Application of Bulk monoid

bulkapp.js

const Task = require('data.task')
const { List, Map } = require('immutable-ext')
const { Pair, Sum, Intersection } = require('./monoid')
const { findArtist, relatedArtists } = require('./spotify')

const Bulk = (...xs) => ({
	xs,
	concat: ys => Bulk(...xs.map( (x, idx) => x.concat(ys.xs[idx]) )),
	bulkMap: (...fs) => Bulk(...xs.map((x, idx) => fs[idx](x))),
	toList: _ => xs,
	inspect: () => `Bulk(${ xs && xs.inspect ? xs.inspect() : require( 'util' ).inspect( xs, false, 3, true )})`,
})

const Union = xs =>
({
	xs: Array.isArray(xs) ? xs : [xs],
	concat: ({xs: ys}) => {
		return Union(xs.concat(ys))
	},
	inspect: () => `Union(${ xs && xs.inspect ? xs.inspect() : require( 'util' ).inspect( xs, false, 3, true )})`,
})

const Unique = xs =>
({
	xs: Array.isArray(xs) ? xs : [xs],
	concat: ({xs: ys}) => {
		const res = [...new Set(xs.concat(ys))]
		return Unique(res)
	},
	inspect: () => `Unique(${ xs && xs.inspect ? xs.inspect() : require( 'util' ).inspect( xs, false, 3, true )})`,
})

const Disjoint = xs =>
({
	xs,
	concat: ({xs: ys}) => {
		xs = Array.isArray(xs) ? xs : [xs]
		ys = Array.isArray(ys) ? ys : [ys]
		const res1 = xs.filter(x => ys.includes(x) === false) // ok
		const res2 = ys.filter(y => xs.includes(y) === false) // ok
		return Disjoint(res1.concat(res2))
	},
	inspect: () => `Disjoint(${ xs && xs.inspect ? xs.inspect() : require( 'util' ).inspect( xs, false, 3, true )})`,
})

/*

- Goal: given an order list, find out following info:
	- Order list by name
	- Total amount
	- Categories of the orders
	- Customer with only one order
	- Customer with multiple orders
*/
const orderA = { customer:'Slash', amount:10, category:['a', 'b']}
const orderB = { customer:'Satriani', amount:20, category:['b', 'c']}
const orderC = { customer:'Vai', amount:30, category:['a', 'd']}
const orderD = { customer:'Slash', amount:15, category:['e', 'd']}

var t = List([orderA, orderB, orderC, orderD])
.foldMap(p => Bulk(
	Union([p.customer]),
	Sum(p.amount),
	Unique(p.category),
	Disjoint(p.customer),
	Union([p.customer]),
))
.bulkMap(
	val => val.xs.join(', '),
	val => val.x,
	val => val.xs,
	val => val.xs,
	val => val.xs.sort().filter((v, idx, arr) => arr[idx+1] === v),
)
.bulkMap(
	val => `Customer List: ${val}`,
	val => `Total Amount: $${val}`,
	val => `Categories: ${val}`,
	val => `With only one order: ${val}`,
	val => `With multiple orders: ${val}`,
)
.toList()
console.log( t )
// =>
// [ 'Customer List: Slash, Satriani, Vai, Slash',
//   'Total Amount: $75',
//   'Categories: a,b,c,d,e',
//   'With only one order: Satriani,Vai',
//   'With multiple orders: Slash' ]