44 lines
955 B
JavaScript
44 lines
955 B
JavaScript
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// KeyPromiseQueue is a simple promise queue
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// used to queue operations per key basis.
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// Once the tail promise in the key-queue fulfills,
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// the chain on that key will be cleared.
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export class KeyPromiseQueue {
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constructor() {
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this.queue = {};
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}
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enqueue(key, operation) {
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const tuple = this.beforeOp(key);
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const toAwait = tuple[1];
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const nextOperation = toAwait.then(operation);
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const wrappedOperation = nextOperation.then(result => {
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this.afterOp(key);
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return result;
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});
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tuple[1] = wrappedOperation;
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return wrappedOperation;
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}
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beforeOp(key) {
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let tuple = this.queue[key];
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if (!tuple) {
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tuple = [0, Promise.resolve()];
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this.queue[key] = tuple;
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}
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tuple[0]++;
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return tuple;
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}
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afterOp(key) {
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const tuple = this.queue[key];
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if (!tuple) {
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return;
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}
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tuple[0]--;
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if (tuple[0] <= 0) {
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delete this.queue[key];
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return;
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}
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}
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}
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