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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,7 +1,35 @@ | ||
| import { expect, test } from "bun:test"; | ||
| import { expect, mock, test } from "bun:test"; | ||
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| import { doSomething } from "."; | ||
| import { Batcher } from "."; | ||
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| test(doSomething.name, () => { | ||
| expect(() => doSomething()).toThrowError("Not implemented yet"); | ||
| test("calls the function once per key", async () => { | ||
| let fn = mock(); | ||
| let batcher = new Batcher(10); | ||
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| let times = Math.floor(Math.random() * 100) + 1; | ||
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| await Promise.all( | ||
| Array.from({ length: times }).map(() => { | ||
| return batcher.call(["key"], fn); | ||
| }), | ||
| ); | ||
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| expect(fn).toHaveBeenCalledTimes(1); | ||
| }); | ||
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| test("caches results and return the same value", async () => { | ||
| let batcher = new Batcher(10); | ||
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| let [value1, value2] = await Promise.all([ | ||
| batcher.call(["key"], async () => { | ||
| await new Promise((resolve) => setTimeout(resolve, 5)); | ||
| return { key: "value" }; | ||
| }), | ||
| batcher.call(["key"], async () => { | ||
| await new Promise((resolve) => setTimeout(resolve, 5)); | ||
| return { key: "value" }; | ||
| }), | ||
| ]); | ||
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| expect(value1).toBe(value2); | ||
| }); |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,82 @@ | ||
| export function doSomething() { | ||
| throw new Error("Not implemented yet"); | ||
| import type { Jsonifiable } from "type-fest"; | ||
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| /** | ||
| * This is our batcher implementation. It is a class that allows us to batch | ||
| * function calls that are identical within a certain time window. This is | ||
| * useful for reducing API calls to external services, for example. | ||
| * | ||
| * The Batcher class has a cache property that stores the results of the | ||
| * function calls. It also has a timeouts property that stores the timeouts | ||
| * for each function call. The batchWindow property is the time window in | ||
| * milliseconds that we use to batch the function calls. | ||
| * | ||
| * The call method takes an array of values as key and an async function fn. | ||
| * It converts the key to a string and stores it in the cache. If the cache | ||
| * already has the key, it returns the cached value. Otherwise, it creates a | ||
| * new promise and sets a timeout for the function call. When the timeout | ||
| * expires, the function is called and the result is resolved. If an error | ||
| * occurs, the promise is rejected. Finally, the timeout is removed from the | ||
| * timeouts property. | ||
| * | ||
| * @example | ||
| * let batcher = new Batcher(10); | ||
| * let [value1, value2] = await Promise.all([ | ||
| * batcher.call(["key"], async () => { | ||
| * await new Promise((resolve) => setTimeout(resolve, 5)); | ||
| * return { key: "value" } | ||
| * }), | ||
| * batcher.call(["key"], async () => { | ||
| * await new Promise((resolve) => setTimeout(resolve, 5)); | ||
| * return { key: "value" } | ||
| * }), | ||
| * ]) | ||
| * console.log(value1 === value2); // true | ||
| */ | ||
| export class Batcher { | ||
| protected readonly cache = new Map<string, Promise<unknown>>(); | ||
| protected readonly timeouts = new Map<string, Timer>(); | ||
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| /** | ||
| * Creates a new instance of the Batcher. | ||
| * @param batchWindow The time window (in milliseconds) to batch function calls. | ||
| */ | ||
| constructor(protected batchWindow?: number) {} | ||
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| /** | ||
| * Calls a function with batching, ensuring multiple identical calls within a time window execute only once. | ||
| * @template TArgs The argument types. | ||
| * @template TResult The return type. | ||
| * @param fn The async function to batch. | ||
| * @param key An array of values used for deduplication. | ||
| * @returns A promise that resolves with the function result. | ||
| */ | ||
| call<TResult, Key extends Jsonifiable>( | ||
| key: Key[], | ||
| fn: () => Promise<TResult>, | ||
| ): Promise<TResult> { | ||
| let cacheKey = JSON.stringify(key); | ||
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| if (this.cache.has(cacheKey)) { | ||
| return this.cache.get(cacheKey) as Promise<TResult>; | ||
| } | ||
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| let promise = new Promise<TResult>((resolve, reject) => { | ||
| let timeout = setTimeout(async () => { | ||
| try { | ||
| let result = await fn(); | ||
| resolve(result); | ||
| } catch (error) { | ||
| reject(error); | ||
| } finally { | ||
| this.timeouts.delete(cacheKey); | ||
| } | ||
| }, this.batchWindow); | ||
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| this.timeouts.set(cacheKey, timeout); | ||
| }); | ||
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| this.cache.set(cacheKey, promise); | ||
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| return promise; | ||
| } | ||
| } |