/**
 *****************************************
 * Created by edonet@163.com
 * Created on 2021-04-02 21:24:10
 *****************************************
 */
'use strict';


/**
 *****************************************
 * 处理函数
 *****************************************
 */
type Handler<T, P> = (state: T, next: () => void | P) => void | P;


/**
 *****************************************
 * 链函数
 *****************************************
 */
type Chain<T, P> = (state: T, callback?: (state: T) => void | P) => void | P;


/**
 *****************************************
 * 函数链
 *****************************************
 */
export function chain<T, P = void>(...args: Handler<T, P>[]): Chain<T, P> {
    const length = args.length;

    // 校验参数
    args.forEach(handler => {
        if (typeof handler !== 'function') {
            throw new Error('expect handler to be a function!');
        }
    });

    // 执行函数
    function invoke(index: number, state: T, callback?: (state: T) => void | P): void | P {
        if (index < length) {
            return args[index](state, () => invoke(index + 1, state, callback));
        }

        // 执行回调
        if (typeof callback === 'function') {
            return callback(state);
        }
    }

    // 返回函数
    return function chained(state, callback) {
        return invoke(0, state, callback);
    };
}