meshcore-bot/modules/url_shortener.py

#!/usr/bin/env python3
"""
Shared URL shortening for MeshCore Bot and web viewer.

Two backends are supported, selected by ``short_url_website_service``:
``gd`` (default) uses the v.gd / is.gd-compatible API
(GET .../create.php?format=simple&url=...), and ``shlink`` POSTs to a self-hosted
Shlink instance's /rest/v3/short-urls with an ``X-Api-Key`` header. Configure the
base URL, service, and optional API key under [External_Data] in config.ini.
"""

from __future__ import annotations

import asyncio
import logging
from typing import Any
from urllib.parse import quote

import requests


def _coerce_url_string(url: Any) -> str:
    """Normalize feed/API link values to a string (feedparser may use dicts with href)."""
    if url is None:
        return ""
    if isinstance(url, str):
        return url.strip()
    if isinstance(url, (bytes, bytearray)):
        try:
            return url.decode("utf-8", errors="replace").strip()
        except Exception:
            return ""
    if isinstance(url, dict):
        href = url.get("href") or url.get("url")
        if href is not None:
            return str(href).strip()
        return ""
    return str(url).strip()


def _safe_config_get(config: Any, section: str, option: str, fallback: str = "") -> str:
    """Read config without raising (missing section, interpolation, etc.)."""
    if config is None:
        return fallback
    try:
        get = getattr(config, "get", None)
        if not callable(get):
            return fallback
        return get(section, option, fallback=fallback)
    except Exception:
        return fallback


DEFAULT_SHORT_URL_BASE = "https://v.gd"

# Hostnames that use the public create.php API without an API key query param.
_VGD_COMPAT_HOSTS = frozenset(
    {
        "v.gd",
        "www.v.gd",
        "is.gd",
        "www.is.gd",
    }
)


def _normalize_base(base: str) -> str:
    b = (base or "").strip().rstrip("/")
    return b if b else DEFAULT_SHORT_URL_BASE


def _is_vgd_compat_host(host: str) -> bool:
    """True for the public v.gd / is.gd hosts, which take no API key."""
    return (host or "").lower().split(":")[0] in _VGD_COMPAT_HOSTS


def _host_allows_key_in_query(host: str) -> bool:
    """True if we may append api_key for this host. v.gd/is.gd public API: False."""
    return not _is_vgd_compat_host(host)


def _base_host(base: str) -> str:
    """Hostname of *base*, tolerating a scheme-less value like ``example.com/x``."""
    from urllib.parse import urlparse

    root = (base or "").strip()
    if "://" not in root:
        root = f"https://{root}"
    parsed = urlparse(root)
    return (parsed.hostname or "").lower()


def _parse_simple_response(body: str) -> str | None:
    text = (body or "").strip()
    if not text:
        return None
    if text.startswith("Error:"):
        return None
    if text.startswith("http"):
        return text
    return None


def _build_create_gd_url(long_url: str, base: str, api_key: str) -> str:
    from urllib.parse import urlparse, urlunparse

    encoded = quote(long_url, safe="")
    root = _normalize_base(base)
    if "://" not in root:
        root = f"https://{root}"
    parsed = urlparse(root)
    netloc = parsed.netloc
    if not netloc and parsed.path:
        netloc = parsed.path.split("/")[0]
    path = (parsed.path or "").rstrip("/") + "/create.php"
    if not path.startswith("/"):
        path = "/" + path
    query = f"format=simple&url={encoded}"
    if api_key and _host_allows_key_in_query(parsed.hostname or ""):
        query = f"{query}&key={quote(api_key, safe='')}"
    rebuilt = urlunparse((parsed.scheme or "https", netloc, path, "", query, ""))
    return rebuilt


def _build_create_shlink_url(base: str) -> str:
    """Build the Shlink create endpoint from *base*.

    Only the base is needed: the long URL travels in the POST body and the API key
    in an ``X-Api-Key`` header, never in the URL.
    """
    from urllib.parse import urlparse, urlunparse

    root = _normalize_base(base)
    if "://" not in root:
        root = f"https://{root}"
    parsed = urlparse(root)
    netloc = parsed.netloc
    if not netloc and parsed.path:
        netloc = parsed.path.split("/")[0]
    path = (parsed.path or "").rstrip("/") + "/rest/v3/short-urls"
    return urlunparse((parsed.scheme or "https", netloc, path, "", "", ""))


def _shorten_url_with_shlink(
    long_url: str,
    base: str,
    api_key: str,
    session: requests.Session | None = None,
    timeout: float = 5.0,
    logger: logging.Logger | None = None,
) -> str:
    """Shorten a URL using Shlink API."""
    import json

    shortener_url = _build_create_shlink_url(base)
    headers = {
        "Content-Type": "application/json",
        "X-Api-Key": api_key,
    }
    payload = json.dumps(
        {"longUrl": long_url, "findIfExists": True, "tags": ["meshcore-bot"]}
    )

    post = session.post if session is not None else requests.post
    response = post(shortener_url, headers=headers, data=payload, timeout=timeout)
    if logger:
        logger.debug("Shlink response: %s", response.text)

    # Shlink reports failures as RFC 7807 problem details, which parse as JSON just
    # fine and simply lack shortUrl. Without this check a bad API key looks
    # identical to a URL that could not be shortened, at DEBUG only.
    if not response.ok:
        if logger:
            logger.warning(
                "Shlink shortener returned HTTP %s: %s",
                getattr(response, "status_code", "?"),
                (response.text or "")[:200],
            )
        return ""

    try:
        data = response.json()
    except ValueError:
        if logger:
            logger.warning("Shlink shortener returned a non-JSON body; not shortening.")
        return ""

    short_url = (data or {}).get("shortUrl")
    if short_url:
        return str(short_url)

    if logger:
        logger.warning("Shlink response carried no shortUrl; not shortening.")
    return ""


def _shorten_url_with_gd(
    long_url: str,
    base: str,
    api_key: str,
    session: requests.Session | None = None,
    timeout: float = 5.0,
    logger: logging.Logger | None = None,
) -> str:
    """Shorten a URL using v.gd / is.gd API."""
    shortener_url = _build_create_gd_url(long_url, base, api_key)

    get = session.get if session is not None else requests.get

    response = get(shortener_url, timeout=timeout)
    # A failing proxy or maintenance page can return a body that looks like a URL.
    # Without this check that body is returned as the short link and transmitted.
    if not response.ok:
        if logger:
            logger.warning(
                "URL shortener returned HTTP %s", getattr(response, "status_code", "?")
            )
        return ""

    short = _parse_simple_response(response.text)
    if short:
        return short

    return ""


def shorten_url_sync(
    url: Any,
    *,
    config: Any,
    session: requests.Session | None = None,
    logger: logging.Logger | None = None,
    timeout: float = 5.0,
) -> str:
    """Shorten a URL using [External_Data] short_url_website (default v.gd).

    Returns the shortened URL or empty string on failure.
    """
    try:
        url_str = _coerce_url_string(url)
        if not url_str:
            return ""

        raw_base = _safe_config_get(config, "External_Data", "short_url_website", "")
        service = (
            _safe_config_get(config, "External_Data", "short_url_website_service", "gd")
            .strip()
            .lower()
        )
        api_key = (
            _safe_config_get(config, "External_Data", "short_url_website_api_key", "")
            or ""
        ).strip()

        if service == "shlink":
            # Deliberately not _normalize_base: its v.gd fallback would POST the
            # operator's API key to an unrelated third party when the base is unset.
            base = (raw_base or "").strip().rstrip("/")
            if not base:
                if logger:
                    logger.warning(
                        "short_url_website_service=shlink requires short_url_website "
                        "(there is no default Shlink instance); skipping."
                    )
                return ""
            if not api_key:
                if logger:
                    logger.warning(
                        "short_url_website_service=shlink requires short_url_website_api_key; skipping."
                    )
                return ""
            if _is_vgd_compat_host(_base_host(base)):
                if logger:
                    logger.warning(
                        "short_url_website_service=shlink points at the public %s API, "
                        "which is not Shlink; skipping rather than sending the API key there.",
                        _base_host(base),
                    )
                return ""
            return _shorten_url_with_shlink(
                url_str,
                base,
                api_key,
                session=session,
                timeout=timeout,
                logger=logger,
            )

        # v.gd / is.gd-compatible: api_key is optional (unused for the public hosts,
        # only appended for self-hosted alternates via _host_allows_key_in_query).
        return _shorten_url_with_gd(
            url_str,
            _normalize_base(raw_base),
            api_key,
            session=session,
            timeout=timeout,
            logger=logger,
        )

    except (requests.exceptions.Timeout, requests.exceptions.ConnectionError) as e:
        # Routine on a mesh node with an intermittent uplink. Logging these at ERROR
        # as "unexpected" floods the log and buries the errors that do need triage.
        if logger:
            logger.debug("URL shortener unreachable: %s", e)
        return ""
    except Exception as e:
        if logger:
            logger.error("Unexpected error shortening URL: %s", e)
        return ""


async def shorten_url(
    url: str,
    *,
    config: Any,
    session: requests.Session | None = None,
    logger: logging.Logger | None = None,
    timeout: float = 5.0,
) -> str:
    """Async wrapper: runs shorten_url_sync in the default executor."""
    if not url:
        return ""
    loop = asyncio.get_event_loop()
    try:
        return await loop.run_in_executor(
            None,
            lambda: shorten_url_sync(
                url,
                config=config,
                session=session,
                logger=logger,
                timeout=timeout,
            ),
        )
    except Exception as e:
        if logger:
            logger.debug("Unexpected error shortening URL: %s", e)
        return ""