105 lines
4.1 KiB
Python
105 lines
4.1 KiB
Python
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"""/api/v2/narrative — serve the precomputed plain-English summary for one day.
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This endpoint is **read-only with respect to the model**. It never calls Ollama,
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never blocks on one, and has no code path that could. It reads one row from the
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derived store and returns it. That is the entire point of the design: inference
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runs on the operator's desktop on a batch cadence
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(``scripts/generate_narratives.py``), so thermograph.org keeps answering at
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database speed whether or not that machine is powered on, whether or not the
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WireGuard mesh is up, and whether or not a GPU is currently present in it.
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A cache miss is an ordinary, expected outcome — a cell nobody has generated for
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yet, or a day beyond what the last batch covered. It answers 200 with
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``narrative: null`` and ``status: "pending"`` rather than 404, because "no
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sentence yet" is not a client error and a frontend should render the page
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without the sentence rather than treat the response as a failure.
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"""
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import datetime
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import hashlib
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import json
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import os
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from fastapi import APIRouter, HTTPException, Query, Request, Response
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from data import grid
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from data import narrator
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from data import store
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router = APIRouter(tags=["narrative"])
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_BASE = os.environ.get("THERMOGRAPH_BASE", "/thermograph").strip("/")
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BASE = f"/{_BASE}" if _BASE else ""
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def _parse_date(value: str | None) -> datetime.date:
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"""Target date, defaulting to today. Mirrors web/app.py's _parse_target_date
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contract (400 on an unparseable date rather than a silent fallback)."""
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if not value:
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return datetime.date.today()
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try:
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return datetime.date.fromisoformat(value)
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except ValueError:
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raise HTTPException(status_code=400, detail="date must be YYYY-MM-DD")
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def _etag_for(cell_id: str, key: str, token: str, stamp) -> str:
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"""Weak ETag over the row's identity *and* its generation stamp.
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Folding the stamp in is what makes a pending response safely cacheable: while
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the narrative is missing the tag is stable (so revalidation is a cheap 304),
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and the moment the batch job writes the row the stamp changes, the tag
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changes, and the client gets the sentence on its next revalidate."""
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raw = f"{cell_id}:{key}:{token}:{stamp if stamp is not None else 'pending'}"
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return f'W/"{hashlib.sha1(raw.encode()).hexdigest()[:20]}"'
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def _not_modified(request: Request, etag: str) -> bool:
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inm = request.headers.get("if-none-match")
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if not inm:
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return False
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tags = {t.strip() for t in inm.split(",")}
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return "*" in tags or etag in tags or etag.removeprefix("W/") in tags
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def api_narrative(
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request: Request,
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lat: float = Query(..., ge=-90, le=90),
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lon: float = Query(..., ge=-180, le=180),
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date: str | None = Query(None, description="target date YYYY-MM-DD (default today)"),
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):
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"""The stored one-sentence summary of how unusual this day was here.
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Percentile-relative, like every other Thermograph surface: it describes where
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the day sits against ~45 years of this location's own history, and by
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construction contains no temperature or rainfall figure (see data/narrator.py
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— the model is never given one). Not a forecast.
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"""
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target = _parse_date(date)
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cell = grid.snap(lat, lon)
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key = narrator.narrative_key(target)
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token = narrator.narrative_token()
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row = store.get_narrative(cell["id"], key, token)
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etag = _etag_for(cell["id"], key, token, (row or {}).get("generated_at"))
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if _not_modified(request, etag):
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return Response(status_code=304, headers={"ETag": etag})
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payload = {
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"cell": {"id": cell["id"],
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"center_lat": cell["center_lat"],
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"center_lon": cell["center_lon"]},
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"date": target.isoformat(),
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"narrative": row["text"] if row else None,
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"status": "ready" if row else "pending",
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"model": row["model"] if row else None,
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"generated_at": row["generated_at"] if row else None,
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}
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return Response(
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content=json.dumps(payload, separators=(",", ":")).encode(),
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media_type="application/json",
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headers={"ETag": etag},
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)
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router.add_api_route("/narrative", api_narrative, methods=["GET"])
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