#!/usr/bin/python2.5
#
# Copyright 2008 the Melange authors.
#
# 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.

"""Functions used to send email messages.

The following are the possible fields of an email message:

  sender: The email address of the sender, the From address. This must be the 
    email address of a registered administrator for the application, or the
    address of the current signed-in user. Administrators can be added to
    an application using the Administration Console. The current user's email
    address can be determined with the Users API.
  to: A recipient's email address (a string) or a list of email addresses to 
    appear on the To: line in the message header.
  cc: A recipient's email address (a string) or a list of email addresses to 
    appear on the Cc: line in the message header.
  bcc: A recipient's email address (a string) or a list of email addresses to 
    receive the message, but not appear in the message header ("blind carbon 
    copy").
  reply_to: An email address to which a recipient should reply instead of the 
    sender address, the Reply-To: field.
  subject: The subject of the message, the Subject: line.
  body: The plaintext body content of the message.
  html: An HTML version of the body content, for recipients that 
    prefer HTML email.
  attachments: The file attachments for the message, as a list of two-value 
    tuples, one tuple for each attachment. Each tuple contains a filename as 
    the first element, and the file contents as the second element.
    An attachment file must be one of the allowed file types, and the 
    filename must end with an extension that corresponds with the type. 
    For a list of allowed types and filename extensions, see Allowed 
    Attachment Types.

Usage:

  context = { 'sender': 'melange-noreply@foo.com',
              'to': 'bob@bar.com',
              'subject': 'You have been invited to become a Host',
              'sender_name': 'Alice',
              'to_name': 'Melange Team',
              'role': 'Host',
              'group': 'Google Summer of Code 2009',
              'invitation_url': 'http://invitation-url'}

  sendMailFromTemplate('soc/mail/invitation.html', context)
"""

__authors__ = [
  '"Lennard de Rijk" <ljvderijk@gmail.com>',
  '"Pawel Solyga" <pawel.solyga@gmail.com',
  ]


from django.template import loader

from google.appengine.api import mail

from soc.logic import dicts


def sendMailFromTemplate(template, context):
  """Sends out an email using a Django template.
  
  If 'html' is present in context dictionary it is overwritten with
  template HTML output.
  
  Args:
    template: the template (or search list of templates) to use
    context: The context supplied to the template and email (dictionary)
  
  Raises:
    Error that corresponds with the first problem it finds iff the message 
    is not properly initialized.

    List of all possible errors:
      http://code.google.com/appengine/docs/mail/exceptions.html
  """
  # render the template and put in context with 'html' as key
  context['html'] = loader.render_to_string(template, dictionary=context)

  # filter out the unneeded values in context to keep sendMail happy
  sendMail(dicts.filter(context, mail.EmailMessage.PROPERTIES))


def sendMail(context):
  """Sends out an email using context to supply the needed information.
  
  Args:
    context : The context supplied to the email message (dictionary)

  Raises:
    Error that corresponds with the first problem it finds iff the message 
    is not properly initialized.

    List of all possible errors:
      http://code.google.com/appengine/docs/mail/exceptions.html
  """
  
  # construct the EmailMessage from the given context
  message = mail.EmailMessage(**context)
  
  message.check_initialized()
  
  # send the message
  message.send()