"""Application commands for document persistence and audience updates."""

import logging
from collections.abc import Mapping, Sequence
from dataclasses import dataclass
from typing import Any

from django.contrib.auth import get_user_model
from django.db import transaction
from django.db.models import Q

from documents.models import Document, DocumentTag
from documents.notifications.handlers import notify_document_audience
from employees.models import Department


logger = logging.getLogger(__name__)
User = get_user_model()


@dataclass(frozen=True)
class DocumentAudienceUpdate:
    recipient_ids: Sequence[int] | None = None
    department_ids: Sequence[int] | None = None
    acknowledgement_recipient_ids: Sequence[int] | None = None
    acknowledgement_department_ids: Sequence[int] | None = None
    tag_ids: Sequence[int] | None = None


def _set_departments(document: Document, department_ids: Sequence[int]) -> None:
    departments = Department.objects.filter(id__in=set(department_ids))
    document.departments.set(departments)
    logger.debug(
        "Document departments updated",
        extra={
            "event": "document.departments.updated",
            "document_id": document.id,
            "requested_count": len(department_ids),
            "updated_count": departments.count(),
        },
    )


def _set_recipients(document: Document, recipient_ids: Sequence[int]) -> None:
    existing_ids = set(document.recipients.values_list("id", flat=True))
    recipients = User.objects.visible_in_ui(include_ids=existing_ids).filter(
        id__in=set(recipient_ids)
    ).filter(
        Q(is_active=True) | Q(id__in=existing_ids)
    )
    document.recipients.set(recipients)
    logger.debug(
        "Document recipients updated",
        extra={
            "event": "document.recipients.updated",
            "document_id": document.id,
            "requested_count": len(recipient_ids),
            "updated_count": recipients.count(),
        },
    )


def _set_acknowledgement_departments(
    document: Document,
    department_ids: Sequence[int],
) -> None:
    document.acknowledgement_departments.set(
        Department.objects.filter(id__in=set(department_ids))
    )


def _set_acknowledgement_recipients(
    document: Document,
    recipient_ids: Sequence[int],
) -> None:
    existing_ids = set(
        document.acknowledgement_recipients.values_list("id", flat=True)
    )
    recipients = User.objects.visible_in_ui(include_ids=existing_ids).filter(
        id__in=set(recipient_ids)
    ).filter(
        Q(is_active=True) | Q(id__in=existing_ids)
    )
    document.acknowledgement_recipients.set(recipients)


def _set_tags(document: Document, tag_ids: Sequence[int]) -> None:
    tags = DocumentTag.objects.filter(id__in=set(tag_ids))
    document.tags.set(tags)
    logger.debug(
        "Document tags updated",
        extra={
            "event": "document.tags.updated",
            "document_id": document.id,
            "requested_count": len(tag_ids),
            "updated_count": tags.count(),
        },
    )


def _apply_audience_update(
    document: Document,
    audience: DocumentAudienceUpdate,
) -> None:
    if not document.acknowledgement_required or document.acknowledgement_for_all:
        document.acknowledgement_recipients.clear()
        document.acknowledgement_departments.clear()
    else:
        if audience.acknowledgement_department_ids is not None:
            _set_acknowledgement_departments(
                document,
                audience.acknowledgement_department_ids,
            )
        if audience.acknowledgement_recipient_ids is not None:
            _set_acknowledgement_recipients(
                document,
                audience.acknowledgement_recipient_ids,
            )

    if document.sent_to_all:
        document.recipients.clear()
        document.departments.clear()
    else:
        if audience.department_ids is not None:
            _set_departments(document, audience.department_ids)
        if audience.recipient_ids is not None:
            _set_recipients(document, audience.recipient_ids)

    if audience.tag_ids is not None:
        _set_tags(document, audience.tag_ids)


@transaction.atomic
def create_document(
    *,
    uploader,
    attributes: Mapping[str, Any],
    audience: DocumentAudienceUpdate,
) -> Document:
    """Create a document, apply its audience and emit one final notification."""
    logger.info(
        "Document creation started",
        extra={
            "event": "document.creation.started",
            "sent_to_all": attributes.get("sent_to_all", True),
            "department_count": len(audience.department_ids or ()),
            "recipient_count": len(audience.recipient_ids or ()),
            "tag_count": len(audience.tag_ids or ()),
            "uploader_id": uploader.id if uploader else None,
        },
    )

    document = Document(uploaded_by=uploader, **dict(attributes))
    document._suppress_document_notifications = True
    document.save()
    _apply_audience_update(document, audience)

    document._suppress_document_notifications = False
    notify_document_audience(document)
    logger.info(
        "Document created",
        extra={
            "event": "document.created",
            "document_id": document.id,
            "sent_to_all": document.sent_to_all,
            "uploader_id": uploader.id if uploader else None,
        },
    )
    return document


@transaction.atomic
def update_document(
    *,
    document_id: int,
    attributes: Mapping[str, Any],
    audience: DocumentAudienceUpdate,
) -> Document:
    """Update document fields and all supplied audience relations atomically."""
    document = Document.objects.select_for_update().get(pk=document_id)
    for field, value in attributes.items():
        setattr(document, field, value)
    document.save()
    _apply_audience_update(document, audience)
    return document