implement EnvService.getDependencyVersion

packages/backend/src/core/EnvService.ts

@@ -3,18 +3,50 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
+import nodePath from 'node:path';
+import nodeFs from 'node:fs';
 import { Injectable } from '@nestjs/common';
+import { bindThis } from '@/decorators.js';
+import { type ManagedMemoryKVCache, CacheManagementService } from '@/core/CacheManagementService.js';
 
 /**
- * Provides access to the process environment variables.
- * This exists for testing purposes, so that a test can mock the environment without corrupting state for other tests.
+ * Provides structured, mockable access to runtime/environment details.
  */
 @Injectable()
 export class EnvService {
+	protected readonly dependencyVersionCache: ManagedMemoryKVCache<string | null>;
+
+	constructor(cacheManagementService: CacheManagementService) {
+		this.dependencyVersionCache = cacheManagementService.createMemoryKVCache<string | null>(Infinity);
+	}
+
 	/**
-	 * Passthrough to process.env
+	 * Returns the environment variables of the process.
+	 * Can be modified, but modifications are not reflected to the operating system environment.
 	 */
-	public get env() {
+	public get env(): Partial<Record<string, string>> {
 		return process.env;
 	}
+
+	/**
+	 * Returns the installed version of a given dependency, or null if not installed.
+	 */
+	@bindThis
+	public async getDependencyVersion(dependency: string): Promise<string | null> {
+		return await this.dependencyVersionCache.fetch(dependency, async () => {
+			const packageJsonPath = nodePath.join(import.meta.dirname, '../../package.json');
+			const packageJsonText = nodeFs.readFileSync(packageJsonPath, 'utf8');
+
+			// No "dependencies" section -> infer not installed.
+			const packageJson = JSON.parse(packageJsonText) as { dependencies?: Partial<Record<string, string>> };
+			if (packageJson.dependencies == null) return null;
+
+			// Not listed -> not installed.
+			const version = packageJson.dependencies['mfm-js'];
+			if (version == null) return null;
+
+			// Just in case some other value is there
+			return String(version);
+		});
+	}
 }