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import os
import uuid
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
import gradio as gr
import time
import json
import logging
from dotenv import load_dotenv
logging.basicConfig(level=logging.INFO, format="%(asctime)s - %(levelname)s - %(message)s")
logger = logging.getLogger(__name__)
load_dotenv()
GEMINI_API_KEY = os.getenv("GEMINI_API_KEY")
if not GEMINI_API_KEY:
raise ValueError("Missing GEMINI_API_KEY")
genai.configure(api_key=GEMINI_API_KEY)
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)
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 instead of answering something not correct.
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):
try:
langchain_history = []
for user, bot in history:
langchain_history.append(HumanMessage(content=user))
langchain_history.append(AIMessage(content=bot))
input_message = HumanMessage(content=user_message)
full_history = langchain_history + [input_message]
full_response = ""
config = {"configurable": {"thread_id": thread_id}}
response = self.app.invoke({"messages": full_history}, config)
complete_response = response["messages"][-1].content
for char in complete_response:
full_response += char
yield full_response
time.sleep(0.01)
except Exception as e:
logger.error(f"LangGraph Error: {e}")
yield f"Error: {type(e).__name__} — {str(e)}"
chatbot = GeminiChatbot()
sessions = load_all_sessions()
def launch_interface():
with gr.Blocks(
theme=gr.themes.Base(),
css="""
body {
background-color: black;
}
.gr-block.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.keys()))
session_names.value = [f"PREVIOUS: {k}" for k in sessions.keys()]
def get_dropdown_choices():
choices = []
for session_id in sessions:
if sessions[session_id]:
choices.append(f"PREVIOUS: {session_id}")
choices.append(f"NEW: {current_thread_id.value}")
return choices
with gr.Column():
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=320)
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")
def start_new_chat():
new_id = str(uuid.uuid4())
sessions[new_id] = []
save_all_sessions(sessions)
display_name = f"NEW: {new_id}"
updated_choices = [f"PREVIOUS: {k}" for k in sessions if sessions[k]] + [display_name]
return (
new_id,
[],
gr.update(choices=updated_choices, value=display_name),
display_name
)
def switch_chat(selected_display_id):
if not selected_display_id:
return current_thread_id.value, [], ""
true_id = selected_display_id.split(": ", 1)[-1]
chat_history = sessions.get(true_id, [])
return true_id, chat_history, selected_display_id
def respond(message, history, thread_id):
if not message.strip():
yield history
return
history.append((message, ""))
yield history
full_response = ""
for chunk in chatbot.get_response(message, history[:-1], thread_id):
full_response = chunk
history[-1] = (message, full_response)
yield history
sessions[thread_id] = history
save_all_sessions(sessions)
def clear_current(thread_id):
sessions[thread_id] = []
save_all_sessions(sessions)
return []
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,
inputs=[msg, chatbot_ui, current_thread_id],
outputs=[chatbot_ui]
).then(
lambda: "", None, msg
)
msg.submit(
respond,
inputs=[msg, chatbot_ui, current_thread_id],
outputs=[chatbot_ui]
).then(
lambda: "", None, msg
)
clear.click(
clear_current,
inputs=[current_thread_id],
outputs=[chatbot_ui]
)
return demo
if __name__ == "__main__":
try:
demo = launch_interface()
demo.launch(share=True)
except Exception as e:
logger.critical(f"App failed: {e}")
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