refactoring continued

packages/core/src/context/sidecar/SidecarLoader.ts

@@ -4,19 +4,21 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import * as fs from 'node:fs';
 import type { Config } from '../../config/config.js';
 import type { SidecarConfig } from './types.js';
 import { defaultSidecarProfile } from './profiles.js';
 import { SchemaValidator } from '../../utils/schemaValidator.js';
 import { sidecarConfigSchema } from './schema.js';
+import type { IFileSystem } from '../system/IFileSystem.js';
+import { NodeFileSystem } from '../system/NodeFileSystem.js';
+
 export class SidecarLoader {
   /**
    * Loads and validates a sidecar config from a specific file path.
    * Throws an error if the file cannot be read, parsed, or fails schema validation.
    */
-  static loadFromFile(sidecarPath: string): SidecarConfig {
-    const fileContent = fs.readFileSync(sidecarPath, 'utf8');
+  static loadFromFile(sidecarPath: string, fileSystem: IFileSystem = new NodeFileSystem()): SidecarConfig {
+    const fileContent = fileSystem.readFileSync(sidecarPath, 'utf8');
 
     if (!fileContent.trim()) {
       throw new Error(`Sidecar configuration file at ${sidecarPath} is empty.`);
@@ -49,18 +51,18 @@ export class SidecarLoader {
    * Generates a Sidecar JSON graph from the experimental config file path or defaults.
    * If a config file is present but invalid, this will THROW to prevent silent misconfiguration.
    */
-  static fromConfig(config: Config): SidecarConfig {
+  static fromConfig(config: Config, fileSystem: IFileSystem = new NodeFileSystem()): SidecarConfig {
     const sidecarPath = config.getExperimentalContextSidecarConfig();
 
-    if (sidecarPath && fs.existsSync(sidecarPath)) {
-      const stat = fs.statSync(sidecarPath);
+    if (sidecarPath && fileSystem.existsSync(sidecarPath)) {
+      const size = fileSystem.statSyncSize(sidecarPath);
       // If the file exists but is completely empty (0 bytes), it's safe to fallback.
-      if (stat.size === 0) {
+      if (size === 0) {
         return defaultSidecarProfile;
       }
 
       // If the file has content, enforce strict validation and throw on failure.
-      return this.loadFromFile(sidecarPath);
+      return this.loadFromFile(sidecarPath, fileSystem);
     }
 
     return defaultSidecarProfile;