feat(core, cli): Introduce high-performance FileSearch engine (#5136)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/core/src/utils/filesearch/crawlCache.ts

@@ -0,0 +1,65 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import crypto from 'node:crypto';
+
+const crawlCache = new Map<string, string[]>();
+const cacheTimers = new Map<string, NodeJS.Timeout>();
+
+/**
+ * Generates a unique cache key based on the project directory and the content
+ * of ignore files. This ensures that the cache is invalidated if the project
+ * or ignore rules change.
+ */
+export const getCacheKey = (
+  directory: string,
+  ignoreContent: string,
+): string => {
+  const hash = crypto.createHash('sha256');
+  hash.update(directory);
+  hash.update(ignoreContent);
+  return hash.digest('hex');
+};
+
+/**
+ * Reads cached data from the in-memory cache.
+ * Returns undefined if the key is not found.
+ */
+export const read = (key: string): string[] | undefined => crawlCache.get(key);
+
+/**
+ * Writes data to the in-memory cache and sets a timer to evict it after the TTL.
+ */
+export const write = (key: string, results: string[], ttlMs: number): void => {
+  // Clear any existing timer for this key to prevent premature deletion
+  if (cacheTimers.has(key)) {
+    clearTimeout(cacheTimers.get(key)!);
+  }
+
+  // Store the new data
+  crawlCache.set(key, results);
+
+  // Set a timer to automatically delete the cache entry after the TTL
+  const timerId = setTimeout(() => {
+    crawlCache.delete(key);
+    cacheTimers.delete(key);
+  }, ttlMs);
+
+  // Store the timer handle so we can clear it if the entry is updated
+  cacheTimers.set(key, timerId);
+};
+
+/**
+ * Clears the entire cache and all active timers.
+ * Primarily used for testing.
+ */
+export const clear = (): void => {
+  for (const timerId of cacheTimers.values()) {
+    clearTimeout(timerId);
+  }
+  crawlCache.clear();
+  cacheTimers.clear();
+};