1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
import fetch from "node-fetch";
import * as fs from "fs";
import { strict as assert } from "assert";
import { NestedError } from "ts-nested-error";
class DownloadFileError extends NestedError {}
/**
* Downloads file from `url` and stores it at `destFilePath` with `destFilePermissions`.
* `onProgress` callback is called on recieveing each chunk of bytes
* 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,
destFilePermissions: number,
onProgress: (readBytes: number, totalBytes: number) => void
): Promise<void> {
const res = await fetch(url).catch(DownloadFileError.rethrow("Failed at initial fetch"));
if (!res.ok) {
console.log("Error", res.status, "while downloading file from", url);
console.dir({ body: await res.text(), headers: res.headers }, { depth: 3 });
throw new DownloadFileError(`Got response ${res.status}`);
}
const totalBytes = Number(res.headers.get('content-length'));
assert(!Number.isNaN(totalBytes), "Sanity check of content-length protocol");
let readBytes = 0;
console.log("Downloading file of", totalBytes, "bytes size from", url, "to", destFilePath);
// Here reject() may be called 2 times. As per ECMAScript standard, 2-d call is ignored
// https://tc39.es/ecma262/#sec-promise-reject-functions
return new Promise<void>((resolve, reject) => res.body
.on("data", (chunk: Buffer) => {
readBytes += chunk.length;
onProgress(readBytes, totalBytes);
})
.on("error", err => reject(
new DownloadFileError(`Read-stream error, read bytes: ${readBytes}`, err)
))
.pipe(fs.createWriteStream(destFilePath, { mode: destFilePermissions }))
.on("error", err => reject(
new DownloadFileError(`Write-stream error, read bytes: ${readBytes}`, err)
))
.on("close", resolve)
);
}
|
