1 files changed, 85 insertions, 0 deletions
diff --git a/scripts/cache/utils.ts b/scripts/cache/utils.ts
new file mode 100644
index 0000000..c095000
--- /dev/null
+++ b/scripts/cache/utils.ts
@@ -0,0 +1,85 @@
+import type { S3Client } from 'bun';
+
+// ============================================================================
+// Types
+// ============================================================================
+
+export interface FileMetadata {
+    checksum: string;
+    size: number;
+}
+
+export interface CacheMetadata {
+    key: string;
+    hash: string;
+    timestamp: number;
+    lastAccessed: number;
+    files: Record<string, FileMetadata>;
+    version: number;
+}
+
+export interface CacheLock {
+    locked: boolean;
+    timestamp: number;
+    instance: string;
+    ttl: number;
+    renewedAt?: number;
+    pid: number;
+    hostname: string;
+}
+
+export interface S3ListObject {
+    key: string;
+    lastModified?: string;
+}
+
+export interface CacheEntry {
+    key: string;
+    timestamp: number;
+    lastAccessed: number;
+    hash: string;
+}
+
+export interface CacheManifest {
+    version: number;
+    caches: CacheEntry[];
+}
+
+// ============================================================================
+// Constants
+// ============================================================================
+
+export const LOCK_TIMEOUT_MS = 30 * 60 * 1000; // 30 minutes (matches Restic)
+export const LOCK_RETRY_START_MS = 5000; // 5 seconds (initial retry delay)
+export const LOCK_RETRY_MAX_MS = 60000; // 60 seconds (max retry delay)
+export const LOCK_MAX_RETRIES = 6; // With exponential backoff: 5s, 10s, 20s, 40s, 60s, 60s
+export const LOCK_DOUBLE_CHECK_MS = 200; // 200ms delay for double-check pattern (matches Restic)
+
+export const METADATA_VERSION = 1;
+export const METADATA_KEY = 'metadata.json';
+export const LOCK_KEY = 'cache.lock';
+
+export const MAX_CACHE_FILES = 7;
+export const MAX_CACHE_AGE_DAYS = 7;
+
+export const TMP_DIR = 'tmp';
+export const STATIC_DIR = 'static';
+export const CACHE_FILE_NAME = 'extensions-cache.tzst';
+
+// Cache configuration
+export const CACHE_PATHS = ['static'];
+export const CACHE_KEY_PREFIX = 'extensions-';
+export const CACHE_RESTORE_KEYS = ['extensions-'];
+export const EXTENSIONS_CONFIG_FILE = 'extensions.json';
+
+// Helper to generate cache key from extensions.json
+export async function generateCacheKey(): Promise<string> {
+    const content = await Bun.file(EXTENSIONS_CONFIG_FILE).arrayBuffer();
+    const hash = new Bun.CryptoHasher('sha256').update(content).digest('hex');
+    return `${CACHE_KEY_PREFIX}${hash}.tzst`;
+}
+
+// Helper to write JSON to S3 file
+export async function writeJsonToS3(s3: S3Client, key: string, data: any): Promise<void> {
+    await Bun.write(s3.file(key), JSON.stringify(data, null, 2));
+}