/*************************************************************
 *
 *  Copyright (c) 2017 The MathJax Consortium
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

/**
 * @fileoverview  Implement FunctionList object
 *
 * @author dpvc@mathjax.org (Davide Cervone)
 */

import {PrioritizedList, PrioritizedListItem} from './PrioritizedList.js';

/*****************************************************************/
/**
 *  The FunctionListItem interface (extends PrioritizedListItem<Function>)
 */

export interface FunctionListItem extends PrioritizedListItem<Function> {}

/*****************************************************************/
/**
 *  Implements the FunctionList class (extends PrioritizedList<Function>)
 */

export class FunctionList extends PrioritizedList<Function> {

    /**
     * Executes the functions in the list (in prioritized order),
     *   passing the given data to the functions.  If any return
     *   false, the list is terminated.
     *
     * @param {any[]} data  The array of arguments to pass to the functions
     * @return {boolean}    False if any function stopped the list by
     *                       returning false, true otherwise
     */
    public execute(...data: any[]) {
        for (const item of this) {
            let result = item.item(...data);
            if (result === false) {
                return false;
            }
        }
        return true;
    }

    /**
     * Executes the functions in the list (in prioritied order) asynchronously,
     *   passing the given data to the functions, and doing the next function
     *   only when the previous one completes.  If the function returns a
     *   Promise, then use that to control the flow.  Otherwise, if the
     *   function returns false, the list is terminated.
     * This function returns a Promise.  If any function in the list fails,
     *   the promise fails.  If any function returns false, the promise
     *   succeeds, but passes false as its argument.  Otherwise it succeeds
     *   and passes true.
     *
     * @param {any[]} data  The array of arguments to pass to the functions
     * @return {Promise}    The promise that is satisfied when the function
     *                       list completes (with argument true or false
     *                       depending on whether some function returned
     *                       false or not).
     */
    public asyncExecute(...data: any[]) {
        let i = -1;
        let items = this.items;
        return new Promise((ok: Function, fail: Function) => {
            (function execute() {
                while (++i < items.length) {
                    let result = items[i].item(...data);
                    if (result instanceof Promise) {
                        result.then(execute).catch(err => fail(err));
                        return;
                    }
                    if (result === false) {
                        ok(false);
                        return;
                    }
                }
                ok(true);
            })();
        });
    }
}