"""SQLAlchemy engine for the warehouse.

Per-connection defaults (search_path, statement_timeout) are baked into the
engine via libpq's `options` connect_arg so we never SET them at the SQL
layer. Read-only mode for query execution is requested via SQLAlchemy's
`execution_options(postgresql_readonly=True)`.
"""

from __future__ import annotations

from functools import lru_cache

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine

from api.config import get_settings

SCHEMA = "financial"
DEFAULT_STATEMENT_TIMEOUT_MS = 10_000


@lru_cache(maxsize=1)
def get_engine() -> Engine:
    url = get_settings().database_url
    if url.startswith("postgresql://"):
        url = url.replace("postgresql://", "postgresql+psycopg://", 1)
    return create_engine(
        url,
        pool_pre_ping=True,
        future=True,
        # libpq -c options run before any SQL the app issues — no need to
        # SET search_path / statement_timeout at execution time.
        connect_args={
            "options": (
                f"-c search_path={SCHEMA},public "
                f"-c statement_timeout={DEFAULT_STATEMENT_TIMEOUT_MS}"
            ),
        },
    )