/**
 *****************************************
 * Created by edonet@163.com
 * Created on 2021-03-28 20:37:49
 *****************************************
 */
'use strict';


/**
 *****************************************
 * 加载依赖
 *****************************************
 */
import { U, F, FOP } from './d';


/**
 *****************************************
 * 解析结果
 *****************************************
 */
type Thenable<T> = (
    T extends (...args: infer P) => void ?
    P extends [err: U, ...rest: infer Q] ?
    Promise<Q extends [] ? void : Q extends [U] ? Q[0] : Q> :
    Promise<void> :
    Promise<void>
);


/**
 *****************************************
 * 重载列表
 *****************************************
 */
type Overloads<T extends U[]> = (
    T extends [head: infer P, ...rest: infer Q] ?
    P extends [...rest: infer A, tail: infer R] ?
    ((...args: A) => Thenable<R>) & Overloads<Q> :
    Record<string, never> :
    Record<string, never>
);


/**
 *****************************************
 * Promisify
 *****************************************
 */
type Promisify<T extends F> = Overloads<FOP<T>>;


/**
 *****************************************
 * Promisify
 *****************************************
 */
export function promisify<T extends F>(handler: T): Promisify<T> {
    function promised(this: unknown, ...args: unknown[]): Promise<unknown> {
        return new Promise((resolve, reject) => {
            let resolved = false;

            // 添加回调
            args.push((err: null | Error, ...rest: unknown[]) => {
                if (resolved) {
                    return;
                }

                // 更新标识
                resolved = true;

                // 执行失败
                if (err) {
                    return reject(err);
                }

                // 执行成功
                resolve(rest.length > 1 ? rest : rest[0]);
            });

            // 执行函数
            handler.apply(this, args);
        });
    }

    // 返回函数
    return promised as unknown as Promisify<T>;
}