.devcontainer/devcontainer.json

@@ -69,7 +69,7 @@
 	},
 
 	// Use 'forwardPorts' to make a list of ports inside the container available locally.
-	"forwardPorts": [ 5001 ],
+	// "forwardPorts": [ 5001 ],
 
 	// Uncomment the next line if you want start specific services in your Docker Compose config.
 	// "runServices": [],
@@ -90,5 +90,6 @@
 		// "terraform": "latest",
 		"azure-cli": {
 			"version": "lts"
+		}
 	}
 }

.gitignore

@@ -164,4 +164,6 @@ cython_debug/
 
 _docs/
 .env
+dotenv
 .DS_Store
+*.pem

.gitlab-ci.yml

 ## Stage names in the pipeline.
 stages:
   - build
+  - test
+  - deploy
 
 variables:
   ## Name for the generated image. Change this if you wish, but watch out
   ## for special characters and spaces!
-  DOCKER_IMAGE_NAME: ${DOCKER_REGISTRY}/tjts5901
-  DOCKER_TAG: latest
+  DOCKER_IMAGE_NAME: ${DOCKER_REGISTRY}/tjts5901teamfrozen
+  DOCKER_TAG: $CI_COMMIT_REF_SLUG
 
   ## (Optional) More verbose output from pipeline. Enabling it might reveal secrets.
   #CI_DEBUG_TRACE: "true"
@@ -43,3 +45,38 @@ build:
           --local dockerfile=. \
           --opt build-arg:CI_COMMIT_SHA=${CI_COMMIT_SHA} \
           --output type=image,name=${DOCKER_IMAGE_NAME}:${DOCKER_TAG},push=true
+        
+## Run the tests. If any of the tests fails, pipeline is rejected.         
+test:
+    ## Optional: include stage and environment name
+    stage: test
+    # environment: testing
+    image: ${DOCKER_IMAGE_NAME}:${DOCKER_TAG}
+    variables:
+      ## Setup variable pointin to mongo service
+      MONGO_URL: mongodb://frozen-mdb:9Llvg8WY1I8bLeBo6t8vZbWMnL6g7pOqJ9OBtj6N6XPlWe0UWt9q8phaiaSdfnrlkgAu2KOPiW3IACDbrIm5Eg==@frozen-mdb.mongo.cosmos.azure.com:10255/?ssl=true&replicaSet=globaldb&retrywrites=false&maxIdleTimeMS=120000&appName=@frozen-mdb@
+
+    ## When job is started, also start these things
+    services:
+    - name: mongo:4.2  # update to reflect same version used on production
+      alias: mongo
+    script:
+        - pip install --disable-pip-version-check -e .[test]
+        - pytest -v
+        - echo "Test were run succesfully!"
+
+include:
+  - template: Jobs/SAST.gitlab-ci.yml
+
+## Deploy latest image to the production
+deploy:
+  stage: deploy
+  environment: production
+  image: docker:20.10.23
+  only:
+    - main
+  script:
+    ## Copy credentials to container
+    - mkdir -p ${HOME}/.docker && echo "${DOCKER_AUTH_CONFIG}" > "${HOME}/.docker/config.json"
+    ## Add the `latest` tag to the image we have build.
+    - docker buildx imagetools create ${DOCKER_IMAGE_NAME}:${DOCKER_TAG} --tag ${DOCKER_IMAGE_NAME}:latest

Dockerfile

@@ -61,6 +61,10 @@ ENV CI_COMMIT_SHA=${CI_COMMIT_SHA}
 ## Save build date and time
 RUN echo "BUILD_DATE=$(date -u +'%Y-%m-%dT%H:%M:%SZ')" >> /app/.env
 
+## Download the currency exchange rates from European Central Bank
+RUN flask update-currency-rates
+
+
 ## To prevent vscode constantly re-installing extensions, we need to create a folder for it.
 ## In devcontainer.json, we mount volume to this folder so that extensions are not lost.
 ## Create vscode extension folder, and change ownership of it.

README.md

@@ -21,3 +21,31 @@ docker run -it -p 5001:5001 -e "FLASK_DEBUG=1" -v "${PWD}:/app" tjts5901
 ```
 
 Please see the `docs/tjts5901` folder for more complete documentation.
+
+## Application address
+```
+https://frozen-app.azurewebsites.net/
+
+```
+## Reporting guideline
+```
+Check out the website and report any issues that you notice. Mark them as issues in the gitlab. Use the bug report template (found in the issues). 
+Please remember to add a date and a time to your report. If there are no issues, please report that as well in form of a short free from gitlab issue. 
+
+We would like you to check out at least the following features (lack on nav bar is known issue)
+
+Registeration https://frozen-app.azurewebsites.net/auth/register
+
+Login https://frozen-app.azurewebsites.net/auth/
+
+Add item for auction https://frozen-app.azurewebsites.net/addItem
+
+Check items at (we know it's ugly) https://frozen-app.azurewebsites.net/listBid
+
+view your profile page (we know it's ugly) https://frozen-app.azurewebsites.net/auth/profile
+
+logout https://frozen-app.azurewebsites.net/auth/logout
+
+Generate token https://frozen-app.azurewebsited.net/auth/profile/yourmail/token (remember to use mail you used for registration)
+
+```
\ No newline at end of file

docker-compose.yml

@@ -5,6 +5,13 @@
 
 version: '3'
 services:
+  # MongoDB container
+  mongodb:
+    image: mongo:4.2
+    restart: unless-stopped
+    ports:
+      - 27017:27017
+      
   tjts5901:
     build:
       context: .
@@ -34,10 +41,10 @@ services:
     ## Don't restart container if it exits. Useful for debugging, not for production.
     restart: 'no'
 
-  # Example for another service, such as a database.
-  # mongodb:
-  #   image: mongo:stable
-  #   restart: unless-stopped
+    ## Start a mongodb container and link it to the app container
+    depends_on:
+      - mongodb
 
 volumes:
   tjts5901-vscode-extensions:
+

docs/WeeklyReport.md

+Weekly report week 1
+
+Everyone: set their local development environment
+
+Mikael: Created a document for way of working and wrote 1 user story
+
+Veera: Wrote 2 user stories
+
+Rayan: Wrote 2 user stories
+
+Arno: started setting up the project in GitLab and in Azure
+
+Top 5 security risks considered (Not much was yet done)
+
+A01:2021-Broken Access Control 
+	Different roles and their access levels to the system were defined. Access control was discussed.
+
+A07:2021-Identification and Authentication Failures 
+	Authentication was decided to be left to third party platform. It was discussed that no default or unsecure credentials should be deployed to the final product.
+
+A09:2021-Security Logging and Monitoring Failures
+	Design of the monitoring view was discussed
+	
+A04:2021-Insecure Design
+	Security taken into account in early design. Security related user stories were discussed.
+
+A05:2021-Security Misconfiguration 
+	It was discussed that no default account should be ever left on the finished product
\ No newline at end of file

docs/WeeklyReport2.md

+Weekly Report week 2
+
+Mikael
+1. wrote 6 user stories
+2. Identified the 5 most concerning security risks for the weeks tasks
+3. Setted up the testing up
+4. Started the Login/registration feature
+
+Arno
+1. Completed setting up the Azure infrastructure and the Gitlab-runner. 
+2. Added application address https://frozen-app.azurewebsites.net/ to README.md
+3. Setup the database on azure
+4. Initial setup of flask application (pages “/”, “/hello” and “/server-info”)
+5. Added initial schemas for user and items into the database
+6. Added test for saving of objects (user and item) into the database (page “/test”)
+7. Considered A02:2021 and A10:2021.
+
+Rayan
+1. Finish local environment
+2. Web page for adding items
+
+Top 5 security risks considered (from OWASP) https://owasp.org/www-project-top-ten/
+
+	
+A10:2021-Server-Side Request Forgery 
+	Data are currently not accessible via internet
+
+A02:2021-Cryptographic Failures 
+	Passwords should be stored encrypted
+
+A05:2021-Security Misconfiguration
+Automated test process for build, unit tests and deployment was setted up to help spot mistakes 
+
+A07:2021-Identification and Authentication Failures 
+	No weak usernames or admin password will be implemented
+
+A01:2021-Broken Access Control 
+	The roles and their access rights have been discussed
+

docs/WeeklyReport3.md

+Weekly Report week 3
+
+Mikael:
+1. Wrote 6 more user stories and added them to gitlab
+2. Added frontend solution for login and registration pages with bootstrap 4 style sheet
+3. Identified the most relevant security issues for the week
+4. Added static testing (SAST)
+
+Arno:
+1. Backend for saving of offers
+2. Backend for loading of offers
+3. Adding image saving feature to add_items page and backend support
+4. Fixing deployment pipeline in gitlab
+5. Code refactoring views.py for compliance with recommendations
+6. Setup logging and monitoring scripts
+7. Setup logging via sentry
+8. Created database unittest
+9. Considered OWASP A09:2021, A01:2021 and A05:2021.
+
+Rayan:
+1. Frontend page for list of items on offer
+
+
+Top 5 security risks considered (from OWASP) https://owasp.org/www-project-top-ten/
+
+A09:2021-Security Logging and Monitoring Failures
+	Setting up logging with sentry, including email notifications on failures
+
+A04:2021-Insecure Design 
+	Need for security testing was identified. User stories were written on that base.
+
+A01:2021-Broken Access Control
+	Added access control this week. Access control cannot be bypassed by modifying the URL anymore (use of login_required feature of flask_login)
+
+A05:2021-Security Misconfiguration 
+No default accounts are used. Unnecessary testing features should be removed before final submission of the project.
+
+A08:2021-Software and Data Integrity Failures 
+	Added static testing to minimise the chance that malicious or vulnerable code gets into the final product.
+	

docs/WeeklyReport4.md

+Weekly Report week 4
+
+Mikael
+
+1. Played Privacy Problems tool (game)
+2. Created a instructions for bug hunt
+3. Created a bug report template for bug hunt
+4. Created multiple bug reports for other teams
+5. Added a navigation bar to the site
+6. Added the weekly report to repository
+
+Arno
+1. Added image resizing feature in addItems
+2. Added image showing feature to items list
+3. Backend for saving of users
+4. Added image feature to db unittest
+5. Added logout function and made sure, that pages are only accessible after login
+6. Reviewed and updated existing user stories;  wrote 4 new user stories as issues in GitLab
+7. Played Privacy Problems tool (game)
+8. Updated db test to take into consideration, that user must now be logged-in
+9. Implemented filter for items in view of items (only open auctions are shown)
+10 Added token generation feature (frontend and backend, including db model)
+11. Added Bid db model
+12. Implemented and tested bidding on items via REST api
+13. Implemented backend support for bidding on items
+14. Adding image feature to item detail page
+15. Shown prices for items now update when someone bids on them (current price instead of starting price)
+
+Rayan
+1. Played Privacy Problems tool (game)
+2. Added biding page
+3. Identified the most notable security risks for the week.
+
+Top 5 security risks considered (from OWASP) https://owasp.org/www-project-top-ten/
+
+A01 Broken Access Control
+Added check for login. Users have now log into the site in order to access any of the pages and can logout
+
+A02 Cryptographic failures
+User information is now saved to the database. Passwords are encrypted  properly. 
+
+A07 identification and Authentication failures
+Implemented a third party authentication to make the authentication stronger. You now must have a token to make a API request
+
+A04:2021-Insecure Design 
+Made sure that no user information (such as emails) were publicly available to be taken advantage of.
+
+A06:2021 – Vulnerable and Outdated Components
+Made sure that all of the used libraries and dependencies are from trusted repositories

dotenv

@@ -14,9 +14,4 @@
 # developers or deployments, as you can simply share the .env file rather than hardcoding the
 # values into the application itself.
 
-FLASK_APP=tjts5901.app
-FLASK_DEBUG=1
-
-# Enable rich logging for more human readable log output. Requires installing
-# `rich` and `flask-rich` packages.
-#RICH_LOGGING=1
+MONGO_URL = "mongodb://localhost:27017/
\ No newline at end of file

etc/resolv.conf

+nameserver 8.8.8.8
\ No newline at end of file

pyproject.toml

@@ -28,6 +28,7 @@ dependencies = {file = ["requirements.txt"]}
 [project.optional-dependencies]
 test = [
   "pytest",
+  "coverage",
 ]
 docs = [
   "mkdocs",

requirements.txt

@@ -2,11 +2,22 @@
 importlib-metadata
 
 # Framework and libraries
-flask
+flask==2.2.2
 python-dotenv
+flask-login
+flask_babel
+datetime
+
+flask-mongoengine==1.0
+Pillow
+CurrencyConverter
 
 # Git hooks
 pre-commit
 
+# Sentry for error reporting
+sentry-sdk[flask]
+sentry-sdk[mongoengine]
+
 # More production-ready web server
 #gunicorn

src/tjts5901/__init__.py

@@ -6,7 +6,14 @@ JYU TJTS5901 Course project
 from importlib_metadata import (PackageNotFoundError,
                                 version)
 
+from .app import create_app
+
 try:
     __version__ = version(__name__)
 except PackageNotFoundError:
     __version__ = "unknown"
+
+__all__ = [
+    "create_app",
+    "__version__",
+]
\ No newline at end of file

src/tjts5901/app.py

@@ -7,7 +7,9 @@ Flask tutorial: https://flask.palletsprojects.com/en/2.2.x/tutorial/
 
 """
 
+import logging
 from os import environ
+import os
 from typing import Dict, Optional
 
 from dotenv import load_dotenv
@@ -18,8 +20,14 @@ from flask import (
     request,
 )
 
+from flask_babel import _
+
 from .utils import get_version
+from .db import init_db
+from .logging import init_logging
+from .i18n import init_babel
 
+logger = logging.getLogger(__name__)
 
 def create_app(config: Optional[Dict] = None) -> Flask:
     """
@@ -29,15 +37,43 @@ def create_app(config: Optional[Dict] = None) -> Flask:
     """
     flask_app = Flask(__name__, instance_relative_config=True)
 
-    if config:
-        flask_app.config.from_mapping(config)
+    flask_app.config.from_mapping(
+        SECRET_KEY='dev',
+        BRAND="The Frozen Auction",
+    )
 
-    # Set flask config variable for "rich" loggin from environment variable.
-    flask_app.config.from_envvar("RICH_LOGGING", silent=True)
+    init_logging(flask_app)
+
+    # load the instance config, if it exists, when not testing
+    if config is None:
+        flask_app.config.from_pyfile('config.py', silent=True)
+    else:
+        flask_app.config.from_mapping(config)
 
-    # Register blueprints
-    from . import views  # pylint: disable=import-outside-toplevel
+    # Initialize logging early, so that we can log the rest of the initialization.
+    init_logging(flask_app)
+
+    # ensure the instance folder exists
+    try:
+        os.makedirs(flask_app.instance_path)
+    except OSError:
+        print('OsError when trying to open flask_app folder. Instance_path not existing.')
+        pass
+    # Initialize the Flask-Babel extension.
+    init_babel(flask_app)
+    # Initialize the database connection.
+    init_db(flask_app)
+
+     # Register blueprints
+    from . import views  
     flask_app.register_blueprint(views.bp, url_prefix='')
+    flask_app.register_blueprint(views.api)
+
+    from .auth import init_auth
+    init_auth(flask_app)
+
+    from .currency import init_currency
+    init_currency(flask_app)
 
     return flask_app
 
@@ -49,13 +85,6 @@ load_dotenv()
 # Create the Flask application.
 app = create_app()
 
-# Initialize "rich" output if enabled. It produces more human readable logs.
-# You need to install `flask-rich` to use this.
-if app.config.get("RICH_LOGGING"):
-    from flask_rich import RichApplication
-    RichApplication(app)
-    app.logger.info("Using [blue]rich[/blue] interface for logging")
-
 
 @app.route("/server-info")
 def server_info() -> Response:
@@ -65,8 +94,18 @@ def server_info() -> Response:
     This is useful for monitoring the server, and for checking that the server is
     running correctly.
     """
+    # Test for database connection
+    database_ping = False
+    try:
+        from .db import db  # pylint: disable=import-outside-toplevel
+        database_ping = db.connection.admin.command('ping').get("ok", False) and True
+    except Exception as exc:  # pylint: disable=broad-except
+        logger.warning("Error querying mongodb server: %r", exc,
+                       exc_info=True,
+                       extra=flask_app.config.get_namespace("MONGODB"))
 
     response = {
+        "database_connectable": database_ping,
         "version": get_version(),
         "build_date": environ.get("BUILD_DATE", None)
     }

src/tjts5901/auth.py

+from datetime import datetime
+import functools
+import logging
+import base64
+
+from flask import (
+    Blueprint, flash, redirect, render_template, request, session, url_for, abort
+)
+from flask_login import (
+    LoginManager,
+    login_user,
+    logout_user,
+    login_required,
+    current_user,
+)
+
+from flask_babel import _
+from werkzeug.security import check_password_hash, generate_password_hash
+from sentry_sdk import set_user
+
+from .models import AccessToken, User, Item
+
+from mongoengine import DoesNotExist
+from mongoengine.queryset.visitor import Q
+
+bp = Blueprint('auth', __name__, url_prefix='/auth')
+logger = logging.getLogger(__name__)
+
+
+def init_auth(app):
+    """
+    Integrate authentication into the application.
+    """
+    app.register_blueprint(bp)
+
+    login_manager = LoginManager()
+    login_manager.login_view = 'auth.login'
+    login_manager.user_loader(load_logged_in_user)
+
+    app.config['AUTH_HEADER_NAME'] = 'Authorization'
+    login_manager.request_loader(load_user_from_request)
+
+    login_manager.init_app(app)
+
+    logger.debug("Initialized authentication")
+
+
+def load_user_from_request(request):
+    """
+    Load a user from the request.
+
+    This function is used by Flask-Login to load a user from the request.
+    """
+    api_key = request.headers.get("Authorization")
+
+    if api_key:
+        api_key = api_key.replace("Bearer ", "", 1)
+        try:
+            token = AccessToken.objects.get(token=api_key)
+            if token.expires and token.expires < datetime.utcnow():
+                logger.warning("Token expired: %s", api_key)
+                return None
+            # User is authenticated
+
+            token.last_used_at = datetime.utcnow()
+            token.save()
+            logger.debug("User authenticated via token: %r", token.user.email, extra={
+                "user": token.user.email,
+                "user_id": str(token.user.id),
+                "token": token.token,
+            })
+            return token.user
+        except DoesNotExist:
+            logger.error("Token not found: %s", api_key)
+
+    return None
+
+
+def load_logged_in_user(user_id):
+    """
+    Load a user from the database, given the user's id.
+    """
+    try:
+        user = User.objects.get(id=user_id)
+        set_user({"id": str(user.id), "email": user.email})
+    except DoesNotExist:
+        logger.error("User not found: %s", user_id)
+        return None
+
+    return user
+
+
+def get_user_by_email(email: str) -> User:
+    """
+    Get a user from the database, given the user's email.
+
+    If the email is 'me', then the current user is returned.
+
+    :param email: The email of the user to get.
+    """
+
+    if email is None:
+        abort(404)
+
+    if email == "me" and current_user.is_authenticated:
+       email = current_user.email
+
+    try:
+        user = User.objects.get_or_404(email=email)
+    except DoesNotExist:
+        logger.error("User not found: %s", email)
+        abort(404)
+
+    return user
+
+
+
+@bp.route('/register', methods=('GET', 'POST'))
+def register():
+    if request.method == 'POST':
+        print("Registering user...")
+        email = request.form['email']
+        password = request.form['password']
+        password2 = request.form['password2']
+        error = None
+
+        if not email:
+            error = 'Username is required.'
+        elif not password:
+            error = 'Password is required.'
+        elif password != password2:
+            error = 'Passwords do not match.'
+
+        if error is None:
+            try:
+                user = User(
+                    email=email,
+                    password=generate_password_hash(password)
+                )
+                user.save()
+                flash("You have been registered. Please log in.")
+
+            except Exception as exc:
+                error = f"Error creating user: {exc!s}"
+            else:
+                return redirect(url_for("auth.login"))
+
+        print("Could not register user:", error)
+        flash(error)
+
+    return render_template('auth/register.html')
+
+
+@bp.route('/login', methods=('GET', 'POST'))
+def login():
+    if request.method == 'POST':
+        email = request.form['email']
+        password = request.form['password']
+
+        error = None
+        try:
+            user = User.objects.get(email=email)
+        except DoesNotExist:
+            error = 'Incorrect username.'
+
+        if user is None:
+            error = 'Incorrect username.'
+        elif not check_password_hash(user['password'], password):
+            error = 'Incorrect password.'
+
+        if error is None:
+            remember_me = bool(request.form.get("remember-me", False))
+            if login_user(user, remember=remember_me):
+
+                flash(f"Hello {email}, You have been logged in.")
+
+                next = request.args.get('next')
+                # Better check that the user actually clicked on a relative link
+                # or else they could redirect you to a malicious website!
+                if next is None or not next.startswith('/'):
+                    next = url_for('views.list_bid')
+
+                return redirect(next)
+            else:
+                error = "Error logging in."
+
+        logger.info("Error logging user in: %r: Error: %s", email, error)
+        flash(error)
+
+    return render_template('auth/login.html')
+
+
+@bp.route('/logout')
+@login_required
+def logout():
+    """
+    Log out the current user.
+
+    Also removes the "remember me" cookie.
+    """
+    logout_user()
+    flash("You have been logged out.")
+    return redirect(url_for('auth.login'))
+
+
+@bp.route('/profile', defaults={'email': 'me'})
+@bp.route('/profile/<email>')
+@login_required
+def profile(email):
+    """
+    Show the user's profile page for the given email.
+
+    If the email is 'me', then the current user's profile is shown.
+    """
+    from .views import get_item_price
+
+    user: User = get_user_by_email(email)
+
+    # List the items user has created
+    items = Item.objects(seller=user).all()
+
+    for item in items:
+        item.current_price = get_item_price(item)
+        item.created_at = item.created_at.strftime("%Y-%m-%d %H:%M:%S") 
+        item.closes_at = item.closes_at.strftime("%Y-%m-%d %H:%M:%S")
+        item.image_base64 = base64.b64encode(item.image.read()).decode('utf-8')
+
+    return render_template('auth/profile.html', user=user, items=items)
+
+
+@bp.route('/profile/<email>/token', methods=('GET', 'POST'))
+@login_required
+def user_access_tokens(email):
+    """
+    Show the user's tokens page for the given email.
+    """
+
+    user: User = get_user_by_email(email)
+    # Fetch all the user tokens that are active or have no expire date
+    tokens = AccessToken.objects(Q(expires__gte=datetime.now()) | Q(expires=None), user=user).all()
+
+
+    token = None
+    if request.method == 'POST':
+        try:
+            name = request.form['name']
+
+            if expires := request.form.get('expires'):
+                expires = datetime.fromisoformat(expires)
+            else:
+                expires = None
+
+            token = AccessToken(
+                user=user,
+                name=name,
+                expires=expires,
+            )
+            token.save()
+        except KeyError as exc:
+            logger.debug("Missing required field: %s", exc)
+            flash(("Required field missing"))
+        except Exception as exc:
+            logger.exception("Error creating token: %s", exc)
+            flash(("Error creating token: %s") % exc)
+        else:
+            flash(("Created token: %s") % token.name)
+
+    return render_template('auth/tokens.html', user=user, tokens=tokens, token=token)
+
+
+@bp.route('/profile/<email>/token/<id>', methods=('POST',))
+def delete_user_access_token(email, id):
+    """
+    Delete an access token.
+    """
+    user = get_user_by_email(email)
+    token = AccessToken.objects.get_or_404(id=id)
+
+    if token.user != user:
+        logger.warning("User %s tried to delete token %s", user.email, token.name, extra={
+            "user": user.email,
+            "token": str(token.id),
+            "token_user": token.user.email,
+        })
+        abort(403)
+
+    token.delete()
+
+    flash(f"Deleted token {token.name}")
+    return redirect(url_for('auth.user_access_tokens', email=token.user.email))
+
+

src/tjts5901/currency.py

+"""
+Currency module.
+
+This module contains the currency module, which is used to convert currencies.
+
+Uses the ECB (European Central Bank) as the source of currency conversion rates.
+
+To update the currency conversion rates, run the following command:
+    $ flask update-currency-rates
+
+"""
+
+from decimal import Decimal
+import logging
+from pathlib import Path
+from zipfile import ZipFile
+import urllib.request
+import click
+from currency_converter import (
+    SINGLE_DAY_ECB_URL,
+    CurrencyConverter,
+)
+
+from flask_babel import (
+    get_locale,
+    format_currency,
+)
+
+from babel.numbers import get_territory_currencies, parse_decimal
+
+from flask import (
+    Flask,
+    current_app,
+    render_template,
+)
+
+from markupsafe import Markup
+
+from .auth import current_user
+
+
+REF_CURRENCY = 'EUR'
+"Reference currency for the currency converter."
+
+
+logger = logging.getLogger(__name__)
+
+
+class CurrencyProxy:
+    """
+    Proxy for the currency converter.
+
+    This class is used to proxy the currency converter instance. This is to
+    ensure that the currency converter is only initialized when it is actually
+    used, and the used conversion list is the most up-to-date.
+    """
+
+    def __init__(self, app: Flask):
+        self._converter = None
+        self._app = app
+        self._converter_updated = 0
+        self._dataset_updated = 0
+
+    def get_currency_converter(self) -> CurrencyConverter:
+        """
+        Get a currency converter instance.
+
+        Automatically updates the currency converter if the dataset has been
+        updated.
+
+        Exceptions:
+            RuntimeError: If the currency file is not configured.
+            FileNotFoundError: If the currency file does not exist.
+
+        :return: A currency converter instance.
+        """
+
+        if not (conversion_file := self._app.config.get('CURRENCY_FILE')):
+            raise RuntimeError('Currency file not configured.')
+
+        # Initialize the currency converter if it has not been initialized yet,
+        # or if the dataset has been updated.
+        self._dataset_updated = Path(conversion_file).stat().st_mtime
+        if self._converter is None or self._dataset_updated > self._converter_updated:
+            logger.info("Initializing currency converter with file %s.", conversion_file)
+            self._converter = CurrencyConverter(
+                currency_file=conversion_file,
+                ref_currency=REF_CURRENCY,
+            )
+            self._converter_updated = self._dataset_updated
+
+        return self._converter
+
+    def __getattr__(self, name):
+        """
+        Proxy all other attributes to the currency converter.
+        """
+        return getattr(self.get_currency_converter(), name)
+
+
+def init_currency(app: Flask):
+    """
+    Initialize the currency module.
+
+    This function initializes the currency module, and registers the currency
+    converter as an extension.
+
+    :param app: The Flask application.
+    :return: None
+    """
+
+    # Set default currency file path
+    app.config.setdefault('CURRENCY_FILE', app.instance_path + '/currency.csv')
+
+    # Register the currency converter as an extension
+    app.extensions['currency_converter'] = CurrencyProxy(app)
+
+    # Register the currency converter as a template filter
+    app.add_template_filter(format_converted_currency, name='localcurrency')
+
+    app.cli.add_command(update_currency_rates)
+
+
+def format_converted_currency(value, currency=None, **kwargs):
+    """
+    Render a currency value in the preferred currency.
+
+    This function renders a currency value in the preferred currency for the
+    current locale. If the preferred currency is not the reference currency,
+    the value is converted to the preferred currency.
+    """
+
+    if currency is None:
+        currency = get_preferred_currency()
+
+    # Convert the value to the preferred currency
+    local_value = convert_currency(value, currency)
+
+    # Format the value
+    html = render_template("money-tag.html",
+                           base_amount=format_currency(value, currency=REF_CURRENCY, format_type='name', **kwargs),
+                           local_amount=format_currency(local_value, currency=currency, **kwargs))
+    return Markup(html)
+
+
+def convert_currency(value, currency=None, from_currency=REF_CURRENCY):
+    """
+    Convert a currency value to the preferred currency.
+
+    This function converts a currency value to the preferred currency for the
+    current locale. If the preferred currency is not the reference currency,
+    the value is converted to the preferred currency.
+    """
+
+    if currency != REF_CURRENCY:
+        return current_app.extensions['currency_converter'].convert(value, from_currency, currency)
+
+    return value
+
+
+def convert_from_currency(value, currency) -> Decimal:
+    """
+    Parses the localized currency value and converts it to the reference currency.
+    """
+
+    locale = get_locale()
+    amount = parse_decimal(value, locale=locale)
+
+    if currency != REF_CURRENCY:
+        amount = Decimal(current_app.extensions['currency_converter'].convert(amount, currency, REF_CURRENCY))
+
+    return amount
+
+
+def get_currencies():
+    """
+    Get the list of supported currencies.
+    """
+
+    return current_app.extensions['currency_converter'].currencies
+
+
+def get_preferred_currency():
+    """
+    Get the preferred currency.
+
+    This function returns the preferred currency for the current locale.
+
+    :return: The preferred currency.
+    """
+
+    if current_user.is_authenticated and current_user.currency:
+        return str(current_user.currency)
+
+    # Fall back to the default currency for the locale
+    if territory := get_locale().territory:
+        currency = get_territory_currencies(territory)[0]
+        if currency in get_currencies():
+            return currency
+        else:
+            logger.warning("Default currency %s is not supported, falling back to %s.", currency, REF_CURRENCY)
+
+    return REF_CURRENCY
+
+
+@click.command()
+def update_currency_rates():
+    """
+    Update currency file from the European Central Bank.
+
+    This command is meant to be run from the command line, and is not meant to be
+    used in the application:
+        $ flask update-currency-rates
+
+    :return: None
+    """
+    click.echo('Updating currency file from the European Central Bank...')
+
+    fd, _ = urllib.request.urlretrieve(SINGLE_DAY_ECB_URL)
+    with ZipFile(fd) as zf:
+        file_name = zf.namelist().pop()
+        with open(current_app.config['CURRENCY_FILE'], 'wb') as f:
+            f.write(zf.read(file_name))
+
+    click.echo('Done.')

src/tjts5901/db.py

+import logging
+from os import environ
+
+from flask_mongoengine import MongoEngine
+
+db = MongoEngine()
+logger = logging.getLogger(__name__)
+
+
+def init_db(app):
+    """
+    Initialize the database connection.
+
+    Fetches the database connection string from the environment variable `MONGO_URL`
+    and, if present, sets the `MONGODB_SETTINGS` configuration variable to use it.
+    """
+
+    # To keep secrets private, we use environment variables to store the database connection string.
+    # `MONGO_URL` is expected to be a valid MongoDB connection string
+    mongodb_url = environ.get("MONGO_URL")
+
+    if mongodb_url is not None:
+        app.config["MONGODB_SETTINGS"] = {
+            "host": mongodb_url,
+        }
+        logger.info("Database connection string found, using it.",
+                    # You can use the `extra` parameter to add extra information to the log message.
+                    # This is useful for debugging, but should be removed in production.
+                    extra={"MONGO_URL": mongodb_url} if app.debug else {})
+
+    else:
+        logger.warning("No database connection string found in env, using defaults.",
+                       extra={"MONGODB_SETTINGS": app.config.get("MONGODB_SETTINGS")} if app.debug else {})
+
+    db.init_app(app)

src/tjts5901/i18n.py

+from enum import Enum
+import os
+from typing import List
+from flask_babel import Babel, get_locale as get_babel_locale
+from babel import Locale
+from babel import __version__ as babel_version
+from flask import (
+    Flask,
+    g,
+    request,
+    session,
+)
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class SupportedLocales(Enum):
+    """
+    Supported locales for the application.
+
+    The values are the locale identifiers used by the Babel library.
+    Order here determines the order in which the locales are presented to the
+    user, and the order in which the locales are tried when the user does not
+    specify a preferred locale.
+    """
+
+    FI = "fi_FI.UTF-8"
+    "Finnish (Finland)"
+
+    SV = "sv_SE.UTF-8"
+    "Swedish (Sweden)"
+
+    EN = "en_GB.UTF-8"
+    "English (United Kingdom)"
+
+    # EN_US = "en_US.UTF-8"
+    # "English (United States)"
+
+
+def init_babel(flask_app: Flask):
+    """
+    Initialize the Flask-Babel extension.
+    """
+
+    # Configure the Flask-Babel extension.
+    # Try setting the default locale from underlying OS. Falls back into English.
+    system_language = Locale.default().language
+    translation_dir = os.path.join(os.path.dirname(__file__), "translations")
+    flask_app.config.setdefault("BABEL_TRANSLATION_DIRECTORIES", translation_dir)
+    flask_app.config.setdefault("BABEL_DEFAULT_LOCALE", system_language)
+
+    # TODO: Set the default timezone from underlying OS.
+
+    babel = Babel(flask_app, locale_selector=get_locale)
+
+    # Register `locales` as jinja variable to be used in templates. Uses the
+    # `Locale` class from the Babel library, so that the locale names can be
+    # translated.
+    locales = {}
+    for locale in SupportedLocales:
+        locales[locale.value] = Locale.parse(locale.value)
+
+    flask_app.jinja_env.globals.update(locales=locales)
+    # Register `get_locale` as jinja function to be used in templates
+    flask_app.jinja_env.globals.update(get_locale=get_babel_locale)
+
+    # If url contains locale parameter, set it as default in session
+    @flask_app.before_request
+    def set_locale():
+        if request.endpoint != "static":
+            if locale := request.args.get('locale'):
+                if locale in (str(l) for l in locales.values()):
+                    logger.debug("Setting locale %s from URL.", locale)
+                    session['locale'] = locale
+                else:
+                    logger.warning("Locale %s not supported.", locale)
+
+    logger.info("Initialized Flask-Babel extension %s.", babel_version,
+                extra=flask_app.config.get_namespace("BABEL_"))
+
+    return babel
+
+
+def get_locale():
+    """
+    Get the locale for user.
+
+    Looks at the user model for the user's preferred locale. If the user has not
+    set a preferred locale, check the browser's Accept-Language header. If the
+    browser does not specify a preferred locale, use the default locale.
+
+    todo: What happens if the user's preferred locale support is dropped from
+    todo: the application?
+
+    :return: Suitable locale for the user.
+    """
+
+    # if a locale was stored in the session, use that
+    if locale := session.get('locale'):
+        logger.debug("Setting locale %s from session.", locale)
+        return locale
+
+    # if a user is logged in, use the locale from the user settings
+    user = getattr(g, 'user', None)
+    if user is not None:
+        logger.debug("Using locale %s from user settings.", user.locale)
+        return user.locale
+
+    # otherwise try to guess the language from the user accept header the
+    # browser transmits.
+
+    # The Accept-Language header is a list of languages the user prefers,
+    # ordered by preference. The first language is the most preferred.
+    # The language is specified as a language tag, which is a combination of
+    # a language code and a country code, separated by a hyphen.
+    # For example, en-GB is English (United Kingdom).
+    # The language code is a two-letter code, and the country code is a
+    # two-letter code, or a three-digit number. The country code is optional.
+    # For example, en is English (no country specified), and en-US is English
+
+    # Convert the Enum of supported locales into a list of language tags.
+    # Fancy way: locales_to_try = [locale.value for locale in SupportedLocales]
+    locales_to_try: List[str] = list()
+    for locale in SupportedLocales:
+        locales_to_try.append(str(locale.value))
+
+    # Get the best match for the Accept-Language header.
+    locale = request.accept_languages.best_match(locales_to_try)
+
+    logger.debug("Best match for Accept-Language header (%s) is %s.",
+                 request.accept_languages, locale)
+
+    return locale
+