Convert all currencies to CRC and poll rates every 6h

Budget/transactions/salarios totals summed Transaction.amount directly,
so USD/EUR entries were treated as CRC and effectively disappeared from
the dashboard (the analytics fix in 9a80f2a only covered analytics).
Adds a shared get_converted_amount_expr() helper driven by the full
Currency enum — USD/EUR via ExchangeRate-API, BTC/XMR via CoinGecko —
and wires it into every func.sum(Transaction.amount) site.

Also starts a background task in the FastAPI lifespan that force-refreshes
every currency 4x/day, persisting USD to the DB and updating in-memory
caches for the rest. Failures are swallowed per-currency so a CoinGecko
outage cannot take out USD/EUR, and the last-known rate is always retained.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/exchange_rate.py

@@ -1,12 +1,21 @@
+import asyncio
+import logging
 import xml.etree.ElementTree as ET
 from datetime import datetime, timedelta
 
 import httpx
+from sqlalchemy import case
 from sqlmodel import Session, col, select
 
 from app.config import settings
+from app.db import engine
 from app.models.models import ExchangeRate
 
+logger = logging.getLogger(__name__)
+
+# Scheduled refresh interval — 4x/day
+REFRESH_INTERVAL_SECONDS = 6 * 3600
+
 # BCCR indicators: 317 = buy, 318 = sell
 BCCR_URL = "https://gee.bccr.fi.cr/Indicadores/Suscripciones/WS/wsindicadoreseconomicos.asmx/ObtenerIndicadoresEconomicos"
 
@@ -23,9 +32,13 @@ _cache: dict[str, tuple[ExchangeRate, datetime]] = {}
 _last_known: ExchangeRate | None = None  # survives cache expiry — always holds the last successful rate
 CACHE_TTL = timedelta(hours=1)
 
-# EUR/CRC mid-market rate cache
-_eur_crc_cache: dict[str, tuple[float, datetime]] = {}
-_last_known_eur_crc: float | None = None
+# Generic X/CRC mid-market rate cache (by currency code)
+_xcrc_cache: dict[str, tuple[float, datetime]] = {}
+_last_known_xcrc: dict[str, float] = {}
+
+# CoinGecko ids for supported crypto codes
+_COINGECKO_IDS = {"BTC": "bitcoin", "XMR": "monero"}
+COINGECKO_URL = "https://api.coingecko.com/api/v3/simple/price"
 
 
 def _fetch_bccr_rate(indicator: int, date_str: str) -> float | None:
@@ -171,10 +184,10 @@ def get_current_rate(session: Session) -> ExchangeRate | None:
     return None
 
 
-def _fetch_eur_crc_mid() -> float | None:
-    """Derive EUR/CRC mid-market rate from ExchangeRate-API (USD-based).
+def _fetch_fiat_crc_mid(code: str) -> float | None:
+    """Derive {code}/CRC mid-market rate from ExchangeRate-API (USD-based).
 
-    EUR/CRC = CRC_per_USD / EUR_per_USD
+    X/CRC = CRC_per_USD / X_per_USD
     """
     try:
         resp = httpx.get(EXCHANGERATE_API_URL, timeout=10)
@@ -182,32 +195,175 @@ def _fetch_eur_crc_mid() -> float | None:
         data = resp.json()
         if data.get("result") == "success":
             crc = data["rates"].get("CRC")
-            eur = data["rates"].get("EUR")
-            if crc and eur:
-                return float(crc) / float(eur)
+            x = data["rates"].get(code)
+            if crc and x:
+                return float(crc) / float(x)
     except Exception:
         pass
     return None
 
 
-def get_eur_crc_rate() -> float | None:
-    """Get current EUR→CRC mid-market rate (cached 1 hour)."""
-    global _last_known_eur_crc
+def _fetch_crypto_crc(code: str) -> float | None:
+    """Fetch {code}/CRC spot from CoinGecko."""
+    coin_id = _COINGECKO_IDS.get(code)
+    if not coin_id:
+        return None
+    try:
+        resp = httpx.get(
+            COINGECKO_URL,
+            params={"ids": coin_id, "vs_currencies": "crc"},
+            timeout=10,
+        )
+        resp.raise_for_status()
+        data = resp.json()
+        price = data.get(coin_id, {}).get("crc")
+        if price:
+            return float(price)
+    except Exception:
+        pass
+    return None
 
-    cached = _eur_crc_cache.get("current")
+
+def get_crc_rate(code: str) -> float | None:
+    """Get current {code}→CRC rate (cached 1 hour). Fiat via ExchangeRate-API, crypto via CoinGecko."""
+    if code == "CRC":
+        return 1.0
+
+    cached = _xcrc_cache.get(code)
     if cached and datetime.utcnow() - cached[1] < CACHE_TTL:
         return cached[0]
 
-    rate = _fetch_eur_crc_mid()
+    if code in _COINGECKO_IDS:
+        rate = _fetch_crypto_crc(code)
+    else:
+        rate = _fetch_fiat_crc_mid(code)
+
     if rate is not None:
-        _eur_crc_cache["current"] = (rate, datetime.utcnow())
-        _last_known_eur_crc = rate
+        _xcrc_cache[code] = (rate, datetime.utcnow())
+        _last_known_xcrc[code] = rate
         return rate
 
-    if _last_known_eur_crc:
-        return _last_known_eur_crc
+    return _last_known_xcrc.get(code)
 
-    return None
+
+def get_crc_multipliers(session: Session) -> dict[str, float]:
+    """Return {currency_code: CRC_multiplier} for every supported currency."""
+    from app.models.models import Currency
+
+    multipliers: dict[str, float] = {"CRC": 1.0}
+
+    usd_rate = get_current_rate(session)
+    if usd_rate:
+        multipliers["USD"] = usd_rate.sell_rate
+
+    for code in (c.value for c in Currency):
+        if code in multipliers:
+            continue
+        rate = get_crc_rate(code)
+        if rate is not None:
+            multipliers[code] = rate
+
+    return multipliers
+
+
+def get_converted_amount_expr(session: Session):
+    """Return a SQLAlchemy expression converting Transaction.amount to CRC.
+
+    Builds a CASE that multiplies by the per-currency CRC rate; CRC passes through.
+    Missing rates fall back to 1.0 (treat as CRC) rather than 0.0 so a transient
+    API outage does not silently zero out foreign-currency totals.
+    """
+    from app.models.models import Transaction
+
+    multipliers = get_crc_multipliers(session)
+    whens = [
+        (Transaction.currency == code, Transaction.amount * mult)
+        for code, mult in multipliers.items()
+        if code != "CRC"
+    ]
+    if not whens:
+        return Transaction.amount
+    return case(*whens, else_=Transaction.amount)
+
+
+def _refresh_usd_rate() -> bool:
+    """Force-fetch USD/CRC from APIs and persist to DB. Returns True on success."""
+    fetched = _fetch_rate_from_apis()
+    if fetched is None:
+        return False
+    buy, sell = fetched
+    with Session(engine) as session:
+        rate = ExchangeRate(date=datetime.utcnow(), buy_rate=buy, sell_rate=sell)
+        session.add(rate)
+        session.commit()
+        session.refresh(rate)
+        _remember(rate)
+    return True
+
+
+def _refresh_other_rate(code: str) -> bool:
+    """Force-fetch {code}/CRC and update in-memory cache. Returns True on success."""
+    if code in _COINGECKO_IDS:
+        rate = _fetch_crypto_crc(code)
+    else:
+        rate = _fetch_fiat_crc_mid(code)
+    if rate is None:
+        return False
+    _xcrc_cache[code] = (rate, datetime.utcnow())
+    _last_known_xcrc[code] = rate
+    return True
+
+
+def refresh_all_rates() -> dict[str, bool]:
+    """Force-refresh every supported currency.
+
+    Each currency is refreshed independently — one failure does not affect others.
+    On success the DB (for USD) and in-memory caches are updated. On failure the
+    previous value is retained via `_last_known_*` / stale-DB fallback, so callers
+    always see the most recent working rate.
+    """
+    from app.models.models import Currency
+
+    results: dict[str, bool] = {}
+
+    try:
+        results["USD"] = _refresh_usd_rate()
+    except Exception:
+        logger.exception("USD rate refresh failed")
+        results["USD"] = False
+
+    for currency in Currency:
+        code = currency.value
+        if code in ("CRC", "USD"):
+            continue
+        try:
+            results[code] = _refresh_other_rate(code)
+        except Exception:
+            logger.exception("%s rate refresh failed", code)
+            results[code] = False
+
+    return results
+
+
+async def refresh_rates_periodically(
+    interval_seconds: int = REFRESH_INTERVAL_SECONDS,
+) -> None:
+    """Background loop that refreshes all currency rates every `interval_seconds`.
+
+    Never raises — failures are logged and the last-known rates are retained.
+    Runs one refresh immediately on startup, then sleeps on the fixed interval.
+    """
+    while True:
+        try:
+            report = await asyncio.to_thread(refresh_all_rates)
+            ok = sorted(k for k, v in report.items() if v)
+            failed = sorted(k for k, v in report.items() if not v)
+            logger.info(
+                "Exchange rate refresh complete: ok=%s failed=%s", ok, failed
+            )
+        except Exception:
+            logger.exception("Exchange rate refresh loop crashed")
+        await asyncio.sleep(interval_seconds)
 
 
 def get_rate_history(session: Session, days: int = 30) -> list[ExchangeRate]: