Merge branch 'db-doc' into 'master'

Documentation for the MatematDatabase Facade

See merge request s3lph/matemat!4

.gitignore

@@ -5,6 +5,7 @@
 *.pyc
 **/*.egg-info/
 *.coverage
+**/.mypy_cache/
 
 *.sqlite3
 *.db

matemat/db/__init__.py

@@ -1,3 +1,3 @@
 
 from .wrapper import DatabaseWrapper
-from .facade import DatabaseFacade as Database
+from .facade import MatematDatabase

matemat/db/facade.py

@@ -8,28 +8,69 @@ from matemat.exceptions import AuthenticationError, DatabaseConsistencyError
 from matemat.db import DatabaseWrapper
 
 
-class DatabaseFacade(object):
+class MatematDatabase(object):
+    """
+    This class provides a facade that abstracts every (TM) needed database access in high level functions.
+
+    Usage example (creating a user, changing the users touchkey, login as that user and delete the user:
+
+    with MatematDatabase('/srv/matemat/production.sqlite3') as db:
+        user: User = db.create_user('testuser', 'supersecurepassword')
+        db.change_touchkey(user, 'supersecurepassword', '048cdef')
+        user2: User = db.login('testuser', touchkey='048cdef')
+        db.delete_user(user2)
+
+    """
 
     def __init__(self, filename: str) -> None:
+        """
+        Create a new database facade.  This does not connect to the SQLite3 database yet.  To actually open the
+        connection, use the Context Manager 'with' syntax (PEP 343), e.g.:
+
+        with MatematDatabase('path/to/database.sqlite3') as db:
+            db.foo()
+
+        :param filename: The SQLite3 database file to use.
+        """
         self.db: DatabaseWrapper = DatabaseWrapper(filename)
 
-    def __enter__(self) -> 'DatabaseFacade':
+    def __enter__(self) -> 'MatematDatabase':
+        # Pass context manager stuff through to the database wrapper
         self.db.__enter__()
         return self
 
     def __exit__(self, exc_type: Type, exc_val: Any, exc_tb: Any) -> None:
+        # Pass context manager stuff through to the database wrapper
         self.db.__exit__(exc_type, exc_val, exc_tb)
 
     def transaction(self, exclusive: bool = True) -> Any:
+        """
+        Begin a new SQLite3 transaction (exclusive by default).  You should never need to use the returned object (an
+        APSW cursor).  It is provided in case there is a real need for it (e.g. for unit testing).
+
+        This function should be used with the Context Manager 'with' syntax (PEP 343), e.g.:
+
+        with db.transaction():
+            db.foo()
+            db.bar()
+
+        :param exclusive: Whether to begin an exclusive transaction or not, defaults to True (exclusive).
+        :return: An APSW cursor.
+        """
         return self.db.transaction(exclusive=exclusive)
 
     def list_users(self) -> List[User]:
+        """
+        Return a list of users in the database.
+        :return: A list of users.
+        """
         users: List[User] = []
         with self.db.transaction(exclusive=False) as c:
             for row in c.execute('''
                 SELECT user_id, username, email, is_admin, is_member
                 FROM users
               '''):
+                # Decompose each row and put the values into a User object
                 user_id, username, email, is_admin, is_member = row
                 users.append(User(user_id, username, email, is_admin, is_member))
         return users
@@ -40,12 +81,25 @@ class DatabaseFacade(object):
                     email: Optional[str] = None,
                     admin: bool = False,
                     member: bool = True) -> User:
+        """
+        Create a new user.
+        :param username: The name of the new user.
+        :param password: The user's password.
+        :param email: The user's email address, defaults to None.
+        :param admin: Whether the user is an administrator, defaults to False.
+        :param member: Whether the user is a member, defaults to True.
+        :return: A User object representing the created user.
+        :raises ValueError: If a user with the same name already exists.
+        """
+        # Hash the password.
         pwhash: str = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt(12))
         user_id: int = -1
         with self.db.transaction() as c:
+            # Look up whether a user with the same name already exists.
             c.execute('SELECT user_id FROM users WHERE username = ?', [username])
             if c.fetchone() is not None:
                 raise ValueError(f'A user with the name \'{username}\' already exists.')
+            # Insert the user into the database.
             c.execute('''
               INSERT INTO users (username, email, password, balance, is_admin, is_member, lastchange)
               VALUES (:username, :email, :pwhash, 0, :admin, :member, STRFTIME('%s', 'now'))
@@ -56,11 +110,22 @@ class DatabaseFacade(object):
                 'admin': admin,
                 'member': member
             })
+            # Fetch the new user's rowid.
             c.execute('SELECT last_insert_rowid()')
             user_id = int(c.fetchone()[0])
         return User(user_id, username, email, admin, member)
 
     def login(self, username: str, password: Optional[str] = None, touchkey: Optional[str] = None) -> User:
+        """
+        Validate a user's password or touchkey, and return a User object on success.  EITHER password OR touchkey must
+        be provided, the other one must be None.
+        :param username: The username to login with.
+        :param password: The user's password.
+        :param touchkey: The user's touchkey.
+        :return: A User object.
+        :raises ValueError: If none or both of password and touchkey are provided.
+        :raises AuthenticationError: If the user does not exist or the password or touchkey is wrong.
+        """
         if (password is None) == (touchkey is None):
             raise ValueError('Exactly one of password and touchkey must be provided')
         with self.db.transaction(exclusive=False) as c:
@@ -80,15 +145,27 @@ class DatabaseFacade(object):
             return User(user_id, username, email, admin, member)
 
     def change_password(self, user: User, oldpass: str, newpass: str, verify_password: bool = True) -> None:
+        """
+        Change a user's password.  Either the old password must be provided (for a password change by the user
+        him-/herself), or verify_password must be set to False (for a password change by an administrator).
+        :param user: User object representing the user to change the password for.
+        :param oldpass: The old password.
+        :param newpass: The new password.
+        :param verify_password: Whether to actually verify the old password, defaults to True.
+        :raises AuthenticationError: If the user does not exist or oldpass is wrong (if verify_password is True).
+        """
         with self.db.transaction() as c:
+            # Fetch the old password.
             c.execute('''
             SELECT password FROM users WHERE user_id = ?
             ''', [user.id])
             row = c.fetchone()
             if row is None:
                 raise AuthenticationError('User does not exist in database.')
+            # Verify the old password, if it should be verified.
             if verify_password and not bcrypt.checkpw(oldpass.encode('utf-8'), row[0]):
                 raise AuthenticationError('Old password does not match.')
+            # Hash the new password and write it to the database.
             pwhash: str = bcrypt.hashpw(newpass.encode('utf-8'), bcrypt.gensalt(12))
             c.execute('''
             UPDATE users SET password = :pwhash, lastchange = STRFTIME('%s', 'now') WHERE user_id = :user_id
@@ -98,15 +175,27 @@ class DatabaseFacade(object):
             })
 
     def change_touchkey(self, user: User, password: str, touchkey: Optional[str], verify_password: bool = True) -> None:
+        """
+        Change a user's touchkey.  Either the old password must be provided (for a password change by the user
+        him-/herself), or verify_password must be set to False (for a password change by an administrator).
+        :param user: User object representing the user to change the password for.
+        :param password: The user's password.
+        :param touchkey: The new touchkey.
+        :param verify_password: Whether to actually verify the password, defaults to True.
+        :raises AuthenticationError: If the user does not exist or password is wrong (if verify_password is True).
+        """
         with self.db.transaction() as c:
+            # Fetch the password.
             c.execute('''
             SELECT password FROM users WHERE user_id = ?
             ''', [user.id])
             row = c.fetchone()
             if row is None:
                 raise AuthenticationError('User does not exist in database.')
+            # Verify the password, if it should be verified.
             if verify_password and not bcrypt.checkpw(password.encode('utf-8'), row[0]):
                 raise AuthenticationError('Password does not match.')
+            # Hash the new touchkey and write it to the database.
             tkhash: str = bcrypt.hashpw(touchkey.encode('utf-8'), bcrypt.gensalt(12)) if touchkey is not None else None
             c.execute('''
             UPDATE users SET touchkey = :tkhash, lastchange = STRFTIME('%s', 'now') WHERE user_id = :user_id
@@ -116,6 +205,11 @@ class DatabaseFacade(object):
             })
 
     def change_user(self, user: User) -> None:
+        """
+        Write changes in the User object to the database.
+        :param user: The user object to update in the database.
+        :raises DatabaseConsistencyError: If the user represented by the object does not exist.
+        """
         with self.db.transaction() as c:
             c.execute('''
             UPDATE users SET
@@ -136,6 +230,11 @@ class DatabaseFacade(object):
                     f'change_user should affect 1 users row, but affected {affected}')
 
     def delete_user(self, user: User) -> None:
+        """
+        Delete the user represented by the User object.
+        :param user: The user to delete.
+        :raises DatabaseConsistencyError: If the user represented by the object does not exist.
+        """
         with self.db.transaction() as c:
             c.execute('''
             DELETE FROM users
@@ -147,6 +246,10 @@ class DatabaseFacade(object):
                     f'delete_user should affect 1 users row, but affected {affected}')
 
     def list_products(self) -> List[Product]:
+        """
+        Return a list of products in the database.
+        :return: A list of products.
+        """
         products: List[Product] = []
         with self.db.transaction(exclusive=False) as c:
             for row in c.execute('''
@@ -158,6 +261,14 @@ class DatabaseFacade(object):
         return products
 
     def create_product(self, name: str, price_member: int, price_non_member: int) -> Product:
+        """
+        Creates a new product.
+        :param name: Name of the product.
+        :param price_member: Price of the product for members.
+        :param price_non_member: Price of the product for non-members.
+        :return: A Product object representing the created product.
+        :raises ValueError: If a product with the same name already exists.
+        """
         product_id: int = -1
         with self.db.transaction() as c:
             c.execute('SELECT product_id FROM products WHERE name = ?', [name])
@@ -196,6 +307,11 @@ class DatabaseFacade(object):
                     f'change_product should affect 1 products row, but affected {affected}')
 
     def delete_product(self, product: Product) -> None:
+        """
+        Write changes in the Product object to the database.
+        :param product: The product object to update in the database.
+        :raises DatabaseConsistencyError: If the product represented by the object does not exist.
+        """
         with self.db.transaction() as c:
             c.execute('''
             DELETE FROM products
@@ -207,7 +323,16 @@ class DatabaseFacade(object):
                     f'delete_product should affect 1 products row, but affected {affected}')
 
     def increment_consumption(self, user: User, product: Product, count: int = 1) -> None:
+        """
+        Decrement the user's balance by the price of the product, decrement the products stock, and create an entry in
+        the statistics table.
+        :param user: The user buying a product.
+        :param product: The product the user is buying.
+        :param count: How many units of the product the user is buying, defaults to 1.
+        :raises DatabaseConsistencyError: If the user or the product does not exist in the database.
+        """
         with self.db.transaction() as c:
+            # Retrieve the consumption entry for the (user, product) pair, if any.
             c.execute('''
             SELECT count
             FROM consumption
@@ -219,6 +344,7 @@ class DatabaseFacade(object):
             })
             row = c.fetchone()
             if row is None:
+                # If the entry does not exist, create a new one.
                 c.execute('''
                 INSERT INTO consumption (user_id, product_id, count)
                 VALUES (:user_id, :product_id, :count)
@@ -228,6 +354,7 @@ class DatabaseFacade(object):
                     'count': count
                 })
             else:
+                # If the entry exists, update the consumption count.
                 c.execute('''
                 UPDATE consumption
                 SET count = count + :count
@@ -237,10 +364,12 @@ class DatabaseFacade(object):
                     'product_id': product.id,
                     'count': count
                 })
+            # Make sure exactly one consumption row was updated/inserted.
             affected = c.execute('SELECT changes()').fetchone()[0]
             if affected != 1:
                 raise DatabaseConsistencyError(
                     f'increment_consumption should affect 1 consumption row, but affected {affected}')
+            # Compute the cost of the transaction and subtract it from the user's account balance.
             c.execute('''
             UPDATE users
             SET balance = balance - :cost
@@ -248,10 +377,12 @@ class DatabaseFacade(object):
                 'user_id': user.id,
                 'cost': count * product.price_member if user.is_member else count * product.price_non_member
             })
+            # Make sure exactly one user row was updated.
             affected = c.execute('SELECT changes()').fetchone()[0]
             if affected != 1:
                 raise DatabaseConsistencyError(
                     f'increment_consumption should affect 1 users row, but affected {affected}')
+            # Subtract the number of purchased units from the product's stock.
             c.execute('''
             UPDATE products
             SET stock = stock - :count
@@ -260,12 +391,19 @@ class DatabaseFacade(object):
                 'product_id': product.id,
                 'count': count
             })
+            # Make sure exactly one product row was updated.
             affected = c.execute('SELECT changes()').fetchone()[0]
             if affected != 1:
                 raise DatabaseConsistencyError(
                     f'increment_consumption should affect 1 products row, but affected {affected}')
 
     def restock(self, product: Product, count: int) -> None:
+        """
+        Update the stock of a product.
+        :param product: The product to restock.
+        :param count: Number of units of the product to add.
+        :raises DatabaseConsistencyError: If the product represented by the object does not exist.
+        """
         with self.db.transaction() as c:
             c.execute('''
             UPDATE products
@@ -280,6 +418,12 @@ class DatabaseFacade(object):
                 raise DatabaseConsistencyError(f'restock should affect 1 products row, but affected {affected}')
 
     def deposit(self, user: User, amount: int) -> None:
+        """
+        Update the account balance of a user.
+        :param user: The user to update the account balance for.
+        :param amount: The amount to add to the account balance.
+        :raises DatabaseConsistencyError: If the user represented by the object does not exist.
+        """
         if amount < 0:
             raise ValueError('Cannot deposit a negative value')
         with self.db.transaction() as c:

matemat/db/test/test_facade.py

@@ -3,14 +3,14 @@ import unittest
 
 import bcrypt
 
-from matemat.db import Database
+from matemat.db import MatematDatabase
 from matemat.exceptions import AuthenticationError, DatabaseConsistencyError
 
 
 class DatabaseTest(unittest.TestCase):
 
     def setUp(self) -> None:
-        self.db = Database(':memory:')
+        self.db = MatematDatabase(':memory:')
 
     def test_create_user(self) -> None:
         with self.db as db: