1 files changed, 97 insertions, 0 deletions

diff --git a/editors/code/src/installation/downloads.ts b/editors/code/src/installation/downloads.ts
new file mode 100644
index 000000000..7ce2e2960
--- /dev/null
+++ b/editors/code/src/installation/downloads.ts
@@ -0,0 +1,97 @@
+import fetch from "node-fetch";
+import * as vscode from "vscode";
+import * as path from "path";
+import * as fs from "fs";
+import * as stream from "stream";
+import * as util from "util";
+import { log, assert } from "../util";
+import { ArtifactReleaseInfo } from "./interfaces";
+
+const pipeline = util.promisify(stream.pipeline);
+
+/**
+ * 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);
+
+    if (!res.ok) {
+        log.error("Error", res.status, "while downloading file from", url);
+        log.error({ body: await res.text(), headers: res.headers });
+
+        throw new Error(`Got response ${res.status} when trying to download a file.`);
+    }
+
+    const totalBytes = Number(res.headers.get('content-length'));
+    assert(!Number.isNaN(totalBytes), "Sanity check of content-length protocol");
+
+    log.debug("Downloading file of", totalBytes, "bytes size from", url, "to", destFilePath);
+
+    let readBytes = 0;
+    res.body.on("data", (chunk: Buffer) => {
+        readBytes += chunk.length;
+        onProgress(readBytes, totalBytes);
+    });
+
+    const destFileStream = fs.createWriteStream(destFilePath, { mode: destFilePermissions });
+
+    await pipeline(res.body, destFileStream);
+    return new Promise<void>(resolve => {
+        destFileStream.on("close", resolve);
+        destFileStream.destroy();
+
+        // Details on workaround: https://github.com/rust-analyzer/rust-analyzer/pull/3092#discussion_r378191131
+        // Issue at nodejs repo: https://github.com/nodejs/node/issues/31776
+    });
+}
+
+/**
+ * Downloads artifact from given `downloadUrl`.
+ * Creates `installationDir` if it is not yet created and puts the artifact under
+ * `artifactFileName`.
+ * Displays info about the download progress in an info message printing the name
+ * of the artifact as `displayName`.
+ */
+export async function downloadArtifactWithProgressUi(
+    { downloadUrl, releaseName }: ArtifactReleaseInfo,
+    artifactFileName: string,
+    installationDir: string,
+    displayName: string,
+) {
+    await fs.promises.mkdir(installationDir).catch(err => assert(
+        err?.code === "EEXIST",
+        `Couldn't create directory "${installationDir}" to download ` +
+        `${artifactFileName} artifact: ${err?.message}`
+    ));
+
+    const installationPath = path.join(installationDir, artifactFileName);
+
+    await vscode.window.withProgress(
+        {
+            location: vscode.ProgressLocation.Notification,
+            cancellable: false, // FIXME: add support for canceling download?
+            title: `Downloading rust-analyzer ${displayName} (${releaseName})`
+        },
+        async (progress, _cancellationToken) => {
+            let lastPrecentage = 0;
+            const filePermissions = 0o755; // (rwx, r_x, r_x)
+            await downloadFile(downloadUrl, installationPath, filePermissions, (readBytes, totalBytes) => {
+                const newPercentage = (readBytes / totalBytes) * 100;
+                progress.report({
+                    message: newPercentage.toFixed(0) + "%",
+                    increment: newPercentage - lastPrecentage
+                });
+
+                lastPrecentage = newPercentage;
+            });
+        }
+    );
+}