Simple SAAS billing engine

Here is a set of function to calculate service due date according to service usage timeline, tariffs, and payments.

It's simple and it does not care about:

• currency
• taxes
• service had to be disabled because of negative balance but it was not (service stopped because of overdue payment continues to collect debt)

Quick start

npm i saas-bill --save

const { getPaymentDue } = require('saas-bill')();

const timeline = [
    {action: "start", date: "2020-01-02"},
]
const tariff = [
    {action: "start", date: "2020-01-02", price: 10000, days: 30.41, creditLimit: 10000},
];
const payments = [
    {date: "2020-01-02", sum: 10000},
];
const due = getPaymentDue(
    timeline,
    tariff,
    payments
);
console.log(due) // to be "2020-03-02"

or

const { getPaymentDue } = require('saas-bill')();
const timeline = [
    {action: "start", date: "2020-01-02"},
    {action: "stop", date: "2020-01-15"},
]
const tariff = [
    {action: "start", date: "2020-01-02", price: 10000, days: 30.41},
];
const payments = [
    {date: "2020-01-02", sum: 10000},
];
const due = getPaymentDue(
    timeline,
    tariff,
    payments
);
console.log(due) // to be "2020-01-04" (service timeline stop date)

Timeline record

Field	Meaning
action	"start" or "stop" ("start" can be omitted) of service work period
date	date of "start" (inclusive) or "stop" (exclusive, service does not work in stop day)

Tariff record

Field	Meaning
action	"start" (can be omitted)
date	tariff activation day
price	price per period
days	number of days in period (30.41 is average month length)
creditLimit	credit limit

Payment record

Field	Meaning
sum	Sum of payment
date	date of payment