new file: README.md
new file: app.py new file: config.json new file: requirements.txt
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SimolZimol
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app.py
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306
app.py
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"""
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Links – Flask Redirect & Link-Preview-Server
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=============================================
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Leitet festgelegte Routen (siehe config.json) auf externe URLs um.
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Damit Social-Media-Plattformen (Facebook, WhatsApp, Twitter/X, LinkedIn …)
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eine korrekte Link-Preview (Open-Graph-Metadaten) der *Ziel*-Seite anzeigen,
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wird bei Crawler-Anfragen nicht direkt weitergeleitet, sondern eine HTML-Seite
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mit den kopierten Metadaten der Zielseite ausgeliefert. Normale Browser
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bekommen eine einfache 302-Weiterleitung.
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"""
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import json
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import logging
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import os
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import re
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import time
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from urllib.parse import urlparse
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import requests
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from bs4 import BeautifulSoup
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from flask import Flask, Response, abort, redirect, request
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# ---------------------------------------------------------------------------
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# Konfiguration
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# ---------------------------------------------------------------------------
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BASE_DIR = os.path.dirname(os.path.abspath(__file__))
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CONFIG_PATH = os.environ.get("LINKS_CONFIG", os.path.join(BASE_DIR, "config.json"))
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CACHE_TTL = int(os.environ.get("LINKS_CACHE_TTL", "3600")) # Sekunden (1 Std.)
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FETCH_TIMEOUT = float(os.environ.get("LINKS_FETCH_TIMEOUT", "10"))
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logging.basicConfig(level=logging.INFO)
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log = logging.getLogger("links")
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app = Flask(__name__)
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# ---------------------------------------------------------------------------
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# Config laden
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# ---------------------------------------------------------------------------
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# Wenn eine Änderung an config.json vorgenommen wird, wird sie automatisch
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# neu geladen (Last-Modified-Check).
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_config_mtime = 0.0
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_routes = {}
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def load_config(force: bool = False) -> dict:
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"""Lädt die Routen-Konfiguration. Liefert dict: {path: {url, ...}}."""
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global _config_mtime, _routes
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try:
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mtime = os.path.getmtime(CONFIG_PATH)
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except FileNotFoundError:
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log.error("config.json nicht gefunden: %s", CONFIG_PATH)
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return {}
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if not force and mtime == _config_mtime and _routes:
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return _routes
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try:
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with open(CONFIG_PATH, "r", encoding="utf-8") as fh:
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data = json.load(fh)
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except (json.JSONDecodeError, OSError) as exc:
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log.error("config.json konnte nicht gelesen werden: %s", exc)
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return _routes
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routes = data.get("routes", {})
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normalized = {}
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for path, target in routes.items():
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path = path if path.startswith("/") else "/" + path
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normalized[path] = target
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_routes = normalized
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_config_mtime = mtime
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log.info("Konfiguration geladen: %d Route(n)", len(_routes))
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return _routes
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# ---------------------------------------------------------------------------
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# Open-Graph-Metadaten sammeln + cachen
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# ---------------------------------------------------------------------------
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_CACHE = {} # url -> {"expires": timestamp, "meta": {...}}
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def _looks_like_bot() -> bool:
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"""Erkennt Social-Media-/Preview-Crawler anhand des User-Agents."""
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ua = request.headers.get("User-Agent", "").lower()
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bots = (
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"facebookexternalhit", "facebot", "twitterbot", "xbot", "linkedinbot",
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"whatsapp", "slackbot", "discordbot", "telegrambot", "pinterest",
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"tumblr", "redditbot", "vkShare", "vkbot", "embedly", "quora link",
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"outbrain", "bingbot", "googlebot", "duckduckbot", "baiduspider",
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"yandex", "skypeuripreview", "snapchat", "line-pc", "tinderbot",
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"curl", "wget", "python-requests", "preview", "bot",
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)
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return any(bot in ua for bot in bots)
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def _extract_meta(soup: BeautifulSoup) -> dict:
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"""Extrahiert die wichtigsten Open-Graph-/Meta-Tags aus der Zielseite."""
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meta = {
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"title": _meta_content(soup, "og:title") or _tag_text(soup, "title") or "",
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"description": _meta_content(soup, "og:description")
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or _meta_content(soup, "description") or "",
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"image": _meta_content(soup, "og:image") or _meta_content(soup, "og:image:url") or "",
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"url": _meta_content(soup, "og:url") or "",
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"site_name": _meta_content(soup, "og:site_name") or "",
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"type": _meta_content(soup, "og:type") or "website",
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"favicon": _favicon(soup),
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}
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# Vorangestelltes Präfix (z. B. "Seite - Titel") entfernen
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if " - " in meta["title"]:
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meta["title"] = meta["title"].split(" - ")[0].strip() or meta["title"]
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return {k: (v or "").strip() for k, v in meta.items()}
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def _meta_content(soup: BeautifulSoup, prop: str) -> str:
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tag = soup.find("meta", attrs={"property": prop}) or soup.find(
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"meta", attrs={"name": prop}
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)
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return tag.get("content", "").strip() if tag else ""
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def _tag_text(soup: BeautifulSoup, name: str) -> str:
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tag = soup.find(name)
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return tag.get_text(strip=True) if tag else ""
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def _favicon(soup: BeautifulSoup) -> str:
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icon = soup.find("link", rel=lambda r: r and "icon" in r.lower())
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return icon.get("href", "") if icon else ""
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def _resolve_absolute(base_url: str, value: str) -> str:
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if not value:
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return ""
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if value.startswith(("http://", "https://", "//")):
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if value.startswith("//"):
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return "https:" + value
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return value
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return requests.compat.urljoin(base_url, value)
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def fetch_meta(target_url: str) -> dict:
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"""Holt die Metadaten der Ziel-URL, mit einfachem TTL-Cache."""
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now = time.time()
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cached = _CACHE.get(target_url)
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if cached and cached["expires"] > now:
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return cached["meta"]
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meta = {"title": "", "description": "", "image": "", "url": target_url,
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"site_name": "", "type": "website", "favicon": ""}
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try:
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resp = requests.get(target_url, timeout=FETCH_TIMEOUT, allow_redirects=True,
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headers={"User-Agent": "Mozilla/5.0 (compatible; LinkPreview/1.0)"})
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resp.raise_for_status()
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if "text/html" not in resp.headers.get("Content-Type", ""):
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raise ValueError("Keine HTML-Seite")
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soup = BeautifulSoup(resp.text, "html.parser")
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meta = _extract_meta(soup)
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base = resp.url or target_url
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meta["image"] = _resolve_absolute(base, meta["image"])
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meta["favicon"] = _resolve_absolute(base, meta["favicon"])
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if not meta["url"]:
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meta["url"] = base
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except Exception as exc: # noqa: BLE001 – Zielseite darf den Server nicht brechen
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log.warning("Metadaten für %s konnten nicht geladen werden: %s", target_url, exc)
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_CACHE[target_url] = {"expires": now + CACHE_TTL, "meta": meta}
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return meta
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def _render_preview_page(target_url: str) -> str:
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"""Baut eine HTML-Seite mit den OG-Metadaten der Zielseite."""
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m = fetch_meta(target_url)
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title = m["title"] or "Link"
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desc = m["description"] or "Dieser Link leitet weiter."
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image = m["image"] or ""
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site_name = m["site_name"] or ""
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favicon = m["favicon"] or ""
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# Noch einmal auf den Ziel-Pfad weiterleiten, falls der Crawler doch
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# weitergehen möchte, und die Metadaten für Bots einsetzen.
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head_tags = (
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f'<meta property="og:title" content="{_escape(title)}" />\n'
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f'<meta property="og:description" content="{_escape(desc)}" />\n'
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f'<meta property="og:url" content="{_escape(m["url"] or target_url)}" />\n'
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f'<meta property="og:type" content="{_escape(m["type"])}" />'
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)
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if image:
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head_tags += f'\n<meta property="og:image" content="{_escape(image)}" />'
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if site_name:
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head_tags += f'\n<meta property="og:site_name" content="{_escape(site_name)}" />'
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if favicon:
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head_tags += f'\n<link rel="icon" href="{_escape(favicon)}" />'
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# Einfache Zwischenseite mit Auto-Weiterleitung nach 0 Sekunden,
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# damit auch Menschen, die die Seite direkt ansehen, weiterkommen.
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html = f"""<!DOCTYPE html>
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<html lang="de">
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<head>
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<meta charset="utf-8" />
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<title>{_escape(title)}</title>
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{head_tags}
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<meta name="referrer" content="no-referrer" />
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<meta http-equiv="refresh" content="0;url={_escape(target_url)}" />
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<style>
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body {{ font-family: -apple-system, Segoe UI, Roboto, sans-serif;
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background:#f6f7f9; color:#1c1e21; display:flex; align-items:center;
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justify-content:center; min-height:100vh; margin:0; }}
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.card {{ background:#fff; border-radius:12px; box-shadow:0 2px 10px rgba(0,0,0,.1);
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max-width:480px; padding:32px; text-align:center; }}
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.card h1 {{ font-size:22px; margin:0 0 8px; }}
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.card p {{ color:#555; margin:0 0 20px; }}
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a.button {{ display:inline-block; background:#1877f2; color:#fff; text-decoration:none;
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padding:10px 22px; border-radius:8px; font-weight:600; }}
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</style>
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</head>
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<body>
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<div class="card">
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<h1>{_escape(title)}</h1>
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<p>{_escape(desc)}</p>
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<a class="button" href="{_escape(target_url)}">Weiter zum Ziel</a>
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</div>
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</body>
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</html>"""
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return html
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def _escape(value: str) -> str:
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"""HTML-Escaping für sichere Einbettung in das Markup."""
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return (
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str(value)
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.replace("&", "&")
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.replace("<", "<")
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.replace(">", ">")
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.replace('"', """)
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.replace("'", "'")
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)
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# ---------------------------------------------------------------------------
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# Routen
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# ---------------------------------------------------------------------------
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@app.route("/")
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def index():
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routes = load_config()
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rows = "".join(
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f'<li><a href="{_escape(p)}">{_escape(p)}</a> → '
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f'<small>{_escape(r)}</small></li>'
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for p, r in sorted(routes.items())
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)
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return (
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"<!DOCTYPE html><html><head><meta charset='utf-8'><title>Links</title></head>"
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"<body><h1>Verfügbare Links</h1><ul>" + (rows or "<li>Keine Routen konfiguriert.</li>")
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+ "</ul></body></html>",
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200,
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{"Content-Type": "text/html; charset=utf-8"},
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)
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@app.route("/<path:path>")
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def link_redirect(path: str):
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routes = load_config()
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target_url = routes.get("/" + path)
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# Alternativ: ohne führenden Slash in der Config?
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if target_url is None:
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target_url = routes.get(path)
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if target_url is None:
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abort(404)
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# Social-Media-Bots / Preview-Crawler bekommen die Metadaten-Seite
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if _looks_like_bot():
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return Response(_render_preview_page(target_url), mimetype="text/html")
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# Alle anderen werden direkt weitergeleitet
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return redirect(target_url, code=302)
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@app.errorhandler(404)
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def not_found(_):
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return (
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"<!DOCTYPE html><html><head><meta charset='utf-8'><title>404</title></head>"
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"<body><h1>404 – Nicht gefunden</h1><p>Dieser Link existiert nicht.</p></body></html>",
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404,
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{"Content-Type": "text/html; charset=utf-8"},
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)
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@app.before_request
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def refresh_config():
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"""Liest config.json bei jeder Anfrage neu, falls sie sich geändert hat."""
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load_config()
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# Lokale Konfiguration beim Start laden
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load_config()
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if __name__ == "__main__":
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# Debug-Server (nur für lokale Entwicklung)
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port = int(os.environ.get("PORT", "5000"))
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app.run(host="0.0.0.0", port=port, debug=True)
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