feat: use file watchers to track the LS CLI status (#48)

License status for LS CLI is now checked via file watchers instead of
periodic checks.

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---
This is **part 2 of 2 in a stack** made with GitButler:
- <kbd>&nbsp;2&nbsp;</kbd> #48 👈 
- <kbd>&nbsp;1&nbsp;</kbd> #47 
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Author: skyrpex

src/utils/license.ts

@@ -1,7 +1,36 @@
+import { homedir, platform } from "node:os";
+import { join } from "node:path";
+
 import type { CancellationToken, LogOutputChannel } from "vscode";
 
 import { execLocalStack } from "./cli.ts";
 
+/**
+ * See https://github.com/localstack/localstack/blob/de861e1f656a52eaa090b061bd44fc1a7069715e/localstack-core/localstack/utils/files.py#L38-L55.
+ * @returns The cache directory for the current platform.
+ */
+const cacheDirectory = () => {
+	switch (platform()) {
+		case "win32":
+			return join(process.env.LOCALAPPDATA!, "cache");
+		case "darwin":
+			return join(homedir(), "Library", "Caches");
+		default:
+			return process.env.XDG_CACHE_HOME ?? join(homedir(), ".cache");
+	}
+};
+
+/**
+ * The file that contains the license information of the LocalStack CLI.
+ *
+ * The license file is stored in the cache directory for the current platform.
+ */
+export const LICENSE_FILENAME = join(
+	cacheDirectory(),
+	"localstack-cli",
+	"license.json",
+);
+
 const LICENSE_VALIDITY_MARKER = "license validity: valid";
 
 export async function checkIsLicenseValid(outputChannel: LogOutputChannel) {

src/utils/setup-status.ts

@@ -13,6 +13,7 @@ import {
 } from "./configure-aws.ts";
 import { createEmitter } from "./emitter.ts";
 import { immediateOnce } from "./immediate-once.ts";
+import { checkIsLicenseValid, LICENSE_FILENAME } from "./license.ts";
 import type { UnwrapPromise } from "./promises.ts";
 import { checkSetupStatus } from "./setup.ts";
 import type { TimeTracker } from "./time-tracker.ts";
@@ -39,6 +40,7 @@ export async function createSetupStatusTracker(
 	const awsProfileTracker = createAwsProfileStatusTracker(outputChannel);
 	const localStackAuthenticationTracker =
 		createLocalStackAuthenticationStatusTracker(outputChannel);
+	const licenseTracker = createLicenseStatusTracker(outputChannel);
 	const end = Date.now();
 	outputChannel.trace(
 		`[setup-status]: Initialized dependencies in ${ms(end - start, { long: true })}`,
@@ -51,6 +53,7 @@ export async function createSetupStatusTracker(
 			Object.values(statuses),
 			awsProfileTracker.status() === "ok",
 			localStackAuthenticationTracker.status() === "ok",
+			licenseTracker.status() === "ok",
 		].some((check) => check === false);
 
 		const newStatus = setupRequired ? "setup_required" : "ok";
@@ -75,6 +78,10 @@ export async function createSetupStatusTracker(
 		checkStatus();
 	});
 
+	licenseTracker.onChange(() => {
+		checkStatus();
+	});
+
 	let timeout: NodeJS.Timeout | undefined;
 	const startChecking = () => {
 		checkStatus();
@@ -225,3 +232,22 @@ function createLocalStackAuthenticationStatusTracker(
 		async () => ((await checkIsAuthenticated()) ? "ok" : "setup_required"),
 	);
 }
+
+/**
+ * Creates a status tracker that monitors the LocalStack license file for changes.
+ * When the file is changed, the provided check function is called to determine the current setup status.
+ * Emits status changes to registered listeners.
+ *
+ * @param outputChannel - Channel for logging output and trace messages.
+ * @returns A {@link StatusTracker} instance for querying status, subscribing to changes, and disposing resources.
+ */
+function createLicenseStatusTracker(
+	outputChannel: LogOutputChannel,
+): StatusTracker {
+	return createFileStatusTracker(
+		outputChannel,
+		"[setup-status.license]",
+		[LICENSE_FILENAME],
+		async () => ((await checkIsLicenseValid(outputChannel)) ? "ok" : "setup_required"),
+	);
+}

src/utils/setup.ts

@@ -5,18 +5,15 @@ import { LOCALSTACK_DOCKER_IMAGE_NAME } from "../constants.ts";
 
 import { exec } from "./exec.ts";
 import { checkLocalstackInstalled } from "./install.ts";
-import { checkIsLicenseValid } from "./license.ts";
 import { spawn } from "./spawn.ts";
 
 export async function checkSetupStatus(outputChannel: LogOutputChannel) {
-	const [isInstalled, isLicenseValid] = await Promise.all([
+	const [isInstalled] = await Promise.all([
 		checkLocalstackInstalled(outputChannel),
-		checkIsLicenseValid(outputChannel),
 	]);
 
 	return {
 		isInstalled,
-		isLicenseValid,
 	};
 }