Synnefo

# Copyright 2013 GRNET S.A. All rights reserved.

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from astakos.quotaholder.exception import NoCapacityError, NoQuantityError

class Operation(object):

    @staticmethod

    def assertions(holding):

        assert(holding.usage_min <= holding.usage_max)

    @classmethod

    def _prepare(cls, holding, quantity, check=True):

        raise NotImplementedError

    @classmethod

    def prepare(cls, holding, quantity, check=True):

        cls.assertions(holding)

        cls._prepare(holding, quantity, check)

    @classmethod

    def _finalize(cls, holding, quantity):

        raise NotImplementedError

    @classmethod

    def finalize(cls, holding, quantity):

        cls.assertions(holding)

        cls._finalize(holding, quantity)

    @classmethod

    def undo(cls, holding, quantity):

        cls.prepare(holding, -quantity, check=False)

    @classmethod

    def revert(cls, holding, quantity):

        # Assertions do not hold when reverting

        cls._prepare(holding, -quantity, check=False)

    @classmethod

    def provision(cls, holding, quantity, importing=True):

        return {'holder': holding.holder,

                'source': holding.source,

                'resource': holding.resource,

                'quantity': quantity if importing else -quantity,

                }

class Import(Operation):

    @classmethod

    def _prepare(cls, holding, quantity, check=True):

        usage_max = holding.usage_max

        new_usage_max = usage_max + quantity

        limit = holding.limit

        if check and new_usage_max > limit:

            holder = holding.holder

            resource = holding.resource

            m = ("%s has not enough capacity of %s." % (holder, resource))

            provision = cls.provision(holding, quantity, importing=True)

            raise NoCapacityError(m,

                                  provision=provision,

                                  limit=limit,

                                  usage=usage_max)

        holding.usage_max = new_usage_max

        holding.save()

    @classmethod

    def _finalize(cls, holding, quantity):

        holding.usage_min += quantity

        holding.save()

class Release(Operation):

    @classmethod

    def _prepare(cls, holding, quantity, check=True):

        usage_min = holding.usage_min

        new_usage_min = usage_min - quantity

        if check and new_usage_min < 0:

            holder = holding.holder

            resource = holding.resource

            m = ("%s attempts to release more %s than it contains." %

                 (holder, resource))

            provision = cls.provision(holding, quantity, importing=False)

            raise NoQuantityError(m,

                                  provision=provision,

                                  available=usage_min)

        holding.usage_min = new_usage_min

        holding.save()

    @classmethod

    def _finalize(cls, holding, quantity):

        holding.usage_max -= quantity

        holding.save()

class Operations(object):

    def __init__(self):

        self.operations = []

    def prepare(self, operation, holding, quantity, force):

        check = not force

        operation.prepare(holding, quantity, check)

        self.operations.append((operation, holding, quantity))

    def revert(self):

        for (operation, holding, quantity) in self.operations:

            operation.revert(holding, quantity)

def finalize(operation, holding, quantity):

    operation.finalize(holding, quantity)

def undo(operation, holding, quantity):

    operation.undo(holding, quantity)