Offer.py

from decimal import Decimal


class Offer(object):
    """A rate offer to download blobs from a host."""

    RATE_ACCEPTED = "RATE_ACCEPTED"
    RATE_TOO_LOW = "RATE_TOO_LOW"
    RATE_UNSET = "RATE_UNSET"

    def __init__(self, offer):
        self._state = None
        self.rate = None
        if isinstance(offer, Decimal):
            self.rate = round(offer, 5)
        elif isinstance(offer, float):
            self.rate = round(Decimal(offer), 5)
        if self.rate is None or self.rate < Decimal(0.0):
            self.unset()

    @property
    def is_accepted(self):
        return self._state is Offer.RATE_ACCEPTED

    @property
    def is_too_low(self):
        return self._state is Offer.RATE_TOO_LOW

    @property
    def is_unset(self):
        return self._state is Offer.RATE_UNSET

    @property
    def message(self):
        if self.is_accepted:
            return Offer.RATE_ACCEPTED
        elif self.is_too_low:
            return Offer.RATE_TOO_LOW
        elif self.is_unset:
            return Offer.RATE_UNSET
        return None

    def accept(self):
        if self.is_unset or self._state is None:
            self._state = Offer.RATE_ACCEPTED

    def reject(self):
        if self.is_unset or self._state is None:
            self._state = Offer.RATE_TOO_LOW

    def unset(self):
        self._state = Offer.RATE_UNSET

    def handle(self, reply_message):
        if reply_message == Offer.RATE_TOO_LOW:
            self.reject()
        elif reply_message == Offer.RATE_ACCEPTED:
            self.accept()
        elif reply_message == Offer.RATE_UNSET:
            self.unset()
        else:
            raise Exception("Unknown offer reply %s" % str(reply_message))