convert.py

"""Serves ``/convert/...`` URLs to convert data from one protocol to another.

URL pattern is ``/convert/SOURCE/DEST``, where ``SOURCE`` and ``DEST`` are the
``LABEL`` constants from the :class:`protocol.Protocol` subclasses.
"""
from datetime import timedelta
import logging
import re
from urllib.parse import quote, unquote

from flask import redirect, request
from granary import as1
from oauth_dropins.webutil import flask_util, util
from oauth_dropins.webutil.flask_util import error

from activitypub import ActivityPub
from common import (
    CACHE_CONTROL,
    LOCAL_DOMAINS,
    subdomain_wrap,
    SUPERDOMAIN,
)
from flask_app import app
import memcache
from models import Object, PROTOCOLS
from protocol import Protocol
from web import Web

logger = logging.getLogger(__name__)


@app.get(f'/convert/<to>/<path:_>')
@memcache.memoize(expire=timedelta(hours=1))
@flask_util.headers(CACHE_CONTROL)
def convert(to, _, from_=None):
    """Converts data from one protocol to another and serves it.

    Fetches the source data if it's not already stored.

    Note that we don't do conneg or otherwise care about the Accept header here,
    we always serve the "to" protocol's format.

    Args:
      to (str): protocol
      from_ (str): protocol, only used when called by
        :func:`convert_source_path_redirect`
    """
    if from_:
        from_proto = PROTOCOLS.get(from_)
        if not from_proto:
            error(f'No protocol found for {from_}', status=404)
        logger.info(f'Overriding any domain protocol with {from_}')
    else:
        from_proto = Protocol.for_request(fed=Protocol)
    if not from_proto:
        error(f'Unknown protocol {request.host.removesuffix(SUPERDOMAIN)}', status=404)

    to_proto = PROTOCOLS.get(to)
    if not to_proto:
        error('Unknown protocol {to}', status=404)

    # don't use urllib.parse.urlencode(request.args) because that doesn't
    # guarantee us the same query param string as in the original URL, and we
    # want exactly the same thing since we're looking up the URL's Object by id
    path_prefix = f'convert/{to}/'
    id = unquote(request.url.removeprefix(request.root_url).removeprefix(path_prefix))

    # our redirects evidently collapse :// down to :/ , maybe to prevent URL
    # parsing bugs? if that happened to this URL, expand it back to ://
    id = re.sub(r'^(https?:/)([^/])', r'\1/\2', id)

    logger.debug(f'Converting from {from_proto.LABEL} to {to}: {id}')

    # load, and maybe fetch. if it's a post/update, redirect to inner object.
    obj = from_proto.load(id)
    if not obj:
        error(f"Couldn't load {id}", status=404)
    elif not obj.as1:
        error(f'Stored object for {id} has no data', status=404)

    type = as1.object_type(obj.as1)
    if type in as1.CRUD_VERBS or type == 'share':
        if obj_id := as1.get_object(obj.as1).get('id'):
            if obj_obj := from_proto.load(obj_id, remote=False):
                if type == 'share':
                    # TODO: should this be Source.base_object? That's broad
                    # though, includes inReplyTo
                    check_bridged_to(obj_obj, to_proto=to_proto)
                elif (type in as1.CRUD_VERBS
                      and obj_obj.as1
                      and obj_obj.as1.keys() - set(['id', 'url', 'objectType'])):
                    logger.info(f'{type} activity, redirecting to Object {obj_id}')
                    return redirect(f'/{path_prefix}{obj_id}', code=301)

    check_bridged_to(obj, to_proto=to_proto)

    # convert and serve
    return to_proto.convert(obj), {
        'Content-Type': to_proto.CONTENT_TYPE,
    }


def check_bridged_to(obj, to_proto):
    """If ``object`` or its owner isn't bridged to ``to_proto``, raises :class:`werkzeug.exceptions.HTTPException`.

    Args:
      obj (models.Object)
      to_proto (subclass of protocol.Protocol)
    """
    # don't serve deletes or deleted objects
    if obj.deleted or obj.type == 'delete':
        error('Deleted', status=410)

    # don't serve for a given protocol if we haven't bridged it there
    if to_proto.HAS_COPIES and not obj.get_copy(to_proto):
        error(f"{obj.key.id()} hasn't been bridged to {to_proto.LABEL}", status=404)

    # check that owner has this protocol enabled
    if owner := as1.get_owner(obj.as1):
        if from_proto := Protocol.for_id(owner):
            user = from_proto.get_by_id(owner)
            if not user:
                error(f"{from_proto.LABEL} user {owner} not found", status=404)
            elif not user.is_enabled(to_proto):
                error(f"{from_proto.LABEL} user {owner} isn't bridged to {to_proto.LABEL}", status=404)


@app.get(f'/convert/<from_>/<to>/<path:_>')
def convert_source_path_redirect(from_, to, _):
    """Old route that included source protocol in path instead of subdomain.

    DEPRECATED! Only kept to support old webmention source URLs.
    """
    if Protocol.for_request() not in (None, 'web'):  # no per-protocol subdomains
        error(f'Try again on fed.brid.gy', status=404)

    # in prod, eg gunicorn, the path somehow gets URL-decoded before we see
    # it, so we need to re-encode.
    new_path = quote(request.full_path.rstrip('?').replace(f'/{from_}/', '/'),
                     safe=':/%')

    if request.host in LOCAL_DOMAINS:
        request.url = request.url.replace(f'/{from_}/', '/')
        return convert(to, None, from_=from_)

    proto = PROTOCOLS.get(from_)
    if not proto:
        error(f'No protocol found for {from_}', status=404)

    return redirect(subdomain_wrap(proto, new_path), code=301)