import inspect

from django.utils import timezone

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'), start=1):
        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 = -1
        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


def cmp_billed_until_or_registered_on(a, b):
    """
    1) billed_until greater first
    2) registered_on smaller first
    """
    if a.billed_until == b.billed_until:
        return (a.registered_on-b.registered_on).days
    elif a.billed_until and b.billed_until:
        return (b.billed_until-a.billed_until).days
    elif a.billed_until:
        return (b.registered_on-a.billed_until).days
    return (b.billed_until-a.registered_on).days


class Interval(object):
    def __init__(self, ini, end, order=None):
        self.ini = ini
        self.end = end
        self.order = order
    
    def __len__(self):
        return max((self.end-self.ini).days, 0)
    
    def __sub__(self, other):
        remaining = []
        if self.ini < other.ini:
            remaining.append(Interval(self.ini, min(self.end, other.ini), self.order))
        if self.end > other.end:
            remaining.append(Interval(max(self.ini,other.end), self.end, self.order))
        return remaining
    
    def __repr__(self):
        now = timezone.now()
        return "Start: %s    End: %s" % ((self.ini-now).days, (self.end-now).days)
    
    def intersect(self, other, remaining_self=None, remaining_other=None):
        if remaining_self is not None:
            remaining_self += (self - other)
        if remaining_other is not None:
            remaining_other += (other - self)
        result = Interval(max(self.ini, other.ini), min(self.end, other.end), self.order)
        if len(result)>0:
            return result
        else:
            return None
    
    def intersect_set(self, others, remaining_self=None, remaining_other=None):
        intersections = []
        for interval in others:
            intersection = self.intersect(interval, remaining_self, remaining_other)
            if intersection:
                intersections.append(intersection)
        return intersections
    

def get_intersections(order_intervals, compensations):
    intersections = []
    for compensation in compensations:
        intersection = compensation.intersect_set(order_intervals)
        length = 0
        for intersection_interval in intersection:
            length += len(intersection_interval)
        intersections.append((length, compensation))
    intersections.sort()
    return intersections

# Intervals should not overlap
def intersect(compensation, order_intervals):
    compensated = []
    not_compensated = []
    unused_compensation = []
    for interval in order_intervals:
        compensated.append(compensation.intersect(interval, unused_compensation, not_compensated))
    return (compensated, not_compensated, unused_compensation)

def apply_compensation(order, compensation):
    remaining_order = []
    remaining_compensation = []
    applied_compensation = compensation.intersect_set(order, remaining_compensation, remaining_order)
    return applied_compensation, remaining_order, remaining_compensation

# TODO can be optimized
def update_intersections(not_compensated, compensations):
    compensation_intervals = []
    for __, compensation in compensations:
        compensation_intervals.append(compensation)
    return get_intersections(not_compensated, compensation_intervals)


def compensate(order, compensations):
    remaining_interval = [order]
    ordered_intersections = get_intersections(remaining_interval, compensations)
    applied_compensations = []
    remaining_compensations = []
    while ordered_intersections and ordered_intersections[len(ordered_intersections)-1][0]>0:
        # Apply the first compensation:
        __, compensation = ordered_intersections.pop()
        (applied_compensation, remaining_interval, remaining_compensation) = apply_compensation(remaining_interval, compensation)
        remaining_compensations += remaining_compensation
        applied_compensations += applied_compensation
        ordered_intersections = update_intersections(remaining_interval, ordered_intersections)
    for __, compensation in ordered_intersections:
        remaining_compensations.append(compensation)
    return remaining_compensations, applied_compensations