"""Small production-schema compatibility helpers.

The project has legacy production databases where some columns may not exist yet.
Use these helpers before introducing optional-column SQL in UI/services.
"""
from __future__ import annotations

from functools import lru_cache

from sqlalchemy import text

from app.db import engine


@lru_cache(maxsize=256)
def has_column(table_name: str, column_name: str, schema_name: str = "public") -> bool:
    table_name = str(table_name or "").strip()
    column_name = str(column_name or "").strip()
    schema_name = str(schema_name or "public").strip() or "public"
    if not table_name or not column_name:
        return False
    with engine.begin() as conn:
        return bool(conn.execute(text("""
            SELECT 1
            FROM information_schema.columns
            WHERE table_schema = :schema_name
              AND table_name = :table_name
              AND column_name = :column_name
            LIMIT 1
        """), {
            "schema_name": schema_name,
            "table_name": table_name,
            "column_name": column_name,
        }).scalar())


def opportunity_customer_column() -> str:
    """Return the customer link column supported by this deployment."""
    if has_column("opportunities", "fiscal_customer_id"):
        return "fiscal_customer_id"
    return "local_customer_id"