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import fetch from "node-fetch";
import { throttle } from "throttle-debounce";
import * as fs from "fs";
import { strict as assert } from "assert";
/**
* Downloads file from `url` and stores it at `destFilePath`.
* `onProgress` callback is periodically called to track the progress of downloading,
* it gets the already read and total amount of bytes to read as its parameters.
*/
export async function downloadFile(
url: string,
destFilePath: fs.PathLike,
onProgress: (readBytes: number, totalBytes: number) => void
): Promise<void> {
onProgress = throttle(200, /* noTrailing: */ true, onProgress);
const response = await fetch(url);
const totalBytes = Number(response.headers.get('content-length'));
assert(!Number.isNaN(totalBytes), "Sanity check of content-length protocol");
let readBytes = 0;
return new Promise<void>((resolve, reject) => response.body
.on("data", (chunk: Buffer) => {
readBytes += chunk.length;
onProgress(readBytes, totalBytes);
})
.on("end", resolve)
.on("error", reject)
.pipe(fs.createWriteStream(destFilePath))
);
}
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