zulip/zerver/views/messages.py

from __future__ import absolute_import

from django.conf import settings
from django.core import validators
from django.core.exceptions import ValidationError
from django.db import connection
from django.db.models import Q
from zerver.decorator import authenticated_api_view, authenticated_json_post_view, \
    has_request_variables, REQ, JsonableError, \
    to_non_negative_int, to_non_negative_float
from django.utils.html import escape as escape_html
from django.views.decorators.csrf import csrf_exempt
from zerver.lib import bugdown
from zerver.lib.actions import recipient_for_emails, do_update_message_flags, \
    compute_mit_user_fullname, compute_irc_user_fullname, compute_jabber_user_fullname, \
    create_mirror_user_if_needed, check_send_message, do_update_message, \
    extract_recipients
from zerver.lib.cache import generic_bulk_cached_fetch
from zerver.lib.query import last_n
from zerver.lib.response import json_success, json_error
from zerver.lib.utils import statsd
from zerver.lib.validator import \
    check_list, check_int, check_dict, check_string, check_bool
from zerver.models import Message, UserProfile, Stream, \
    Recipient, UserMessage, bulk_get_recipients, get_recipient, \
    get_user_profile_by_email, get_stream, valid_stream_name, \
    parse_usermessage_flags, to_dict_cache_key_id, extract_message_dict, \
    stringify_message_dict, is_super_user, is_super_user_api, \
    resolve_email_to_domain, get_realm, get_active_streams, \
    bulk_get_streams

import sqlalchemy
from sqlalchemy import func
from sqlalchemy.sql import select, join, column, literal_column, literal, and_, \
    or_, not_, union_all, alias

import re
import ujson

from zerver.lib.rest import rest_dispatch as _rest_dispatch
rest_dispatch = csrf_exempt((lambda request, *args, **kwargs: _rest_dispatch(request, globals(), *args, **kwargs)))

# This is a Pool that doesn't close connections.  Therefore it can be used with
# existing Django database connections.
class NonClosingPool(sqlalchemy.pool.NullPool):
    def status(self):
        return "NonClosingPool"

    def _do_return_conn(self, conn):
        pass

    def recreate(self):
        return self.__class__(creator=self._creator,
                              recycle=self._recycle,
                              use_threadlocal=self._use_threadlocal,
                              reset_on_return=self._reset_on_return,
                              echo=self.echo,
                              logging_name=self._orig_logging_name,
                              _dispatch=self.dispatch)

sqlalchemy_engine = None
def get_sqlalchemy_connection():
    global sqlalchemy_engine
    if sqlalchemy_engine is None:
        def get_dj_conn():
            connection.ensure_connection()
            return connection.connection
        sqlalchemy_engine = sqlalchemy.create_engine('postgresql://',
                                                     creator=get_dj_conn,
                                                     poolclass=NonClosingPool,
                                                     pool_reset_on_return=False)
    sa_connection = sqlalchemy_engine.connect()
    sa_connection.execution_options(autocommit=False)
    return sa_connection

@authenticated_json_post_view
def json_get_old_messages(request, user_profile):
    return get_old_messages_backend(request, user_profile)

class BadNarrowOperator(Exception):
    def __init__(self, desc):
        self.desc = desc

    def to_json_error_msg(self):
        return 'Invalid narrow operator: ' + self.desc

# When you add a new operator to this, also update zerver/lib/narrow.py
class NarrowBuilder(object):
    def __init__(self, user_profile, msg_id_column):
        self.user_profile = user_profile
        self.msg_id_column = msg_id_column

    def __call__(self, query, term):
        # We have to be careful here because we're letting users call a method
        # by name! The prefix 'by_' prevents it from colliding with builtin
        # Python __magic__ stuff.
        operator = term['operator']
        operand = term['operand']

        negated = term.get('negated', False)

        method_name = 'by_' + operator.replace('-', '_')
        method = getattr(self, method_name, None)
        if method is None:
            raise BadNarrowOperator('unknown operator ' + operator)

        if negated:
            maybe_negate = not_
        else:
            maybe_negate = lambda cond: cond

        return method(query, operand, maybe_negate)

    def by_is(self, query, operand, maybe_negate):
        if operand == 'private':
            query = query.select_from(join(query.froms[0], "zerver_recipient",
                                           column("recipient_id") ==
                                           literal_column("zerver_recipient.id")))
            cond = or_(column("type") == Recipient.PERSONAL,
                       column("type") == Recipient.HUDDLE)
            return query.where(maybe_negate(cond))
        elif operand == 'starred':
            cond = column("flags").op("&")(UserMessage.flags.starred.mask) != 0
            return query.where(maybe_negate(cond))
        elif operand == 'mentioned' or operand == 'alerted':
            cond = column("flags").op("&")(UserMessage.flags.mentioned.mask) != 0
            return query.where(maybe_negate(cond))
        raise BadNarrowOperator("unknown 'is' operand " + operand)

    _alphanum = frozenset(
        'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789')

    def _pg_re_escape(self, pattern):
        """
        Escape user input to place in a regex

        Python's re.escape escapes unicode characters in a way which postgres
        fails on, u'\u03bb' to u'\\\u03bb'. This function will correctly escape
        them for postgres, u'\u03bb' to u'\\u03bb'.
        """
        s = list(pattern)
        for i, c in enumerate(s):
            if c not in self._alphanum:
                if c == '\000':
                    s[1] = '\\000'
                elif ord(c) >= 128:
                    # convert the character to hex postgres regex will take
                    # \uXXXX
                    s[i] = '\\u{:0>4x}'.format(ord(c))
                else:
                    s[i] = '\\' + c
        return ''.join(s)

    def by_stream(self, query, operand, maybe_negate):
        stream = get_stream(operand, self.user_profile.realm)
        if stream is None:
            raise BadNarrowOperator('unknown stream ' + operand)

        if self.user_profile.realm.domain == "mit.edu":
            # MIT users expect narrowing to "social" to also show messages to /^(un)*social(.d)*$/
            # (unsocial, ununsocial, social.d, etc)
            m = re.search(r'^(?:un)*(.+?)(?:\.d)*$', stream.name, re.IGNORECASE)
            if m:
                base_stream_name = m.group(1)
            else:
                base_stream_name = stream.name

            matching_streams = get_active_streams(self.user_profile.realm).filter(
                name__iregex=r'^(un)*%s(\.d)*$' % (self._pg_re_escape(base_stream_name),))
            matching_stream_ids = [matching_stream.id for matching_stream in matching_streams]
            recipients = bulk_get_recipients(Recipient.STREAM, matching_stream_ids).values()
            cond = column("recipient_id").in_([recipient.id for recipient in recipients])
            return query.where(maybe_negate(cond))

        recipient = get_recipient(Recipient.STREAM, type_id=stream.id)
        cond = column("recipient_id") == recipient.id
        return query.where(maybe_negate(cond))

    def by_topic(self, query, operand, maybe_negate):
        if self.user_profile.realm.domain == "mit.edu":
            # MIT users expect narrowing to topic "foo" to also show messages to /^foo(.d)*$/
            # (foo, foo.d, foo.d.d, etc)
            m = re.search(r'^(.*?)(?:\.d)*$', operand, re.IGNORECASE)
            if m:
                base_topic = m.group(1)
            else:
                base_topic = operand

            # Additionally, MIT users expect the empty instance and
            # instance "personal" to be the same.
            if base_topic in ('', 'personal', '(instance "")'):
                regex = r'^(|personal|\(instance ""\))(\.d)*$'
            else:
                regex = r'^%s(\.d)*$' % (self._pg_re_escape(base_topic),)

            cond = column("subject").op("~*")(regex)
            return query.where(maybe_negate(cond))

        cond = func.upper(column("subject")) == func.upper(literal(operand))
        return query.where(maybe_negate(cond))

    def by_sender(self, query, operand, maybe_negate):
        try:
            sender = get_user_profile_by_email(operand)
        except UserProfile.DoesNotExist:
            raise BadNarrowOperator('unknown user ' + operand)

        cond = column("sender_id") == literal(sender.id)
        return query.where(maybe_negate(cond))

    def by_near(self, query, operand, maybe_negate):
        return query

    def by_id(self, query, operand, maybe_negate):
        cond = self.msg_id_column == literal(operand)
        return query.where(maybe_negate(cond))

    def by_pm_with(self, query, operand, maybe_negate):
        if ',' in operand:
            # Huddle
            try:
                emails = [e.strip() for e in operand.split(',')]
                recipient = recipient_for_emails(emails, False,
                    self.user_profile, self.user_profile)
            except ValidationError:
                raise BadNarrowOperator('unknown recipient ' + operand)
            cond = column("recipient_id") == recipient.id
            return query.where(maybe_negate(cond))
        else:
            # Personal message
            self_recipient = get_recipient(Recipient.PERSONAL, type_id=self.user_profile.id)
            if operand == self.user_profile.email:
                # Personals with self
                cond = and_(column("sender_id") == self.user_profile.id,
                            column("recipient_id") == self_recipient.id)
                return query.where(maybe_negate(cond))

            # Personals with other user; include both directions.
            try:
                narrow_profile = get_user_profile_by_email(operand)
            except UserProfile.DoesNotExist:
                raise BadNarrowOperator('unknown user ' + operand)

            narrow_recipient = get_recipient(Recipient.PERSONAL, narrow_profile.id)
            cond = or_(and_(column("sender_id") == narrow_profile.id,
                            column("recipient_id") == self_recipient.id),
                       and_(column("sender_id") == self.user_profile.id,
                            column("recipient_id") == narrow_recipient.id))
            return query.where(maybe_negate(cond))

    def by_search(self, query, operand, maybe_negate):
        tsquery = func.plainto_tsquery(literal("zulip.english_us_search"), literal(operand))
        ts_locs_array = func.ts_match_locs_array
        query = query.column(ts_locs_array(literal("zulip.english_us_search"),
                                           column("rendered_content"),
                                           tsquery).label("content_matches"))
        # We HTML-escape the subject in Postgres to avoid doing a server round-trip
        query = query.column(ts_locs_array(literal("zulip.english_us_search"),
                                           func.escape_html(column("subject")),
                                           tsquery).label("subject_matches"))

        # Do quoted string matching.  We really want phrase
        # search here so we can ignore punctuation and do
        # stemming, but there isn't a standard phrase search
        # mechanism in Postgres
        for term in re.findall('"[^"]+"|\S+', operand):
            if term[0] == '"' and term[-1] == '"':
                term = term[1:-1]
                term = '%' + connection.ops.prep_for_like_query(term) + '%'
                cond = or_(column("content").ilike(term),
                           column("subject").ilike(term))
                query = query.where(maybe_negate(cond))

        cond = column("search_tsvector").op("@@")(tsquery)
        return query.where(maybe_negate(cond))

def highlight_string(string, locs):
    highlight_start = '<span class="highlight">'
    highlight_stop = '</span>'
    pos = 0
    result = ''
    for loc in locs:
        (offset, length) = loc
        result += string[pos:offset]
        result += highlight_start
        result += string[offset:offset + length]
        result += highlight_stop
        pos = offset + length
    result += string[pos:]
    return result

def get_search_fields(rendered_content, subject, content_matches, subject_matches):
    return dict(match_content=highlight_string(rendered_content, content_matches),
                match_subject=highlight_string(escape_html(subject), subject_matches))

def narrow_parameter(json):
    # FIXME: A hack to support old mobile clients
    if json == '{}':
        return None

    data = ujson.loads(json)
    if not isinstance(data, list):
        raise ValueError("argument is not a list")

    def convert_term(elem):
        # We have to support a legacy tuple format.
        if isinstance(elem, list):
            if (len(elem) != 2
                or any(not isinstance(x, str) and not isinstance(x, unicode)
                       for x in elem)):
                raise ValueError("element is not a string pair")
            return dict(operator=elem[0], operand=elem[1])

        if isinstance(elem, dict):
            validator = check_dict([
                ('operator', check_string),
                ('operand', check_string),
            ])

            error = validator('elem', elem)
            if error:
                raise JsonableError(error)

            # whitelist the fields we care about for now
            return dict(
                operator=elem['operator'],
                operand=elem['operand'],
                negated=elem.get('negated', False),
            )

        raise ValueError("element is not a dictionary")

    return map(convert_term, data)

def is_public_stream(stream, realm):
    if not valid_stream_name(stream):
        raise JsonableError("Invalid stream name")
    stream = get_stream(stream, realm)
    if stream is None:
        return False
    return stream.is_public()


def ok_to_include_history(narrow, realm):
    # There are occasions where we need to find Message rows that
    # have no corresponding UserMessage row, because the user is
    # reading a public stream that might include messages that
    # were sent while the user was not subscribed, but which they are
    # allowed to see.  We have to be very careful about constructing
    # queries in those situations, so this function should return True
    # only if we are 100% sure that we're gonna add a clause to the
    # query that narrows to a particular public stream on the user's realm.
    # If we screw this up, then we can get into a nasty situation of
    # polluting our narrow results with messages from other realms.
    include_history = False
    if narrow is not None:
        for term in narrow:
            if term['operator'] == "stream" and not term.get('negated', False):
                if is_public_stream(term['operand'], realm):
                    include_history = True
        # Disable historical messages if the user is narrowing on anything
        # that's a property on the UserMessage table.  There cannot be
        # historical messages in these cases anyway.
        for term in narrow:
            if term['operator'] == "is":
                include_history = False

    return include_history

def exclude_muting_conditions(user_profile):
    muted_topics = ujson.loads(user_profile.muted_topics)
    if muted_topics:
        muted_streams = bulk_get_streams(user_profile.realm,
                                         [muted[0] for muted in muted_topics])
        muted_recipients = bulk_get_recipients(Recipient.STREAM,
                                               [stream.id for stream in muted_streams.itervalues()])
        recipient_map = dict((s.name.lower(), muted_recipients[s.id].id)
                             for s in muted_streams.itervalues())

        muted_topics = [m for m in muted_topics if m[0].lower() in recipient_map]

        if muted_topics:
            def mute_cond(muted):
                stream_cond = column("recipient_id") == recipient_map[muted[0].lower()]
                topic_cond = func.upper(column("subject")) == func.upper(muted[1])
                return and_(stream_cond, topic_cond)

            condition = not_(or_(*map(mute_cond, muted_topics)))
            return [condition]

    return []

@has_request_variables
def get_old_messages_backend(request, user_profile,
                             anchor = REQ(converter=int),
                             num_before = REQ(converter=to_non_negative_int),
                             num_after = REQ(converter=to_non_negative_int),
                             narrow = REQ('narrow', converter=narrow_parameter, default=None),
                             use_first_unread_anchor = REQ(default=False, converter=ujson.loads),
                             apply_markdown=REQ(default=True,
                                                converter=ujson.loads)):
    include_history = ok_to_include_history(narrow, user_profile.realm)

    if include_history and not use_first_unread_anchor:
        query = select([column("id").label("message_id")], None, "zerver_message")
        inner_msg_id_col = literal_column("zerver_message.id")
    elif narrow is None:
        query = select([column("message_id"), column("flags")],
                       column("user_profile_id") == literal(user_profile.id),
                       "zerver_usermessage")
        inner_msg_id_col = column("message_id")
    else:
        # TODO: Don't do this join if we're not doing a search
        query = select([column("message_id"), column("flags")],
                       column("user_profile_id") == literal(user_profile.id),
                       join("zerver_usermessage", "zerver_message",
                            literal_column("zerver_usermessage.message_id") ==
                            literal_column("zerver_message.id")))
        inner_msg_id_col = column("message_id")

    num_extra_messages = 1
    is_search = False

    if narrow is not None:
        # Add some metadata to our logging data for narrows
        verbose_operators = []
        for term in narrow:
            if term['operator'] == "is":
                verbose_operators.append("is:" + term['operand'])
            else:
                verbose_operators.append(term['operator'])
        request._log_data['extra'] = "[%s]" % (",".join(verbose_operators),)

        # Build the query for the narrow
        num_extra_messages = 0
        build = NarrowBuilder(user_profile, inner_msg_id_col)
        for term in narrow:
            if term['operator'] == 'search' and not is_search:
                query = query.column("subject").column("rendered_content")
                is_search = True
            query = build(query, term)

    # We add 1 to the number of messages requested if no narrow was
    # specified to ensure that the resulting list always contains the
    # anchor message.  If a narrow was specified, the anchor message
    # might not match the narrow anyway.
    if num_after != 0:
        num_after += num_extra_messages
    else:
        num_before += num_extra_messages

    sa_conn = get_sqlalchemy_connection()
    if use_first_unread_anchor:
        condition = column("flags").op("&")(UserMessage.flags.read.mask) == 0

        # We exclude messages on muted topics when finding the first unread
        # message in this narrow
        muting_conditions = exclude_muting_conditions(user_profile)
        if muting_conditions:
            condition = and_(condition, *muting_conditions)

        first_unread_query = query.where(condition)
        first_unread_query = first_unread_query.order_by(inner_msg_id_col.asc()).limit(1)
        first_unread_result = list(sa_conn.execute(first_unread_query).fetchall())
        if len(first_unread_result) > 0:
            anchor = first_unread_result[0][0]
        else:
            anchor = 10000000000000000

    before_query = None
    after_query = None
    if num_before != 0:
        before_anchor = anchor
        if num_after != 0:
            # Don't include the anchor in both the before query and the after query
            before_anchor = anchor - 1
        before_query = query.where(inner_msg_id_col <= before_anchor) \
                            .order_by(inner_msg_id_col.desc()).limit(num_before)
    if num_after != 0:
        after_query = query.where(inner_msg_id_col >= anchor) \
                           .order_by(inner_msg_id_col.asc()).limit(num_after)

    if num_before == 0 and num_after == 0:
        # This can happen when a narrow is specified.
        after_query = query.where(inner_msg_id_col == anchor)

    if before_query is not None:
        if after_query is not None:
            query = union_all(before_query.self_group(), after_query.self_group())
        else:
            query = before_query
    else:
        query = after_query
    main_query = alias(query)
    query = select(main_query.c, None, main_query).order_by(column("message_id").asc())
    # This is a hack to tag the query we use for testing
    query = query.prefix_with("/* get_old_messages */")
    query_result = list(sa_conn.execute(query).fetchall())

    # The following is a little messy, but ensures that the code paths
    # are similar regardless of the value of include_history.  The
    # 'user_messages' dictionary maps each message to the user's
    # UserMessage object for that message, which we will attach to the
    # rendered message dict before returning it.  We attempt to
    # bulk-fetch rendered message dicts from memcached using the
    # 'messages' list.
    search_fields = dict()
    message_ids = []
    user_message_flags = {}
    if include_history:
        message_ids = [row[0] for row in query_result]

        # TODO: This could be done with an outer join instead of two queries
        user_message_flags = dict((user_message.message_id, user_message.flags_list()) for user_message in
                                  UserMessage.objects.filter(user_profile=user_profile,
                                                             message__id__in=message_ids))
        for row in query_result:
            message_id = row[0]
            if user_message_flags.get(message_id) is None:
                user_message_flags[message_id] = ["read", "historical"]
            if is_search:
                (_, subject, rendered_content, content_matches, subject_matches) = row
                search_fields[message_id] = get_search_fields(rendered_content, subject,
                                                              content_matches, subject_matches)
    else:
        for row in query_result:
            message_id = row[0]
            flags = row[1]
            user_message_flags[message_id] = parse_usermessage_flags(flags)

            message_ids.append(message_id)

            if is_search:
                (_, _, subject, rendered_content, content_matches, subject_matches) = row
                search_fields[message_id] = get_search_fields(rendered_content, subject,
                                                              content_matches, subject_matches)

    cache_transformer = lambda row: Message.build_dict_from_raw_db_row(row, apply_markdown)
    id_fetcher = lambda row: row['id']

    message_dicts = generic_bulk_cached_fetch(lambda message_id: to_dict_cache_key_id(message_id, apply_markdown),
                                              Message.get_raw_db_rows,
                                              message_ids,
                                              id_fetcher=id_fetcher,
                                              cache_transformer=cache_transformer,
                                              extractor=extract_message_dict,
                                              setter=stringify_message_dict)

    message_list = []
    for message_id in message_ids:
        msg_dict = message_dicts[message_id]
        msg_dict.update({"flags": user_message_flags[message_id]})
        msg_dict.update(search_fields.get(message_id, {}))
        message_list.append(msg_dict)

    statsd.incr('loaded_old_messages', len(message_list))
    ret = {'messages': message_list,
           "result": "success",
           "msg": ""}
    return json_success(ret)

@authenticated_json_post_view
def json_update_flags(request, user_profile):
    return update_message_flags(request, user_profile);

@has_request_variables
def update_message_flags(request, user_profile,
                      messages=REQ('messages', validator=check_list(check_int)),
                      operation=REQ('op'), flag=REQ('flag'),
                      all=REQ('all', validator=check_bool, default=False)):
    request._log_data["extra"] = "[%s %s]" % (operation, flag)
    do_update_message_flags(user_profile, operation, flag, messages, all)
    return json_success({'result': 'success',
                         'messages': messages,
                         'msg': ''})

def create_mirrored_message_users(request, user_profile, recipients):
    if "sender" not in request.POST:
        return (False, None)

    sender_email = request.POST["sender"].strip().lower()
    referenced_users = set([sender_email])
    if request.POST['type'] == 'private':
        for email in recipients:
            referenced_users.add(email.lower())

    if request.client.name == "zephyr_mirror":
        user_check = mit_to_mit
        fullname_function = compute_mit_user_fullname
    elif request.client.name == "irc_mirror":
        user_check = same_realm_irc_user
        fullname_function = compute_irc_user_fullname
    elif request.client.name == "jabber_mirror":
        user_check = same_realm_user
        fullname_function = compute_jabber_user_fullname
    else:
        # Unrecognized mirroring client
        return (False, None)

    for email in referenced_users:
        # Check that all referenced users are in our realm:
        if not user_check(user_profile, email):
            return (False, None)

    # Create users for the referenced users, if needed.
    for email in referenced_users:
        create_mirror_user_if_needed(user_profile.realm, email, fullname_function)

    sender = get_user_profile_by_email(sender_email)
    return (True, sender)

def mit_to_mit(user_profile, email):
    # Are the sender and recipient both @mit.edu addresses?
    # We have to handle this specially, inferring the domain from the
    # e-mail address, because the recipient may not existing in Zulip
    # and we may need to make a stub MIT user on the fly.
    try:
        validators.validate_email(email)
    except ValidationError:
        return False

    domain = resolve_email_to_domain(email)

    return user_profile.realm.domain == "mit.edu" and domain == "mit.edu"

def same_realm_irc_user(user_profile, email):
    # Check whether the target email address is an IRC user in the
    # same realm as user_profile, i.e. if the domain were example.com,
    # the IRC user would need to be username@irc.example.com
    try:
        validators.validate_email(email)
    except ValidationError:
        return False

    domain = resolve_email_to_domain(email)

    return user_profile.realm.domain == domain.replace("irc.", "")

def same_realm_user(user_profile, email):
    try:
        validators.validate_email(email)
    except ValidationError:
        return False

    domain = resolve_email_to_domain(email)

    return user_profile.realm.domain == domain

@authenticated_api_view
def api_send_message(request, user_profile):
    return send_message_backend(request, user_profile)

@authenticated_json_post_view
def json_send_message(request, user_profile):
    return send_message_backend(request, user_profile)

# We do not @require_login for send_message_backend, since it is used
# both from the API and the web service.  Code calling
# send_message_backend should either check the API key or check that
# the user is logged in.
@has_request_variables
def send_message_backend(request, user_profile,
                         message_type_name = REQ('type'),
                         message_to = REQ('to', converter=extract_recipients),
                         forged = REQ(default=False),
                         subject_name = REQ('subject', lambda x: x.strip(), None),
                         message_content = REQ('content'),
                         domain = REQ('domain', default=None),
                         local_id = REQ(default=None, converter=to_non_negative_float),
                         queue_id = REQ(default=None)):
    client = request.client
    is_super_user = is_super_user_api(request)
    if forged and not is_super_user:
        return json_error("User not authorized for this query")

    realm = None
    if domain and domain != user_profile.realm.domain:
        if not is_super_user:
            # The email gateway bot needs to be able to send messages in
            # any realm.
            return json_error("User not authorized for this query")
        realm = get_realm(domain)
        if not realm:
            return json_error("Unknown domain " + domain)

    if client.name in ["zephyr_mirror", "irc_mirror", "jabber_mirror"]:
        # Here's how security works for mirroring:
        #
        # For private messages, the message must be (1) both sent and
        # received exclusively by users in your realm, and (2)
        # received by the forwarding user.
        #
        # For stream messages, the message must be (1) being forwarded
        # by an API superuser for your realm and (2) being sent to a
        # mirrored stream (any stream for the Zephyr and Jabber
        # mirrors, but only streams with names starting with a "#" for
        # IRC mirrors)
        #
        # The security checks are split between the below code
        # (especially create_mirrored_message_users which checks the
        # same-realm constraint) and recipient_for_emails (which
        # checks that PMs are received by the forwarding user)
        if "sender" not in request.POST:
            return json_error("Missing sender")
        if message_type_name != "private" and not is_super_user:
            return json_error("User not authorized for this query")
        (valid_input, mirror_sender) = \
            create_mirrored_message_users(request, user_profile, message_to)
        if not valid_input:
            return json_error("Invalid mirrored message")
        if client.name == "zephyr_mirror" and user_profile.realm.domain != "mit.edu":
            return json_error("Invalid mirrored realm")
        if (client.name == "irc_mirror" and message_type_name != "private" and
            not message_to[0].startswith("#")):
            return json_error("IRC stream names must start with #")
        sender = mirror_sender
    else:
        sender = user_profile

    ret = check_send_message(sender, client, message_type_name, message_to,
                             subject_name, message_content, forged=forged,
                             forged_timestamp = request.POST.get('time'),
                             forwarder_user_profile=user_profile, realm=realm,
                             local_id=local_id, sender_queue_id=queue_id)
    return json_success({"id": ret})

@authenticated_json_post_view
def json_update_message(request, user_profile):
    return update_message_backend(request, user_profile)

@has_request_variables
def update_message_backend(request, user_profile,
                           message_id=REQ(converter=to_non_negative_int),
                           subject=REQ(default=None),
                           propagate_mode=REQ(default="change_one"),
                           content=REQ(default=None)):
    if subject is None and content is None:
        return json_error("Nothing to change")
    do_update_message(user_profile, message_id, subject, propagate_mode, content)
    return json_success()

@authenticated_json_post_view
@has_request_variables
def json_fetch_raw_message(request, user_profile,
                           message_id=REQ(converter=to_non_negative_int)):
    try:
        message = Message.objects.get(id=message_id)
    except Message.DoesNotExist:
        return json_error("No such message")

    if message.sender != user_profile:
        return json_error("Message was not sent by you")

    return json_success({"raw_content": message.content})

@has_request_variables
def render_message_backend(request, user_profile, content=REQ):
    rendered_content = bugdown.convert(content, user_profile.realm.domain)
    return json_success({"rendered": rendered_content})

@authenticated_json_post_view
def json_messages_in_narrow(request, user_profile):
    return messages_in_narrow_backend(request, user_profile)

@has_request_variables
def messages_in_narrow_backend(request, user_profile,
                               msg_ids = REQ(validator=check_list(check_int)),
                               narrow = REQ(converter=narrow_parameter)):
    # Note that this function will only work on messages the user
    # actually received

    # TODO: We assume that the narrow is a search.  For now this works because
    # the browser only ever calls this function for searches, since it can't
    # apply that narrow operator itself.

    query = select([column("message_id"), column("subject"), column("rendered_content")],
                   and_(column("user_profile_id") == literal(user_profile.id),
                        column("message_id").in_(msg_ids)),
                   join("zerver_usermessage", "zerver_message",
                        literal_column("zerver_usermessage.message_id") ==
                        literal_column("zerver_message.id")))

    build = NarrowBuilder(user_profile, column("message_id"))
    for term in narrow:
        query = build(query, term)

    sa_conn = get_sqlalchemy_connection()
    query_result = list(sa_conn.execute(query).fetchall())

    search_fields = dict()
    for row in query_result:
        (message_id, subject, rendered_content, content_matches, subject_matches) = row
        search_fields[message_id] = get_search_fields(rendered_content, subject,
                                                      content_matches, subject_matches)

    return json_success({"messages": search_fields})