docs: finalize README with migrations, tests and vCard notes

Reviewed-on: #1

README.md

@@ -23,3 +23,44 @@ python app.py
 ```
 
 Das Formular ist dann unter http://127.0.0.1:5000/ erreichbar.
+
+Migrations (Flask-Migrate / Alembic)
+---------------------------------
+
+Das Projekt verwendet jetzt Flask-Migrate (Alembic) für Datenbank-Migrationen. Ablauf lokal:
+
+```bash
+# virtuelles Environment aktivieren
+source .venv/bin/activate
+
+# Migrationen initialisieren (nur einmal)
+export FLASK_APP=app.py
+flask db init
+
+# Neue Migration auf Basis der Models erzeugen
+flask db migrate -m "Beschreibung der Änderung"
+
+# Migration anwenden
+flask db upgrade
+```
+
+Hinweis: Wenn die Datenbank bereits Tabellen enthält, benutze `flask db stamp head`, damit Alembic den aktuellen Stand als angewendet markiert.
+
+Tests
+-----
+
+Die Tests laufen mit pytest:
+
+```bash
+source .venv/bin/activate
+python -m pytest -q
+```
+
+vCard Export
+-----------
+
+Nach dem Absenden eines Anmeldeformulars wird eine vCard 4.0 im Ordner `vcards/` erzeugt. Dateiname-Muster:
+
+```
+Nachname_Vorname_<id>.vcf
+```

app.py

@@ -5,6 +5,7 @@ import re
 from utils import generate_vcard
 import logging
 from logging.handlers import RotatingFileHandler
+from flask_migrate import Migrate
 
 BASE_DIR = os.path.dirname(os.path.abspath(__file__))
 DB_PATH = os.path.join(BASE_DIR, 'anmeldung.db')
@@ -14,6 +15,8 @@ app.config['SQLALCHEMY_DATABASE_URI'] = f'sqlite:///{DB_PATH}'
 app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
 
 db = SQLAlchemy(app)
+# Flask-Migrate (Alembic) integration
+migrate = Migrate(app, db)
 
 # --- logging setup -------------------------------------------------
 LOG_DIR = os.path.join(BASE_DIR, 'logs')
@@ -129,12 +132,18 @@ def index():
 @app.route('/danke')
 def danke():
     id = request.args.get('id')
-    adresse = Adresse.query.get(id)
+    # Use session.get to avoid SQLAlchemy LegacyAPIWarning and cast id to int if present
+    adresse = db.session.get(Adresse, int(id)) if id else None
     return render_template('danke.html', adresse=adresse)
 
 
 if __name__ == '__main__':
-    # Ensure DB exists
+    # In development only: if there is no migrations directory, create tables automatically.
-    if not os.path.exists(DB_PATH):
+    # In all other cases prefer using Flask-Migrate (flask db upgrade).
+    migrations_dir = os.path.join(BASE_DIR, 'migrations')
+    if not os.path.exists(migrations_dir):
+        app.logger.info('No migrations directory found; creating database tables with db.create_all()')
         db.create_all()
+    else:
+        app.logger.info('Migrations directory present; please use "flask db upgrade" to update the database schema')
     app.run(debug=True)

migrations/README

@@ -0,0 +1 @@
+Single-database configuration for Flask.

migrations/alembic.ini

@@ -0,0 +1,50 @@
+# A generic, single database configuration.
+
+[alembic]
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic,flask_migrate
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[logger_flask_migrate]
+level = INFO
+handlers =
+qualname = flask_migrate
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

migrations/env.py

@@ -0,0 +1,113 @@
+import logging
+from logging.config import fileConfig
+
+from flask import current_app
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+logger = logging.getLogger('alembic.env')
+
+
+def get_engine():
+    try:
+        # this works with Flask-SQLAlchemy<3 and Alchemical
+        return current_app.extensions['migrate'].db.get_engine()
+    except (TypeError, AttributeError):
+        # this works with Flask-SQLAlchemy>=3
+        return current_app.extensions['migrate'].db.engine
+
+
+def get_engine_url():
+    try:
+        return get_engine().url.render_as_string(hide_password=False).replace(
+            '%', '%%')
+    except AttributeError:
+        return str(get_engine().url).replace('%', '%%')
+
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+config.set_main_option('sqlalchemy.url', get_engine_url())
+target_db = current_app.extensions['migrate'].db
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def get_metadata():
+    if hasattr(target_db, 'metadatas'):
+        return target_db.metadatas[None]
+    return target_db.metadata
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url, target_metadata=get_metadata(), literal_binds=True
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    # this callback is used to prevent an auto-migration from being generated
+    # when there are no changes to the schema
+    # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
+    def process_revision_directives(context, revision, directives):
+        if getattr(config.cmd_opts, 'autogenerate', False):
+            script = directives[0]
+            if script.upgrade_ops.is_empty():
+                directives[:] = []
+                logger.info('No changes in schema detected.')
+
+    conf_args = current_app.extensions['migrate'].configure_args
+    if conf_args.get("process_revision_directives") is None:
+        conf_args["process_revision_directives"] = process_revision_directives
+
+    connectable = get_engine()
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=get_metadata(),
+            **conf_args
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

migrations/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}

requirements-dev.txt

@@ -1 +1,2 @@
 pytest
+Flask-Migrate>=4.0

requirements.txt

@@ -1,2 +1,4 @@
 Flask>=2.0
 Flask-SQLAlchemy>=3.0
+Flask-Migrate>=4.0
+alembic>=1.9