modules/personal.py

def mortgage_calculator(principal: float, annual_rate: float, years: int) -> dict:
    """
    Calculates monthly mortgage payments.
    annual_rate: e.g., 0.05 for 5%
    """
    monthly_rate = annual_rate / 12
    num_payments = years * 12
    
    if monthly_rate == 0:
        monthly_payment = principal / num_payments
    else:
        monthly_payment = principal * (monthly_rate * (1 + monthly_rate)**num_payments) / ((1 + monthly_rate)**num_payments - 1)
        
    total_paid = monthly_payment * num_payments
    total_interest = total_paid - principal
    
    return {
        "monthly_payment": monthly_payment,
        "total_paid": total_paid,
        "total_interest": total_interest,
        "num_payments": num_payments
    }

def savings_projection(initial: float, monthly_addition: float, annual_rate: float, years: int) -> dict:
    """
    Projects the future value of savings.
    """
    monthly_rate = annual_rate / 12
    num_months = years * 12
    
    current = initial
    history = [{"month": 0, "balance": current}]
    
    for m in range(1, num_months + 1):
        current = (current * (1 + monthly_rate)) + monthly_addition
        if m % 12 == 0:
            history.append({"year": m // 12, "balance": current})
            
    return {
        "future_value": current,
        "total_contributions": initial + (monthly_addition * num_months),
        "interest_earned": current - (initial + (monthly_addition * num_months)),
        "history": history
    }