app.py

import streamlit as st
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build
from google.auth.transport.requests import Request
from googleapiclient.errors import HttpError
import pickle
import os
import hashlib

# Constants
CREDS_FILE = 'token.pickle'
CREDENTIALS_FILE = 'details.json'
SCOPES = ['https://www.googleapis.com/auth/spreadsheets']
SPREADSHEET_ID = "17KIBySu21Oh0ajtyo4A9jUTjnwOIl69KlqNlTfszrXQ"
RANGE_NAME = "Sheet1!A:C"

# Google Sheets API setup with OAuth
def get_gsheet_service(creds):
    try:
        service = build('sheets', 'v4', credentials=creds)
        return service
    except HttpError as err:
        st.error(f"Failed to create service: {err}")
        return None

def append_data_to_sheet(service, spreadsheet_id, range_name, values):
    try:
        body = {
            'values': values
        }
        result = service.spreadsheets().values().append(
            spreadsheetId=spreadsheet_id,
            range=range_name,
            valueInputOption="RAW",
            body=body
        ).execute()
        return result
    except HttpError as err:
        st.error(f"Failed to append data: {err}")
        return None

def read_data_from_sheet(service, spreadsheet_id, range_name):
    try:
        result = service.spreadsheets().values().get(spreadsheetId=spreadsheet_id, range=range_name).execute()
        return result.get('values', [])
    except HttpError as err:
        st.error(f"Failed to read data: {err}")
        return []

# Function to hash passwords
def hash_password(password):
    return hashlib.sha256(password.encode()).hexdigest()

# OAuth flow setup
def get_credentials():
    if os.path.exists(CREDS_FILE):
        with open(CREDS_FILE, 'rb') as token:
            creds = pickle.load(token)
        if creds and creds.valid:
            return creds
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
            with open(CREDS_FILE, 'wb') as token:
                pickle.dump(creds, token)
            return creds
    flow = InstalledAppFlow.from_client_secrets_file(CREDENTIALS_FILE, SCOPES)
    creds = flow.run_local_server(port=0)
    with open(CREDS_FILE, 'wb') as token:
        pickle.dump(creds, token)
    return creds

# Sign Up Page
def signup(service):
    st.subheader("Sign Up")
    
    with st.form(key='signup_form'):
        new_username = st.text_input("Username")
        new_password = st.text_input("Password", type="password")
        signup_button = st.form_submit_button("Sign Up")
    
    if signup_button:
        if new_username and new_password:
            # Check if username already exists
            user_data = read_data_from_sheet(service, SPREADSHEET_ID, RANGE_NAME)
            for user in user_data:
                if user[0] == new_username:
                    st.error("Username already exists. Please choose a different username.")
                    return
            
            # Hash the password
            hashed_password = hash_password(new_password)
            
            # Store the username and hashed password
            values = [[new_username, hashed_password]]
            result = append_data_to_sheet(service, SPREADSHEET_ID, RANGE_NAME, values)
            
            if result:
                st.success("Signup successful! Please go to the login page.")
            else:
                st.error("Failed to sign up.")
        else:
            st.error("Please provide both a username and password.")

# Login Page
def login(service):
    st.subheader("Login")
    
    with st.form(key='login_form'):
        username = st.text_input("Username")
        password = st.text_input("Password", type="password")
        login_button = st.form_submit_button("Login")
    
    if login_button:
        if username and password:
            # Hash the password
            hashed_password = hash_password(password)
            
            # Read data from Google Sheets
            user_data = read_data_from_sheet(service, SPREADSHEET_ID, RANGE_NAME)
            
            # Verify login credentials
            for user in user_data:
                if user[0] == username and user[1] == hashed_password:
                    st.success("Login successful!")
                    return True
            st.error("Invalid username or password.")
        else:
            st.error("Please enter both username and password.")
    return False

# Streamlit app
def main():
    st.title("Google Sheets Authentication System")
    
    # Get OAuth credentials
    creds = get_credentials()
    
    # Create a service object
    service = get_gsheet_service(creds)
    
    if service:
        # Choose between login and signup
        page = st.sidebar.selectbox("Choose a page", ["Login", "Signup"])
        
        if page == "Login":
            logged_in = login(service)
            if logged_in:
                st.write("You are logged in! You can add more functionality here.")
        elif page == "Signup":
            signup(service)
    else:
        st.error("Failed to create the service.")

if __name__ == "__main__":
    main()