from PLC.Config import Config
from PLC.Faults import *

from datetime import datetime, timedelta
from pyaspects.meta import MetaAspect
import memcache

class BaseRateLimit(object):

    def __init__(self):
        self.config = Config("/etc/planetlab/plc_config")

        self.prefix = "ratelimit"
        self.minutes = 3 # The time period
        self.requests = 10 # Number of allowed requests in that time period
        self.expire_after = (self.minutes + 1) * 60

    def before(self, wobj, data, *args, **kwargs):
        # ratelimit_128.112.139.115_201011091532 = 1
        # ratelimit_128.112.139.115_201011091533 = 14
        # ratelimit_128.112.139.115_201011091534 = 11
        # Now, on every request we work out the keys for the past five minutes and use get_multi to retrieve them. 
        # If the sum of those counters exceeds the maximum allowed for that time period, we block the request.

        api_method_name = wobj.name
        api_method_source = wobj.source

        if api_method_source == None or api_method_source[0] == self.config.PLC_API_HOST:
            return

        mc = memcache.Client(['%s:11211'] % self.config.PLC_API_HOST)
        now = datetime.now()
        current_key = '%s_%s_%s' % (self.prefix, api_method_source[0], now.strftime('%Y%m%d%H%M'))

        keys_to_check = ['%s_%s_%s' % (self.prefix, api_method_source[0], (now - timedelta(minutes = minute)).strftime('%Y%m%d%H%M')) for minute in range(self.minutes + 1)]

        try:
            mc.incr(current_key)
        except ValueError:
            mc.set(current_key, 1, time=self.expire_after)

        result = mc.get_multi(keys_to_check)
        total_requests = 0
        for i in result:
            total_requests += result[i]

        if total_requests > self.requests:
            raise PLCPermissionDenied, "Maximum allowed number of API calls exceeded"

    def after(self, wobj, data, *args, **kwargs):
        return

class RateLimitAspect_class(BaseRateLimit):
    __metaclass__ = MetaAspect
    name = "ratelimitaspect_class"

    def __init__(self):
        BaseRateLimit.__init__(self)

    def before(self, wobj, data, *args, **kwargs):
        BaseRateLimit.before(self, wobj, data, *args, **kwargs)

    def after(self, wobj, data, *args, **kwargs):
        BaseRateLimit.after(self, wobj, data, *args, **kwargs)

RateLimitAspect = RateLimitAspect_class