Refactor chat function to improve message handling and LLM interaction

app.py

@@ -5,22 +5,42 @@ from utils import load_users
 AUTHS = load_users('user.csv')
 
 
+# somewhere near the top of app.py:
+SYSTEM_PROMPT = (
+    "Du bist DevalBot, ein konversationeller Assistent des Deutschen Evaluierungsinstituts "
+    "für Entwicklungsbewertung (DEval). DEval bietet staatlichen und zivilgesellschaftlichen "
+    "Organisationen in der Entwicklungszusammenarbeit unabhängige und wissenschaftlich fundierte "
+    "Evaluierungen. Deine Hauptsprache ist Deutsch; antworte daher standardmäßig auf Deutsch. "
+    "Du kannst zudem bei statistischen Analysen und Programmierung in Stata und R unterstützen."
+)
+
 def chat(user_message, history):
-    # append the user message
-    messages = history + [{"role":"user","content":user_message}]
-
-    # pick the right LLM
-    llm = claude_llm 
-    full = ""
-    # stream tokens as they arrive
-    for token in llm.stream(user_message):
-        full += token
-        # yield an updated history snapshot
-        yield messages + [{"role":"assistant","content": full}]
-
-    # final history
-    messages.append({"role":"assistant","content":full})
-    yield messages
+    # 1) ignore empty
+    if not user_message or not user_message.strip():
+        return
+
+    # 2) build the UI history (what Gradio shows)
+    ui_history = history + [{"role":"user","content":user_message}]
+
+    # 3) build the actual text prompt we’ll send to Claude
+    prompt_lines = [SYSTEM_PROMPT]
+    for msg in history:
+        # capitalize role for clarity
+        role = msg["role"].capitalize()
+        prompt_lines.append(f"{role}: {msg['content']}")
+    prompt_lines.append(f"User: {user_message}")
+    prompt_lines.append("Assistant:")         # Claude will continue from here
+    full_prompt = "\n".join(prompt_lines)
+
+    # 4) stream from the LLM
+    full_resp = ""
+    for token in claude_llm.stream(full_prompt):
+        full_resp += token
+        yield ui_history + [{"role":"assistant","content": full_resp}]
+
+    # 5) final append
+    ui_history.append({"role":"assistant","content": full_resp})
+    yield ui_history
 
 
 with gr.Blocks(css_paths=["static/deval.css"],theme = gr.themes.Default(primary_hue="blue", secondary_hue="yellow"),) as demo: