(function (global) {
    'use strict';

    var DEFAULT_BUDGET_MS = 2;

    /**
     * 空闲切片调度：单次回调预算默认 2ms，可跨帧续跑。
     * @param {function(function():boolean):void} work 入参 isExpired()，返回 false 表示还有剩余工作
     * @param {number=} budgetMs
     */
    function runIdle(work, budgetMs) {
        var budget = budgetMs > 0 ? budgetMs : DEFAULT_BUDGET_MS;
        var schedule = function (fn) {
            if (typeof global.requestIdleCallback === 'function') {
                global.requestIdleCallback(fn, { timeout: 200 });
            } else {
                global.setTimeout(fn, 0);
            }
        };
        var step = function () {
            var start = performance.now();
            var expired = function () {
                return performance.now() - start >= budget;
            };
            var more = true;
            try {
                work(expired);
                // work 约定：若需续跑，在内部检测 expired 后自行再次 schedule；此处兼容返回值
            } catch (e) {
                console.warn('[调试工作台] idle 任务失败', e);
                more = false;
            }
            return more;
        };
        // 简化：提供 runChunks 辅助
        schedule(function () { step(); });
    }

    /**
     * 分片遍历数组。
     * @param {Array} list
     * @param {function(*,number):void} visit
     * @param {function():void=} onDone
     * @param {number=} budgetMs
     */
    function forEachChunk(list, visit, onDone, budgetMs) {
        var i = 0;
        var budget = budgetMs > 0 ? budgetMs : DEFAULT_BUDGET_MS;
        var tick = function () {
            var start = performance.now();
            while (i < list.length && performance.now() - start < budget) {
                visit(list[i], i);
                i += 1;
            }
            if (i < list.length) {
                if (typeof global.requestIdleCallback === 'function') {
                    global.requestIdleCallback(tick, { timeout: 200 });
                } else {
                    global.setTimeout(tick, 0);
                }
            } else if (onDone) {
                onDone();
            }
        };
        tick();
    }

    global.PWIdle = {
        budgetMs: DEFAULT_BUDGET_MS,
        run: runIdle,
        forEachChunk: forEachChunk,
    };
})(window);