ticker-validate: add /api/ticker/historical with weekend-walkback

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/routers/ticker_validate.py

@@ -76,3 +76,81 @@ async def validate_ticker(
         "currency": quote.currency,
         "as_of": quote.as_of,
     }
+
+
+async def fetch_yahoo_historical(
+    client: httpx.AsyncClient,
+    symbol: str,
+    target_iso: str,
+) -> tuple[float | None, str | None, str | None]:
+    """Fetch the close on ``target_iso`` or the nearest preceding trading
+    day's close (within the available history window).
+
+    Returns ``(close, currency, actual_iso)`` or ``(None, None, None)``
+    when no usable data exists. Raises on provider-level HTTP errors
+    (the caller wraps these into a friendly ``ok:false`` response).
+    """
+    range_param = _yahoo_range_covering(target_iso)
+    r = await client.get(
+        YAHOO_CHART.format(symbol=symbol),
+        params={"interval": "1d", "range": range_param,
+                "includePrePost": "false"},
+        headers=UA,
+        timeout=15,
+    )
+    r.raise_for_status()
+    result = r.json().get("chart", {}).get("result")
+    if not result:
+        return None, None, None
+    res = result[0]
+    currency = (res.get("meta") or {}).get("currency")
+    timestamps = res.get("timestamp") or []
+    closes = (res.get("indicators", {}).get("quote") or [{}])[0].get("close") or []
+    series = [(t, c) for t, c in zip(timestamps, closes) if c is not None]
+    if not series:
+        return None, None, None
+    target_dt = datetime.strptime(target_iso, "%Y-%m-%d").replace(tzinfo=timezone.utc)
+    # Add a 24h buffer so the target day itself is included (Yahoo
+    # timestamps are at market open, not midnight).
+    cutoff_ts = int(target_dt.timestamp()) + 86400
+    selected: tuple[int, float] | None = None
+    for t, c in series:
+        if t <= cutoff_ts:
+            selected = (t, c)
+        else:
+            break
+    if selected is None:
+        return None, None, None
+    actual_iso = datetime.fromtimestamp(selected[0], timezone.utc).strftime("%Y-%m-%d")
+    return selected[1], currency, actual_iso
+
+
+@router.get(
+    "/ticker/historical",
+    dependencies=[Depends(require_paid)],
+)
+async def get_historical(symbol: str, date: str) -> dict:
+    """Historical daily close. If ``date`` is a non-trading day we walk
+    back to the last preceding trading day and surface ``actual_date``
+    so the UI can show the user which date we actually used."""
+    symbol = symbol.strip().upper()[:32]
+    if not symbol:
+        return {"ok": False, "error": "symbol required"}
+    try:
+        target = datetime.strptime(date, "%Y-%m-%d").date()
+    except ValueError:
+        raise HTTPException(status_code=400, detail="invalid date format (YYYY-MM-DD)")
+    if target > datetime.now(timezone.utc).date():
+        raise HTTPException(status_code=400, detail="date cannot be in the future")
+
+    async with httpx.AsyncClient(follow_redirects=True, timeout=15) as client:
+        try:
+            close, currency, actual = await fetch_yahoo_historical(client, symbol, date)
+        except Exception as e:
+            log.warning("ticker.historical.failed", symbol=symbol,
+                        date=date, error=str(e)[:200])
+            return {"ok": False, "error": "Couldn't fetch historical price"}
+
+    if close is None:
+        return {"ok": False, "error": "No data for that date"}
+    return {"ok": True, "close": close, "currency": currency, "actual_date": actual}