feat(cli): make cli actually be able to update

src/cli/main.ts

@@ -0,0 +1,20 @@
+import yargs from "yargs";
+import { standalone } from "../../config.json";
+import { SelfUpdateUtility } from "./update";
+
+if (standalone) SelfUpdateUtility.init();
+
+yargs(process.argv.slice(2)).command(
+  "update",
+  "update",
+  {
+    url: {
+      alias: "u",
+      describe: "the URL to download the new executable from",
+    },
+  },
+  async (argv) => {
+    if (typeof argv.url === "string")
+      await SelfUpdateUtility.get().updateCLI(argv.url);
+  },
+);

src/cli/update.ts

@@ -1,30 +1,90 @@
-#!/usr/bin/env ts-node
-
-import { renameSync, unlinkSync, createWriteStream } from "fs";
+import { renameSync, unlinkSync, createWriteStream, existsSync } from "fs";
 import child_process = require("child_process");
 import { get as httpGet, type IncomingMessage } from "http";
-import { standalone } from "../config.json";
+import { standalone } from "../../config.json";
 
 /**
  * self updates the cli executable
  * @warning DO NOT USE THIS IF NOT PART OF STANDALONE EXECUTABLE
  */
-export async function updateCLI(downloadUrl: string): Promise<void> {
-  if (!standalone)
-    throw new Error(
-      "LemLink is not part of a standalone executable, and thus cannot self update",
-    );
+export class SelfUpdateUtility {
+  /**
+   * So how the heck does this CLI update itself?
+   *
+   * 1. Attempt to download new executable from downloadUrl to newPath
+   * 2. Rename current executable to oldPath
+   * 3. Rename newly downloaded executable to filePath
+   * 4. On startup of the cli, we attempt to remove oldPath
+   */
+
+  protected readonly filePath: string; // normal executable path
+  protected readonly newPath: string; // the new executable that will be downloaded
+  protected readonly oldPath: string;
+
+  private static singleton?: SelfUpdateUtility;
+  /**
+   * self updates the cli executable
+   * @warning DO NOT USE THIS IF NOT PART OF STANDALONE EXECUTABLE
+   */
+  private constructor() {
+    if (!standalone)
+      throw new Error(
+        "LemLink is not part of a standalone executable, and thus cannot self update",
+      );
+    const nodeExecutablePath = process.env._;
+    if (nodeExecutablePath === undefined) {
+      throw new Error("Could not find node executable path");
+    }
+
+    this.filePath = nodeExecutablePath;
+    this.newPath = this.filePath + "-new";
+    this.oldPath = this.filePath + "-old";
+
+    this.attemptToDeleteOldPathFile();
+  }
+
+  /**
+   * Should be run at the start of CLI program
+   */
+  public static init(): void {
+    if (this.singleton !== undefined) {
+      console.error(
+        "Self Update Utility has already been initialized, canceling init..",
+      );
+      return;
+    }
+    this.singleton = new SelfUpdateUtility();
+  }
+
+  public static get(): SelfUpdateUtility {
+    if (this.singleton === undefined)
+      throw new Error(
+        "Self Update Utility was not initialized at the start of CLI program!!",
+      );
+    return this.singleton;
+  }
+
+  /**
+   * @returns true if oldPath exists, false if otherwise
+   */
+  private attemptToDeleteOldPathFile(): boolean {
+    if (existsSync(this.oldPath)) {
+      unlinkSync(this.oldPath);
+      return true;
+    }
+    return false;
+  }
 
-  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-  const filePath = process.env._!;
-  const newPath = filePath + "-new";
-  const oldPath = filePath + "-old";
-  try {
-    console.log("attempting to delete old file");
-    unlinkSync(oldPath);
-  } catch (err) {
+  /**
+   * Replaces the current CLI executable with the one found at {@link downloadUrl}
+   * @param downloadUrl url from which a new executable should be downloaded
+   */
+  public async updateCLI(downloadUrl: string): Promise<void> {
+    /**
+     * See top of this file for info on how this works
+     */
     console.log("Downloading new file...");
-    const fileStream = createWriteStream(newPath);
+    const fileStream = createWriteStream(this.newPath);
 
     const response = await new Promise<IncomingMessage>((resolve) =>
       httpGet(downloadUrl, resolve),
@@ -37,8 +97,8 @@ export async function updateCLI(downloadUrl: string): Promise<void> {
     console.log("File downloaded successfully.");
 
     console.log("Replacing current file...");
-    renameSync(filePath, oldPath);
-    renameSync(newPath, filePath);
+    renameSync(this.filePath, this.oldPath);
+    renameSync(this.newPath, this.filePath);
     console.log("Replaced current file successfully!");
 
     console.log("Restarting...");