from typing import AsyncGenerator

from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import declarative_base

from app.core.config import settings

engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG if hasattr(settings, "DEBUG") else False,
)

async_session_factory = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

Base = declarative_base()


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise


async def seed_default_datasources(session: AsyncSession):
    from app.core.datasource_defaults import DEFAULT_DATASOURCES
    from app.models.datasource import DataSource

    for source, info in DEFAULT_DATASOURCES.items():
        existing = await session.get(DataSource, info["id"])
        if existing:
            existing.name = info["name"]
            existing.source = source
            existing.module = info["module"]
            existing.priority = info["priority"]
            existing.frequency_minutes = info["frequency_minutes"]
            existing.collector_class = source
            if existing.config is None:
                existing.config = "{}"
            continue

        session.add(
            DataSource(
                id=info["id"],
                name=info["name"],
                source=source,
                module=info["module"],
                priority=info["priority"],
                frequency_minutes=info["frequency_minutes"],
                collector_class=source,
                config="{}",
                is_active=True,
            )
        )

    await session.commit()


async def init_db():
    import app.models.user  # noqa: F401
    import app.models.gpu_cluster  # noqa: F401
    import app.models.task  # noqa: F401
    import app.models.data_snapshot  # noqa: F401
    import app.models.datasource  # noqa: F401
    import app.models.datasource_config  # noqa: F401
    import app.models.alert  # noqa: F401
    import app.models.collected_data  # noqa: F401
    import app.models.system_setting  # noqa: F401

    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
        await conn.execute(
            text(
                """
                ALTER TABLE collected_data
                ADD COLUMN IF NOT EXISTS snapshot_id INTEGER,
                ADD COLUMN IF NOT EXISTS task_id INTEGER,
                ADD COLUMN IF NOT EXISTS entity_key VARCHAR(255),
                ADD COLUMN IF NOT EXISTS is_current BOOLEAN DEFAULT TRUE,
                ADD COLUMN IF NOT EXISTS previous_record_id INTEGER,
                ADD COLUMN IF NOT EXISTS change_type VARCHAR(20),
                ADD COLUMN IF NOT EXISTS change_summary JSONB DEFAULT '{}'::jsonb,
                ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ
                """
            )
        )
        await conn.execute(
            text(
                """
                ALTER TABLE collection_tasks
                ADD COLUMN IF NOT EXISTS phase VARCHAR(30) DEFAULT 'queued'
                """
            )
        )
        await conn.execute(
            text(
                """
                CREATE INDEX IF NOT EXISTS idx_collected_data_source_source_id
                ON collected_data (source, source_id)
                """
            )
        )
        await conn.execute(
            text(
                """
                UPDATE collected_data
                SET entity_key = source || ':' || COALESCE(source_id, id::text)
                WHERE entity_key IS NULL
                """
            )
        )
        await conn.execute(
            text(
                """
                UPDATE collected_data
                SET is_current = TRUE
                WHERE is_current IS NULL
                """
            )
        )

    async with async_session_factory() as session:
        await seed_default_datasources(session)