bridgy-fed/ids.py

"""Translates user ids, handles, and object ids between protocols.

https://fed.brid.gy/docs#translate
"""
import logging
import re
from threading import Lock
from urllib.parse import urljoin, urlparse

from cachetools import cached, LRUCache
from flask import request
from google.cloud.ndb.query import FilterNode, Query
from granary.bluesky import BSKY_APP_URL_RE, web_url_to_at_uri
from oauth_dropins.webutil import util

from common import (
    LOCAL_DOMAINS,
    PRIMARY_DOMAIN,
    PROTOCOL_DOMAINS,
    subdomain_wrap,
    SUPERDOMAIN,
)
import models

logger = logging.getLogger(__name__)

# Protocols to check User.copies and Object.copies before translating
# populated in models.reset_protocol_properties
COPIES_PROTOCOLS = None

# Webfinger allows all sorts of characters that ATProto handles don't,
# notably _ and ~. Map those to -.
# ( : (colon) is mostly just used in the fake protocols in unit tests.)
# https://www.rfc-editor.org/rfc/rfc7565.html#section-7
# https://atproto.com/specs/handle
# https://github.com/snarfed/bridgy-fed/issues/982
# https://github.com/swicg/activitypub-webfinger/issues/9
ATPROTO_DASH_CHARS = ('_', '~', ':')

# can't use translate_user_id because Web.owns_id checks valid_domain, which
# doesn't allow our protocol subdomains
BOT_ACTOR_AP_IDS = tuple(f'https://{domain}/{domain}' for domain in PROTOCOL_DOMAINS)


@cached(LRUCache(10000), lock=Lock())
def web_ap_base_domain(user_domain):
    """Returns the full Bridgy Fed domain to use for a given Web user.

    Specifically, returns ``http://localhost/` if we're running locally,
    ``https://[ap_subdomain].brid.gy/`` for the Web entity for this domain if it
    exists, otherwise ``https://web.brid.gy/``.

    Args:
      user_domain (str)

    Returns:
      str:
    """
    if (request.host in LOCAL_DOMAINS and
            not (user_domain == PRIMARY_DOMAIN or user_domain in PROTOCOL_DOMAINS)):
        return request.host_url

    from web import Web
    if user := Web.get_by_id(user_domain):
        return f'https://{user.ap_subdomain}{SUPERDOMAIN}/'

    return f'https://web{SUPERDOMAIN}/'


def translate_user_id(*, id, from_, to):
    """Translate a user id from one protocol to another.

    TODO: unify with :func:`translate_object_id`.

    Args:
      id (str)
      from_ (protocol.Protocol)
      to (protocol.Protocol)

    Returns:
      str: the corresponding id in ``to``
    """
    assert id and from_ and to, (id, from_, to)
    assert from_.owns_id(id) is not False or from_.LABEL == 'ui', \
        (id, from_.LABEL, to.LABEL)

    parsed = urlparse(id)
    if from_.LABEL == 'web' and parsed.path.strip('/') == '':
        # home page; replace with domain
        id = parsed.netloc

    # bsky.app profile URL to DID
    if to.LABEL == 'atproto':
        if match := BSKY_APP_URL_RE.match(id):
            repo = match.group('id')
            if repo.startswith('did:'):
                return repo

            from atproto import ATProto
            try:
                return ATProto.handle_to_id(repo)
            except (AssertionError, ValueError) as e:
                logger.warning(e)
                return None

    if from_ == to:
        return id

    # follow use_instead
    user = from_.get_by_id(id)
    if user:
        id = user.key.id()

    if from_.LABEL in COPIES_PROTOCOLS or to.LABEL in COPIES_PROTOCOLS:
        if user:
            if copy := user.get_copy(to):
                return copy
        if orig := models.get_original(id):
            if isinstance(orig, to):
                return orig.key.id()

    match from_.LABEL, to.LABEL:
        case _, 'atproto' | 'nostr':
            logger.warning(f"Can't translate user id {id} to {to.LABEL} , haven't copied it there yet!")
            return None

        case 'web', 'activitypub':
            return urljoin(web_ap_base_domain(id), id)

        case 'activitypub', 'web':
            return id

        case _, 'activitypub' | 'web':
            return subdomain_wrap(from_, f'/{to.ABBREV}/{id}')

        # only for unit tests
        case _, 'fake' | 'other' | 'eefake':
            return f'{to.LABEL}:u:{id}'
        case 'fake' | 'other', _:
            return id

    assert False, (id, from_.LABEL, to.LABEL)


def normalize_user_id(*, id, proto):
    """Normalizes a user id to its canonical representation in a given protocol.

    Examples:

    * Web:
      * user.com => user.com
      * www.user.com => user.com
      * https://user.com/ => user.com
    * ATProto:
      * did:plc:123 => did:plc:123
      * https://bsky.app/profile/did:plc:123 => did:plc:123

    Args:
      id (str)
      proto (protocol.Protocol)

    Returns:
      str: the normalized user id
    """
    normalized = translate_user_id(id=id, from_=proto, to=proto)

    if proto.LABEL == 'web':
        normalized = util.domain_from_link(normalized)

    return normalized


def profile_id(*, id, proto):
    """Returns the profile object id for a given user id.

    Examples:

    * Web: user.com => https:///user.com/
    * ActivityPub: https://inst.ance/alice => https://inst.ance/alice
    * ATProto: did:plc:123 => at://did:plc:123/app.bsky.actor.profile/self

    Args:
      id (str)
      proto (protocol.Protocol)

    Returns:
      str: the profile id
    """
    assert proto.owns_id(id) is not False, (id, proto.LABEL)

    match proto.LABEL:
        case 'atproto':
            return f'at://{id}/app.bsky.actor.profile/self'

        case 'fake':
            return id.replace('fake:', 'fake:profile:')

        case 'web':
            return f'https://{id}/'

        case _:
            return id


def translate_handle(*, handle, from_, to, enhanced):
    """Translates a user handle from one protocol to another.

    Args:
      handle (str)
      from_ (protocol.Protocol)
      to (protocol.Protocol)
      enhanced (bool): whether to convert to an "enhanced" handle based on the
        user's domain

    Returns:
      str: the corresponding handle in ``to``

    Raises:
      ValueError: if the user's handle is invalid, eg begins or ends with an
        underscore or dash
    """
    assert handle and from_ and to, (handle, from_, to)
    if not from_.LABEL == 'ui':
        if from_.owns_handle(handle, allow_internal=True) is False:
            raise ValueError(f'input handle {handle} is not valid for {from_.LABEL}')

    if from_ == to:
        return handle

    output = None
    match from_.LABEL, to.LABEL:
        case _, 'activitypub':
            domain = f'{from_.ABBREV}{SUPERDOMAIN}'
            if enhanced or handle == PRIMARY_DOMAIN or handle in PROTOCOL_DOMAINS:
                domain = handle
            output = f'@{handle}@{domain}'

        case _, 'atproto':
            output = handle.lstrip('@').replace('@', '.')
            for from_char in ATPROTO_DASH_CHARS:
                output = output.replace(from_char, '-')

            if enhanced or handle == PRIMARY_DOMAIN or handle in PROTOCOL_DOMAINS:
                pass
            else:
                output = f'{output}.{from_.ABBREV}{SUPERDOMAIN}'

        case 'activitypub', 'web':
            user, instance = handle.lstrip('@').split('@')
            # TODO: get this from the actor object's url field?
            output = (f'https://{user}' if user == instance
                    else f'https://{instance}/@{user}')

        case _, 'web':
            output = handle

        # only for unit tests
        case _, 'fake' | 'other' | 'eefake':
            output = f'{to.LABEL}:handle:{handle}'

    assert output, (handle, from_.LABEL, to.LABEL)
    # don't check Web handles because they're sometimes URLs, eg
    # @user@instance => https://instance/@user
    if to.LABEL != 'web' and to.owns_handle(output, allow_internal=True) is False:
        raise ValueError(f'translated handle {output} is not valid for {to.LABEL}')

    return output


def translate_object_id(*, id, from_, to):
    """Translates a user handle from one protocol to another.

    TODO: unify with :func:`translate_user_id`.

    Args:
      id (str)
      from_ (protocol.Protocol)
      to (protocol.Protocol)

    Returns:
      str: the corresponding id in ``to``
    """
    assert id and from_ and to, (id, from_, to)
    assert from_.owns_id(id) is not False or from_.LABEL == 'ui'

    # bsky.app profile URL to DID
    if to.LABEL == 'atproto':
        if match := BSKY_APP_URL_RE.match(id):
            repo = match.group('id')
            handle = None
            if not repo.startswith('did:'):
                handle = repo
                from atproto import ATProto
                try:
                    repo = ATProto.handle_to_id(repo)
                except (AssertionError, ValueError) as e:
                    logger.warning(e)
                    return None

            return web_url_to_at_uri(id, handle=handle, did=repo)

    if from_ == to:
        return id

    if from_.LABEL in COPIES_PROTOCOLS or to.LABEL in COPIES_PROTOCOLS:
        if obj := from_.load(id, remote=False):
            if copy := obj.get_copy(to):
                return copy
        if orig := models.get_original(id):
            return orig.key.id()

    match from_.LABEL, to.LABEL:
        case _, 'atproto' | 'nostr':
            logger.warning(f"Can't translate object id {id} to {to.LABEL} , haven't copied it there yet!")
            return id

        case 'web', 'activitypub':
            return urljoin(web_ap_base_domain(util.domain_from_link(id)), f'/r/{id}')

        case _, 'activitypub' | 'web':
            return subdomain_wrap(from_, f'/convert/{to.ABBREV}/{id}')

        # only for unit tests
        case _, 'fake' | 'other' | 'eefake':
            return f'{to.LABEL}:o:{from_.ABBREV}:{id}'

    assert False, (id, from_.LABEL, to.LABEL)