Add migration support with Alembic; implement migration scripts and configuration

migration/README

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+Generic single-database configuration.

migration/alembic_scipt.py

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+import os
+from alembic.config import Config
+from alembic.script import ScriptDirectory
+from alembic.runtime.migration import MigrationContext
+from alembic import command
+from sqlalchemy import create_engine
+from alembic import command
+from dotenv import load_dotenv
+import logging
+
+#Logging
+
+logging.basicConfig(
+    filename='app.log',  # Log to a file
+    level=logging.DEBUG,  # Log everything (DEBUG and above)
+    format='%(asctime)s %(levelname)s %(message)s'
+)
+
+logging.info('Application started')
+try:
+    logging.debug('Debug info here')
+except Exception as e:
+    logging.exception('An error occurred')
+
+
+load_dotenv()
+db_name = os.getenv("DB_NAME")
+db_psswd = os.getenv("DB_PASSWORD")
+db_user = os.getenv("DB_USER")
+db_port = os.getenv("DB_PORT") or "3306"
+db_host = os.getenv("DB_HOST")
+if db_host == None:
+    os._exit(1)
+engine_url = f"mariadb+mariadbconnector://{db_user}:{db_psswd}@{db_host}:{db_port}/{db_name}"
+
+base_dir = os.path.dirname(__file__)
+ini_path = os.path.join(base_dir, "..", "alembic.ini")
+alembic_cfg = Config(ini_path)
+alembic_cfg.set_section_option(alembic_cfg.config_ini_section, "sqlalchemy.url", engine_url)
+script = ScriptDirectory.from_config(alembic_cfg)
+
+engine = create_engine(engine_url)
+
+def check_db():
+    with engine.connect() as conn:
+        context = MigrationContext.configure(conn)
+        current_rev = context.get_current_revision()
+    head_rev = script.get_current_head()
+    if current_rev != head_rev:
+        command.upgrade(alembic_cfg, "head")
+        return False
+
+def auto_lookup():
+    command.revision(alembic_cfg, message="add tables and rows", autogenerate=True)
+    script = ScriptDirectory.from_config(alembic_cfg)
+    head_rev = script.get_revision(script.get_current_head())
+    with open(head_rev.path) as f:
+        content = f.read()
+    if "pass\n    # ### end Alembic commands ###" in content:
+        os.remove(head_rev.path)
+        command.stamp(alembic_cfg, "head")
+        logging.info("No changes DB detected")
+    else:
+        command.upgrade(alembic_cfg, "head")
+        logging.info("New DB changes, upgrade table")
+
+auto_lookup()

migration/env.py

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+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+from models import Base
+
+metadata = Base.metadata
+
+# 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.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+target_metadata = metadata
+
+# 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 run_migrations_offline() -> None:
+    """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=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)

migration/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, Sequence[str], None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}