feat(cache): add in-memory caching for repo and community activity fetches

app.py

@@ -41,6 +41,34 @@ rate_limiter = RateLimiter(calls_per_second=10)
 recent_activity_rate_limiter = RateLimiter(calls_per_second=1.0)
 
 
+# ============================================================
+# Simple in-memory cache
+# ============================================================
+CACHE = {}
+CACHE_TTL = 60 * 10  # 10 minutes
+CACHE_LOCK = threading.Lock()
+
+
+def get_cache(key):
+    with CACHE_LOCK:
+        entry = CACHE.get(key)
+        if not entry:
+            return None
+
+        value, timestamp = entry
+        if time.time() - timestamp > CACHE_TTL:
+            del CACHE[key]
+            return None
+
+        print(f"[CACHE HIT] {key}")
+        return value
+
+
+def set_cache(key, value):
+    with CACHE_LOCK:
+        CACHE[key] = (value, time.time())
+
+
 # ============================================================
 # Public cache only
 # ============================================================
@@ -502,10 +530,16 @@ def fetch_all_community_activity(username: str, selected_year: int):
     username = (username or "").strip()
     selected_year = int(selected_year)
 
+    cache_key = (username.lower(), selected_year, "community")
+    cached = get_cache(cache_key)
+    if cached:
+        return cached
+
     if not username:
         state = empty_community_state(selected_year)
         state["fetched"] = True
         state["logs"] = "No username provided."
+        set_cache(cache_key, state)
         return state
 
     pr_opened = fetch_user_discussion_activity(username, selected_year, "pr_opened")
@@ -522,7 +556,7 @@ def fetch_all_community_activity(username: str, selected_year: int):
         ]
     )
 
-    return {
+    result = {
         "username": username,
         "selected_year": selected_year,
         "fetched": True,
@@ -533,6 +567,9 @@ def fetch_all_community_activity(username: str, selected_year: int):
         "logs": combined_logs,
     }
 
+    set_cache(cache_key, result)
+    return result
+
 
 # ============================================================
 # Contribution grid helpers
@@ -867,6 +904,12 @@ def build_app_state(
             "auth_text": "No username provided.",
         }
 
+    scope = "repo_private" if is_own_profile else "repo_public"
+    cache_key = (username.lower(), selected_year, scope)
+    cached = get_cache(cache_key)
+    if cached:
+        return cached
+
     if profile is not None and is_own_profile:
         auth_text = (
             f'Logged in as <b>{html.escape(viewer_username)}</b>. '
@@ -889,7 +932,7 @@ def build_app_state(
             token=token_for_fetch,
         )
 
-    return {
+    result = {
         "username": username,
         "selected_year": selected_year,
         "viewer_username": viewer_username,
@@ -900,6 +943,9 @@ def build_app_state(
         "auth_text": auth_text,
     }
 
+    set_cache(cache_key, result)
+    return result
+
 
 def render_app_state(app_state: dict | None, visibility_mode: str | None):
     if not app_state or not app_state.get("username"):