feat(server): per-key quota + response cache (v3.8.0) (#18)

Add two new features for LAN sharing governance:

Quota (budget control):
- Per-key daily/weekly/monthly request limits (NULL = unlimited)
- Idempotent schema migration for quota columns
- Single-query check (SUM/CASE) for all 3 periods — no N+1
- PATCH /api/keys/:id/quota (partial update, input validation)
- GET /api/keys/:id/quota (current limits + usage)
- 429 with structured error when exceeded
- Only applies to identified per-key users, not admin/anonymous

Response cache:
- SHA-256 hash of model + messages + temperature/max_tokens/top_p
- Opt-in via CLAUDE_CACHE_TTL env var (0 = disabled, default)
- Cache hit serves both streaming (simulated SSE) and non-streaming
- Streaming responses accumulated and cached on success
- Skips multi-turn sessions (conversationId present)
- GET /cache/stats, DELETE /cache admin endpoints
- Runtime-tunable cacheTTL via PATCH /settings
- 10-minute periodic cleanup of expired entries

Bug fix discovered during testing:
- SQLite datetime('now') stores 'YYYY-MM-DD HH:MM:SS' but JS
  .toISOString() produces 'YYYY-MM-DDTHH:MM:SS.sssZ'. String
  comparison breaks for same-day ranges. Added sqliteDatetime()
  helper for correct format matching.

Code review fixes:
- DELETE /api/keys/:id no longer shadows /quota sub-routes
- updateKeyQuota uses partial UPDATE (only SET provided fields)
- cacheHash includes temperature/max_tokens/top_p in hash
- Replaced raw getDb() in server.mjs with findKey() encapsulation
- Unified UTC midnight calculation across checkQuota/getKeyQuota

Includes 24-test integration suite (test-features.mjs).

Co-authored-by: Tao Deng <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

keys.mjs

@@ -1,7 +1,7 @@
 // keys.mjs — API key management and usage tracking for OCP LAN mode
 // Uses Node.js built-in SQLite (node:sqlite) — zero external dependencies.
 import { DatabaseSync } from "node:sqlite";
-import { randomBytes } from "node:crypto";
+import { randomBytes, createHash } from "node:crypto";
 import { join } from "node:path";
 import { mkdirSync } from "node:fs";
 import { homedir } from "node:os";
@@ -47,7 +47,31 @@ function initSchema() {
 
     CREATE INDEX IF NOT EXISTS idx_usage_created ON usage_log(created_at);
     CREATE INDEX IF NOT EXISTS idx_usage_key ON usage_log(key_id);
+
+    CREATE TABLE IF NOT EXISTS response_cache (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      hash TEXT UNIQUE NOT NULL,
+      model TEXT NOT NULL,
+      response TEXT NOT NULL,
+      created_at TEXT NOT NULL DEFAULT (datetime('now')),
+      last_hit_at TEXT,
+      hits INTEGER NOT NULL DEFAULT 0
+    );
+    CREATE INDEX IF NOT EXISTS idx_cache_hash ON response_cache(hash);
+    CREATE INDEX IF NOT EXISTS idx_cache_created ON response_cache(created_at);
   `);
+
+  // Idempotent migrations: add quota columns if they don't exist yet.
+  for (const col of [
+    "ALTER TABLE api_keys ADD COLUMN quota_daily INTEGER DEFAULT NULL",
+    "ALTER TABLE api_keys ADD COLUMN quota_weekly INTEGER DEFAULT NULL",
+    "ALTER TABLE api_keys ADD COLUMN quota_monthly INTEGER DEFAULT NULL",
+  ]) {
+    try { db.exec(col); } catch (e) {
+      // SQLite throws "duplicate column name" if already present — safe to ignore.
+      if (!e.message?.includes("duplicate column")) throw e;
+    }
+  }
 }
 
 // ── Key CRUD ──
@@ -63,7 +87,7 @@ export function createKey(name) {
 export function listKeys() {
   const d = getDb();
   return d.prepare(
-    "SELECT id, key, name, created_at, revoked FROM api_keys ORDER BY created_at DESC"
+    "SELECT id, key, name, created_at, revoked, quota_daily, quota_weekly, quota_monthly FROM api_keys ORDER BY created_at DESC"
   ).all().map(({ key, ...rest }) => ({
     ...rest,
     keyPreview: key.slice(0, 8) + "..." + key.slice(-4),
@@ -155,6 +179,184 @@ export function getRecentUsage(limit = 50) {
   `).all(limit);
 }
 
+// ── SQLite datetime helper ──
+// SQLite datetime('now') stores as 'YYYY-MM-DD HH:MM:SS' (no T, no Z).
+// JavaScript .toISOString() produces 'YYYY-MM-DDTHH:MM:SS.sssZ'.
+// String comparison between the two breaks for same-day ranges (T > space).
+// This helper formats Date to match SQLite's format for correct comparisons.
+function sqliteDatetime(date) {
+  return date.toISOString().replace("T", " ").replace(/\.\d{3}Z$/, "");
+}
+
+// ── Quota management ──
+
+// Returns { period, limit, used, resetsIn } if a quota is exceeded, null otherwise.
+// Anonymous/admin callers (keyId === null) are never subject to quotas.
+export function checkQuota(keyId, _keyName) {
+  if (keyId === null || keyId === undefined) return null;
+
+  const d = getDb();
+  const keyRow = d.prepare(
+    "SELECT quota_daily, quota_weekly, quota_monthly FROM api_keys WHERE id = ? AND revoked = 0"
+  ).get(keyId);
+  if (!keyRow) return null;
+
+  const now = new Date();
+
+  // UTC period boundaries (SQLite-compatible format)
+  const startOfToday = sqliteDatetime(new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate())));
+  const sevenDaysAgo = sqliteDatetime(new Date(Date.now() - 7 * 86400000));
+  const thirtyDaysAgo = sqliteDatetime(new Date(Date.now() - 30 * 86400000));
+
+  // Next reset times for human display
+  const tomorrowUTC = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate() + 1));
+  function msToHuman(ms) {
+    if (ms <= 0) return "now";
+    const h = Math.floor(ms / 3600000);
+    const m = Math.floor((ms % 3600000) / 60000);
+    if (h >= 24) { const d = Math.floor(h / 24); return `${d}d ${h % 24}h`; }
+    return h > 0 ? `${h}h ${m}m` : `${m}m`;
+  }
+
+  // Single query for all periods (widest window = monthly)
+  const row = d.prepare(`
+    SELECT
+      SUM(CASE WHEN created_at >= ? THEN 1 ELSE 0 END) as daily_cnt,
+      SUM(CASE WHEN created_at >= ? THEN 1 ELSE 0 END) as weekly_cnt,
+      COUNT(*) as monthly_cnt
+    FROM usage_log
+    WHERE key_id = ? AND success = 1 AND created_at >= ?
+  `).get(startOfToday, sevenDaysAgo, keyId, thirtyDaysAgo);
+
+  const checks = [
+    { period: "daily",   limit: keyRow.quota_daily,   used: row?.daily_cnt ?? 0,   resetsIn: msToHuman(tomorrowUTC - now) },
+    { period: "weekly",  limit: keyRow.quota_weekly,  used: row?.weekly_cnt ?? 0,  resetsIn: "rolling 7-day window" },
+    { period: "monthly", limit: keyRow.quota_monthly, used: row?.monthly_cnt ?? 0, resetsIn: "rolling 30-day window" },
+  ];
+
+  for (const { period, limit, used, resetsIn } of checks) {
+    if (limit === null || limit === undefined) continue;
+    if (used >= limit) {
+      return { period, limit, used, resetsIn };
+    }
+  }
+
+  return null;
+}
+
+// Set quota for a key. Only updates fields explicitly present in the input object.
+// Pass null to clear a specific limit. Omit a field to leave it unchanged.
+export function updateKeyQuota(idOrName, updates = {}) {
+  const d = getDb();
+  const setClauses = [];
+  const params = [];
+  if ("daily" in updates)  { setClauses.push("quota_daily = ?");  params.push(updates.daily ?? null); }
+  if ("weekly" in updates) { setClauses.push("quota_weekly = ?"); params.push(updates.weekly ?? null); }
+  if ("monthly" in updates){ setClauses.push("quota_monthly = ?");params.push(updates.monthly ?? null); }
+  if (setClauses.length === 0) return false;
+  params.push(idOrName, idOrName);
+  const result = d.prepare(
+    `UPDATE api_keys SET ${setClauses.join(", ")} WHERE id = ? OR name = ?`
+  ).run(...params);
+  return result.changes > 0;
+}
+
+// Returns { daily: { limit, used }, weekly: { limit, used }, monthly: { limit, used } }
+export function getKeyQuota(keyId) {
+  const d = getDb();
+  const keyRow = d.prepare(
+    "SELECT quota_daily, quota_weekly, quota_monthly FROM api_keys WHERE id = ?"
+  ).get(keyId);
+  if (!keyRow) return null;
+
+  const now = new Date();
+  const startOfToday  = sqliteDatetime(new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate())));
+  const sevenDaysAgo  = sqliteDatetime(new Date(Date.now() - 7 * 86400000));
+  const thirtyDaysAgo = sqliteDatetime(new Date(Date.now() - 30 * 86400000));
+
+  const row = d.prepare(`
+    SELECT
+      SUM(CASE WHEN created_at >= ? THEN 1 ELSE 0 END) as daily_cnt,
+      SUM(CASE WHEN created_at >= ? THEN 1 ELSE 0 END) as weekly_cnt,
+      COUNT(*) as monthly_cnt
+    FROM usage_log
+    WHERE key_id = ? AND success = 1 AND created_at >= ?
+  `).get(startOfToday, sevenDaysAgo, keyId, thirtyDaysAgo);
+
+  return {
+    daily:   { limit: keyRow.quota_daily   ?? null, used: row?.daily_cnt ?? 0 },
+    weekly:  { limit: keyRow.quota_weekly  ?? null, used: row?.weekly_cnt ?? 0 },
+    monthly: { limit: keyRow.quota_monthly ?? null, used: row?.monthly_cnt ?? 0 },
+  };
+}
+
+// ── Response cache ──
+
+// Generate a cache key from model + messages + request params that affect output
+export function cacheHash(model, messages, opts = {}) {
+  const h = createHash("sha256");
+  h.update(model);
+  if (opts.temperature != null) h.update(`t:${opts.temperature}`);
+  if (opts.max_tokens != null) h.update(`mt:${opts.max_tokens}`);
+  if (opts.top_p != null) h.update(`tp:${opts.top_p}`);
+  for (const m of messages) {
+    h.update(m.role || "");
+    h.update(typeof m.content === "string" ? m.content : JSON.stringify(m.content));
+  }
+  return h.digest("hex");
+}
+
+// Look up a cached response. Returns { response, hits } or null.
+// Also updates last_hit_at and increments hits counter on hit.
+export function getCachedResponse(hash, ttlMs) {
+  const d = getDb();
+  const cutoff = sqliteDatetime(new Date(Date.now() - ttlMs));
+  const row = d.prepare(
+    "SELECT id, response, hits FROM response_cache WHERE hash = ? AND created_at >= ?"
+  ).get(hash, cutoff);
+  if (!row) return null;
+  // Update hit stats
+  d.prepare("UPDATE response_cache SET hits = hits + 1, last_hit_at = datetime('now') WHERE id = ?").run(row.id);
+  return { response: row.response, hits: row.hits + 1 };
+}
+
+// Store a response in the cache
+export function setCachedResponse(hash, model, response) {
+  const d = getDb();
+  // Upsert: if hash already exists (race condition), just update
+  d.prepare(`
+    INSERT INTO response_cache (hash, model, response) VALUES (?, ?, ?)
+    ON CONFLICT(hash) DO UPDATE SET response = excluded.response, created_at = datetime('now'), hits = 0
+  `).run(hash, model, response);
+}
+
+// Clear all cached responses, or expired ones only
+export function clearCache(ttlMs = null) {
+  const d = getDb();
+  if (ttlMs === null) {
+    const result = d.prepare("DELETE FROM response_cache").run();
+    return result.changes;
+  }
+  const cutoff = sqliteDatetime(new Date(Date.now() - ttlMs));
+  const result = d.prepare("DELETE FROM response_cache WHERE created_at < ?").run(cutoff);
+  return result.changes;
+}
+
+// Get cache statistics
+export function getCacheStats() {
+  const d = getDb();
+  const total = d.prepare("SELECT COUNT(*) as cnt FROM response_cache").get()?.cnt ?? 0;
+  const totalHits = d.prepare("SELECT SUM(hits) as total FROM response_cache").get()?.total ?? 0;
+  const sizeBytes = d.prepare("SELECT SUM(LENGTH(response)) as size FROM response_cache").get()?.size ?? 0;
+  return { entries: total, totalHits, sizeBytes };
+}
+
+// Find a key by id or name (returns { id, name } or null)
+export function findKey(idOrName) {
+  const d = getDb();
+  return d.prepare("SELECT id, name FROM api_keys WHERE id = ? OR name = ?").get(idOrName, idOrName) || null;
+}
+
 export function closeDb() {
   if (db) { db.close(); db = null; }
 }