app.py

import streamlit as st
import pymongo
import bcrypt
import os
import json
from dotenv import load_dotenv
import streamlit_authenticator as stauth

# Load environment variables
load_dotenv()

if os.path.exists("secrets.json"):
    with open("secrets.json") as f:
        secrets = json.load(f)
        os.environ.update(secrets)

MONGO_URI = os.getenv("MONGO_URI")
SECRET_KEY = os.getenv("SECRET_KEY")

if not MONGO_URI or not SECRET_KEY:
    st.error("Missing environment variables! Please check your Hugging Face Secrets.")
    st.stop()

# Connect to MongoDB
client = pymongo.MongoClient(MONGO_URI)
db = client["user_database"]
users_collection = db["users"]

# Function to hash passwords
def hash_password(password):
    return bcrypt.hashpw(password.encode("utf-8"), bcrypt.gensalt()).decode("utf-8")

# Function to verify passwords
def verify_password(password, hashed):
    return bcrypt.checkpw(password.encode("utf-8"), hashed.encode("utf-8"))

# UI Customization
st.set_page_config(page_title="Secure Login App", page_icon="🔒", layout="centered")

# Light/Dark Mode Toggle
theme_mode = st.toggle("🌞 Light / 🌙 Dark Mode", value=True)

if theme_mode:
    st.markdown(
        """
        <style>
        body { background-color: #f0f2f6; color: black; }
        .stTextInput>div>div>input, .stButton>button { background-color: white; }
        </style>
        """,
        unsafe_allow_html=True
    )
else:
    st.markdown(
        """
        <style>
        body { background-color: #1e1e1e; color: white; }
        .stTextInput>div>div>input, .stButton>button { background-color: #333; color: white; }
        </style>
        """,
        unsafe_allow_html=True
    )

# Login and Signup Flow
if "signup_mode" not in st.session_state:
    st.session_state.signup_mode = False

if not st.session_state.signup_mode:
    st.subheader("🔑 Login to Your Account")

    username = st.text_input("Username")
    password = st.text_input("Password", type="password")

    if st.button("Login"):
        user = users_collection.find_one({"username": username})
        if user and verify_password(password, user["password"]):
            st.success(f"Welcome {username}!")
        else:
            st.error("Invalid credentials. Please try again.")

    # Hyperlink to switch to signup
    if st.button("Sign up instead"):
        st.session_state.signup_mode = True
        st.rerun()

else:
    st.subheader("📝 Create a New Account")

    new_username = st.text_input("Choose a Username")
    new_password = st.text_input("Choose a Password", type="password")
    confirm_password = st.text_input("Confirm Password", type="password")

    if st.button("Sign Up"):
        if new_password != confirm_password:
            st.error("Passwords do not match.")
        elif users_collection.find_one({"username": new_username}):
            st.error("Username already exists.")
        else:
            hashed_password = hash_password(new_password)
            users_collection.insert_one({"username": new_username, "password": hashed_password})
            st.success("Account created successfully! You can now log in.")
    
    # Hyperlink to switch back to login
    if st.button("Back to Login"):
        st.session_state.signup_mode = False
        st.rerun()