runtime.js

/**
 * External dependencies
 */
import { create } from 'rungen';
import { map } from 'lodash';
import isPromise from 'is-promise';

/**
 * Internal dependencies
 */
import { isActionOfType, isAction } from './is-action';

/**
 * Create a co-routine runtime.
 *
 * @param {Object}    controls Object of control handlers.
 * @param {Function}  dispatch Unhandled action dispatch.
 *
 * @return {Function} co-routine runtime
 */
export default function createRuntime( controls = {}, dispatch ) {
	const rungenControls = map(
		controls,
		( control, actionType ) => (
			value,
			next,
			iterate,
			yieldNext,
			yieldError
		) => {
			if ( ! isActionOfType( value, actionType ) ) {
				return false;
			}
			const routine = control( value );
			if ( isPromise( routine ) ) {
				// Async control routine awaits resolution.
				routine.then( yieldNext, yieldError );
			} else {
				yieldNext( routine );
			}
			return true;
		}
	);

	const unhandledActionControl = ( value, next ) => {
		if ( ! isAction( value ) ) {
			return false;
		}
		dispatch( value );
		next();
		return true;
	};
	rungenControls.push( unhandledActionControl );

	const rungenRuntime = create( rungenControls );

	return ( action ) =>
		new Promise( ( resolve, reject ) =>
			rungenRuntime(
				action,
				( result ) => {
					if ( isAction( result ) ) {
						dispatch( result );
					}
					resolve( result );
				},
				reject
			)
		);
}