import inspect

from orchestra.apps.accounts.models import Account


def get_related_objects(origin, max_depth=2):
    """
    Introspects origin object and return the first related service object
    
    WARNING this is NOT an exhaustive search but a compromise between cost and
            flexibility. A more comprehensive approach may be considered if
            a use-case calls for it.
    """
    
    def related_iterator(node):
        for field in node._meta.virtual_fields:
            if hasattr(field, 'ct_field'):
                yield getattr(node, field.name)
        for field in node._meta.fields:
            if field.rel:
                yield getattr(node, field.name)
    
    # BFS model relation transversal
    queue = [[origin]]
    while queue:
        models = queue.pop(0)
        if len(models) > max_depth:
            return None
        node = models[-1]
        if len(models) > 1:
            if hasattr(node, 'account') or isinstance(node, Account):
                return node
        for related in related_iterator(node):
            if related and related not in models:
                new_models = list(models)
                new_models.append(related)
                queue.append(new_models)

def get_register_or_cancel_events(porders, order, ini, end):
    assert ini <= end, "ini > end"
    CANCEL = 'cancel'
    REGISTER = 'register'
    changes = {}
    counter = 0
    for num, porder in enumerate(porders.order_by('registered_on')):
        if porder == order:
            position = num
        if porder.cancelled_on:
            cancel = porder.cancelled_on
            if porder.billed_until and porder.cancelled_on < porder.billed_until:
                cancel = porder.billed_until
            if cancel > ini and cancel < end:
                changes.setdefault(cancel, [])
                changes[cancel].append((CANCEL, num))
        if porder.registered_on <= ini:
            counter += 1
        elif porder.registered_on < end:
            changes.setdefault(porder.registered_on, [])
            changes[porder.registered_on].append((REGISTER, num))
    pointer = ini
    total = float((end-ini).days)
    for date in sorted(changes.keys()):
        yield counter, position, (date-pointer).days/total
        for change, num in changes[date]:
            if change is CANCEL:
                counter -= 1
                if num < position:
                    position -= 1
            else:
                counter += 1
        pointer = date
    yield counter, position, (end-pointer).days/total


def get_register_or_renew_events(handler, porders, order, ini, end):
    total = float((end-ini).days)
    for sini, send in handler.get_pricing_slots(ini, end):
        counter = 0
        position = 0
        for porder in porders.order_by('registered_on'):
            if porder == order:
                position = abs(position)
            elif position < 0:
                position -= 1
            if porder.registered_on >= sini and porder.registered_on < send:
                counter += 1
            elif porder.billed_until > send or porder.cancelled_on > send:
                counter += 1
        yield counter, position, (send-sini)/total