add apply-interest script

README.md

@@ -2,6 +2,12 @@
 
 This is a collection of useful scripts to help you manage your Actual Budget.
 
+- [Requirements](#requirements)
+- [Configuration](#configuration)
+- [Installation](#installation)
+- Scripts:
+  - [Loan Interest Calculator](#loan-interest-calculator)
+
 ## Requirements
 
 - [Actual Budget](https://actualbudget.org/)
@@ -24,8 +30,40 @@ ACTUAL_FILE_PASSWORD="<file password>"
 
 # optional, if you want to use a different cache directory
 ACTUAL_CACHE_DIR="./cache"
+
+# optional, name of the payee for added interest transactions
+IMPORTER_INTEREST_PAYEE_NAME="Loan Interest"
 ```
 
 ## Installation
 
 Run `npm install` to install any required dependencies.
+
+## Scripts
+
+### Loan Interest Calculator
+
+This script calculates the interest for a loan account and adds the interest
+transactions to Actual Budget.
+
+For each account that you want to automaitcally calculate interest for, you
+need to edit the account notes and add the following tags:
+
+- `interestRate:0.0X` sets the interest rate to X percent (note: be sure to
+    enter the rate as a decimal and not a percentage)
+- `interestDay:XX` sets the day of the month that the interest is calculated
+
+As an example, if your loan is at 4.5% interest and you want to insert an
+interest transaction on the 28th of the month, set the account note to
+`interestRate:0.045 interestDay:28`.
+
+You can optionally change the payee used for the interest transactions by
+setting `IMPORTER_INTEREST_PAYEE_NAME` in the `.env` file.
+
+To run:
+
+```console
+$ node apply-interest.js
+```
+
+It is recommended to run this script once per month.