initial structure implemented

docs -> _docs

db/connection.py

@@ -0,0 +1,49 @@
+from typing import AsyncGenerator
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+
+from models.config import DatabaseConfig
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+_engine = None
+_session_factory = None
+
+
+def get_engine(config: DatabaseConfig):
+    global _engine
+    if _engine is None:
+        url = f"postgresql+asyncpg://{config.username}:{config.password}@{config.host}:{config.port}/{config.database}"
+        _engine = create_async_engine(
+            url,
+            pool_size=config.pool_size,
+            max_overflow=config.max_overflow,
+            pool_timeout=config.pool_timeout,
+            pool_recycle=config.pool_recycle,
+        )
+    return _engine
+
+
+def get_session_factory(config: DatabaseConfig):
+    global _session_factory
+    if _session_factory is None:
+        engine = get_engine(config)
+        _session_factory = async_sessionmaker(engine, expire_on_commit=False)
+    return _session_factory
+
+
+async def get_session(config: DatabaseConfig) -> AsyncGenerator[AsyncSession, None]:
+    factory = get_session_factory(config)
+    async with factory() as session:
+        yield session
+
+
+async def init_db(config: DatabaseConfig) -> None:
+    engine = get_engine(config)
+    async with engine.begin() as conn:
+        from .models import Base
+        await conn.run_sync(Base.metadata.create_all)
+