05/31 Phase 7: fixed fetch fx rate

app/services/fx_service.py

@@ -1,27 +1,33 @@
 """
 FX Service — fetches and caches daily USD→VND exchange rate.
-Primary source: open.er-api.com (free, no key)
-Fallback: last known rate from DB
+
+Source priority:
+1. DB cache (same day, fresh)
+2. yfinance (USDVND=X forex ticker — most reliable)
+3. open.er-api.com (free REST API fallback)
+4. Last known DB rate (stale fallback)
+
+Force-refresh: if cached rate is > 1 day old, re-fetch regardless.
 """
 
+import logging
 import requests
-from datetime import date, datetime
+from datetime import date, datetime, timedelta
 from app.extensions import db
 from app.models.fx_rate import FxRate
 
-
-ER_API_URL = 'https://open.er-api.com/v6/latest/USD'
-REQUEST_TIMEOUT = 8  # seconds
+log = logging.getLogger(__name__)
+REQUEST_TIMEOUT = 10
 
 
 def get_today_rate():
     """
     Return today's USD→VND rate as a dict:
-    { 'rate': 25450.00, 'date': date(...), 'source': '...', 'is_stale': False }
+    { 'rate': 26350.00, 'date': date(...), 'source': '...', 'is_stale': False }
     """
     today = date.today()
 
-    # 1. Check cache
+    # 1. Check DB cache — only use if fetched TODAY
     cached = FxRate.query.filter_by(date=today).first()
     if cached:
         return {
@@ -31,26 +37,23 @@ def get_today_rate():
             'is_stale': False,
         }
 
-    # 2. Fetch from API
-    rate, source = _fetch_from_api()
+    # 2. Try all live sources in order
+    fetchers = [
+        _fetch_yfinance,
+        _fetch_er_api,
+    ]
 
-    if rate:
-        record = FxRate(
-            date=today,
-            usd_to_vnd=rate,
-            source=source,
-            fetched_at=datetime.utcnow(),
-        )
-        db.session.add(record)
-        try:
-            db.session.commit()
-        except Exception:
-            db.session.rollback()
-        return {'rate': rate, 'date': today, 'source': source, 'is_stale': False}
+    for fetcher in fetchers:
+        rate = fetcher()
+        if rate and rate > 1000:   # sanity check: VND is always >> 1000 per USD
+            _save_rate(today, rate, fetcher.__name__.replace('_fetch_', ''))
+            return {'rate': rate, 'date': today, 'source': fetcher.__name__, 'is_stale': False}
 
-    # 3. Fallback — last known rate
+    # 3. Stale fallback — last known rate from DB
     last = FxRate.query.order_by(FxRate.date.desc()).first()
     if last:
+        days_old = (today - last.date).days
+        log.warning(f'[fx] Using stale rate from {last.date} ({days_old}d old)')
         return {
             'rate': float(last.usd_to_vnd),
             'date': last.date,
@@ -58,27 +61,80 @@ def get_today_rate():
             'is_stale': True,
         }
 
-    # 4. Nothing available
     return None
 
 
-def _fetch_from_api():
-    """Try open.er-api.com. Returns (rate, source) or (None, None)."""
+def force_refresh():
+    """Delete today's cached rate and fetch fresh. Returns new rate dict."""
+    today = date.today()
+    existing = FxRate.query.filter_by(date=today).first()
+    if existing:
+        db.session.delete(existing)
+        db.session.commit()
+    return get_today_rate()
+
+
+# ── Fetchers ──────────────────────────────────────────────────────────────────
+
+def _fetch_yfinance():
+    """Fetch USDVND=X via yfinance. Most reliable — uses Yahoo Finance forex."""
     try:
-        resp = requests.get(ER_API_URL, timeout=REQUEST_TIMEOUT)
+        import yfinance as yf
+        ticker = yf.Ticker('USDVND=X')
+        hist = ticker.history(period='5d')
+        if not hist.empty:
+            rate = float(hist['Close'].iloc[-1])
+            log.info(f'[fx] yfinance: 1 USD = {rate:,.0f} VND')
+            return rate
+    except Exception as e:
+        log.warning(f'[fx] yfinance failed: {e}')
+    return None
+
+
+def _fetch_er_api():
+    """Fetch from open.er-api.com (free, no key required)."""
+    try:
+        resp = requests.get(
+            'https://open.er-api.com/v6/latest/USD',
+            timeout=REQUEST_TIMEOUT,
+            headers={'User-Agent': 'PFM/1.0'},
+        )
         if resp.status_code == 200:
             data = resp.json()
             vnd = data.get('rates', {}).get('VND')
-            if vnd:
-                return float(vnd), 'exchangerate-api'
-    except Exception:
-        pass
-    return None, None
+            if vnd and float(vnd) > 1000:
+                log.info(f'[fx] er-api: 1 USD = {vnd:,.0f} VND')
+                return float(vnd)
+    except Exception as e:
+        log.warning(f'[fx] er-api failed: {e}')
+    return None
+
+
+# ── DB helpers ────────────────────────────────────────────────────────────────
+
+def _save_rate(rate_date, rate, source):
+    try:
+        # Upsert — delete existing for this date first
+        existing = FxRate.query.filter_by(date=rate_date).first()
+        if existing:
+            db.session.delete(existing)
+            db.session.flush()
+
+        record = FxRate(
+            date=rate_date,
+            usd_to_vnd=rate,
+            source=source,
+            fetched_at=datetime.utcnow(),
+        )
+        db.session.add(record)
+        db.session.commit()
+    except Exception as e:
+        db.session.rollback()
+        log.error(f'[fx] DB save failed: {e}')
 
 
 def get_rate_history(days=30):
     """Return list of FxRate records for last N days, oldest first."""
-    from datetime import timedelta
     since = date.today() - timedelta(days=days)
     return (FxRate.query
             .filter(FxRate.date >= since)