import streamlit as st
import datetime

# Initialize session state
if "balance" not in st.session_state:
    st.session_state.balance = 0
if "transactions" not in st.session_state:
    st.session_state.transactions = []
if "multiple" not in st.session_state:
    st.session_state.multiple = 5  # default multiple

# Function to calculate round-up
def round_up(transaction, multiple):
    rounded = ((transaction + multiple - 1) // multiple) * multiple
    savings = rounded - transaction
    return rounded, savings

# App title
st.title("💰 Smart Round-Up Savings (User Controlled)")

st.markdown("*Choose your round-up multiple:*")
multiple = st.selectbox("Round to nearest:", [5, 10, 20, 50], index=[5,10,20,50].index(st.session_state.multiple))
st.session_state.multiple = multiple

# Transaction input
transaction = st.number_input("Enter transaction amount (₹):", min_value=1, step=1)

if st.button("Add Transaction"):
    rounded, savings = round_up(transaction, st.session_state.multiple)
    st.session_state.balance += savings
    st.session_state.transactions.append(
        {"amount": transaction, "rounded": rounded, "savings": savings, "date": datetime.date.today()}
    )
    st.success(f"Spent ₹{transaction} → Rounded to ₹{rounded} → Saved ₹{savings}")

# Show Smart Pot Balance
st.metric("💰 Smart Pot Balance", f"₹{st.session_state.balance}")

# Show transaction history
st.subheader("📜 Transaction History")
if st.session_state.transactions:
    for t in reversed(st.session_state.transactions[-5:]):
        st.write(f"🟢 ₹{t['amount']} → ₹{t['rounded']} (Saved ₹{t['savings']}) on {t['date']}")
else:
    st.write("No transactions yet.")

# Monthly reminder simulation
if st.button("📅 New Month"):
    st.info(f"Last month you saved ₹{st.session_state.balance} with multiples of ₹{st.session_state.multiple}.")
    st.info("👉 Do you want to keep it the same, lower for less pressure, or increase for faster savings?")