#!/usr/bin/env python
#
# Copyright 2007 Google 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.
#

"""CronInfo tools.

A library for working with CronInfo records, describing cron entries for an
application. Supports loading the records from yaml.
"""



from google.appengine.cron import groc
from google.appengine.api import validation
from google.appengine.api import yaml_builder
from google.appengine.api import yaml_listener
from google.appengine.api import yaml_object

_URL_REGEX = r'^/.*$'


_TIMEZONE_REGEX = r'^.{0,100}$'

_DESCRIPTION_REGEX = r'^.{0,499}$'


class GrocValidator(validation.Validator):
  """Checks that a schedule is in valid groc format."""

  def Validate(self, value):
    """Validates a schedule."""
    if value is None:
      raise validation.MissingAttribute('schedule must be specified')
    if not isinstance(value, basestring):
      raise TypeError('schedule must be a string, not \'%r\''%type(value))
    schedule = groc.CreateParser(value)
    try:
      schedule.timespec()
    except groc.GrocException, e:
      raise validation.ValidationError('schedule \'%s\' failed to parse: %s'%(
          value, e.args[0]))
    return value


CRON = 'cron'

URL = 'url'
SCHEDULE = 'schedule'
TIMEZONE = 'timezone'
DESCRIPTION = 'description'


class MalformedCronfigurationFile(Exception):
  """Configuration file for Cron is malformed."""
  pass


class CronEntry(validation.Validated):
  """A cron entry describes a single cron job."""
  ATTRIBUTES = {
      URL: _URL_REGEX,
      SCHEDULE: GrocValidator(),
      TIMEZONE: validation.Optional(_TIMEZONE_REGEX),
      DESCRIPTION: validation.Optional(_DESCRIPTION_REGEX)
  }


class CronInfoExternal(validation.Validated):
  """CronInfoExternal describes all cron entries for an application."""
  ATTRIBUTES = {
      CRON: validation.Optional(validation.Repeated(CronEntry))
  }


def LoadSingleCron(cron_info):
  """Load a cron.yaml file or string and return a CronInfoExternal object."""
  builder = yaml_object.ObjectBuilder(CronInfoExternal)
  handler = yaml_builder.BuilderHandler(builder)
  listener = yaml_listener.EventListener(handler)
  listener.Parse(cron_info)

  cron_info = handler.GetResults()
  if len(cron_info) < 1:
    raise MalformedCronfigurationFile('Empty cron configuration.')
  if len(cron_info) > 1:
    raise MalformedCronfigurationFile('Multiple cron sections '
                                      'in configuration.')
  return cron_info[0]