feat: prevent duplicate cards, merge contexts, and display star badge when word is in library

app/main.py

@@ -285,9 +285,24 @@ async def api_lookup(
     if not query_str:
         raise HTTPException(status_code=400, detail="Query term cannot be empty")
     data = await lookup_term(query_str)
+
+    # Check if this term already exists in user's dictionary
+    with get_db() as conn:
+        existing = conn.execute(
+            "SELECT id, term, translation, context_sentence, tags, collection, srs_state, srs_reps FROM vocabulary_cards WHERE user_id = ? AND lower(trim(term)) = lower(trim(?))",
+            (user["id"], query_str),
+        ).fetchone()
+        if existing:
+            data["in_library"] = True
+            data["library_card"] = dict(existing)
+        else:
+            data["in_library"] = False
+            data["library_card"] = None
+
     return data
 
 
+
 @app.api_route("/api/audio", methods=["GET", "HEAD"])
 async def api_audio_proxy():
     # Audio feature disabled
@@ -386,7 +401,42 @@ async def api_get_cards(
 
 @app.post("/api/cards")
 async def api_create_card(card: CardCreateRequest, user: dict = Depends(require_user)):
+    clean_term = card.term.strip()
     with get_db() as conn:
+        existing = conn.execute(
+            "SELECT * FROM vocabulary_cards WHERE user_id = ? AND lower(trim(term)) = lower(trim(?))",
+            (user["id"], clean_term),
+        ).fetchone()
+
+        if existing:
+            # Word already exists in library!
+            existing_row = dict(existing)
+            new_ctx = (card.context_sentence or "").strip()
+            old_ctx = (existing_row.get("context_sentence") or "").strip()
+            updated_ctx = old_ctx
+            if new_ctx and new_ctx not in old_ctx:
+                updated_ctx = f"{old_ctx}\n\n{new_ctx}" if old_ctx else new_ctx
+
+            # Merge tags
+            old_tags = set([t.strip() for t in (existing_row.get("tags") or "").split(",") if t.strip()])
+            new_tags = [t.strip() for t in (card.tags or "").split(",") if t.strip()]
+            for t in new_tags:
+                old_tags.add(t)
+            updated_tags = ", ".join(sorted(old_tags)) if old_tags else "general"
+
+            conn.execute(
+                """
+                UPDATE vocabulary_cards
+                SET context_sentence = ?, tags = ?, updated_at = CURRENT_TIMESTAMP
+                WHERE id = ?
+                """,
+                (updated_ctx, updated_tags, existing_row["id"]),
+            )
+            updated_row = conn.execute("SELECT * FROM vocabulary_cards WHERE id = ?", (existing_row["id"],)).fetchone()
+            res = dict(updated_row)
+            res["already_exists"] = True
+            return res
+
         cursor = conn.execute(
             """
             INSERT INTO vocabulary_cards (
@@ -397,7 +447,7 @@ async def api_create_card(card: CardCreateRequest, user: dict = Depends(require_
             """,
             (
                 user["id"],
-                card.term.strip(),
+                clean_term,
                 card.translation.strip(),
                 (card.context_sentence or "").strip(),
                 (card.phonetic or "").strip(),
@@ -414,6 +464,7 @@ async def api_create_card(card: CardCreateRequest, user: dict = Depends(require_
         return dict(row)
 
 
+
 @app.put("/api/cards/{card_id}")
 async def api_update_card(card_id: int, update: CardUpdateRequest, user: dict = Depends(require_user)):
     with get_db() as conn: