index.js

'use strict';
const path = require('path');

const ADAPTERS = require(path.join(__dirname, './adapters/index'));

const PROTOCOL_ADAPTER_INTERFACE = class Adapter_Interface {
	/**
	 * Creates an interface
	 * @param  {Object} [options={}] A set of properties defined by keys with their allowed types as values. Each property will be required by newly constructed classes from this interface
	 */
	constructor (options = {}) {
		this.interface = (this.interface && typeof this.interface === 'object') ? this.interface : {};
		for (let key in options) {
			this.interface[key] = options[key];
		}
	}
	/**
	 * Constructs a new object with a prototype defined by the .adapter ensuring that instantiated class conforms to interface requirements
	 * @param  {Object} [options={}] Values to be passed to class constructor (.adapter should be reserved for either customer class or string that matches key in ADAPTERS)
	 * @param {string|Function} options.adapter Required to specify type of adapter to be constructed or a class constructor that can be instantiated with new keyword
	 * @param {string|Function} options.protocol Alias for options.adapter. If set options.adapter will be ignored
	 * @return {Object}         Returns an instantiated adapter class
	 */
	create (options = {}) {
		options.adapter = (options.protocol) ? options.protocol : options.adapter;
		let Adapter = (typeof options.adapter === 'string') ? ADAPTERS[options.adapter] : options.adapter;
		if (!Adapter) throw new Error('Could not find a corresponding adapter - for custom adapters pass the constructor as the "adapter" options');
		let adapter = new Adapter(options);
		let errors = [];
		for (let key in this.interface) {
			if (this.interface[key] !== typeof adapter[key]) errors.push(`${ key } is invalid type ${ typeof adapter[key] } and should be ${ this.interface[key] }`);
		}
		if (errors.length) {
			let compiledErrors = errors.reduce((result, error, index) => {
				if (index === errors.length - 1) result += error;
				else result += `${ error }, `;
				return result;
			}, '');
			throw new Error(compiledErrors);
		}
		return adapter;
	}
};

module.exports = new PROTOCOL_ADAPTER_INTERFACE({
	error: 'function',
	warn: 'function',
	respond: 'function',
	exception: 'function',
	redirect: 'function'
});