refactor: split src into domain / application / infrastructure layers

Replace the history-driven lib/ + utils/ split with DDD layers:
- domain/: aggregate, repositories, value objects, pure parsers/format
- application/: feed-service, email-processor, feed-fetcher, stats
- infrastructure/: logging, auth, KV/R2 adapters, HTTP, framework glue

Pure file relocation; imports updated mechanically. Behaviour unchanged.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/application/stats.ts

@@ -0,0 +1,148 @@
+import { Counters, Env, StatsResponse } from "../types";
+import { logger } from "../infrastructure/logger";
+import { FeedRepository } from "../domain/feed-repository";
+import { CountersRepository } from "../domain/counters-repository";
+import { WebSubSubscriptionRepository } from "../domain/websub-subscription-repository";
+import { FeedId } from "../domain/value-objects/feed-id";
+import { getAttachmentBucket } from "../infrastructure/attachments";
+
+const EMPTY_COUNTERS: Counters = {
+  feeds_created: 0,
+  feeds_deleted: 0,
+  emails_received: 0,
+  emails_rejected: 0,
+  unsubscribes_sent: 0,
+};
+
+export async function getCounters(kv: KVNamespace): Promise<Counters> {
+  try {
+    const stored = await new CountersRepository(kv).getRaw();
+    return { ...EMPTY_COUNTERS, ...(stored || {}) };
+  } catch (error) {
+    logger.error("Error reading counters", { error: String(error) });
+    return { ...EMPTY_COUNTERS };
+  }
+}
+
+/**
+ * Read-modify-write the counters singleton. KV has no atomic increment, so
+ * concurrent invocations can lose updates — accepted given KV's eventual
+ * consistency and this app's low volume (see email-processor.ts storeEmail).
+ * Never throws: counter failures must not break ingestion or admin flows.
+ */
+export async function bumpCounters(
+  kv: KVNamespace,
+  changes: Partial<Omit<Counters, "first_seen">>,
+): Promise<void> {
+  try {
+    const current = await getCounters(kv);
+
+    current.feeds_created += changes.feeds_created ?? 0;
+    current.feeds_deleted += changes.feeds_deleted ?? 0;
+    current.emails_received += changes.emails_received ?? 0;
+    current.emails_rejected += changes.emails_rejected ?? 0;
+    current.unsubscribes_sent += changes.unsubscribes_sent ?? 0;
+    if (changes.last_email_at) current.last_email_at = changes.last_email_at;
+    if (changes.last_feed_created_at)
+      current.last_feed_created_at = changes.last_feed_created_at;
+    if (!current.first_seen) current.first_seen = new Date().toISOString();
+
+    await new CountersRepository(kv).put(current);
+  } catch (error) {
+    logger.error("Error updating counters", { error: String(error) });
+  }
+}
+
+export async function countKeysByPrefix(
+  kv: KVNamespace,
+  prefix: string,
+): Promise<number> {
+  return new FeedRepository(kv).countKeysByPrefix(prefix);
+}
+
+export async function getStats(env: Env): Promise<StatsResponse> {
+  const repo = FeedRepository.from(env);
+  const [counters, feeds, websubCount] = await Promise.all([
+    getCounters(env.EMAIL_STORAGE),
+    repo.listFeeds(),
+    WebSubSubscriptionRepository.from(env).countKeys(),
+  ]);
+
+  return {
+    ...counters,
+    active_feeds: feeds.length,
+    websub_subscriptions_active: websubCount,
+    attachments_enabled: !!getAttachmentBucket(env),
+  };
+}
+
+/** Sum the byte size and object count of every attachment stored in R2. */
+export async function scanR2Usage(
+  bucket: R2Bucket,
+): Promise<{ bytes: number; count: number }> {
+  let bytes = 0;
+  let count = 0;
+  let cursor: string | undefined;
+  try {
+    do {
+      const listed = await bucket.list({ cursor });
+      for (const obj of listed.objects) {
+        bytes += obj.size;
+        count += 1;
+      }
+      cursor = listed.truncated ? listed.cursor : undefined;
+    } while (cursor);
+  } catch (error) {
+    logger.error("Error scanning R2 usage", { error: String(error) });
+  }
+  return { bytes, count };
+}
+
+/**
+ * Estimate KV storage used. KV exposes no size API, so we sum the per-email
+ * sizes already recorded in each feed's metadata — email bodies dominate KV
+ * usage. Feed config/websub/stats keys are excluded, so this is a lower-bound
+ * estimate.
+ */
+export async function scanKvUsage(kv: KVNamespace): Promise<{ bytes: number }> {
+  let bytes = 0;
+  try {
+    const repo = new FeedRepository(kv);
+    const feeds = await repo.listFeeds();
+    for (const feed of feeds) {
+      const metadata = await repo.getMetadata(FeedId.fromTrusted(feed.id));
+      if (!metadata) continue;
+      for (const email of metadata.emails) {
+        bytes += email.size ?? 0;
+      }
+    }
+  } catch (error) {
+    logger.error("Error estimating KV usage", { error: String(error) });
+  }
+  return { bytes };
+}
+
+/**
+ * Overwrite the storage-usage snapshot fields on the counters singleton.
+ * Unlike bumpCounters these are set (not incremented). Never throws.
+ */
+export async function setStorageSnapshot(
+  kv: KVNamespace,
+  snapshot: {
+    attachments_bytes: number;
+    attachments_count: number;
+    kv_bytes_estimated: number;
+  },
+): Promise<void> {
+  try {
+    const current = await getCounters(kv);
+    current.attachments_bytes = snapshot.attachments_bytes;
+    current.attachments_count = snapshot.attachments_count;
+    current.kv_bytes_estimated = snapshot.kv_bytes_estimated;
+    current.storage_scanned_at = new Date().toISOString();
+    if (!current.first_seen) current.first_seen = new Date().toISOString();
+    await new CountersRepository(kv).put(current);
+  } catch (error) {
+    logger.error("Error writing storage snapshot", { error: String(error) });
+  }
+}