microblog.pub/app/webfinger.py

from typing import Any
from urllib.parse import urlparse

import httpx
from loguru import logger

from app import config


async def webfinger(
    resource: str,
) -> dict[str, Any] | None:  # noqa: C901
    """Mastodon-like WebFinger resolution to retrieve the activity stream Actor URL."""
    logger.info(f"performing webfinger resolution for {resource}")
    protos = ["https", "http"]
    if resource.startswith("http://"):
        protos.reverse()
        host = urlparse(resource).netloc
    elif resource.startswith("https://"):
        host = urlparse(resource).netloc
    else:
        if resource.startswith("acct:"):
            resource = resource[5:]
        if resource.startswith("@"):
            resource = resource[1:]
        _, host = resource.split("@", 1)
        resource = "acct:" + resource

    is_404 = False

    async with httpx.AsyncClient() as client:
        for i, proto in enumerate(protos):
            try:
                url = f"{proto}://{host}/.well-known/webfinger"
                resp = await client.get(
                    url,
                    params={"resource": resource},
                    headers={
                        "User-Agent": config.USER_AGENT,
                    },
                    follow_redirects=True,
                )
                resp.raise_for_status()
                break
            except httpx.HTTPStatusError as http_error:
                logger.exception("HTTP error")
                if http_error.response.status_code in [403, 404, 410]:
                    is_404 = True
                    continue
                raise
            except httpx.HTTPError:
                logger.exception("req failed")
                # If we tried https first and the domain is "http only"
                if i == 0:
                    continue
                break
    if is_404:
        return None

    return resp.json()


async def get_remote_follow_template(resource: str) -> str | None:
    data = await webfinger(resource)
    if data is None:
        return None
    for link in data["links"]:
        if link.get("rel") == "http://ostatus.org/schema/1.0/subscribe":
            return link.get("template")
    return None


async def get_actor_url(resource: str) -> str | None:
    """Mastodon-like WebFinger resolution to retrieve the activity stream Actor URL.

    Returns:
        the Actor URL or None if the resolution failed.
    """
    data = await webfinger(resource)
    if data is None:
        return None
    for link in data["links"]:
        if (
            link.get("rel") == "self"
            and link.get("type") == "application/activity+json"
        ):
            return link.get("href")
    return None