SOURCE

class TaskQueue {
    constructor(max) {
        this.max = max;
        this.taskList = [];
        this.aborted = false;
    }

    restore() {
        this.aborted = false;
    }

    clear() {
        this.taskList = [];
        this.aborted = true;
    }

    async start(callSucc = () => { }, callErr = () => { }, allow = () => true) {
        if (this.aborted) {
            callErr('aborted')
            return;
        }
        let len = this.taskList.length;

        if (!len) {
            return;
        }

        let min = Math.min(this.max, len);

        for (let i = 0; i < min; i++) {
            // 开始占用一个任务的空间
            this.max--;
            const task = this.taskList.shift();
            task&&task().then(res => {
                if (allow(res)) {
                    callSucc(res);
                }
            }).catch(error => {
                callErr(error)
            }).finally(() => {
                this.max++;
                this.start(callSucc, callErr);
            })
        }
    }

    addTask(task) {
        this.taskList.push(task);
        return this;
    }
}