How do I integrate loan repayment tracking into my personal finance program?

To integrate loan repayment tracking into your personal finance program, you'll want to consider a few key factors: the type of loans you have, the interest rates and repayment schedules, and how you want to handle late payments, fees, and changes to the interest rate. First, let's talk about APIs and libraries that can help you with this. You've mentioned Plaid and Quandl, which are both great options for tracking financial data, but they might not be the best fit for loan repayment tracking specifically.

A better option might be to use a library like loan.js or mortgage.js, which are designed specifically for calculating loan payments and amortization schedules. These libraries can help you calculate how much you owe, how much you've paid, and when your next payment is due, taking into account factors like interest rates and repayment schedules. You can also use a library like date.js to handle date-related calculations, such as determining when your next payment is due.

In terms of using a single API to track all of your loans, it's possible, but it might not be the most effective approach. Different types of loans (e.g. mortgages, car loans, student loans) may have different requirements and calculations, so you may need to use a different API or library for each type of loan. However, you can use a single API to track your loan data, such as the Loan Tracker API or the Debt Snowball API, which can help you manage and track your loan payments and balances.

To handle late payments, fees, and changes to the interest rate, you'll want to consider using a library or framework that can help you model these scenarios. For example, you could use a finite state machine to model the different states of your loan (e.g