"""Coding queue and batch coding operations for Gutachten classification."""

from datetime import datetime, timezone

from sqlalchemy.orm import Session

from app.core.exceptions import CaseNotFoundError
from app.models.case import Case


def get_coding_queue(
    db: Session,
    fallgruppe: str | None = None,
    page: int = 1,
    per_page: int = 50,
) -> tuple[list[Case], int]:
    """Get cases with gutachten=True but no gutachten_typ yet.

    These cases have received a Gutachten but still need classification
    (Bestaetigung/Alternative) and therapy-change coding.

    Returns:
        Tuple of (cases, total_count) for pagination.
    """
    query = db.query(Case).filter(
        Case.gutachten == True,  # noqa: E712
        Case.gutachten_typ == None,  # noqa: E711
    )
    if fallgruppe:
        query = query.filter(Case.fallgruppe == fallgruppe)

    total = query.count()
    cases = (
        query.order_by(Case.datum.desc())
        .offset((page - 1) * per_page)
        .limit(per_page)
        .all()
    )
    return cases, total


def update_coding(
    db: Session,
    case_id: int,
    gutachten_typ: str,
    therapieaenderung: str,
    ta_diagnosekorrektur: bool = False,
    ta_unterversorgung: bool = False,
    ta_uebertherapie: bool = False,
    user_id: int | None = None,
) -> Case:
    """Set coding for a single case.

    Validates gutachten_typ and therapieaenderung values, then persists the
    coding classification along with the user and timestamp.

    Raises:
        CaseNotFoundError: If no case with the given ID exists.
        ValueError: If gutachten_typ or therapieaenderung have invalid values.
    """
    case = db.query(Case).filter(Case.id == case_id).first()
    if not case:
        raise CaseNotFoundError()

    if gutachten_typ not in ("Bestätigung", "Alternative"):
        raise ValueError(f"Invalid gutachten_typ: {gutachten_typ}")
    if therapieaenderung not in ("Ja", "Nein"):
        raise ValueError(f"Invalid therapieaenderung: {therapieaenderung}")

    case.gutachten_typ = gutachten_typ
    case.therapieaenderung = therapieaenderung
    case.ta_diagnosekorrektur = ta_diagnosekorrektur
    case.ta_unterversorgung = ta_unterversorgung
    case.ta_uebertherapie = ta_uebertherapie
    case.coding_completed_by = user_id
    case.coding_completed_at = datetime.now(timezone.utc)

    db.commit()
    db.refresh(case)
    return case


def batch_update_coding(
    db: Session,
    updates: list[dict],
    user_id: int | None = None,
) -> dict:
    """Batch update coding for multiple cases.

    Each dict in *updates* must contain at minimum:
        - ``case_id`` (int)
        - ``gutachten_typ`` (str)
        - ``therapieaenderung`` (str)
    and optionally the ``ta_*`` boolean flags.

    Returns:
        Dict with ``updated`` count and ``errors`` list of error messages.
    """
    updated = 0
    errors: list[str] = []
    for item in updates:
        case_id = item.get("case_id")
        try:
            params = {k: v for k, v in item.items() if k != "case_id"}
            update_coding(db, case_id, user_id=user_id, **params)
            updated += 1
        except Exception as exc:
            errors.append(f"Case {case_id}: {exc}")
    return {"updated": updated, "errors": errors}