Create app.py

app.py

@@ -0,0 +1,224 @@
+import os
+import uuid
+import json
+import time
+import gradio as gr
+import logging
+
+# Load local .env only if it exists
+from dotenv import load_dotenv
+load_dotenv()
+
+import google.generativeai as genai
+
+from langgraph.graph import START, MessagesState, StateGraph
+from langgraph.checkpoint.memory import MemorySaver
+from langchain_core.messages import HumanMessage, AIMessage
+from langchain_core.prompts.chat import (
+    ChatPromptTemplate,
+    SystemMessagePromptTemplate,
+    MessagesPlaceholder,
+    HumanMessagePromptTemplate,
+)
+from langchain_google_genai import ChatGoogleGenerativeAI
+
+# === Logging ===
+logging.basicConfig(level=logging.INFO, format="%(asctime)s - %(levelname)s - %(message)s")
+logger = logging.getLogger(__name__)
+
+# === Load API Key ===
+os.environ["GOOGLE_API_KEY"] = os.getenv["GEMINI_API_KEY"]
+
+# GEMINI_API_KEY = os.getenv("GEMINI_API_KEY")
+# if not GEMINI_API_KEY:
+    #raise ValueError("GEMINI_API_KEY is missing. Set it as an environment variable or Hugging Face Secret.")
+
+genai.configure(api_key=GEMINI_API_KEY)
+
+# === Chat Storage ===
+HISTORY_FILE = "chat_history.json"
+
+def load_all_sessions():
+    if os.path.exists(HISTORY_FILE):
+        with open(HISTORY_FILE, "r", encoding="utf-8") as f:
+            return json.load(f)
+    return {}
+
+def save_all_sessions(sessions):
+    with open(HISTORY_FILE, "w", encoding="utf-8") as f:
+        json.dump(sessions, f, indent=2)
+
+sessions = load_all_sessions()
+
+# === Gemini LLM Chatbot ===
+class GeminiChatbot:
+    def __init__(self):
+        self.setup_model()
+
+    def setup_model(self):
+        system_template = """
+        You are a helpful, respectful and honest assistant. Always answer as helpfully as possible, while being safe.
+        Your answers should be informative, engaging, and accurate. If a question doesn't make any sense, or isn't factually coherent, explain why.
+        If you don't know the answer to a question, please don't share false information.
+        """
+
+        self.prompt = ChatPromptTemplate.from_messages([
+            SystemMessagePromptTemplate.from_template(system_template),
+            MessagesPlaceholder(variable_name="chat_history"),
+            HumanMessagePromptTemplate.from_template("{input}")
+        ])
+
+        self.model = ChatGoogleGenerativeAI(
+            model="gemini-2.0-flash",
+            temperature=0.7,
+            top_p=0.95,
+            google_api_key=GEMINI_API_KEY,
+            convert_system_message_to_human=True
+        )
+
+        def call_model(state: MessagesState):
+            chat_history = state["messages"][:-1]
+            user_input = state["messages"][-1].content
+            formatted_messages = self.prompt.format_messages(chat_history=chat_history, input=user_input)
+            response = self.model.invoke(formatted_messages)
+            return {"messages": response}
+
+        workflow = StateGraph(state_schema=MessagesState)
+        workflow.add_node("model", call_model)
+        workflow.add_edge(START, "model")
+
+        self.memory = MemorySaver()
+        self.app = workflow.compile(checkpointer=self.memory)
+
+    def get_response(self, user_message, history, thread_id):
+        from langchain_core.messages import HumanMessage, AIMessage
+
+        try:
+            # Format chat history for LangChain
+            langchain_history = []
+            for user, bot in history:
+                langchain_history.append(HumanMessage(content=user))
+                langchain_history.append(AIMessage(content=bot))
+
+            input_msg = HumanMessage(content=user_message)
+            full_history = langchain_history + [input_msg]
+            config = {"configurable": {"thread_id": thread_id}}
+
+            # Get final response
+            response = self.app.invoke({"messages": full_history}, config)
+            full_text = response["messages"][-1].content
+
+            full_response = ""
+            for char in full_text:
+                full_response += char
+                yield full_response
+                time.sleep(0.01)
+
+        except Exception as e:
+            logger.error(f"Response error: {e}")
+            yield f"⚠ Error: {type(e).__name__} — {str(e)}"
+
+
+chatbot = GeminiChatbot()
+
+# === Gradio UI ===
+def launch_interface():
+    with gr.Blocks(
+        theme=gr.themes.Base(),
+        css="""
+        body { background-color: black; }
+        .gr-textbox textarea { background-color: #2f2f2f; color: white; }
+        .gr-chatbot { background-color: #2f2f2f; color: white; }
+        .gr-button, .gr-dropdown {
+            margin: 5px auto;
+            display: block;
+            width: 50%;
+        }
+        .gr-markdown h2 { text-align: center; color: white; }
+        """
+    ) as demo:
+        demo.title = "LangChain Powered ChatBot"
+        gr.Markdown("## LangChain Powered ChatBot")
+
+        current_thread_id = gr.State()
+        session_names = gr.State()
+        history = gr.State([])
+
+        if not sessions:
+            new_id = str(uuid.uuid4())
+            sessions[new_id] = []
+            save_all_sessions(sessions)
+            current_thread_id.value = new_id
+            session_names.value = [f"NEW: {new_id}"]
+        else:
+            current_thread_id.value = next(iter(sessions))
+            session_names.value = [f"PREVIOUS: {k}" for k in sessions if sessions[k]]
+
+        def get_dropdown_choices():
+            return [f"PREVIOUS: {k}" for k in sessions if sessions[k]] + [f"NEW: {current_thread_id.value}"]
+
+        # UI
+        new_chat_btn = gr.Button("New Chat", variant="primary")
+        session_selector = gr.Dropdown(
+            label="Chats",
+            choices=get_dropdown_choices(),
+            value=f"NEW: {current_thread_id.value}",
+            interactive=True
+        )
+
+        chatbot_ui = gr.Chatbot(label="Conversation", height=350)
+
+        with gr.Row():
+            msg = gr.Textbox(placeholder="Ask a question...", container=False, scale=9)
+            send = gr.Button("Send", variant="primary", scale=1)
+
+        clear = gr.Button("Clear Current Chat")
+
+        # === Event Functions ===
+        def start_new_chat():
+            new_id = str(uuid.uuid4())
+            sessions[new_id] = []
+            save_all_sessions(sessions)
+            display = f"NEW: {new_id}"
+            updated = [f"PREVIOUS: {k}" for k in sessions if sessions[k]] + [display]
+            return new_id, [], gr.update(choices=updated, value=display), display
+
+        def switch_chat(display_id):
+            true_id = display_id.split(": ", 1)[-1]
+            return true_id, sessions.get(true_id, []), display_id
+
+        def respond(message, history, thread_id):
+            if not message.strip():
+                yield history
+                return
+            history.append((message, ""))
+            yield history
+
+            for chunk in chatbot.get_response(message, history[:-1], thread_id):
+                history[-1] = (message, chunk)
+                yield history
+
+            sessions[thread_id] = history
+            save_all_sessions(sessions)
+
+        def clear_chat(thread_id):
+            sessions[thread_id] = []
+            save_all_sessions(sessions)
+            return []
+
+        # === Bind Events ===
+        new_chat_btn.click(start_new_chat, outputs=[current_thread_id, chatbot_ui, session_selector, session_selector])
+        session_selector.change(switch_chat, inputs=session_selector, outputs=[current_thread_id, chatbot_ui, session_selector])
+        send.click(respond, [msg, chatbot_ui, current_thread_id], [chatbot_ui]).then(lambda: "", None, msg)
+        msg.submit(respond, [msg, chatbot_ui, current_thread_id], [chatbot_ui]).then(lambda: "", None, msg)
+        clear.click(clear_chat, inputs=[current_thread_id], outputs=[chatbot_ui])
+
+    return demo
+
+# === Run App ===
+if __name__ == "__main__":
+    try:
+        demo = launch_interface()
+        demo.launch()
+    except Exception as e:
+        logger.critical(f"App failed: {e}")