from sqlalchemy import inspect, text
from sqlalchemy.engine import Engine


def migrate_schema(engine: Engine) -> None:
    """Apply lightweight schema updates for existing deployments."""
    inspector = inspect(engine)
    tables = set(inspector.get_table_names())
    statements: list[str] = []

    if "parse_jobs" in tables:
        columns = {col["name"] for col in inspector.get_columns("parse_jobs")}
        if "interval_seconds" not in columns:
            statements.append(
                "ALTER TABLE parse_jobs ADD COLUMN interval_seconds INTEGER NOT NULL DEFAULT 3600"
            )
        if "is_active" not in columns:
            statements.append(
                "ALTER TABLE parse_jobs ADD COLUMN is_active BOOLEAN NOT NULL DEFAULT TRUE"
            )
        if "profile_id" not in columns:
            statements.append("ALTER TABLE parse_jobs ADD COLUMN profile_id INTEGER")
        if "channel_id" not in columns:
            statements.append("ALTER TABLE parse_jobs ADD COLUMN channel_id INTEGER")

    # create_all handles new tables; FKs on existing DBs may need indexes
    if "parse_jobs" in tables:
        # Re-inspect after potential adds is not needed for FK constraints here —
        # create_all + nullable FKs are enough for MVP; optional constraints below.
        pass

    if not statements:
        return

    with engine.begin() as conn:
        for stmt in statements:
            conn.execute(text(stmt))