app.py

from langchain import OpenAI, SQLDatabase
from langchain_experimental.sql import SQLDatabaseChain
from langchain_openai import AzureChatOpenAI, ChatOpenAI
import pandas as pd
import time
from langchain_core.prompts.prompt import PromptTemplate
import re
from sqlalchemy import create_engine, text
import psycopg2
from psycopg2 import sql
import streamlit as st
from langchain_core.messages import AIMessage, HumanMessage
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.runnables import RunnablePassthrough
from langchain_core.output_parsers import StrOutputParser
from langchain_groq import ChatGroq
from langchain_community.callbacks import get_openai_callback
import os
from langchain_openai import ChatOpenAI
# llm = ChatOpenAI(temperature=0.7, model="gpt-3.5-turbo")


def init_database(user: str, password: str, host: str, port: str, database: str, sslmode: str = None) -> SQLDatabase:
    """Initialize a connection to the PostgreSQL database."""
    try:
        db_uri = f"postgresql+psycopg2://{user}:{password}@{host}:{port}/{database}"
        if sslmode:
            db_uri += f"?sslmode={sslmode}"
        
        db = SQLDatabase.from_uri(db_uri)
        return db
    except Exception as e:
        st.error("Unable to connect to the database. Please check your credentials and try again.")
        st.stop()  # Stop further execution if an error occurs

def answer_sql(question: str, db: SQLDatabase, chat_history: list, llm) -> str:
    """Generate SQL answer based on the user's question and database content."""
    try:
        prompt = PromptTemplate(
            input_variables=['input', 'table_info', 'top_k'],
            template="""You are a PostgreSQL expert. Given an input question,
                        first create a syntactically correct PostgreSQL query to run,
                        then look at the results of the query and return the answer to the input question.
                        Unless the user specifies in the question a specific number of records to obtain, query for at most {top_k} results using the LIMIT clause as per PostgreSQL.
                        Wrap each column name in double quotes (") to denote them as delimited identifiers.
                        Only use the following tables:\n{table_info}\n\nQuestion: {input}')"""
        )

        QUERY = f"""
        Given an input question, look at the results of the query and return the answer in natural language to the user's question with all the records of SQLResult.
        {question}
        """

        db_chain = SQLDatabaseChain(
            llm=llm, 
            database=db, 
            top_k=100, 
            verbose=True, 
            use_query_checker=True, 
            prompt=prompt, 
            return_intermediate_steps=True
        )

        with get_openai_callback() as cb:
            response = db_chain.invoke({
                "query": QUERY.format(question=question),
                "chat_history": chat_history,
            })["result"]

            print("*" * 55)
            print(f"Total Tokens : {cb.total_tokens}")
            print(f"Prompt Tokens : {cb.prompt_tokens}")
            print(f"Completion Tokens : {cb.completion_tokens}")
            print(f"Total Cost (USD) : ${cb.total_cost}")
            print("*" * 55)

        return response
    except Exception as e:
        st.error("A technical error occurred. Please try again later.")
        st.stop()

if "chat_history" not in st.session_state:
    st.session_state.chat_history = [
      AIMessage(content="Hello! I'm your SQL assistant. Ask me anything about your database."),
    ]

st.set_page_config(page_title="Chat with Postgres", page_icon=":speech_balloon:")
st.title("Chat with Postgres DB")
st.sidebar.image("https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSfbBOY1t6ZMwLejpwbGVQ9p3LKplwt45yxEzeDsEEPibRm4JqIYF3xav53PNRLJwWkdw&usqp=CAU", use_container_width=True)

# Get API key from user
with st.sidebar:
    st.subheader("API Key and Database Credentials")
    
    # Take OpenAI API key from the user
    openai_api_key = st.text_input("Enter your OpenAI API Key:", type="password")
    
    # Database connection fields
    db_type = st.radio("Is your PostgreSQL database on a local server or in the cloud?", ("Local", "Cloud"))
    if db_type == "Local":
        st.write("Enter your local database credentials.")
        host = st.text_input("Host", value="localhost")
        port = st.text_input("Port", value="5432")
        user = st.text_input("User", value="postgres")
        password = st.text_input("Password", type="password")
        database = st.text_input("Database", value="testing_3")
    elif db_type == "Cloud":
        st.write("Enter your cloud database credentials.")
        host = st.text_input("Host (e.g., your-db-host.aws.com)")
        port = st.text_input("Port", value="5432")
        user = st.text_input("User")
        password = st.text_input("Password", type="password")
        database = st.text_input("Database")
        sslmode = st.selectbox("SSL Mode", ["require", "verify-ca", "verify-full", "disable"])

    if st.button("Connect"):
        if openai_api_key:
            os.environ["OPENAI_API_KEY"] = openai_api_key  # Set the OpenAI API key in the environment
            llm = ChatOpenAI(temperature=0.7, model="gpt-3.5-turbo") # Initialize model with user's API key
            try:
                db = init_database(user, password, host, port, database, sslmode if db_type == "Cloud" else None)
                st.session_state.db = db
                st.session_state.llm = llm
                st.success("Connected to the database!")
            except Exception as e:
                st.error("Failed to connect to the database. Please check your details and try again.")
        else:
            st.error("Please enter your OpenAI API key.")

# Main chat interface
for message in st.session_state.chat_history:
    if isinstance(message, AIMessage):
        with st.chat_message("AI"):
            st.markdown(message.content)
    elif isinstance(message, HumanMessage):
        with st.chat_message("Human"):
            st.markdown(message.content)

user_query = st.chat_input("Type a message...")
if user_query:
    st.session_state.chat_history.append(HumanMessage(content=user_query))
    with st.chat_message("Human"):
        st.markdown(user_query)

    with st.chat_message("AI"):
        response = answer_sql(user_query, st.session_state.db, st.session_state.chat_history, st.session_state.llm)
        st.markdown(response)

    st.session_state.chat_history.append(AIMessage(content=response))