1 files changed, 27 insertions, 5 deletions
diff --git a/fnme/data.py b/fnme/data.py
index bdec6df..17f30c5 100644
--- a/fnme/data.py
+++ b/fnme/data.py
@@ -1,13 +1,35 @@
-from io import StringIO
+import os
+from pathlib import Path
 from typing import Optional
 
 import pandas as pd
 import requests
+from platformdirs import user_cache_path
 
 from fnme.constants import ENDPOINT, HEADERS
 
 
-def get_latest_data() -> tuple[pd.DataFrame, Optional[str]]:
-    response = requests.get(ENDPOINT, headers=HEADERS, timeout=10)
-    response.raise_for_status()
-    return pd.read_csv(StringIO(response.text)), response.headers.get("Last-Modified")
+def get_latest_data() -> tuple[pd.DataFrame, str | None]:
+    cache_dir = Path(user_cache_path(appname="fnme", appauthor=False))
+    csv_path = cache_dir / "latest_data.csv"
+    timestamp_path = cache_dir / "timestamp.txt"
+
+    cache_dir.mkdir(parents=True, exist_ok=True)
+
+    remote_last_modified = requests.head(
+        ENDPOINT, headers=HEADERS, timeout=10
+    ).headers.get("Last-Modified")
+
+    cached_last_modified = (
+        timestamp_path.read_text() if timestamp_path.exists() else None
+    )
+
+    if not csv_path.exists() or remote_last_modified != cached_last_modified:
+        response = requests.get(ENDPOINT, headers=HEADERS, timeout=10)
+        response.raise_for_status()
+        last_modified = response.headers.get("Last-Modified")
+        csv_path.write_text(response.text, encoding="utf-8")
+        timestamp_path.write_text(last_modified or "")
+        return pd.read_csv(csv_path), last_modified
+
+    return pd.read_csv(csv_path), cached_last_modified