Update app.py

app.py

@@ -135,10 +135,20 @@ def check_plagiarism(text, topic):
     return hits
 
 def generate_apa_citation(title, url, source, year=None):
-    year = year or datetime.datetime.now().year
-    label = {"arxiv": "*arXiv*", "semantic": "*Semantic Scholar*", "web": "*Web Source*"}.get(source, "*Web*")
+    title = title or "Untitled Source"
+    url = url or "Unavailable URL"
+    year = year if isinstance(year, int) and 1900 <= year <= datetime.datetime.now().year else "n.d."
+    
+    source_map = {
+        "arxiv": "*arXiv*",
+        "semantic": "*Semantic Scholar*",
+        "web": "*Web Source*"
+    }
+    label = source_map.get(source, "*External Source*")
+    
     return f"{title}. ({year}). {label}. {url}"
 
+
 def merge_duplicates(entries):
     unique = []
     seen_titles = []
@@ -264,7 +274,7 @@ if research_button and topic:
             st.info("ℹ️ No image previews available.")
 
         # 🔹 Generate report
-        citations = [generate_apa_citation(m['title'], m['url'], m['source'], m.get('year')) for m in merged]
+        citations = [generate_apa_citation(m.get('title'), m.get('url'), m.get('source'), m.get('year')) for m in merged]
         combined_text = "\n\n".join([
             f"- [{m['title']}]({m['url']}) ({m.get('year', 'n.d.')})\n> {m.get('snippet', m.get('summary', ''))[:300]}..."
             for m in merged