perf(price): parallelize price fetching with thread pool for faster processing

- Use ThreadPoolExecutor to fetch stock prices concurrently across multiple holdings
- Pre-fetch FX rates for unique non-GBP currencies before parallel price fetching
- Group price fetching and FX calculation into separate processing phases
- Reduce I/O wait time by executing network requests in parallel instead of sequentially

price.py

@@ -4,6 +4,7 @@ import csv
 import sys
 import requests
 from bs4 import BeautifulSoup
+from concurrent.futures import ThreadPoolExecutor, as_completed
 
 FX_CACHE = {}
 
@@ -18,6 +19,9 @@ def get_fx_rate(currency):
     FX_CACHE[currency] = rate
     return rate
 
+def get_currency(market):
+    return {"GB": "GBP", "US": "USD"}.get(market, "GBP")
+
 def get_price(market, ticker):
     url = f"https://web.freetrade.io/universe/{market}/{ticker}"
     response = requests.get(url, headers={
@@ -29,39 +33,37 @@ def get_price(market, ticker):
         return float(m.group(1).replace(",", ""))
     return None
 
-def get_currency(market):
-    return {"GB": "GBP", "US": "USD"}.get(market, "GBP")
-
 holdings_file = sys.argv[1] if len(sys.argv) > 1 else "holdings.csv"
 
-results = []
+holdings = []
 with open(holdings_file) as f:
     reader = csv.reader(f)
     for row in reader:
-        ticker, market, shares = row[0].strip(), row[1].strip(), float(row[2].strip())
+        ticker, market = row[0].strip(), row[1].strip()
+        shares = float(row[2].strip())
         currency = get_currency(market)
-        price = get_price(market, ticker)
-        if price is None:
-            results.append({
-                "ticker": ticker,
-                "market": market,
-                "currency": currency,
-                "shares": shares,
-                "price": None,
-                "fx_rate": None,
-                "total_value_gbp": None
-            })
-            continue
-        fx = get_fx_rate(currency)
-        total_gbp = round(price * shares * fx, 2)
-        results.append({
-            "ticker": ticker,
-            "market": market,
-            "currency": currency,
-            "shares": shares,
-            "price": price,
-            "fx_rate": fx,
-            "total_value_gbp": total_gbp
-        })
+        holdings.append({"ticker": ticker, "market": market, "shares": shares, "currency": currency})
 
-print(json.dumps(results, indent=2))
+unique_currencies = {h["currency"] for h in holdings if h["currency"] != "GBP"}
+for currency in unique_currencies:
+    get_fx_rate(currency)
+
+with ThreadPoolExecutor(max_workers=10) as pool:
+    future_to_idx = {
+        pool.submit(get_price, h["market"], h["ticker"]): i
+        for i, h in enumerate(holdings)
+    }
+    for future in as_completed(future_to_idx):
+        idx = future_to_idx[future]
+        holdings[idx]["price"] = future.result()
+
+for h in holdings:
+    if h["price"] is not None:
+        fx = FX_CACHE.get(h["currency"], 1.0)
+        h["fx_rate"] = fx
+        h["total_value_gbp"] = round(h["price"] * h["shares"] * fx, 2)
+    else:
+        h["fx_rate"] = None
+        h["total_value_gbp"] = None
+
+print(json.dumps(holdings, indent=2))