travel-agent-app.py

import streamlit as st
from langchain_openai import ChatOpenAI
from langchain_core.tools import tool
from langchain.agents import create_openai_tools_agent, AgentExecutor
from langchain_core.prompts import ChatPromptTemplate
from langchain_community.tools import DuckDuckGoSearchRun
import os
from dotenv import load_dotenv

load_dotenv()

# ----------------------------
# Streamlit Page Config
# ----------------------------
st.set_page_config(page_title="AI Travel Planner", layout="wide")
st.title("🌍 Agentic AI Holiday Planner")

# ----------------------------
# LLM
# ----------------------------
llm = ChatOpenAI(
    model="gpt-4.1",
    temperature=0.4
)

# ----------------------------
# Tools
# ----------------------------
@tool
def budget_estimator(days: int, total_budget: int) -> str:
    """Estimate daily budget split."""
    per_day = total_budget / days
    return f"Recommended daily budget: ₹{round(per_day)}"

@tool
def weather_lookup(city: str) -> str:
    """Mock weather info."""
    return f"{city} usually has pleasant travel weather this season."

search_tool = DuckDuckGoSearchRun()

tools = [budget_estimator, weather_lookup, search_tool]

# ----------------------------
# Prompt
# ----------------------------
prompt = ChatPromptTemplate.from_messages([
    ("system", """
You are an expert AI travel planner.

You must:
- Research destination
- Suggest day-by-day itinerary
- Recommend hotels and food
- Estimate budget breakdown
- Consider weather
- Provide travel tips
- Output clean structured format
"""),
    ("human", "{input}"),
    ("placeholder", "{agent_scratchpad}")
])

agent = create_openai_tools_agent(llm, tools, prompt)

executor = AgentExecutor(
    agent=agent,
    tools=tools,
    verbose=False
)

# ----------------------------
# UI Inputs
# ----------------------------
col1, col2 = st.columns(2)

with col1:
    destination = st.text_input("Destination", "Bali")
    days = st.number_input("Number of Days", min_value=1, max_value=15, value=5)
    budget = st.number_input("Total Budget (₹)", min_value=10000, value=150000)

with col2:
    travelers = st.selectbox("Travel Type", ["Family", "Couple", "Solo", "Friends"])
    preferences = st.text_area("Preferences",
                                "Beaches, temples, kid-friendly activities")

# ----------------------------
# Run Agent
# ----------------------------
if st.button("Plan My Trip ✈️"):

    user_query = f"""
    Plan a {days}-day {travelers} holiday trip to {destination}.
    Total budget ₹{budget}.
    Preferences: {preferences}.
    """

    with st.spinner("Planning your trip..."):
        result = executor.invoke({"input": user_query})

    st.subheader("🗺️ Your Travel Plan")
    st.write(result["output"])