# Copyright 2016 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file or at
# https://developers.google.com/open-source/licenses/bsd

"""Handler to process inbound email with issue comments and commands."""
from __future__ import print_function
from __future__ import division
from __future__ import absolute_import

import email
import logging
import os
import re
import time
import six
from six.moves import urllib

import flask
import ezt

from google.appengine.api import mail
if six.PY2:
  from google.appengine.ext.webapp.mail_handlers import BounceNotification
else:
  from google.appengine.api.mail import BounceNotification


import settings
from features import alert2issue
from features import commitlogcommands
from features import notify_helpers
from framework import authdata
from framework import emailfmt
from framework import exceptions
from framework import framework_constants
from framework import monorailcontext
from framework import permissions
from framework import sql
from framework import template_helpers
from proto import project_pb2


TEMPLATE_PATH_BASE = framework_constants.TEMPLATE_PATH

MSG_TEMPLATES = {
    'banned': 'features/inboundemail-banned.ezt',
    'body_too_long': 'features/inboundemail-body-too-long.ezt',
    'project_not_found': 'features/inboundemail-project-not-found.ezt',
    'not_a_reply': 'features/inboundemail-not-a-reply.ezt',
    'no_account': 'features/inboundemail-no-account.ezt',
    'no_artifact': 'features/inboundemail-no-artifact.ezt',
    'no_perms': 'features/inboundemail-no-perms.ezt',
    'replies_disabled': 'features/inboundemail-replies-disabled.ezt',
    }


class InboundEmail(object):
  """Servlet to handle inbound email messages."""

  def __init__(self, services=None):
    self.services = services or flask.current_app.config['services']
    self._templates = {}
    self.request = flask.request
    for name, template_path in MSG_TEMPLATES.items():
      self._templates[name] = template_helpers.MonorailTemplate(
          TEMPLATE_PATH_BASE + template_path,
          compress_whitespace=False, base_format=ezt.FORMAT_RAW)

  def HandleInboundEmail(self, project_addr=None):
    if self.request.method == 'POST':
      self.post(project_addr)
    elif self.request.method == 'GET':
      self.get(project_addr)
    return ''

  def get(self, project_addr=None):
    logging.info('\n\n\nGET for InboundEmail and project_addr is %r',
                 project_addr)
    self.Handler(
        mail.InboundEmailMessage(self.request.get_data()),
        urllib.parse.unquote(project_addr))

  def post(self, project_addr=None):
    logging.info('\n\n\nPOST for InboundEmail and project_addr is %r',
                 project_addr)
    self.Handler(
        mail.InboundEmailMessage(self.request.get_data()),
        urllib.parse.unquote(project_addr))

  def Handler(self, inbound_email_message, project_addr):
    """Process an inbound email message."""
    msg = inbound_email_message.original
    email_tasks = self.ProcessMail(msg, project_addr)

    if email_tasks:
      notify_helpers.AddAllEmailTasks(email_tasks)

  def ProcessMail(self, msg, project_addr):
    """Process an inbound email message."""
    # TODO(jrobbins): If the message is HUGE, don't even try to parse
    # it. Silently give up.

    (from_addr, to_addrs, cc_addrs, references, incident_id, subject,
     body) = emailfmt.ParseEmailMessage(msg)

    logging.info('Proj addr:   %r', project_addr)
    logging.info('From addr:   %r', from_addr)
    logging.info('Subject:     %r', subject)
    logging.info('To:          %r', to_addrs)
    logging.info('Cc:          %r', cc_addrs)
    logging.info('References:  %r', references)
    logging.info('Incident Id: %r', incident_id)
    logging.info('Body:        %r', body)

    # If message body is very large, reject it and send an error email.
    if emailfmt.IsBodyTooBigToParse(body):
      return _MakeErrorMessageReplyTask(
          project_addr, from_addr, self._templates['body_too_long'])

    # Make sure that the project reply-to address is in the To: line.
    if not emailfmt.IsProjectAddressOnToLine(project_addr, to_addrs):
      return None

    project_name, verb, trooper_queue = emailfmt.IdentifyProjectVerbAndLabel(
        project_addr)

    is_alert = bool(verb and verb.lower() == 'alert')
    error_addr = from_addr
    local_id = None
    author_addr = from_addr

    if is_alert:
      error_addr = settings.alert_escalation_email
      author_addr = settings.alert_service_account
    else:
      local_id = emailfmt.IdentifyIssue(project_name, subject)
      if not local_id:
        logging.info('Could not identify issue: %s %s', project_addr, subject)
        # No error message, because message was probably not intended for us.
        return None

    cnxn = sql.MonorailConnection()
    if self.services.cache_manager:
      self.services.cache_manager.DoDistributedInvalidation(cnxn)

    project = self.services.project.GetProjectByName(cnxn, project_name)
    # Authenticate the author_addr and perm check.
    try:
      mc = monorailcontext.MonorailContext(
          self.services, cnxn=cnxn, requester=author_addr, autocreate=is_alert)
      mc.LookupLoggedInUserPerms(project)
    except exceptions.NoSuchUserException:
      return _MakeErrorMessageReplyTask(
          project_addr, error_addr, self._templates['no_account'])

    # TODO(zhangtiff): Add separate email templates for alert error cases.
    if not project or project.state != project_pb2.ProjectState.LIVE:
      return _MakeErrorMessageReplyTask(
          project_addr, error_addr, self._templates['project_not_found'])

    if not project.process_inbound_email:
      return _MakeErrorMessageReplyTask(
          project_addr, error_addr, self._templates['replies_disabled'],
          project_name=project_name)

    # Verify that this is a reply to a notification that we could have sent.
    is_development = os.environ['SERVER_SOFTWARE'].startswith('Development')
    if not (is_alert or is_development):
      for ref in references:
        if emailfmt.ValidateReferencesHeader(ref, project, from_addr, subject):
          break  # Found a message ID that we could have sent.
        if emailfmt.ValidateReferencesHeader(
            ref, project, from_addr.lower(), subject):
          break  # Also match all-lowercase from-address.
      else: # for-else: if loop completes with no valid reference found.
        return _MakeErrorMessageReplyTask(
            project_addr, from_addr, self._templates['not_a_reply'])

    # Note: If the issue summary line is changed, a new thread is created,
    # and replies to the old thread will no longer work because the subject
    # line hash will not match, which seems reasonable.

    if mc.auth.user_pb.banned:
      logging.info('Banned user %s tried to post to %s',
                   from_addr, project_addr)
      return _MakeErrorMessageReplyTask(
          project_addr, error_addr, self._templates['banned'])

    # If the email is an alert, switch to the alert handling path.
    if is_alert:
      alert2issue.ProcessEmailNotification(
          self.services, cnxn, project, project_addr, from_addr,
          mc.auth, subject, body, incident_id, msg, trooper_queue)
      return None

    # This email is a response to an email about a comment.
    self.ProcessIssueReply(
        mc, project, local_id, project_addr, body)

    return None

  def ProcessIssueReply(
      self, mc, project, local_id, project_addr, body):
    """Examine an issue reply email body and add a comment to the issue.

    Args:
      mc: MonorailContext with cnxn and the requester email, user_id, perms.
      project: Project PB for the project containing the issue.
      local_id: int ID of the issue being replied to.
      project_addr: string email address used for outbound emails from
          that project.
      body: string email body text of the reply email.

    Returns:
      A list of follow-up work items, e.g., to notify other users of
      the new comment, or to notify the user that their reply was not
      processed.

    Side-effect:
      Adds a new comment to the issue, if no error is reported.
    """
    try:
      issue = self.services.issue.GetIssueByLocalID(
          mc.cnxn, project.project_id, local_id)
    except exceptions.NoSuchIssueException:
      issue = None

    if not issue or issue.deleted:
      # The referenced issue was not found, e.g., it might have been
      # deleted, or someone messed with the subject line.  Reject it.
      return _MakeErrorMessageReplyTask(
          project_addr, mc.auth.email, self._templates['no_artifact'],
          artifact_phrase='issue %d' % local_id,
          project_name=project.project_name)

    can_view = mc.perms.CanUsePerm(
        permissions.VIEW, mc.auth.effective_ids, project,
        permissions.GetRestrictions(issue))
    can_comment = mc.perms.CanUsePerm(
        permissions.ADD_ISSUE_COMMENT, mc.auth.effective_ids, project,
        permissions.GetRestrictions(issue))
    if not can_view or not can_comment:
      return _MakeErrorMessageReplyTask(
          project_addr, mc.auth.email, self._templates['no_perms'],
          artifact_phrase='issue %d' % local_id,
          project_name=project.project_name)

    # TODO(jrobbins): if the user does not have EDIT_ISSUE and the inbound
    # email tries to make an edit, send back an error message.

    lines = body.strip().split('\n')
    uia = commitlogcommands.UpdateIssueAction(local_id)
    uia.Parse(mc.cnxn, project.project_name, mc.auth.user_id, lines,
              self.services, strip_quoted_lines=True)
    uia.Run(mc, self.services)


def _MakeErrorMessageReplyTask(
    project_addr, sender_addr, template, **callers_page_data):
  """Return a new task to send an error message email.

  Args:
    project_addr: string email address that the inbound email was delivered to.
    sender_addr: string email address of user who sent the email that we could
        not process.
    template: EZT template used to generate the email error message.  The
        first line of this generated text will be used as the subject line.
    callers_page_data: template data dict for body of the message.

  Returns:
    A list with a single Email task that can be enqueued to
    actually send the email.

  Raises:
    ValueError: if the template does begin with a "Subject:" line.
  """
  email_data = {
      'project_addr': project_addr,
      'sender_addr': sender_addr
      }
  email_data.update(callers_page_data)

  generated_lines = template.GetResponse(email_data)
  subject, body = generated_lines.split('\n', 1)
  if subject.startswith('Subject: '):
    subject = subject[len('Subject: '):]
  else:
    raise ValueError('Email template does not begin with "Subject:" line.')

  email_task = dict(to=sender_addr, subject=subject, body=body,
                    from_addr=emailfmt.NoReplyAddress())
  logging.info('sending email error reply: %r', email_task)

  return [email_task]


BAD_WRAP_RE = re.compile('=\r\n')
BAD_EQ_RE = re.compile('=3D')


class BouncedEmail(object):
  """Handler to notice when email to given user is bouncing."""

  # For docs on AppEngine's bounce email see:
  # https://cloud.google.com/appengine/docs/standard/python3/reference
  # /services/bundled/google/appengine/api/mail/BounceNotification

  def __init__(self, services=None):
    self.services = services or flask.current_app.config['services']

  def postBouncedEmail(self):
    try:
      # Context: https://crbug.com/monorail/11083
      bounce_message = BounceNotification(flask.request.form)
      self.receive(bounce_message)
    except AttributeError:
      # Context: https://crbug.com/monorail/2105
      raw_message = flask.request.form.get('raw-message')
      logging.info('raw_message %r', raw_message)
      raw_message = BAD_WRAP_RE.sub('', raw_message)
      raw_message = BAD_EQ_RE.sub('=', raw_message)
      logging.info('fixed raw_message %r', raw_message)
      mime_message = email.message_from_string(raw_message)
      logging.info('get_payload gives %r', mime_message.get_payload())
      new_form_dict = flask.request.form.copy()
      new_form_dict['raw-message'] = mime_message
      # Retry with mime_message
      bounce_message = BounceNotification(new_form_dict)
      self.receive(bounce_message)
    return ''


  def receive(self, bounce_message):
    email_addr = bounce_message.original.get('to')
    logging.info('Bounce was sent to: %r', email_addr)

    # TODO(crbug.com/monorail/8727): The problem is likely no longer happening.
    # but we are adding permanent logging so we don't have to keep adding
    # expriring logpoints.
    if '@intel' in email_addr:  # both intel.com and intel-partner.
      logging.info('bounce notification: %r', bounce_message.notification)
      logging.info('bounce message original: %r', bounce_message.original)
      # The original message's headers are the closest we get to the
      # servers involved in the failed communication.
      original_message = bounce_message.original_raw_message.original
      if original_message is not None:
        logging.info(
            'bounce message original headers: %r', original_message.items())

    services = self.services
    cnxn = sql.MonorailConnection()

    try:
      user_id = services.user.LookupUserID(cnxn, email_addr)
      user = services.user.GetUser(cnxn, user_id)
      user.email_bounce_timestamp = int(time.time())
      services.user.UpdateUser(cnxn, user_id, user)
    except exceptions.NoSuchUserException:
      logging.info('User %r not found, ignoring', email_addr)
      logging.info('Received bounce post ... [%s]', flask.request)
      logging.info('Bounce original: %s', bounce_message.original)
      logging.info('Bounce notification: %s', bounce_message.notification)