truncated-list/index.js

Create a list of items with truncating lines to the specified maximum number

'use strict';

const {inspect} = require('util');

const inspectWithKind = require('inspect-with-kind');

const ERR = 'Expected every value of the given iterable object to be a string';
const NUM_ERR = 'Expected a maximum number of list items (positive integer)';

function createListItem(line) {
	return `* ${line}`;
}

module.exports = function abbreviatedList(...args) {
	const argLen = args.length;

	if (argLen !== 2) {
		throw new RangeError(`Expected 2 arguments (<Iterable<string>>, <integer>), but got ${
			argLen === 0 ? 'no' : argLen
		} arguments instead.`);
	}

	const [lines, max] = args;

	if (!lines || typeof lines !== 'object' || typeof lines[Symbol.iterator] !== 'function') {
		throw new TypeError(`Expected an iterable object except for string, but got ${
			inspectWithKind(lines)
		}.`);
	}

	if (typeof max !== 'number') {
		throw new TypeError(`${NUM_ERR}, but got a non-number value ${inspectWithKind(max)}.`);
	}

	if (max <= 0) {
		throw new TypeError(`${NUM_ERR}, but got a non-positive value ${max}.`);
	}

	if (!Number.isFinite(max)) {
		throw new TypeError(`${NUM_ERR}, but got ${max}.`);
	}

	if (max > Number.MAX_SAFE_INTEGER) {
		throw new TypeError(`${NUM_ERR}, but got a too large number.`);
	}

	if (!Number.isInteger(max)) {
		throw new TypeError(`${NUM_ERR}, but got a non-integer number ${max}.`);
	}

	const arr = [...lines];

	for (const line of arr) {
		if (typeof line !== 'string') {
			throw new TypeError(`${ERR}, but included ${inspectWithKind(line)}.`);
		}

		if (line.length === 0) {
			throw new Error(`${ERR.replace('a string', 'a non-empty string')}, but included '' (empty string).`);
		}

		if (line.indexOf('\n') !== -1) {
			throw new Error(`${ERR.replace('a string', 'a single-line string')}, but included a multiline string ${
				inspect(line)
			}.`);
		}
	}

	const surplus = arr.length - max;

	if (surplus <= 0) {
		return arr.map(createListItem).join('\n');
	}

	return `${arr.slice(0, max).map(createListItem).join('\n')}\n  ... and ${surplus} more`;
};