app.py

import streamlit as st
import json
import os
from cryptography.fernet import Fernet, InvalidToken

# Initialize session state
if 'username' not in st.session_state:
    st.session_state.username = ''
if 'scratch_pad' not in st.session_state:
    st.session_state.scratch_pad = ''

# Load or create user history file
history_file = 'user_history.json'
if not os.path.exists(history_file):
    with open(history_file, 'w') as file:
        json.dump({}, file)

# Load user history
with open(history_file, 'r') as file:
    user_history = json.load(file)

# Generate encryption key
key = Fernet.generate_key()
fernet = Fernet(key)

def save_session(username, password):
    st.session_state.username = username
    st.session_state.scratch_pad = st.session_state.scratch_pad
    encrypted_password = fernet.encrypt(password.encode()).decode()
    user_history[username] = {
        'password': encrypted_password,
        'scratch_pad': st.session_state.scratch_pad
    }
    with open(history_file, 'w') as file:
        json.dump(user_history, file)

def register_user(username, password):
    if username not in user_history:
        save_session(username, password)
        st.success("User registered successfully!")
    else:
        st.warning("Username already exists. Please choose a different username.")


def login_user(username, password):
    if username in user_history:
        encrypted_password = user_history[username]['password']
        try:
            decrypted_password = fernet.decrypt(encrypted_password.encode()).decode()
            if password == decrypted_password:
                st.session_state.username = username
                st.session_state.scratch_pad = user_history[username]['scratch_pad']
                st.success("Logged in successfully!")
                return True
            else:
                st.error("Incorrect password. Please try again.")
        except InvalidToken:
            st.error("Invalid password. Please try again.")
    else:
        st.warning("Username not found. Please register first.")
    return False
    
def reset_password(username):
    if username in user_history:
        new_password = Fernet.generate_password(8).decode()
        save_session(username, new_password)
        st.success(f"Password reset successful. Your new password is: {new_password}")
    else:
        st.warning("Username not found.")

st.title("Memory of Me - State Aware Authentication and User Data Memory")

if st.session_state.username:
    st.subheader(f"Welcome back, {st.session_state.username}!")
    scratch_pad = st.text_area("Scratch Pad", value=st.session_state.scratch_pad, height=200)
    if st.button("💾 Save"):
        save_session(st.session_state.username, '')
    if st.button("🔑 Reset Password"):
        reset_password(st.session_state.username)
else:
    username = st.text_input("Username:")
    password = st.text_input("Password:", type="password")
    col1, col2 = st.columns(2)
    with col1:
        if st.button("🔑 Login"):
            if login_user(username, password):
                st.experimental_rerun()
    with col2:
        if st.button("📝 Register"):
            register_user(username, password)