import streamlit as st
import pandas as pd
import plotly.express as px
from datetime import datetime

# Initialize session state for persistent data
if 'expenses' not in st.session_state:
    st.session_state.expenses = []
if 'salary' not in st.session_state:
    st.session_state.salary = 0

# Set page title
st.title("Expense Tracker")

# Sidebar for user inputs
with st.sidebar:
    st.header("Enter Your Salary")
    salary = st.number_input("Monthly Salary", value=st.session_state.salary, step=100)
    st.session_state.salary = salary

    st.header("Add Expense")
    expense_date = st.date_input("Date", datetime.now())
    expense_category = st.selectbox("Category", ["Food", "Transport", "Entertainment", "Bills", "Other"])
    expense_amount = st.number_input("Amount", min_value=0.0, step=0.01)
    add_expense = st.button("Add Expense")

# Add expense to session state
if add_expense:
    st.session_state.expenses.append({
        "date": expense_date,
        "category": expense_category,
        "amount": expense_amount
    })

# Convert expenses to DataFrame
df = pd.DataFrame(st.session_state.expenses)

# Calculate total expenses and current balance
total_expenses = df["amount"].sum() if not df.empty else 0
current_balance = st.session_state.salary - total_expenses

# Main dashboard
st.header("Dashboard")

# Display current balance
st.metric(label="Current Balance", value=f"{current_balance:,.2f}")

# Show expenses DataFrame
st.subheader("Expenses")
if not df.empty:
    st.dataframe(df)

    # Plot expenses by category
    fig = px.pie(df, names='category', values='amount', title='Expenses by Category')
    st.plotly_chart(fig)

    # Plot expenses over time
    df['date'] = pd.to_datetime(df['date'])
    fig = px.bar(df, x='date', y='amount', color='category', title='Expenses Over Time')
    st.plotly_chart(fig)
else:
    st.write("No expenses added yet.")

# Allow user to clear all data
if st.button("Clear All Data"):
    st.session_state.expenses = []
    st.experimental_rerun()

# Additional creativity: Monthly budget and savings goals
st.sidebar.header("Monthly Budget and Savings Goals")
monthly_budget = st.sidebar.number_input("Monthly Budget", min_value=0, value=0, step=100)
savings_goal = st.sidebar.number_input("Savings Goal", min_value=0, value=0, step=100)

# Display budget and savings status
st.sidebar.metric(label="Total Expenses", value=f"${total_expenses:,.2f}")
st.sidebar.metric(label="Monthly Budget Remaining", value=f"${monthly_budget - total_expenses:,.2f}")
st.sidebar.metric(label="Savings Towards Goal", value=f"${current_balance - (monthly_budget - total_expenses):,.2f}")

st.sidebar.text("Tip: Adjust your expenses to meet your savings goal!")