1 files changed, 87 insertions, 0 deletions
diff --git a/packages/core/src/services/fileDiscoveryService.ts b/packages/core/src/services/fileDiscoveryService.ts
new file mode 100644
index 00000000..5329507e
--- /dev/null
+++ b/packages/core/src/services/fileDiscoveryService.ts
@@ -0,0 +1,87 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { GitIgnoreParser, GitIgnoreFilter } from '../utils/gitIgnoreParser.js';
+import { isGitRepository } from '../utils/gitUtils.js';
+import * as path from 'path';
+
+export interface FileDiscoveryOptions {
+  respectGitIgnore?: boolean;
+  includeBuildArtifacts?: boolean;
+  isGitRepo?: boolean;
+}
+
+export class FileDiscoveryService {
+  private gitIgnoreFilter: GitIgnoreFilter | null = null;
+  private projectRoot: string;
+
+  constructor(projectRoot: string) {
+    this.projectRoot = path.resolve(projectRoot);
+  }
+
+  async initialize(options: FileDiscoveryOptions = {}): Promise<void> {
+    const isGitRepo = options.isGitRepo ?? isGitRepository(this.projectRoot);
+
+    if (options.respectGitIgnore !== false && isGitRepo) {
+      const parser = new GitIgnoreParser(this.projectRoot);
+      await parser.initialize();
+      this.gitIgnoreFilter = parser;
+    }
+  }
+
+  /**
+   * Filters a list of file paths based on git ignore rules
+   */
+  filterFiles(
+    filePaths: string[],
+    options: FileDiscoveryOptions = {},
+  ): string[] {
+    return filePaths.filter((filePath) => {
+      // Always respect git ignore unless explicitly disabled
+      if (options.respectGitIgnore !== false && this.gitIgnoreFilter) {
+        if (this.gitIgnoreFilter.isIgnored(filePath)) {
+          return false;
+        }
+      }
+
+      return true;
+    });
+  }
+
+  /**
+   * Gets patterns that would be ignored for debugging/transparency
+   */
+  getIgnoreInfo(): { gitIgnored: string[] } {
+    return {
+      gitIgnored: this.gitIgnoreFilter?.getIgnoredPatterns() || [],
+    };
+  }
+
+  /**
+   * Checks if a single file should be ignored
+   */
+  shouldIgnoreFile(
+    filePath: string,
+    options: FileDiscoveryOptions = {},
+  ): boolean {
+    const isGitRepo = options.isGitRepo ?? isGitRepository(this.projectRoot);
+    if (
+      options.respectGitIgnore !== false &&
+      isGitRepo &&
+      this.gitIgnoreFilter
+    ) {
+      return this.gitIgnoreFilter.isIgnored(filePath);
+    }
+    return false;
+  }
+
+  /**
+   * Returns whether the project is a git repository
+   */
+  isGitRepository(options: FileDiscoveryOptions = {}): boolean {
+    return options.isGitRepo ?? isGitRepository(this.projectRoot);
+  }
+}