_code == 404
+    assert "No books found" in response.get_json()["error"]
 
 
-def test_get_book_returns_404_when_books_is_none(client):
-    with patch("app.routes.books", None):
-        response = client.get("/books")
-        assert response.status_code == 404
-        assert "No books found" in response.get_json()["error"]
-
-
-# -------- Tests for filter GET /books by delete ----------------
-
-
-def test_get_books_excludes_deleted_books_and_omits_state_field(client):
-    # Add a book so we have a known ID
-    with patch(
-        "app.routes.books",
-        [
-            {
-                "id": "1",
-                "title": "The Great Adventure",
-                "synopsis": "A thrilling adventure through the jungles of South America.",
-                "author": "Jane Doe",
-                "links": {
-                    "self": "/books/1",
-                    "reservations": "/books/1/reservations",
-                    "reviews": "/books/1/reviews",
-                },
-                "state": "deleted",
+@patch("app.routes.fetch_active_books")
+def test_get_book_returns_404_when_books_is_none(mock_fetch, client):
+    none_data = None
+    mock_fetch.return_value = none_data
+    response = client.get("/books")
+    assert response.status_code == 404
+    assert "No books found" in response.get_json()["error"]
+
+
+@patch("app.services.book_service.find_books")
+def test_get_books_retrieves_and_formats_books_correctly(mock_find_books, client):
+    """
+    GIVEN a mocked database service
+    WHEN the /books endpoint is called
+    THEN the service layer correctly queries the database for non-deleted books
+    AND the API response is correctly formatted with absolute URLs
+    """
+    # ARRANGE
+    filtered_db_result = [
+        {
+            "_id": "2",
+            "title": "Mystery of the Old Manor",
+            "author": "John Smith",
+            "synopsis": "A detective story set in an old manor with many secrets.",
+            "links": {
+                "self": "/books/2",
+                "reservations": "/books/2/reservations",
+                "reviews": "/books/2/reviews",
+            },
+            "state": "active",
+        },
+        {
+            "_id": "3",
+            "title": "The Science of Everything",
+            "author": "Alice Johnson",
+            "synopsis": "An in-depth look at the scientific principles that govern our world.",
+            "links": {
+                "self": "/books/3",
+                "reservations": "/books/3/reservations",
+                "reviews": "/books/3/reviews",
             },
-            {
-                "id": "2",
-                "title": "Mystery of the Old Manor",
-                "synopsis": "A detective story set in an old manor with many secrets.",
-                "author": "John Smith",
-                "links": {
-                    "self": "/books/2",
-                    "reservations": "/books/2/reservations",
-                    "reviews": "/books/2/reviews",
-                },
-                "state": "active",
+            # No 'state' field, correctly simulating a record that is implicitly active.
+        },
+    ]
+    mock_find_books.return_value = filtered_db_result
+
+    base_url = "http://localhost"
+    expected_response_items = [
+        {
+            "id": "2",  # Renamed from _id
+            "title": "Mystery of the Old Manor",
+            "author": "John Smith",
+            "synopsis": "A detective story set in an old manor with many secrets.",
+            "links": {
+                "self": f"{base_url}/books/2",
+                "reservations": f"{base_url}/books/2/reservations",
+                "reviews": f"{base_url}/books/2/reviews",
             },
-            {
-                "id": "3",
-                "title": "The Science of Everything",
-                "synopsis": "An in-depth look at the scientific principles that govern our world.",
-                "author": "Alice Johnson",
-                "links": {
-                    "self": "/books/3",
-                    "reservations": "/books/3/reservations",
-                    "reviews": "/books/3/reviews",
-                },
+        },
+        {
+            "id": "3",  # Renamed from _id
+            "title": "The Science of Everything",
+            "author": "Alice Johnson",
+            "synopsis": "An in-depth look at the scientific principles that govern our world.",
+            "links": {
+                "self": f"{base_url}/books/3",
+                "reservations": f"{base_url}/books/3/reservations",
+                "reviews": f"{base_url}/books/3/reviews",
             },
-        ],
-    ):
-        response = client.get("/books")
-        assert response.status_code == 200
-
-        data = response.get_json()
-        assert "items" in data
-        books = data["items"]
+        },
+    ]
 
-        # Check right object is returned
-        assert len(books) == 2
-        for book in books:
-            assert "state" not in book
-        assert books[0].get("id") == "2"
-        assert books[1].get("title") == "The Science of Everything"
+    # ACT
+    response = client.get("/books")
 
+    # ASSERT
+    assert response.status_code == 200
+    # 1) Service layer called with correct filter
+    expected_db_filter = {"state": {"$ne": "deleted"}}
+    mock_find_books.assert_called_once_with(ANY, query_filter=expected_db_filter)
+    # 2) Response formatting is exactly as expected
+    response_data = response.get_json()
+    assert response_data["items"] == expected_response_items
+    assert len(response_data["items"]) == 2
 
 # -------- Tests for GET a single resource ----------------
 

From 5162fb5012c2932a371f39f368d0f770be149ac1 Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 13:16:45 +0100
Subject: [PATCH 14/21] Apply formatting to mongo_helper and routes

---
 app/datastore/mongo_helper.py |  2 +-
 app/routes.py                 | 14 +++++++-------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/app/datastore/mongo_helper.py b/app/datastore/mongo_helper.py
index 140ddb0..a9d6f5b 100644
--- a/app/datastore/mongo_helper.py
+++ b/app/datastore/mongo_helper.py
@@ -45,7 +45,7 @@ def find_books(collection, query_filter=None, projection=None, limit=None) -> Cu
         limit: The maximum number of results to return. Defaults to None.
 
     Returns:
-        A pymongo Cursor for the query results. 
+        A pymongo Cursor for the query results.
     """
     query_filter = query_filter or {}
     cursor = collection.find(query_filter, projection)
diff --git a/app/routes.py b/app/routes.py
index 953e703..51b7559 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -8,8 +8,7 @@
 
 from app.datastore.mongo_db import get_book_collection
 from app.datastore.mongo_helper import insert_book_to_mongo
-from app.services.book_service import (fetch_active_books,
-                                       format_books_for_api)
+from app.services.book_service import fetch_active_books, format_books_for_api
 from app.utils.api_security import require_api_key
 from app.utils.helper import append_hostname
 from data import books
@@ -105,11 +104,12 @@ def get_all_books():
             # Return HTTP error in controller layer
             return jsonify({"error": error}), 500
 
-        return jsonify({
-            "total_count": len(all_formatted_books),
-            "items": all_formatted_books
-        }), 200
-
+        return (
+            jsonify(
+                {"total_count": len(all_formatted_books), "items": all_formatted_books}
+            ),
+            200,
+        )
 
     @app.route("/books/<string:book_id>", methods=["GET"])
     def get_book(book_id):

From e6cf2894a4d810c335639faa426a77abb7c75d4d Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 13:27:32 +0100
Subject: [PATCH 15/21] Update failin test with mock database patch

---
 tests/test_app.py | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/tests/test_app.py b/tests/test_app.py
index 2bc8cda..9b68efa 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -306,6 +306,7 @@ def test_get_books_retrieves_and_formats_books_correctly(mock_find_books, client
     assert response_data["items"] == expected_response_items
     assert len(response_data["items"]) == 2
 
+
 # -------- Tests for GET a single resource ----------------
 
 
@@ -580,22 +581,41 @@ def test_append_host_to_links_in_post(client, _insert_book_to_db):
     ), f"Link should end with the resource path '{expected_path}'"
 
 
-def test_append_host_to_links_in_get(client):
+@patch("app.services.book_service.find_books")
+def test_append_host_to_links_in_get(mock_find_books, client):
+
+    # ARRANGE: Provide sample data for the mock to return
+    mock_find_books.return_value = [
+        {
+            "_id": "123",
+            "title": "A Test Book",
+            "author": "The Tester",
+            "synopsis": "A book for testing.",
+            "links": {
+                "self": "/books/123",
+                "reservations": "/books/123",
+                "reviews": "/books/123",
+            },
+        }
+    ]
+
+    # ACT
     response = client.get("/books")
+    response_data = response.get_json()
 
+    # ASSERT
     assert response.status_code == 200
-    assert response.headers["content-type"] == "application/json"
 
-    # Get the response data
-    response_data = response.get_json()
+    book = response_data["items"][0]
+    assert response.headers["content-type"] == "application/json"
     assert isinstance(response_data, dict)
     assert "total_count" in response_data
     assert "items" in response_data
-
     # response_data["items"]["links"]["self"]
     for book in response_data["items"]:
         new_book_id = book.get("id")
         assert book["links"]["self"].startswith("http://localhost")
+        assert book["links"]["self"] == "http://localhost/books/123"
         assert book["links"]["reservations"].startswith("http://localhost")
         assert book["links"]["reviews"].startswith("http://localhost")
         assert book["links"]["self"].endswith(f"books/{new_book_id}")

From be7c671b19893b11645e2218f56c07bb90765c3c Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 14:09:07 +0100
Subject: [PATCH 16/21] Handle database connection failures gracefully on GET
 /books

---
 app/routes.py     | 10 +++++++++-
 tests/test_app.py | 23 ++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/app/routes.py b/app/routes.py
index 51b7559..ac55c69 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -4,6 +4,7 @@
 import uuid
 
 from flask import jsonify, request
+from pymongo.errors import ConnectionFailure
 from werkzeug.exceptions import HTTPException, NotFound
 
 from app.datastore.mongo_db import get_book_collection
@@ -90,7 +91,14 @@ def get_all_books():
         return them in a JSON response
         including the total count.
         """
-        raw_books = fetch_active_books()
+        try:
+            raw_books = fetch_active_books()
+        except ConnectionFailure:
+            error_payload = {
+                "error": "The database service is temporarily unavailable."
+            }
+
+            return jsonify(error_payload), 503
 
         if not raw_books:
             return jsonify({"error": "No books found"}), 404
diff --git a/tests/test_app.py b/tests/test_app.py
index 9b68efa..8db5d55 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -3,7 +3,7 @@
 from unittest.mock import ANY, MagicMock, patch
 
 import pytest
-from pymongo.errors import ServerSelectionTimeoutError
+from pymongo.errors import ConnectionFailure, ServerSelectionTimeoutError
 
 from app import create_app
 from app.datastore.mongo_db import get_book_collection
@@ -307,6 +307,27 @@ def test_get_books_retrieves_and_formats_books_correctly(mock_find_books, client
     assert len(response_data["items"]) == 2
 
 
+@patch("app.services.book_service.get_book_collection")
+def test_get_books_handles_database_connection_error(mock_get_collection, client):
+    """
+    GIVEN the database connection fails
+    WHEN the /books endpoint is called
+    THEN a 503 Service Unavailable error should be returned with a friendly message.
+    """
+    # ARRANGE: Configure the mock to raise the exception when called
+    mock_get_collection.side_effect = ConnectionFailure("Could not connect to DB")
+
+    # ACT
+    response = client.get("/books")
+
+    # ASSERT
+    assert response.status_code == 503  # Now asserting the correct code
+
+    # This assertion will now pass because your controller is returning the correct message
+    expected_error = "The database service is temporarily unavailable."
+    assert expected_error == response.get_json()["error"]
+
+
 # -------- Tests for GET a single resource ----------------
 
 

From 0ec345d25c90acd73819464accd01ab3eadb13bc Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 14:43:08 +0100
Subject: [PATCH 17/21] Add tests for find_books db wrapper for 100% coverage

---
 tests/test_mongo_helper.py | 56 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/tests/test_mongo_helper.py b/tests/test_mongo_helper.py
index cbae6d4..094476d 100644
--- a/tests/test_mongo_helper.py
+++ b/tests/test_mongo_helper.py
@@ -2,7 +2,7 @@
 
 from unittest.mock import MagicMock
 
-from app.datastore.mongo_helper import insert_book_to_mongo
+from app.datastore.mongo_helper import find_books, insert_book_to_mongo
 
 
 def test_insert_book_to_mongo_calls_replace_one_with_upsert():
@@ -29,3 +29,57 @@ def test_insert_book_to_mongo_calls_replace_one_with_upsert():
         new_book,  # Argument 2: The replacement document
         upsert=True,  # Argument 3: The upsert keyword argument
     )
+
+
+def test_find_books_calls_find_with_filter_and_projection():
+    # Arrange
+    mock_collection = MagicMock()
+    mock_cursor = MagicMock()
+
+    mock_collection.find.return_value = mock_cursor
+
+    # Define the inputs for our function.
+    test_filter = {"author": "Jane Doe"}
+    test_projection = {"_id": 0, "title": 1}
+
+    # Act
+    result_cursor = find_books(
+        collection=mock_collection, query_filter=test_filter, projection=test_projection
+    )
+
+    # Assert
+    mock_collection.find.assert_called_once_with(test_filter, test_projection)
+    mock_cursor.limit.assert_not_called()
+    assert result_cursor == mock_cursor
+
+
+def test_find_books_applies_limit_when_provided():
+    """
+    GIVEN a mock collection and a limit
+    WHEN find_books is called with a positive limit
+    THEN it should call the limit method on the cursor with the correct value.
+    """
+    # Arrange
+    mock_collection = MagicMock()
+    mock_cursor = MagicMock()
+    # Create a NEW mock for the final cursor after .limit() is called.
+    mock_limited_cursor = MagicMock()
+
+    mock_collection.find.return_value = mock_cursor
+    # Teach the first cursor what to do when .limit() is called.
+    mock_cursor.limit.return_value = mock_limited_cursor
+
+    test_limit = 10
+
+    # Act
+    result_cursor = find_books(collection=mock_collection, limit=test_limit)
+
+    # Assert
+    # 1. Check that find() was called (this time with a default filter).
+    mock_collection.find.assert_called_once()
+
+    # 2. CRUCIAL: Check that the .limit() method was called exactly once
+    mock_cursor.limit.assert_called_once_with(test_limit)
+
+    # 3. Check that the function returned the FINAL cursor from the chain.
+    assert result_cursor == mock_limited_cursor

From 7c01565da75bc5007934ab581f0807da81a28eef Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 15:07:56 +0100
Subject: [PATCH 18/21] Update ConnectionFailure payload to reflect error
 schema

---
 app/routes.py     | 6 +++++-
 tests/test_app.py | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/app/routes.py b/app/routes.py
index ac55c69..b14d50b 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -95,7 +95,11 @@ def get_all_books():
             raw_books = fetch_active_books()
         except ConnectionFailure:
             error_payload = {
-                "error": "The database service is temporarily unavailable."
+                "error": {
+                    "code": 503,
+                    "name": "Service Unavailable",
+                    "message": "The database service is temporarily unavailable.",
+                }
             }
 
             return jsonify(error_payload), 503
diff --git a/tests/test_app.py b/tests/test_app.py
index 8db5d55..46f5e0f 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -325,7 +325,7 @@ def test_get_books_handles_database_connection_error(mock_get_collection, client
 
     # This assertion will now pass because your controller is returning the correct message
     expected_error = "The database service is temporarily unavailable."
-    assert expected_error == response.get_json()["error"]
+    assert expected_error in response.json["error"]["message"]
 
 
 # -------- Tests for GET a single resource ----------------

From c8f9cf75196aa7933b76c4c4f7a4a27df09e372d Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 15:09:17 +0100
Subject: [PATCH 19/21] Update openapi.yml GET to reflect 503 response

---
 openapi.yml | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/openapi.yml b/openapi.yml
index 7be90bf..8386217 100644
--- a/openapi.yml
+++ b/openapi.yml
@@ -162,6 +162,12 @@ components:
         application/json:
           schema:
             $ref: '#/components/schemas/StandardError'
+    ServiceUnavailable:
+      description: The service is temporarily unavailable, likely due to a database connection issue or server maintenance.
+      content:
+        application/json:
+          schema:
+            $ref: '#/components/schemas/StandardError'
     InternalServerError:
       description: An unexpected error occurred on the server.
       content:
@@ -230,7 +236,9 @@ paths:
         '404':
           $ref: '#/components/responses/NotFound' 
         '500':
-          $ref: '#/components/responses/InternalServerError' 
+          $ref: '#/components/responses/InternalServerError'
+        '503':
+          $ref: '#/components/responses/ServiceUnavailable'
   # --------------------------------------------
   /books/{book_id}: 
   # --------------------------------------------

From cb9e4b6c4dbb61427cc0b1da83dc329b0449ebba Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 15:24:12 +0100
Subject: [PATCH 20/21] Update app/datastore/mongo_helper.py

Fix docstring to reflect parameter name, copilot review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 app/datastore/mongo_helper.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/datastore/mongo_helper.py b/app/datastore/mongo_helper.py
index a9d6f5b..ed8bee9 100644
--- a/app/datastore/mongo_helper.py
+++ b/app/datastore/mongo_helper.py
@@ -40,7 +40,7 @@ def find_books(collection, query_filter=None, projection=None, limit=None) -> Cu
 
     Args:
         collection: The pymongo collection object.
-        filter: The MongoDB query filter. Defaults to None (find all).
+        query_filter: The MongoDB query filter. Defaults to None (find all).
         projection: The fields to include/exclude. Defaults to None (all fields).
         limit: The maximum number of results to return. Defaults to None.
 

From bf4114958e00637287459e3ac61bdaa4ff35daeb Mon Sep 17 00:00:00 2001
From: codesungrape <miss.s.rai@outlook.com>
Date: Thu, 24 Jul 2025 15:24:51 +0100
Subject: [PATCH 21/21] Update tests/test_app.py

Copilot review- fix spelling error

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 tests/test_app.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_app.py b/tests/test_app.py
index 46f5e0f..8a7ebc6 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -174,7 +174,7 @@ def test_get_all_books_returns_all_books(mock_fetch, mock_format, client):
     assert response.status_code == 200
     assert response.headers["content-type"] == "application/json"
 
-    # Assert the repsonse body
+    # Assert the response body
     response_data = response.get_json()
     assert isinstance(response_data, dict)
     assert response_data["total_count"] == 2