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refactor: move fixture generation to worker
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,185 @@ | ||
| import { uuid } from "./utils"; | ||
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| interface WorkerMessage { | ||
| requestId: string; | ||
| targetSizeInBytes: number; | ||
| seed: string; | ||
| } | ||
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| interface WorkerResponse { | ||
| requestId: string; | ||
| text: string; | ||
| } | ||
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| /** | ||
| * Generates the Worker code as a string using the Function.prototype.toString() strategy. | ||
| * This ensures that the Worker code is self-contained and not transformed by the bundler. | ||
| * The worker code is written as a function and then converted to a string. | ||
| */ | ||
| function generateTextOfSizeWorkerCode(): string { | ||
| const workerFunction = () => { | ||
| // Define types for internal worker usage | ||
| interface WorkerMessage { | ||
| requestId: string; | ||
| targetSizeInBytes: number; | ||
| seed: string; | ||
| } | ||
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| interface WorkerResponse { | ||
| requestId: string; | ||
| text: string; | ||
| } | ||
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| /** | ||
| * Utility function to convert a seed string into a numerical hash. | ||
| * | ||
| * @param str - The seed string to hash. | ||
| * @returns A numerical hash derived from the input string. | ||
| */ | ||
| function hashCode(str: string): number { | ||
| let hash = 0; | ||
| for (let i = 0; i < str.length; i++) { | ||
| hash = (hash * 31 + str.charCodeAt(i)) >>> 0; // Ensure unsigned 32-bit integer | ||
| } | ||
| return hash; | ||
| } | ||
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| /** | ||
| * Seeded pseudo-random number generator using Linear Congruential Generator (LCG). | ||
| * | ||
| * @param seed - The seed string to initialize the generator. | ||
| * @returns A function that generates a pseudo-random number between 0 (inclusive) and 1 (exclusive). | ||
| */ | ||
| function seededRandom(seed: string): () => number { | ||
| let state: number = hashCode(seed); | ||
| const a: number = 1664525; | ||
| const c: number = 1013904223; | ||
| const m: number = 2 ** 32; | ||
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| /** | ||
| * Generates the next pseudo-random number in the sequence. | ||
| * | ||
| * @returns A pseudo-random number between 0 (inclusive) and 1 (exclusive). | ||
| */ | ||
| function random(): number { | ||
| state = (a * state + c) >>> 0; // Update state with LCG formula | ||
| return state / m; | ||
| } | ||
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| return random; | ||
| } | ||
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| /** | ||
| * Calculates the byte size of a string using UTF-8 encoding. | ||
| * | ||
| * @param str - The string whose byte size is to be calculated. | ||
| * @returns The byte size of the input string. | ||
| */ | ||
| function calculateByteSize(str: string): number { | ||
| return new TextEncoder().encode(str).length; | ||
| } | ||
|
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| /** | ||
| * Listener for messages from the main thread. | ||
| * Generates a deterministic random text string based on the provided seed and target size. | ||
| */ | ||
| self.onmessage = (event: MessageEvent): void => { | ||
| const data: WorkerMessage = event.data; | ||
| const { requestId, targetSizeInBytes, seed } = data; | ||
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| const rand: () => number = seededRandom(seed); | ||
| const estimatedChars: number = Math.ceil(targetSizeInBytes); | ||
| const charArray: string[] = new Array(estimatedChars); | ||
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| for (let i = 0; i < estimatedChars; i++) { | ||
| // Generate a random printable ASCII character (codes 33 to 126) | ||
| charArray[i] = String.fromCharCode(33 + Math.floor(rand() * 94)); | ||
| } | ||
|
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| let result: string = charArray.join(""); | ||
|
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| // Ensure the generated result matches the exact target size | ||
| while (calculateByteSize(result) > targetSizeInBytes) { | ||
| result = result.slice(0, -1); | ||
| } | ||
|
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| const response: WorkerResponse = { requestId, text: result }; | ||
| // Send the generated text back to the main thread | ||
| postMessage(response); | ||
| }; | ||
| }; | ||
|
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| // Convert the worker function to a string and invoke it immediately | ||
| return `(${workerFunction.toString()})();`; | ||
| } | ||
|
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| /** | ||
| * Creates a Web Worker from a given code string by converting it to a Blob URL. | ||
| * | ||
| * @param code The Worker code as a string. | ||
| * @returns A new Worker instance. | ||
| */ | ||
| function createWorkerFromCode(code: string): Worker { | ||
| const blob: Blob = new Blob([code], { type: "application/javascript" }); | ||
| const blobURL: string = URL.createObjectURL(blob); | ||
| return new Worker(blobURL); | ||
| } | ||
|
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| /** | ||
| * Asynchronously generates a deterministic random text string of a specified byte size | ||
| * by offloading the task to a Web Worker. Supports multiple concurrent requests using requestId. | ||
| * | ||
| * @param targetSizeInBytes The desired byte size of the generated string. | ||
| * @param seed Optional seed for the random number generator. Defaults to "default". | ||
| * @returns A Promise that resolves to the generated string. | ||
| */ | ||
| export async function generateTextOfSize( | ||
| targetSizeInBytes: number, | ||
| seed = "default" | ||
| ): Promise<string> { | ||
| return new Promise<string>((resolve, reject) => { | ||
| const requestId: string = uuid(); | ||
|
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| // Generate the worker code and create a new worker | ||
| const workerCode: string = generateTextOfSizeWorkerCode(); | ||
| const worker: Worker = createWorkerFromCode(workerCode); | ||
|
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| /** | ||
| * Handler for messages from the worker. | ||
| * Resolves the promise if the response matches the requestId. | ||
| */ | ||
| const handleMessage = (event: MessageEvent): void => { | ||
| const data: WorkerResponse = event.data; | ||
| if (data.requestId === requestId) { | ||
| resolve(data.text); | ||
| cleanup(); | ||
| } | ||
| }; | ||
|
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| /** | ||
| * Handler for errors from the worker. | ||
| * Rejects the promise and cleans up the worker. | ||
| */ | ||
| const handleError = (error: ErrorEvent): void => { | ||
| reject(error); | ||
| cleanup(); | ||
| }; | ||
|
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| /** | ||
| * Cleans up event listeners and terminates the worker. | ||
| */ | ||
| const cleanup = (): void => { | ||
| worker.removeEventListener("message", handleMessage); | ||
| worker.removeEventListener("error", handleError); | ||
| worker.terminate(); | ||
| }; | ||
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| // Attach event listeners | ||
| worker.addEventListener("message", handleMessage); | ||
| worker.addEventListener("error", handleError); | ||
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| // Send the message with the requestId | ||
| const message: WorkerMessage = { requestId, targetSizeInBytes, seed }; | ||
| worker.postMessage(message); | ||
| }); | ||
| } |
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