import logging

from django.db import transaction
from django.db.models import Q, Sum
from django.db.models.functions import Coalesce
from django.utils import timezone

from manufacturing.models import EntityOperation
from shiftflow.models import DealEntityProgress, DealItem, ProductionTask, WorkItem

logger = logging.getLogger('mes')


def _workitem_op_code(wi: WorkItem) -> str:
    if getattr(wi, 'operation_id', None) and getattr(wi, 'operation', None):
        code = (wi.operation.code or '').strip()
        if code:
            return code
    return (wi.stage or '').strip()


def _target_qty_for_workitem(wi: WorkItem) -> int | None:
    if getattr(wi, 'delivery_batch_id', None):
        qty = (
            ProductionTask.objects.filter(
                deal_id=wi.deal_id,
                delivery_batch_id=wi.delivery_batch_id,
                entity_id=wi.entity_id,
            )
            .values_list('quantity_ordered', flat=True)
            .first()
        )
        return int(qty) if qty is not None else None

    di = DealItem.objects.filter(deal_id=wi.deal_id, entity_id=wi.entity_id).first()
    return int(di.quantity) if di else None


@transaction.atomic
def advance_progress_and_generate_next_workitem(*, workitem_id: int) -> int | None:
    wi = (
        WorkItem.objects.select_for_update(of=('self',))
        .select_related('operation')
        .filter(id=int(workitem_id))
        .first()
    )
    if not wi:
        return None

    op_code = _workitem_op_code(wi)
    if not op_code:
        return None

    target_qty = _target_qty_for_workitem(wi)
    if target_qty is None:
        return None

    progress, _ = DealEntityProgress.objects.select_for_update(of=('self',)).get_or_create(
        deal_id=wi.deal_id,
        delivery_batch_id=(int(wi.delivery_batch_id) if getattr(wi, 'delivery_batch_id', None) else None),
        entity_id=wi.entity_id,
        defaults={'current_seq': 1},
    )

    cur = int(progress.current_seq or 1)
    cur_eo = EntityOperation.objects.select_related('operation').filter(entity_id=wi.entity_id, seq=cur).first()
    if not cur_eo or not cur_eo.operation:
        return None

    cur_code = (cur_eo.operation.code or '').strip()
    if cur_code != op_code:
        return None

    wi_qs = WorkItem.objects.filter(deal_id=wi.deal_id, entity_id=wi.entity_id).filter(Q(operation__code=op_code) | Q(stage=op_code))
    if getattr(wi, 'delivery_batch_id', None):
        wi_qs = wi_qs.filter(delivery_batch_id=wi.delivery_batch_id)
    else:
        wi_qs = wi_qs.filter(delivery_batch_id__isnull=True)

    total_done = wi_qs.aggregate(s=Coalesce(Sum('quantity_done'), 0))['s']
    if int(total_done or 0) < int(target_qty):
        return None

    progress.current_seq = cur + 1
    progress.save(update_fields=['current_seq'])

    next_eo = (
        EntityOperation.objects.select_related('operation', 'operation__workshop')
        .filter(entity_id=wi.entity_id, seq=int(progress.current_seq))
        .first()
    )
    if not next_eo or not next_eo.operation:
        return None

    next_op = next_eo.operation
    next_code = (next_op.code or '').strip()

    planned_qs = WorkItem.objects.filter(deal_id=wi.deal_id, entity_id=wi.entity_id)
    if getattr(wi, 'delivery_batch_id', None):
        planned_qs = planned_qs.filter(delivery_batch_id=wi.delivery_batch_id)
    else:
        planned_qs = planned_qs.filter(delivery_batch_id__isnull=True)

    planned_total = planned_qs.filter(Q(operation_id=next_op.id) | Q(operation__code=next_code) | Q(stage=next_code)).aggregate(
        s=Coalesce(Sum('quantity_plan'), 0)
    )['s']

    remaining_to_plan = max(0, int(target_qty) - int(planned_total or 0))
    if remaining_to_plan <= 0:
        return None

    created = WorkItem.objects.create(
        deal_id=wi.deal_id,
        delivery_batch_id=(int(wi.delivery_batch_id) if getattr(wi, 'delivery_batch_id', None) else None),
        entity_id=wi.entity_id,
        operation_id=next_op.id,
        stage=(next_code or next_op.name or '')[:32],
        workshop_id=(int(next_op.workshop_id) if getattr(next_op, 'workshop_id', None) else None),
        machine_id=None,
        quantity_plan=int(remaining_to_plan),
        quantity_done=0,
        status='planned',
        date=timezone.localdate(),
    )
    logger.info(
        'route_flow:created_next_workitem id=%s deal_id=%s batch_id=%s entity_id=%s op=%s qty=%s',
        created.id,
        created.deal_id,
        getattr(created, 'delivery_batch_id', None),
        created.entity_id,
        next_code or '',
        created.quantity_plan,
    )
    return int(created.id)