"""Async SQLAlchemy engine, session factory, and Base model."""
from __future__ import annotations

from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase

from app.config import settings

engine = create_async_engine(settings.database_url, echo=False, pool_pre_ping=True)
SessionLocal = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)


class Base(DeclarativeBase):
    pass


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with SessionLocal() as session:
        yield session


async def init_db() -> None:
    """Create tables and apply lightweight dev migrations."""
    from app import models  # noqa: F401
    from sqlalchemy import text

    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
        # Dev migration: locations → vessels (rename legacy table/columns)
        await conn.execute(
            text(
                """
                DO $$
                BEGIN
                  IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'locations')
                     AND NOT EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'vessels')
                  THEN
                    ALTER TABLE locations RENAME TO vessels;
                  END IF;
                  IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'devices' AND column_name = 'location_id')
                  THEN
                    ALTER TABLE devices RENAME COLUMN location_id TO vessel_id;
                  END IF;
                  IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'tasks' AND column_name = 'location_id')
                  THEN
                    ALTER TABLE tasks RENAME COLUMN location_id TO vessel_id;
                  END IF;
                  IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'devices' AND column_name = 'catalog_key')
                  THEN
                    ALTER TABLE devices ADD COLUMN catalog_key VARCHAR(64);
                  END IF;
                END $$;
                """
            )
        )
        # Indexes for hot query paths (idempotent; covers pre-existing DBs).
        for stmt in (
            "CREATE INDEX IF NOT EXISTS ix_tasks_vessel_id ON tasks (vessel_id)",
            "CREATE INDEX IF NOT EXISTS ix_task_events_task_id_id ON task_events (task_id, id)",
            "CREATE INDEX IF NOT EXISTS ix_approval_requests_task_status "
            "ON approval_requests (task_id, status)",
        ):
            await conn.execute(text(stmt))