#!/usr/bin/env python3

# Copyright 2014 Brett Slatkin, Pearson Education Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Preamble to mimick book environment
import logging
from pprint import pprint
from sys import stdout as STDOUT


# Example 1
from datetime import datetime, timedelta

class Bucket(object):
    def __init__(self, period):
        self.period_delta = timedelta(seconds=period)
        self.reset_time = datetime.now()
        self.quota = 0

    def __repr__(self):
        return 'Bucket(quota=%d)' % self.quota

bucket = Bucket(60)
print(bucket)


# Example 2
def fill(bucket, amount):
    now = datetime.now()
    if now - bucket.reset_time > bucket.period_delta:
        bucket.quota = 0
        bucket.reset_time = now
    bucket.quota += amount


# Example 3
def deduct(bucket, amount):
    now = datetime.now()
    if now - bucket.reset_time > bucket.period_delta:
        return False
    if bucket.quota - amount < 0:
        return False
    bucket.quota -= amount
    return True


# Example 4
bucket = Bucket(60)
fill(bucket, 100)
print(bucket)


# Example 5
if deduct(bucket, 99):
    print('Had 99 quota')
else:
    print('Not enough for 99 quota')
print(bucket)


# Example 6
if deduct(bucket, 3):
    print('Had 3 quota')
else:
    print('Not enough for 3 quota')
print(bucket)


# Example 7
class Bucket(object):
    def __init__(self, period):
        self.period_delta = timedelta(seconds=period)
        self.reset_time = datetime.now()
        self.max_quota = 0
        self.quota_consumed = 0

    def __repr__(self):
        return ('Bucket(max_quota=%d, quota_consumed=%d)' %
                (self.max_quota, self.quota_consumed))


# Example 8
    @property
    def quota(self):
        return self.max_quota - self.quota_consumed


# Example 9
    @quota.setter
    def quota(self, amount):
        delta = self.max_quota - amount
        if amount == 0:
            # Quota being reset for a new period
            self.quota_consumed = 0
            self.max_quota = 0
        elif delta < 0:
            # Quota being filled for the new period
            assert self.quota_consumed == 0
            self.max_quota = amount
        else:
            # Quota being consumed during the period
            assert self.max_quota >= self.quota_consumed
            self.quota_consumed += delta


# Example 10
bucket = Bucket(60)
print('Initial', bucket)
fill(bucket, 100)
print('Filled', bucket)

if deduct(bucket, 99):
    print('Had 99 quota')
else:
    print('Not enough for 99 quota')

print('Now', bucket)

if deduct(bucket, 3):
    print('Had 3 quota')
else:
    print('Not enough for 3 quota')

print('Still', bucket)