add first implementation

api/app.py

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+from fastapi import FastAPI, HTTPException
+from fastapi.responses import JSONResponse
+import feedparser
+import re
+import datetime as dt
+from email.utils import parsedate_to_datetime
+
+app = FastAPI()
+
+BASE = "https://www.umwelt.sachsen.de/umwelt/infosysteme/hwims/portal/web/feed/wasserstand-pegel-{}"
+
+def parse_number(pattern, text):
+    m = re.search(pattern, text, re.I)
+    return float(m.group(1).replace(",", ".")) if m else None
+
+def parse_text(pattern, text):
+    m = re.search(pattern, text, re.I)
+    return m.group(1).strip() if m else None
+
+def clean_text(text):
+    text = re.sub(r"<br\s*/?>", "\n", text, flags=re.I)
+    text = re.sub(r"<[^>]+>", " ", text)
+    return text
+
+def extract_station_name(title: str):
+    if not title:
+        return None
+
+    m = re.search(r"Pegel\s+(.+)$", title)
+    return m.group(1).strip() if m else title
+
+def parse_timestamp(entry):
+    if entry.get("dc_date"):
+        return entry.get("dc_date")
+
+    if entry.get("published"):
+        return parsedate_to_datetime(entry.get("published")).isoformat()
+
+    return None
+
+def parse_entry(entry):
+    text = clean_text(entry.get("description", ""))
+
+    return {
+        "timestamp": parse_timestamp(entry),
+        "title": entry.get("title"),
+        "water_level_cm": parse_number(
+            r"Wasserstand:\s*([0-9]+(?:[,.][0-9]+)?)\s*cm", text
+        ),
+        "flow_m3s": parse_number(
+            r"Durchfluss:\s*([0-9]+(?:[,.][0-9]+)?)\s*m³/s", text
+        ),
+        "flood_alert_level": parse_text(
+            r"Meldestufe:\s*([^\n\r]+)", text
+        ),
+    }
+
+@app.get("/api/pegel/{pegel_id}")
+def get_pegel(pegel_id: str):
+    if not re.fullmatch(r"\d{6,}", pegel_id):
+        raise HTTPException(400, "Ungültige Pegel-ID")
+
+    url = BASE.format(pegel_id)
+    feed = feedparser.parse(url)
+
+    if not feed.entries:
+        raise HTTPException(404, "Keine Daten gefunden")
+
+    entries = [parse_entry(entry) for entry in feed.entries]
+
+    return JSONResponse({
+        "station_id": pegel_id,
+        "station_title": extract_station_name(feed.feed.get("title")),
+        "count": len(entries),
+        "latest": entries[0],
+        "entries": entries,
+        "source": url,
+        "fetched_at": dt.datetime.now(dt.UTC).isoformat(),
+    })

requirements.txt

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+fastapi
+feedparser