[Init] Initial commit - NetMesh terminal manager

application/state/sftp/directoryListingCache.ts

@@ -0,0 +1,69 @@
+import type { SftpFileEntry } from "../../../domain/models";
+
+export interface DirectoryListingCacheEntry {
+  files: SftpFileEntry[];
+  timestamp: number;
+}
+
+export type DirectoryListingCache = Map<string, DirectoryListingCacheEntry>;
+
+export const MAX_DIRECTORY_CACHE_ENTRIES = 128;
+export const MAX_DIRECTORY_CACHE_FILES = 20_000;
+
+function removeExpiredEntries(
+  cache: DirectoryListingCache,
+  now: number,
+  ttlMs: number,
+): void {
+  for (const [key, entry] of cache) {
+    if (now - entry.timestamp >= ttlMs) cache.delete(key);
+  }
+}
+
+export function getDirectoryCacheEntry(
+  cache: DirectoryListingCache,
+  key: string,
+  now: number,
+  ttlMs: number,
+): DirectoryListingCacheEntry | undefined {
+  removeExpiredEntries(cache, now, ttlMs);
+  const entry = cache.get(key);
+  if (!entry) return undefined;
+  cache.delete(key);
+  cache.set(key, entry);
+  return entry;
+}
+
+export function setDirectoryCacheEntry(
+  cache: DirectoryListingCache,
+  key: string,
+  entry: DirectoryListingCacheEntry,
+  options: {
+    now?: number;
+    ttlMs?: number;
+    maxEntries?: number;
+    maxFiles?: number;
+  } = {},
+): void {
+  const now = options.now ?? Date.now();
+  const ttlMs = options.ttlMs ?? 10_000;
+  const maxEntries = options.maxEntries ?? MAX_DIRECTORY_CACHE_ENTRIES;
+  const maxFiles = options.maxFiles ?? MAX_DIRECTORY_CACHE_FILES;
+  removeExpiredEntries(cache, now, ttlMs);
+  cache.delete(key);
+  // A cache budget must remain a hard bound. Truncating a directory listing
+  // would be incorrect, so oversized listings are served to the caller but
+  // deliberately not retained.
+  if (entry.files.length > maxFiles || maxEntries < 1) return;
+  cache.set(key, entry);
+
+  let totalFiles = 0;
+  for (const value of cache.values()) totalFiles += value.files.length;
+  while (cache.size > 1 && (cache.size > maxEntries || totalFiles > maxFiles)) {
+    const oldestKey = cache.keys().next().value as string | undefined;
+    if (!oldestKey) break;
+    const oldest = cache.get(oldestKey);
+    cache.delete(oldestKey);
+    totalFiles -= oldest?.files.length ?? 0;
+  }
+}