import streamlit as st
import pandas as pd
import numpy as np
import plotly.express as px

def calculate_present_value(cash_flows, discount_rate):
    years = np.arange(1, len(cash_flows)+1)
    present_values = cash_flows / (1 + discount_rate) ** years
    return np.sum(present_values)

st.title('PV calc')

# Input cash flows
st.subheader('Ingresar los Cash Flows 10 años:')
cash_flows = []
for i in range(1, 11):
    cash_flow = st.number_input(f"Cash Flow para el Año {i}:", value=10000.0, step=1000.0, format="%.2f")
    cash_flows.append(cash_flow)

# tasa
discount_rate = st.number_input('Ingrese la tasa de descuento (ejemplo: 0.05 para 5%):', value=0.05, step=0.01, format="%.2f")

if st.button('Calcular Valor Presente'):
    cash_flows = np.array(cash_flows)
    pv = calculate_present_value(cash_flows, discount_rate)
    st.success(f"El valor presente calculado es: ${pv:,.2f}")

    df = pd.DataFrame({
        'Año': np.arange(1, 11),
        'Cash Flow': cash_flows
    })

    fig = px.scatter(df, x='Año', y='Cash Flow', title="Cash Flows vs. Tiempo", labels={'Cash Flow': 'Cash Flow ($)', 'Año': 'Año'})
    st.plotly_chart(fig)