from django.db.models.signals import post_save, m2m_changed, pre_delete
from django.dispatch import receiver
from django.utils.translation import gettext_lazy as _

from AKModel.availability.models import Availability
from AKModel.models import AK, AKSlot, Room, Event, AKOwner, ConstraintViolation


def update_constraint_violations(new_violations, existing_violations_to_check):
    """
    Update existing constraint violations (subset for which new violations were computed) based on these new violations.
    This will add all new violations without a match, preserve the matching ones
    and delete the obsolete ones (those without a match from the newly calculated violations).

    :param new_violations: list of new (not yet saved) violations that exist after the last change
    :type new_violations: list[ConstraintViolation]
    :param existing_violations_to_check: list of related violations currently in the db
    :type existing_violations_to_check: list[ConstraintViolation]
    """
    for new_violation in new_violations:
        found_match = False
        for existing_violation in existing_violations_to_check:
            if existing_violation.matches(new_violation):
                # Remove from existing violations set since it should stay in db
                existing_violations_to_check.remove(existing_violation)
                found_match = True
                break

        # Only save new violation if no match was found
        if not found_match:
            new_violation.save()

    # Cleanup obsolete violations (ones without matches computed under current conditions)
    for outdated_violation in existing_violations_to_check:
        outdated_violation.delete()


def update_cv_reso_deadline_for_slot(slot):
    """
    Update constraint violation AK_AFTER_RESODEADLINE for given slot

    :param slot: slot to check/update
    :type slot: AKSlot
    """
    event = slot.event
    if slot.ak.reso and slot.event.reso_deadline and slot.start:
        # Update only if reso_deadline exists
        # if event was changed and reso_deadline is removed, CVs will be deleted by event changed handler
        violation_type = ConstraintViolation.ViolationType.AK_AFTER_RESODEADLINE
        new_violations = []
        if slot.end > event.reso_deadline:
            c = ConstraintViolation(
                type=violation_type,
                level=ConstraintViolation.ViolationLevel.VIOLATION,
                event=event,
            )
            c.aks_tmp.add(slot.ak)
            c.ak_slots_tmp.add(slot)
            new_violations.append(c)
        update_constraint_violations(new_violations, list(slot.constraintviolation_set.filter(type=violation_type)))


def check_capacity_for_slot(slot: AKSlot):
    """
    Check whether this slot violates the capacity requirement

    :param slot: slot to check
    :type slot: AKSlot
    :return: Violation (if any) or None
    :rtype: ConstraintViolation or None
    """
    if slot.room:
        if slot.room.capacity >= 0:
            if slot.room.capacity < slot.ak.interest:
                c = ConstraintViolation(
                    type=ConstraintViolation.ViolationType.ROOM_CAPACITY_EXCEEDED,
                    level=ConstraintViolation.ViolationLevel.VIOLATION,
                    event=slot.event,
                    room=slot.room,
                    comment=_("Not enough space for AK interest (Interest: %(interest)d, Capacity: %(capacity)d)")
                            % {'interest': slot.ak.interest, 'capacity': slot.room.capacity},
                )
                c.ak_slots_tmp.add(slot)
                c.aks_tmp.add(slot.ak)
                return c
            elif slot.room.capacity < slot.ak.interest + 5 or slot.room.capacity < slot.ak.interest * 1.25:
                c = ConstraintViolation(
                    type=ConstraintViolation.ViolationType.ROOM_CAPACITY_EXCEEDED,
                    level=ConstraintViolation.ViolationLevel.WARNING,
                    event=slot.event,
                    room=slot.room,
                    comment=_("Space is too close to AK interest (Interest: %(interest)d, Capacity: %(capacity)d)")
                            % {'interest': slot.ak.interest, 'capacity': slot.room.capacity}
                )
                c.ak_slots_tmp.add(slot)
                c.aks_tmp.add(slot.ak)
                return c
        return None


@receiver(post_save, sender=AK)
def ak_changed_handler(sender, instance: AK, **kwargs):
    # Changes might affect: Reso intention, Category, Interest
    # TODO Reso intention changes

    # Check room capacities
    violation_type = ConstraintViolation.ViolationType.ROOM_CAPACITY_EXCEEDED
    new_violations = []
    for slot in instance.akslot_set.all():
        cv = check_capacity_for_slot(slot)
        if cv is not None:
            new_violations.append(cv)

    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(m2m_changed, sender=AK.owners.through)
def ak_owners_changed_handler(sender, instance: AK, action: str, **kwargs):
    """
    Owners of AK changed
    """
    # Only signal after change (post_add, post_delete, post_clear) are relevant
    if not action.startswith("post"):
        return

    # print(f"{instance} changed")

    event = instance.event

    # Owner(s) changed: Might affect multiple AKs by the same owner(s) at the same time
    violation_type = ConstraintViolation.ViolationType.OWNER_TWO_SLOTS
    new_violations = []

    slots_of_this_ak: [AKSlot] = instance.akslot_set.filter(start__isnull=False)

    # For all owners (after recent change)...
    for owner in instance.owners.all():
        # ...find other slots that might be overlapping...

        for ak in owner.ak_set.all():
            # ...find overlapping slots...
            if ak != instance:
                for slot in slots_of_this_ak:
                    for other_slot in ak.akslot_set.filter(start__isnull=False):
                        if slot.overlaps(other_slot):
                            # ...and create a temporary violation if necessary...
                            c = ConstraintViolation(
                                type=violation_type,
                                level=ConstraintViolation.ViolationLevel.VIOLATION,
                                event=event,
                                ak_owner=owner
                            )
                            c.aks_tmp.add(instance)
                            c.aks_tmp.add(other_slot.ak)
                            c.ak_slots_tmp.add(slot)
                            c.ak_slots_tmp.add(other_slot)
                            new_violations.append(c)

        #print(f"{owner} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(m2m_changed, sender=AK.conflicts.through)
def ak_conflicts_changed_handler(sender, instance: AK, action: str, **kwargs):
    """
    Conflicts of AK changed
    """
    # Only signal after change (post_add, post_delete, post_clear) are relevant
    if not action.startswith("post"):
        return

    # print(f"{instance} changed")

    event = instance.event

    # Conflict(s) changed: Might affect multiple AKs that are conflicts of each other
    violation_type = ConstraintViolation.ViolationType.AK_CONFLICT_COLLISION
    new_violations = []

    slots_of_this_ak: [AKSlot] = instance.akslot_set.filter(start__isnull=False)
    conflicts_of_this_ak: [AK] = instance.conflicts.all()

    for ak in conflicts_of_this_ak:
        if ak != instance:
            for other_slot in ak.akslot_set.filter(start__isnull=False):
                for slot in slots_of_this_ak:
                    # ...find overlapping slots...
                    if slot.overlaps(other_slot):
                        # ...and create a temporary violation if necessary...
                        c = ConstraintViolation(
                            type=violation_type,
                            level=ConstraintViolation.ViolationLevel.VIOLATION,
                            event=event,
                        )
                        c.aks_tmp.add(instance)
                        c.ak_slots_tmp.add(slot)
                        c.ak_slots_tmp.add(other_slot)
                        new_violations.append(c)

        # print(f"{instance} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(m2m_changed, sender=AK.prerequisites.through)
def ak_prerequisites_changed_handler(sender, instance: AK, action: str, **kwargs):
    """
    Prerequisites of AK changed
    """
    # Only signal after change (post_add, post_delete, post_clear) are relevant
    if not action.startswith("post"):
        return

    # print(f"{instance} changed")

    event = instance.event

    # Conflict(s) changed: Might affect multiple AKs that are conflicts of each other
    violation_type = ConstraintViolation.ViolationType.AK_BEFORE_PREREQUISITE
    new_violations = []

    slots_of_this_ak: [AKSlot] = instance.akslot_set.filter(start__isnull=False)
    prerequisites_of_this_ak: [AK] = instance.prerequisites.all()

    for ak in prerequisites_of_this_ak:
        if ak != instance:
            for other_slot in ak.akslot_set.filter(start__isnull=False):
                for slot in slots_of_this_ak:
                    # ...find overlapping slots...
                    if other_slot.end > slot.start:
                        # ...and create a temporary violation if necessary...
                        c = ConstraintViolation(
                            type=violation_type,
                            level=ConstraintViolation.ViolationLevel.VIOLATION,
                            event=event,
                        )
                        c.aks_tmp.add(instance)
                        c.ak_slots_tmp.add(slot)
                        c.ak_slots_tmp.add(other_slot)
                        new_violations.append(c)

        # print(f"{instance} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(m2m_changed, sender=AK.requirements.through)
def ak_requirements_changed_handler(sender, instance: AK, action: str, **kwargs):
    """
    Requirements of AK changed
    """
    # Only signal after change (post_add, post_delete, post_clear) are relevant
    if not action.startswith("post"):
        return

    # print(f"{instance} changed")

    event = instance.event

    # Requirement(s) changed: Might affect slots and rooms
    violation_type = ConstraintViolation.ViolationType.REQUIRE_NOT_GIVEN
    new_violations = []

    slots_of_this_ak: [AKSlot] = instance.akslot_set.filter(start__isnull=False)

    # For all requirements (after recent change)...
    for slot in slots_of_this_ak:

        room = slot.room
        room_requirements = room.properties.all()

        for requirement in instance.requirements.all():

            if not requirement in room_requirements:
                # ...and create a temporary violation if necessary...
                c = ConstraintViolation(
                    type=violation_type,
                    level=ConstraintViolation.ViolationLevel.VIOLATION,
                    event=event,
                    requirement=requirement,
                    room=room,
                )
                c.aks_tmp.add(instance)
                c.ak_slots_tmp.add(slot)
                new_violations.append(c)

    # print(f"{instance} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(post_save, sender=AKSlot)
def akslot_changed_handler(sender, instance: AKSlot, **kwargs):
    # Changes might affect: Duplicate parallel, Two in room, Resodeadline
    # print(f"{sender} changed")
    event = instance.event

    # == Check for two parallel slots by one of the owners ==

    violation_type = ConstraintViolation.ViolationType.OWNER_TWO_SLOTS
    new_violations = []

    if instance.start:
        # For all owners (after recent change)...
        for owner in instance.ak.owners.all():
            # ...find other slots that might be overlapping...

            for ak in owner.ak_set.all():
                # ...find overlapping slots...
                if ak != instance.ak:
                    for other_slot in ak.akslot_set.filter(start__isnull=False):
                        if instance.overlaps(other_slot):
                            # ...and create a temporary violation if necessary...
                            c = ConstraintViolation(
                                type=violation_type,
                                level=ConstraintViolation.ViolationLevel.VIOLATION,
                                event=event,
                                ak_owner=owner
                            )
                            c.aks_tmp.add(instance.ak)
                            c.aks_tmp.add(other_slot.ak)
                            c.ak_slots_tmp.add(instance)
                            c.ak_slots_tmp.add(other_slot)
                            new_violations.append(c)

            # print(f"{owner} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == Check for two aks in the same room at the same time ==

    violation_type = ConstraintViolation.ViolationType.ROOM_TWO_SLOTS
    new_violations = []

    # For all slots in this room...
    if instance.room:
        for other_slot in instance.room.akslot_set.all():
            if other_slot != instance:
                # ... find overlapping slots...
                if instance.overlaps(other_slot):
                    # ...and create a temporary violation if necessary...
                    c = ConstraintViolation(
                        type=violation_type,
                        level=ConstraintViolation.ViolationLevel.WARNING,
                        event=event,
                        room=instance.room
                    )
                    c.aks_tmp.add(instance.ak)
                    c.aks_tmp.add(other_slot.ak)
                    c.ak_slots_tmp.add(instance)
                    c.ak_slots_tmp.add(other_slot)
                    new_violations.append(c)

        # print(f"Multiple slots in room {instance.room}: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the slot that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == Check for reso ak after reso deadline ==

    update_cv_reso_deadline_for_slot(instance)

    # == Check for two slots of the same AK at the same time (warning) ==

    violation_type = ConstraintViolation.ViolationType.AK_SLOT_COLLISION
    new_violations = []

    if instance.start:
        # For all other slots of this ak...
        for other_slot in instance.ak.akslot_set.filter(start__isnull=False):
            if other_slot != instance:
                # ... find overlapping slots...
                if instance.overlaps(other_slot):
                    # ...and create a temporary violation if necessary...
                    c = ConstraintViolation(
                        type=violation_type,
                        level=ConstraintViolation.ViolationLevel.WARNING,
                        event=event,
                    )
                    c.aks_tmp.add(instance.ak)
                    c.ak_slots_tmp.add(instance)
                    c.ak_slots_tmp.add(other_slot)
                    new_violations.append(c)

    # ... and compare to/update list of existing violations of this type
    # belonging to the slot that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == Check for slot outside availability ==

    # An AK's availability changed: Might affect AK slots scheduled outside the permitted time
    violation_type = ConstraintViolation.ViolationType.SLOT_OUTSIDE_AVAIL
    new_violations = []

    if instance.start:
        availabilities_of_this_ak: [Availability] = instance.ak.availabilities.all()

        covered = False

        for availability in availabilities_of_this_ak:
            covered = availability.start <= instance.start and availability.end >= instance.end
            if covered:
                break
        if not covered:
            c = ConstraintViolation(
                type=violation_type,
                level=ConstraintViolation.ViolationLevel.VIOLATION,
                event=event
            )
            c.aks_tmp.add(instance.ak)
            c.ak_slots_tmp.add(instance)
            new_violations.append(c)

    # print(f"{instance.ak} has the following slots outside availabilities: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == Check for requirement not fulfilled by room ==

    # Room(s) changed: Might affect slots and rooms
    violation_type = ConstraintViolation.ViolationType.REQUIRE_NOT_GIVEN
    new_violations = []

    if instance.room:

        room_requirements = instance.room.properties.all()

        for requirement in instance.ak.requirements.all():

            if requirement not in room_requirements:
                # ...and create a temporary violation if necessary...
                c = ConstraintViolation(
                    type=violation_type,
                    level=ConstraintViolation.ViolationLevel.VIOLATION,
                    event=event,
                    requirement=requirement,
                    room=instance.room,
                )
                c.aks_tmp.add(instance.ak)
                c.ak_slots_tmp.add(instance)
                new_violations.append(c)

    # print(f"{instance} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == check for simultaneous slots of conflicting AKs ==

    violation_type = ConstraintViolation.ViolationType.AK_CONFLICT_COLLISION
    new_violations = []

    if instance.start:
        conflicts_of_this_ak: [AK] = instance.ak.conflicts.all()

        for ak in conflicts_of_this_ak:
            if ak != instance.ak:
                for other_slot in ak.akslot_set.filter(start__isnull=False):
                    # ...find overlapping slots...
                    if instance.overlaps(other_slot):
                        # ...and create a temporary violation if necessary...
                        c = ConstraintViolation(
                            type=violation_type,
                            level=ConstraintViolation.ViolationLevel.VIOLATION,
                            event=event,
                        )
                        c.aks_tmp.add(instance.ak)
                        c.ak_slots_tmp.add(instance)
                        c.ak_slots_tmp.add(other_slot)
                        new_violations.append(c)

            # print(f"{instance} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.ak.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == check for missing prerequisites ==

    violation_type = ConstraintViolation.ViolationType.AK_BEFORE_PREREQUISITE
    new_violations = []

    if instance.start:
        prerequisites_of_this_ak: [AK] = instance.ak.prerequisites.all()

        for ak in prerequisites_of_this_ak:
            if ak != instance.ak:
                for other_slot in ak.akslot_set.filter(start__isnull=False):
                    # ...find slots in the wrong order...
                    if other_slot.end > instance.start:
                        # ...and create a temporary violation if necessary...
                        c = ConstraintViolation(
                            type=violation_type,
                            level=ConstraintViolation.ViolationLevel.VIOLATION,
                            event=event,
                        )
                        c.aks_tmp.add(instance.ak)
                        c.ak_slots_tmp.add(instance)
                        c.ak_slots_tmp.add(other_slot)
                        new_violations.append(c)

            # print(f"{instance} has the following conflicts: {new_violations}")

    # ... and compare to/update list of existing violations of this type
    # belonging to the AK that was recently changed (important!)
    existing_violations_to_check = list(instance.ak.constraintviolation_set.filter(type=violation_type))
    # print(existing_violations_to_check)
    update_constraint_violations(new_violations, existing_violations_to_check)

    # == Check for room capacity ==
    cv = check_capacity_for_slot(instance)
    new_violations = [cv] if cv is not None else []

    # Compare to/update list of existing violations of this type for this slot
    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=ConstraintViolation.ViolationType.ROOM_CAPACITY_EXCEEDED))
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(pre_delete, sender=AKSlot)
def akslot_deleted_handler(sender, instance: AKSlot, **kwargs):
    # Manually clean up or remove constraint violations that belong to this slot since there is no cascade deletion
    # for many2many relationships. Explicitly listening for AK deletion signals is not necessary since they will
    # transitively trigger this signal and we always set both AK and AKSlot references in a constraint violation
    # print(f"{instance} deleted")

    for cv in instance.constraintviolation_set.all():
        # Make sure not delete CVs that e.g., show three parallel slots in a single room
        if cv.ak_slots.count() <= 2:
            cv.delete()


@receiver(post_save, sender=Room)
def room_changed_handler(sender, instance: Room, **kwargs):
    # Changes might affect: Room size

    # Check room capacities
    violation_type = ConstraintViolation.ViolationType.ROOM_CAPACITY_EXCEEDED
    new_violations = []
    for slot in instance.akslot_set.all():
        cv = check_capacity_for_slot(slot)
        if cv is not None:
            new_violations.append(cv)

    existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
    update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(m2m_changed, sender=Room.properties.through)
def room_requirements_changed_handler(sender, instance: Room, action: str, **kwargs):
    """
    Requirements of room changed
    """
    # Only signal after change (post_add, post_delete, post_clear) are relevant
    if not action.startswith("post"):
        return

    # print(f"{instance} changed")

    event = instance.event

    # TODO React to changes


@receiver(post_save, sender=Availability)
def availability_changed_handler(sender, instance: Availability, **kwargs):
    # Changes might affect: category availability, AK availability, Room availability
    # print(f"{instance} changed")

    event = instance.event

    # An AK's availability changed: Might affect AK slots scheduled outside the permitted time
    if instance.ak:
        violation_type = ConstraintViolation.ViolationType.SLOT_OUTSIDE_AVAIL
        new_violations = []

        availabilities_of_this_ak: [Availability] = instance.ak.availabilities.all()
        slots_of_this_ak: [AKSlot] = instance.ak.akslot_set.filter(start__isnull=False)

        for slot in slots_of_this_ak:
            covered = False
            for availability in availabilities_of_this_ak:
                covered = availability.start <= slot.start and availability.end >= slot.end
                if covered:
                    break
            if not covered:
                c = ConstraintViolation(
                    type=violation_type,
                    level=ConstraintViolation.ViolationLevel.VIOLATION,
                    event=event
                )
                c.aks_tmp.add(instance.ak)
                c.ak_slots_tmp.add(slot)
                new_violations.append(c)

        # print(f"{instance.ak} has the following slots outside availabilities: {new_violations}")

        # ... and compare to/update list of existing violations of this type
        # belonging to the AK that was recently changed (important!)
        existing_violations_to_check = list(instance.ak.constraintviolation_set.filter(type=violation_type))
        # print(existing_violations_to_check)
        update_constraint_violations(new_violations, existing_violations_to_check)


@receiver(post_save, sender=Event)
def event_changed_handler(sender, instance: Event, **kwargs):
    # == Check for reso ak after reso deadline (which might have changed) ==
    if instance.reso_deadline:
        for slot in instance.akslot_set.filter(start__isnull=False, ak__reso=True):
            update_cv_reso_deadline_for_slot(slot)
    else:
        # No reso deadline, delete all violations
        violation_type = ConstraintViolation.ViolationType.AK_AFTER_RESODEADLINE
        existing_violations_to_check = list(instance.constraintviolation_set.filter(type=violation_type))
        update_constraint_violations([], existing_violations_to_check)