"""Job number lookup abstraction — the seam for the future Infor VISUAL ERP
integration.

Today, Job Number is free text: the default NullJobLookupService accepts any
value and returns no enrichment. When PESCO is ready to integrate VISUAL,
implement VisualJobLookupService below, set JOB_LOOKUP_PROVIDER=visual (plus
the VISUAL_DB_* variables) in .env, and restart — no schema or frontend
changes required:

* the NCR schema already stores the job number exactly as entered, plus a
  related `job_info` row (part_id, part_description, customer_name,
  work_order_status) that any provider can populate at NCR creation;
* the frontend job-number field already calls GET /api/jobs/{job_number}/lookup
  as the user types and displays whatever enrichment comes back, so
  validation/autocomplete light up automatically with a real provider.
"""
import logging
from dataclasses import dataclass
from typing import Protocol

from app.config import get_settings

logger = logging.getLogger(__name__)


@dataclass
class JobInfoData:
    part_id: str | None = None
    part_description: str | None = None
    customer_name: str | None = None
    work_order_status: str | None = None
    source: str = "null"


class JobLookupService(Protocol):
    async def lookup(self, job_number: str) -> JobInfoData | None:
        """Return read-only enrichment for a job number, or None when the job
        is unknown / the provider has nothing to add. Implementations must
        never raise for a merely-unknown job number."""
        ...


class NullJobLookupService:
    """Default provider: job numbers are accepted as-is, no enrichment."""

    async def lookup(self, job_number: str) -> JobInfoData | None:  # noqa: ARG002
        return None


class VisualJobLookupService:
    """PLACEHOLDER for the future Infor VISUAL Manufacturing (SQL Server)
    integration. Not implemented yet — selecting JOB_LOOKUP_PROVIDER=visual
    today raises at startup with a pointer here.

    Implementation notes (verified against PESCO's VISUAL 10 schema):

    * Connect read-only to the VISUAL SQL Server database (VISUAL_DB_* env
      vars) with a dedicated SELECT-only SQL login. Use `aioodbc` or `pymssql`.
      NEVER write to VISUAL tables — hundreds of triggers maintain derived
      values and direct writes bypass application validation.

    * A PESCO "job number" corresponds to a work order base id (typically
      with lot/split/sub qualifiers). WORK_ORDER's primary key is composite:
      (TYPE, BASE_ID, LOT_ID, SPLIT_ID, SUB_ID); manufacturing work orders
      have TYPE = 'W'. Parse the entered job number into BASE_ID (and LOT_ID
      when the shop uses BASE/LOT notation, e.g. "12345/1") and query:

        SELECT TOP 1 wo.BASE_ID, wo.LOT_ID, wo.SUB_ID, wo.PART_ID,
                     wo.STATUS, wo.DESIRED_QTY, wo.CREATE_DATE,
                     p.DESCRIPTION AS PART_DESCRIPTION
        FROM WORK_ORDER wo
        LEFT JOIN PART p ON p.ID = wo.PART_ID
        WHERE wo.TYPE = 'W' AND wo.BASE_ID = :base_id
        ORDER BY wo.LOT_ID, wo.SPLIT_ID, wo.SUB_ID

      STATUS is a one-char code (R=released, C=closed, etc.) — map it to a
      readable label for work_order_status.

    * Customer enrichment goes through the demand/supply linkage:
      DEMAND_SUPPLY_LINK rows with SUPPLY_TYPE='WO' and SUPPLY_BASE_ID =
      wo.BASE_ID (match SUPPLY_LOT_ID/SUPPLY_SPLIT_ID/SUPPLY_SUB_ID when
      present) point at customer-order demand (DEMAND_TYPE='CO',
      DEMAND_BASE_ID = CUST_ORDER_LINE.CUST_ORDER_ID, DEMAND_SEQ_NO = line
      no). Join CUSTOMER_ORDER -> CUSTOMER for the customer name.

    * Return JobInfoData(part_id=..., part_description=...,
      customer_name=..., work_order_status=..., source="visual").
      Return None when no WORK_ORDER row matches. Wrap connection errors in
      logging + return None so an ERP outage never blocks NCR entry.
    """

    def __init__(self) -> None:
        settings = get_settings()
        raise NotImplementedError(
            "VisualJobLookupService is a documented stub. Implement it per the "
            "notes in app/services/job_lookup.py, or set JOB_LOOKUP_PROVIDER=null. "
            f"(Configured VISUAL host: {settings.visual_db_host or 'unset'})"
        )

    async def lookup(self, job_number: str) -> JobInfoData | None:
        raise NotImplementedError


_service: JobLookupService | None = None


def get_job_lookup_service() -> JobLookupService:
    global _service
    if _service is None:
        provider = get_settings().job_lookup_provider
        if provider == "visual":
            _service = VisualJobLookupService()  # raises: intentionally loud
        else:
            _service = NullJobLookupService()
        logger.info("Job lookup provider: %s", provider)
    return _service