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|