Vahina

** Decision tree / workflow for node.js **

This module is a simple decision tree module that aims to make it easier to replicate complex business workflows in code as closely as possible.

Usage

Installation

Vahina can be installed from npm. Since it is built on the power of ES6 generators, it requires node >= 0.11.x and must be run using node --harmony flag.

npm install vahina --save

Example

Consider the following flow chart representing an approval process for a bank transaction:

This can be coded in code as follows:

    var vahina = require('vahina');
 
    function *enoughMoney() {
        return (yield accountsModel.balance(this.fromAccount)) > this.amount;
    }
 
    function *processPayment() {
        yield accountsModel.process(this.fromAccount, this.toAccount, this.amount);
        return 'approved';
    }
 
    function *userType() {
        return yield userModel.getType(this.fromAccount);
    }
 
    function *overdraftAvailable() {
        return yield accountsModel.allowedToOverdraw(fromAccount);
    }
 
    function *processOverdraft() {
        yield processPayment.call(this);
        // call some other remote api
        yield overdraft.process(this.fromAccount);
        return 'approved';
    }
 
    var paymentFlow = {
        condition: enoughMoney,
        branch: {
            true: processPayment,
            false: {
                condition: userType,
                branch: {
                    personal: 'rejected',
                    business: {
                        condition: overdraftAvailable,
                        branch: {
                            true: processOverdraft,
                            false: 'rejected'
                        }
                    }
                }
            }
        }
    };
 
    var transaction = { fromAccount: 123, toAccount: 456, amount: 200 };
 
    // wrap call to vahina since no error guarding is offered by default
    // this is left upto the user
    var result;
    try {
        result = yield vahina.run(transaction, approvalFlow);
    } catch(e) {
        console.error(e);
        result = 'rejected';
    }

A generator function must be provided as the condition. The value returned by the condition is searched for as the branch. The matching branch is then yielded if it is a generator function, else the value assigned to the branch is returned.

Changelog

v0.0.1

• Initial commit