export default class BlockingQueue {
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#items = [];
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#waiters = []; // {resolve, reject, min, timer, onTimeout}
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/* 空队列一次性闸门 */
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#emptyPromise = null;
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#emptyResolve = null;
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/* 生产者：把数据塞进去 */
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enqueue(item, ...restItems) {
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if (restItems.length === 0) {
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this.#items.push(item);
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}
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// 如果有额外参数，批量处理所有项
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else {
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const items = [item, ...restItems].filter(i => i);
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if (items.length === 0) return;
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this.#items.push(...items);
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}
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// 若有空队列闸门，一次性放行所有等待者
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if (this.#emptyResolve) {
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this.#emptyResolve();
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this.#emptyResolve = null;
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this.#emptyPromise = null;
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}
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// 唤醒所有正在等的 waiter
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this.#wakeWaiters();
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}
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/* 消费者：min 条或 timeout ms 先到谁 */
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async dequeue(min = 1, timeout = Infinity, onTimeout = null) {
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// 1. 若空，等第一次数据到达（所有调用共享同一个 promise）
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if (this.#items.length === 0) {
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await this.#waitForFirstItem();
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}
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// 立即满足
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if (this.#items.length >= min) {
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return this.#flush();
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}
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// 需要等待
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return new Promise((resolve, reject) => {
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let timer = null;
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const waiter = { resolve, reject, min, onTimeout, timer };
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// 超时逻辑
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if (Number.isFinite(timeout)) {
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waiter.timer = setTimeout(() => {
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this.#removeWaiter(waiter);
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if (onTimeout) onTimeout(this.#items.length);
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resolve(this.#flush());
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}, timeout);
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}
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this.#waiters.push(waiter);
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});
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}
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/* 空队列闸门生成器 */
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#waitForFirstItem() {
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if (!this.#emptyPromise) {
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this.#emptyPromise = new Promise(r => (this.#emptyResolve = r));
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}
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return this.#emptyPromise;
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}
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/* 内部：每次数据变动后，检查哪些 waiter 已满足 */
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#wakeWaiters() {
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for (let i = this.#waiters.length - 1; i >= 0; i--) {
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const w = this.#waiters[i];
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if (this.#items.length >= w.min) {
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this.#removeWaiter(w);
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w.resolve(this.#flush());
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}
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}
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}
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#removeWaiter(waiter) {
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const idx = this.#waiters.indexOf(waiter);
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if (idx !== -1) {
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this.#waiters.splice(idx, 1);
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if (waiter.timer) clearTimeout(waiter.timer);
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}
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}
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#flush() {
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const snapshot = [...this.#items];
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this.#items.length = 0;
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return snapshot;
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}
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/* 当前缓存长度（不含等待者） */
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get length() {
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return this.#items.length;
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}
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/* 清空队列（保持对象引用，不影响等待者） */
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clear() {
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this.#items.length = 0;
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}
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}
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