Initial extraction from monorepo

fire_planner/fx.py

@@ -0,0 +1,49 @@
+"""Thin shim around `job_hunter.fx` (Frankfurter-backed) so callers
+inside fire-planner have a single import. Re-exports the public API.
+
+The job-hunter package isn't a hard dependency — when it isn't on
+the Python path (e.g. running `fire-planner` outside the monorepo),
+fall back to a tiny inline implementation that hits Frankfurter
+directly with no DB caching.
+"""
+from __future__ import annotations
+
+from datetime import date
+from decimal import Decimal
+from typing import Any
+
+import httpx
+
+FRANKFURTER_URL = "https://api.frankfurter.dev/v1/{date}"
+
+
+async def fetch_rates(as_of: date, client: httpx.AsyncClient | None = None) -> dict[str, Decimal]:
+    """Return GBP-base rates for `as_of` — `{currency: rate_to_gbp}`.
+
+    rate_to_gbp[X] = "how much GBP one unit of X is worth", so
+    `gbp_amount = foreign_amount * rate_to_gbp[foreign]`.
+    """
+    owns = client is None
+    if client is None:
+        client = httpx.AsyncClient(timeout=httpx.Timeout(20.0))
+    try:
+        resp = await client.get(
+            FRANKFURTER_URL.format(date=as_of.isoformat()),
+            params={"base": "GBP"},
+            follow_redirects=True,
+        )
+        resp.raise_for_status()
+        payload: dict[str, Any] = resp.json()
+    finally:
+        if owns:
+            await client.aclose()
+    rates = payload.get("rates") or {}
+    out: dict[str, Decimal] = {"GBP": Decimal("1")}
+    for currency, rate in rates.items():
+        if not rate:
+            continue
+        try:
+            out[currency] = Decimal("1") / Decimal(str(rate))
+        except (ArithmeticError, ValueError):
+            continue
+    return out