Start work on the database code

The code isn't finished yet and isn't ready for use!

config/template_config.ini

@@ -3,7 +3,7 @@
 # Config file parameters
 [Config]
 ; Config file version. DO NOT EDIT THIS!
-version = 3
+version = 4
 ; Set this to no when you are done editing the file
 is_template = yes
 
@@ -20,3 +20,4 @@ long_polling_timeout = 30
 # Database parameters
 [Database]
 ; The database engine you want to use. Refer to http://docs.sqlalchemy.org/en/latest/core/engines.html for the possible settings.
+engine = sqlite://

database.py

@@ -1,27 +1,99 @@
-from sqlalchemy import Table, Column, BigInteger, Numeric, String, Text, MetaData, ForeignKey
+from sqlalchemy import create_engine, Column, ForeignKey
+from sqlalchemy import Integer, BigInteger, String, Numeric, Text
+from sqlalchemy.ext.declarative import declarative_base
+import configloader
+import telegram
 import decimal
+import strings
+from html import escape
 
-# Create a metadata object containing info about the tables in the database
-metadata = MetaData()
+# Create a (lazy) database engine
+engine = create_engine(configloader.config["Database"]["engine"])
 
-# Metadata for the users table
-# TODO: maybe add a 'credit' column
-users = Table("users", metadata,
-              Column("telegram_user_id", BigInteger, primary_key=True),
-              Column("first_name", String, nullable=False),
-              Column("last_name", String),
-              Column("username", String))
+# Create a base class to define all the database subclasses
+TableDeclarativeBase = declarative_base(bind=engine)
 
-# Metadata for the admins table
-# TODO: add columns for all the possible permissions
-admins = Table("admins", metadata,
-               Column("telegram_user_id", ForeignKey("users.telegram_user_id"), primary_key=True))
+# Define all the database tables using the sqlalchemy declarative base
+class User(TableDeclarativeBase):
+    """A Telegram user who used the bot at least once."""
 
-# Metadata for the products table
-products = Table("products", metadata,
-                 Column("product_name", String, primary_key=True),
-                 Column("description", Text),
-                 Column("price", Numeric(...)))
+    # Telegram data
+    user_id = Column(BigInteger, primary_key=True)
+    first_name = Column(String, nullable=False)
+    last_name = Column(String)
+    username = Column(String)
 
-#TODO: many things are still missing...
-raise NotImplementedError()
+    # Current wallet credit
+    credit = Column(Numeric, nullable=False)
+
+    # Extra table parameters
+    __tablename__ = "users"
+
+    def __init__(self, telegram_user: telegram.User):
+        # Get the data from telegram
+        self.id = telegram_user.id
+        self.first_name = telegram_user.first_name
+        self.last_name = telegram_user.last_name
+        self.username = telegram_user.username
+        # The starting wallet value is 0
+        self.credit = decimal.Decimal("0")
+
+    def __str__(self):
+        """Describe the user in the best way possible given the available data."""
+        if self.username is not None:
+            return f"@{self.username}"
+        elif self.last_name is not None:
+            return f"{self.first_name} {self.last_name}"
+        else:
+            return self.first_name
+
+    def __repr__(self):
+        return f"<User {self} having {self.credit} credit>"
+
+
+class Product(TableDeclarativeBase):
+    """A purchasable product."""
+
+    # Product name
+    name = Column(String, primary_key=True)
+    # Product description
+    description = Column(Text)
+    # Product price, if null product is not for sale
+    price = Column(Numeric)
+    # Image filename
+    image = Column(String)
+    # Stock quantity, if null product has infinite stock
+    stock = Column(Integer)
+
+    # Extra table parameters
+    __tablename__ = "product"
+
+    # No __init__ is needed, the default one is sufficient
+
+    def __str__(self):
+        """Return the product details formatted with Telegram HTML. The image is omitted."""
+        return f"<b>{escape(self.name)}</b>\n" \
+               f"{escape(self.description)}\n" \
+               f"<i>{format(strings.in_stock_format_string, quantity=self.stock) if self.stock is not None else ''}</i>\n" \
+               f"{format(strings.currency_format_string, symbol=strings.currency_symbol, value=self.price)}"
+
+    def __repr__(self):
+        return f"<Product {self.name}>"
+
+    # TODO: add get image (and set image?) method(s)
+
+
+class Transactions(TableDeclarativeBase):
+    """A greed wallet transaction.
+    Wallet credit ISN'T calculated from these, but they can be used to recalculate it."""
+
+    # The internal transaction ID
+    transaction_id = Column(BigInteger, primary_key=True)
+    # The user whose credit is affected by this transaction
+    user_id = Column(BigInteger, ForeignKey("users.id"), nullable=False)
+    # The value of this transaction. Can be both negative and positive.
+    value = Column(Numeric, nullable=False)
+    # Extra notes on the transaction
+    notes = Column(Text)
+
+    # TODO: there still are some missing fields

strings.py

@@ -2,6 +2,15 @@
 # Can be edited, but DON'T REMOVE THE REPLACEMENT FIELDS (words surrounded by {curly braces})
 # TODO: maybe add a preformat to all strings in this file
 
+# Currency symbol
+currency_symbol = "€"
+
+# Positioning of the currency symbol
+currency_format_string = "{symbol} {value}"
+
+# Quantity of a product in stock
+in_stock_format_string = "{quantity} disponibili"
+
 # Answer: the start command was sent and the bot should welcome the user
 conversation_after_start = "Ciao!\n" \
                            "Benvenuto su greed!"