app.py

import math
import pandas as pd
import gradio as gr


def emi_calc(P, annual_rate, years):
    # Validate inputs
    if P is None or P <= 0:
        return "Enter valid principal.", pd.DataFrame()

    if annual_rate is None or annual_rate < 0:
        return "Enter valid rate.", pd.DataFrame()

    if years is None or years <= 0:
        return "Enter valid tenure.", pd.DataFrame()

    # Convert
    P = float(P)
    r = (float(annual_rate) / 100.0) / 12.0
    n = int(round(float(years) * 12))

    if n <= 0:
        return "Tenure is too small.", pd.DataFrame()

    # EMI formula
    if r == 0:
        emi = P / n
    else:
        emi = P * r * ((1 + r) ** n) / (((1 + r) ** n) - 1)

    total = emi * n
    interest_total = total - P

    md = (
        f"### Results\n"
        f"- Monthly EMI: ₹{emi:,.2f}\n"
        f"- Total Interest: ₹{interest_total:,.2f}\n"
        f"- Total Payable: ₹{total:,.2f}\n"
        f"- Tenure: {n} months"
    )

    # Amortization schedule
    bal = P
    rows = []
    for m in range(1, n + 1):
        interest = bal * r
        principal = emi - interest

        # Adjust last month to avoid tiny rounding balance
        if m == n:
            principal = bal
            emi_last = principal + interest
            bal = 0.0
            rows.append([m, round(emi_last, 2), round(principal, 2), round(interest, 2), round(bal, 2)])
            break

        bal -= principal
        rows.append([m, round(emi, 2), round(principal, 2), round(interest, 2), round(bal, 2)])

    df = pd.DataFrame(rows, columns=["Month", "EMI", "Principal Paid", "Interest Paid", "Balance"])
    return md, df


with gr.Blocks(title="Loan EMI Calculator") as demo:
    gr.Markdown("## Simple Loan EMI Calculator")

    with gr.Row():
        P = gr.Number(label="Loan Amount (₹)", value=500000, precision=0)
        rate = gr.Number(label="Annual Interest Rate (%)", value=9.0, precision=2)
        years = gr.Number(label="Tenure (Years)", value=5, precision=2)

    btn = gr.Button("Calculate")
    out_md = gr.Markdown()
    out_df = gr.Dataframe(interactive=False)

    btn.click(emi_calc, inputs=[P, rate, years], outputs=[out_md, out_df])

demo.launch()