EMI計算機

def calculate_emi(principal: float, annual_rate: float, months: int) -> dict:
    """Calculate EMI and generate amortization schedule."""
    monthly_rate = annual_rate / 100 / 12
    if monthly_rate == 0:
        emi = principal / months
    else:
        emi = principal * monthly_rate * (1 + monthly_rate) ** months / (
            (1 + monthly_rate) ** months - 1
        )

    schedule = []
    balance = principal
    total_interest = 0
    for month in range(1, months + 1):
        interest = balance * monthly_rate
        principal_part = emi - interest
        balance -= principal_part
        total_interest += interest
        schedule.append({
            "month": month,
            "emi": round(emi, 2),
            "principal": round(principal_part, 2),
            "interest": round(interest, 2),
            "balance": round(max(balance, 0), 2),
        })

    return {
        "emi": round(emi, 2),
        "total_payment": round(emi * months, 2),
        "total_interest": round(total_interest, 2),
        "schedule": schedule,
    }

result = calculate_emi(principal=500000, annual_rate=8.5, months=240)
print(f"Monthly EMI: {result['emi']}")
print(f"Total Payment: {result['total_payment']}")
print(f"Total Interest: {result['total_interest']}")