"""CRUD des affectations. Une affectation est valide dès sa création (pas
d'étape de confirmation). La création passe par le moteur de validation : une
violation bloquante interdit l'enregistrement, les avertissements sont
renvoyés."""

import uuid

from fastapi import APIRouter, Depends, HTTPException, Response, status
from sqlmodel import Session, select

from app.api._common import owned_or_404
from app.api.deps import get_edition
from app.api.schemas import (
    AssignmentCreate,
    AssignmentRead,
    AssignmentUpdate,
    AssignmentValidateRequest,
    AssignmentValidateResult,
    AssignmentWriteResult,
)
from app.auth.deps import (
    current_account_in_edition,
    ensure_can_write_shift,
    require_staff,
)
from app.db import get_session
from app.models import Account, Assignment, Edition, Role, Shift, Volunteer
from app.validation import has_blocking, validate
from app.validation.loader import build_validation_input

router = APIRouter(
    prefix="/editions/{edition_id}/assignments", tags=["assignments"]
)


def _pair_or_422(
    session: Session, edition_id: uuid.UUID, volunteer_id: uuid.UUID, shift_id: uuid.UUID
) -> tuple[Volunteer, Shift]:
    volunteer = session.get(Volunteer, volunteer_id)
    shift = session.get(Shift, shift_id)
    if (
        volunteer is None
        or shift is None
        or volunteer.edition_id != edition_id
        or shift.edition_id != edition_id
    ):
        raise HTTPException(
            status_code=422, detail={"code": "assignment.wrong_edition"}
        )
    return volunteer, shift


def _forbidden() -> HTTPException:
    return HTTPException(status_code=403, detail={"code": "error.forbidden"})


def _ensure_can_read(account: Account, volunteer_id: uuid.UUID) -> None:
    if account.role in (Role.COORDINATOR, Role.LEAD):
        return
    if account.volunteer_id == volunteer_id:
        return
    raise _forbidden()


@router.post(
    "/validate", response_model=AssignmentValidateResult, tags=["assignments"]
)
def validate_assignment(
    payload: AssignmentValidateRequest,
    edition: Edition = Depends(get_edition),
    _guard: Account = Depends(require_staff),
    session: Session = Depends(get_session),
) -> AssignmentValidateResult:
    volunteer, shift = _pair_or_422(
        session, edition.id, payload.volunteer_id, payload.shift_id
    )
    violations = validate(
        build_validation_input(
            session=session, edition=edition, volunteer=volunteer, shift=shift
        )
    )
    return AssignmentValidateResult(
        blocking=has_blocking(violations), violations=violations
    )


@router.post(
    "", response_model=AssignmentWriteResult, status_code=status.HTTP_201_CREATED
)
def create_assignment(
    payload: AssignmentCreate,
    edition: Edition = Depends(get_edition),
    account: Account = Depends(current_account_in_edition),
    session: Session = Depends(get_session),
) -> AssignmentWriteResult:
    volunteer, shift = _pair_or_422(
        session, edition.id, payload.volunteer_id, payload.shift_id
    )
    ensure_can_write_shift(account, session, shift)
    existing = session.exec(
        select(Assignment)
        .where(Assignment.volunteer_id == volunteer.id)
        .where(Assignment.shift_id == shift.id)
    ).first()
    if existing is not None:
        raise HTTPException(
            status_code=409, detail={"code": "assignment.duplicate"}
        )

    violations = validate(
        build_validation_input(
            session=session,
            edition=edition,
            volunteer=volunteer,
            shift=shift,
        )
    )
    if has_blocking(violations):
        raise HTTPException(
            status_code=422,
            detail={
                "code": "error.validation_failed",
                "violations": [v.model_dump() for v in violations],
            },
        )

    assignment = Assignment(
        edition_id=edition.id,
        volunteer_id=volunteer.id,
        shift_id=shift.id,
        source=payload.source,
        locked=payload.locked,
    )
    session.add(assignment)
    session.commit()
    session.refresh(assignment)
    return AssignmentWriteResult(assignment=assignment, warnings=violations)


@router.get("", response_model=list[AssignmentRead])
def list_assignments(
    volunteer_id: uuid.UUID | None = None,
    shift_id: uuid.UUID | None = None,
    edition: Edition = Depends(get_edition),
    account: Account = Depends(current_account_in_edition),
    session: Session = Depends(get_session),
) -> list[Assignment]:
    if account.role is Role.VOLUNTEER:
        # Un bénévole ne voit que ses propres affectations.
        if volunteer_id not in (None, account.volunteer_id):
            raise _forbidden()
        volunteer_id = account.volunteer_id
    stmt = select(Assignment).where(Assignment.edition_id == edition.id)
    if volunteer_id is not None:
        stmt = stmt.where(Assignment.volunteer_id == volunteer_id)
    if shift_id is not None:
        stmt = stmt.where(Assignment.shift_id == shift_id)
    return list(session.exec(stmt))


@router.get("/{assignment_id}", response_model=AssignmentRead)
def get_assignment(
    assignment_id: uuid.UUID,
    edition: Edition = Depends(get_edition),
    account: Account = Depends(current_account_in_edition),
    session: Session = Depends(get_session),
) -> Assignment:
    assignment = owned_or_404(
        session.get(Assignment, assignment_id), edition.id
    )
    _ensure_can_read(account, assignment.volunteer_id)
    return assignment


@router.patch("/{assignment_id}", response_model=AssignmentWriteResult)
def update_assignment(
    assignment_id: uuid.UUID,
    payload: AssignmentUpdate,
    edition: Edition = Depends(get_edition),
    account: Account = Depends(current_account_in_edition),
    session: Session = Depends(get_session),
) -> AssignmentWriteResult:
    assignment = owned_or_404(
        session.get(Assignment, assignment_id), edition.id
    )
    ensure_can_write_shift(
        account, session, session.get(Shift, assignment.shift_id)
    )
    changes = payload.model_dump(exclude_unset=True)
    for field, value in changes.items():
        setattr(assignment, field, value)

    # `source` / `locked` ne changent pas le résultat de validation ; on le
    # rejoue seulement pour renvoyer les avertissements courants.
    warnings = validate(
        build_validation_input(
            session=session,
            edition=edition,
            volunteer=session.get(Volunteer, assignment.volunteer_id),
            shift=session.get(Shift, assignment.shift_id),
            exclude_assignment_id=assignment.id,
        )
    )
    session.commit()
    session.refresh(assignment)
    return AssignmentWriteResult(assignment=assignment, warnings=warnings)


@router.delete("/{assignment_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_assignment(
    assignment_id: uuid.UUID,
    edition: Edition = Depends(get_edition),
    account: Account = Depends(current_account_in_edition),
    session: Session = Depends(get_session),
) -> Response:
    assignment = owned_or_404(
        session.get(Assignment, assignment_id), edition.id
    )
    ensure_can_write_shift(
        account, session, session.get(Shift, assignment.shift_id)
    )
    session.delete(assignment)
    session.commit()
    return Response(status_code=status.HTTP_204_NO_CONTENT)