import {
  SERVICE_WORKER_BOUNDS,
  isOwnedStaticCacheName,
  staticCacheName,
  type ServiceWorkerHandlerId,
  type ServiceWorkerProtocolIdentity,
  type StaticAssetManifestV1,
} from "../../contracts/service-worker.ts";
import {
  createServiceWorkerMessage,
  parseServiceWorkerMessage,
} from "./service-worker-protocol.ts";
import {
  classifyFetch,
  installStaticAssets,
  selectCachesToDelete,
} from "./service-worker-static-assets.ts";

/**
 * §17.9–§17.15. Worker-side lifecycle, expressed against structural types so it
 * can be unit-tested outside a real Service Worker global and compiled under
 * `tsconfig.service-worker.json` without pulling in DOM globals.
 */

export type WorkerClientLike = Readonly<{
  id: string;
  url: string;
  postMessage(message: unknown): void;
}>;

export type WorkerScopeLike = Readonly<{
  caches: Readonly<{
    open(cacheName: string): Promise<Cache>;
    keys(): Promise<readonly string[]>;
    delete(cacheName: string): Promise<boolean>;
  }>;
  clients: Readonly<{
    matchAll(
      options?: Readonly<{
        type?: "window";
        includeUncontrolled?: boolean;
      }>,
    ): Promise<
      readonly WorkerClientLike[]
    >;
  }>;
  registrationScope: string;
  skipWaiting(): Promise<void>;
  fetcher: typeof fetch;
  digest(bytes: Uint8Array): Promise<string>;
}>;

export type WorkerRuntimeConfig = Readonly<{
  identity: ServiceWorkerProtocolIdentity;
  handlers: readonly ServiceWorkerHandlerId[];
  manifest: StaticAssetManifestV1 | null;
  runtimeConfigUrl: string;
  releaseManifestUrl: string;
}>;

/**
 * SW-URL-01. Root-relative generated URLs become absolute same-origin URLs
 * exactly once. Anything that escapes the scope origin is dropped rather than
 * silently classified.
 */
function canonicalManifestUrls(
  assets: readonly Readonly<{ url: string }>[],
  scopeHref: string,
): readonly string[] {
  let base: URL;
  try {
    base = new URL(scopeHref);
  } catch {
    return [];
  }
  const canonical: string[] = [];
  for (const asset of assets) {
    try {
      const absolute = new URL(asset.url, base);
      if (absolute.origin !== base.origin) continue;
      canonical.push(absolute.href);
    } catch {
      // A manifest URL that cannot be canonicalized is never classified.
    }
  }
  return canonical;
}

const ACTIVATION_MARKER_URL =
  "https://clean-architecture.invalid/__service-worker-activation-v1__";
const ACTIVATION_MARKER_MAX_BYTES = 256;

type ActivationMarker = Readonly<{
  cacheName: string;
  activationSequence: number;
}>;

export function createServiceWorkerRuntime(
  scope: WorkerScopeLike,
  config: WorkerRuntimeConfig,
) {
  const staticEnabled = config.handlers.includes("PWA_STATIC_ASSETS");
  /**
   * SW-URL-01. The generated manifest stores root-relative URLs while `Request`
   * exposes absolute ones, so comparing the two directly classified every
   * verified asset as a network fallback. Canonicalize once against the
   * registration scope, re-check same-origin, and share that identity across
   * install cache keys, fetch classification and cache lookup or delete.
   */
  const manifestUrls: ReadonlySet<string> = Object.freeze(
    new Set(
      staticEnabled
        ? canonicalManifestUrls(
            config.manifest?.assets ?? [],
            scope.registrationScope,
          )
        : [],
    ),
  );
  const consumedNonces = new Set<string>();
  type PendingActivation = Readonly<{
    requesterBuildId: string;
    expectedClientIds: ReadonlySet<string>;
    acknowledgedClientIds: Set<string>;
    resolve(drained: boolean): void;
    timer: ReturnType<typeof setTimeout>;
  }>;
  const pendingActivations = new Map<string, PendingActivation>();

  /**
   * §17.9. Without the static asset handler the install step opens zero caches;
   * it only registers lifecycle, push and sync handlers.
   */
  async function onInstall(): Promise<void> {
    if (!staticEnabled || !config.manifest) return;
    const outcome = await installStaticAssets(config.manifest, {
      caches: scope.caches,
      fetcher: scope.fetcher,
      digest: scope.digest,
    });
    if (outcome.kind === "REJECTED") {
      throw new Error(`STATIC_INSTALL_REJECTED:${outcome.code}`);
    }
  }

  /**
   * §17.15. Delete only owned caches outside the current and one previous
   * revision. `clients.claim()` is never called (§17.12).
   */
  async function onActivate(): Promise<number> {
    if (!staticEnabled || !config.manifest) return 0;
    const current = staticCacheName(config.manifest.setDigest);
    const names = await scope.caches.keys();
    const owned = names.filter(isOwnedStaticCacheName);
    const currentCache = await scope.caches.open(current);
    const oldCaches = owned.filter((name) => name !== current);
    const markers: ActivationMarker[] = [];
    for (const name of oldCaches) {
      const marker = await readActivationMarker(await scope.caches.open(name), name);
      if (marker) markers.push(marker);
    }
    const currentMarker = await readActivationMarker(currentCache, current);
    const highestOld = markers.reduce<ActivationMarker | null>(
      (highest, marker) =>
        !highest || marker.activationSequence >= highest.activationSequence
          ? marker
          : highest,
      null,
    );
    const previous = highestOld?.cacheName ?? oldCaches.at(-1) ?? null;
    if (
      !currentMarker ||
      currentMarker.activationSequence < (highestOld?.activationSequence ?? 0)
    ) {
      const nextSequence = (highestOld?.activationSequence ?? 0) + 1;
      if (!Number.isSafeInteger(nextSequence)) {
        throw new Error("SERVICE_WORKER_ACTIVATION_SEQUENCE_EXHAUSTED");
      }
      await currentCache.put(
        ACTIVATION_MARKER_URL,
        new Response(
          JSON.stringify({
            schemaVersion: 1,
            cacheName: current,
            activationSequence: nextSequence,
          }),
          {
            status: 200,
            headers: { "content-type": "application/json" },
          },
        ),
      );
    }
    const stale = selectCachesToDelete(names, current, previous);
    let deleted = 0;
    for (const name of stale) {
      if (await scope.caches.delete(name)) deleted += 1;
    }
    void SERVICE_WORKER_BOUNDS.retainedPreviousCaches;
    return deleted;
  }

  /**
   * §18.5–§18.7. A verified cache hit is returned; anything else goes to the
   * network and is never written back into the active cache at runtime.
   */
  async function onFetch(
    request: Readonly<{ method: string; url: string; mode?: string }>,
  ): Promise<Response | null> {
    const classification = classifyFetch({
      method: request.method,
      requestUrl: request.url,
      isNavigation: request.mode === "navigate",
      runtimeConfigUrl: config.runtimeConfigUrl,
      releaseManifestUrl: config.releaseManifestUrl,
      manifestUrls,
    });
    if (classification !== "VERIFIED_CACHE_FIRST") return null;

    // SW-01. Only the current release cache may answer. A CacheStorage-wide
    // match could return a previous release's response for the same URL, and
    // the subsequent delete would then target a cache that was never read.
    const currentCacheName = config.manifest
      ? staticCacheName(config.manifest.setDigest)
      : null;
    if (!currentCacheName) return null;
    // SW-RR-04. Both `open` and `match` are storage calls that can throw
    // synchronously or reject. Either one escaping here rejects `respondWith`
    // itself, so the entry never reaches its network fallback and the page
    // gets a network error instead of the live response.
    let cached: Response | undefined;
    let currentCache: Cache;
    try {
      currentCache = await scope.caches.open(currentCacheName);
      cached = await currentCache.match(request.url);
    } catch {
      return null;
    }
    if (!cached) return null;
    if (cached.status !== 200 || cached.type === "opaque") {
      // §18.6. An invalid hit is deleted from the cache it was read from and
      // treated as a release mismatch.
      await currentCache.delete(request.url).catch(() => false);
      return null;
    }
    return cached;
  }

  /**
   * §17.11. The waiting worker validates the request, drains every controlled
   * client, and only then calls `skipWaiting()`.
   */
  async function onActivateRequest(
    data: unknown,
  ): Promise<"ACCEPTED" | "REJECTED" | "IGNORED"> {
    const parsed = parseServiceWorkerMessage(data);
    if (!parsed.ok || parsed.message.kind !== "ACTIVATE_REQUEST") return "IGNORED";
    const nonce = parsed.message.nonce;
    if (!nonce || consumedNonces.has(nonce)) return "REJECTED";
    if (
      parsed.message.targetBuildId !== undefined &&
      parsed.message.targetBuildId !== config.identity.buildId
    ) {
      return "REJECTED";
    }
    consumedNonces.add(nonce);
    if (consumedNonces.size > 64) {
      const oldest = consumedNonces.values().next().value;
      if (oldest !== undefined) consumedNonces.delete(oldest);
    }

    const candidates = await scope.clients.matchAll({
      type: "window",
      includeUncontrolled: true,
    });
    const clients = candidates.filter((client) =>
      isClientWithinRegistrationScope(client.url, scope.registrationScope),
    );
    const drained = await drainClients(
      clients,
      nonce,
      parsed.message.sourceBuildId,
    );
    if (!drained) {
      notifyClients(clients, "ACTIVATE_REJECTED", parsed.message.sourceBuildId, nonce);
      return "REJECTED";
    }

    // SW-08. `skipWaiting()` is the activation commit. It must succeed before
    // any client is told the activation was accepted, and its failure is a
    // rejection rather than an accepted-then-failed activation.
    try {
      await scope.skipWaiting();
    } catch {
      notifyClients(clients, "ACTIVATE_REJECTED", parsed.message.sourceBuildId, nonce);
      return "REJECTED";
    }
    // Post-commit notifications are per-client best effort.
    notifyClients(clients, "ACTIVATE_ACCEPTED", parsed.message.sourceBuildId, nonce);
    notifyClients(
      clients,
      "ACTIVATED_RELOAD_REQUIRED",
      parsed.message.sourceBuildId,
      nonce,
    );
    return "ACCEPTED";
  }

  /**
   * SW-08. One client's `postMessage()` throwing must not break the whole
   * activation event; delivery is isolated per client.
   */
  function notifyClients(
    clients: readonly WorkerClientLike[],
    kind: "ACTIVATE_REJECTED" | "ACTIVATE_ACCEPTED" | "ACTIVATED_RELOAD_REQUIRED",
    targetBuildId: string,
    nonce: string,
  ): void {
    for (const client of clients) {
      try {
        client.postMessage(
          createServiceWorkerMessage({
            kind,
            sourceBuildId: config.identity.buildId,
            targetBuildId,
            nonce,
          }),
        );
      } catch {
        // A dead client cannot change the already committed activation.
      }
    }
  }

  async function drainClients(
    clients: readonly WorkerClientLike[],
    nonce: string,
    requesterBuildId: string,
  ): Promise<boolean> {
    // SW-07. No in-scope client means nothing dirty to drain, so the set is
    // vacuously drained. A `clients.matchAll()` failure still rejects upstream.
    if (clients.length === 0) return true;
    const drained = new Promise<boolean>((resolve) => {
      const timer = setTimeout(() => {
        pendingActivations.delete(nonce);
        resolve(false);
      }, SERVICE_WORKER_BOUNDS.clientDrainMs);
      pendingActivations.set(
        nonce,
        Object.freeze({
          requesterBuildId,
          expectedClientIds: new Set(clients.map((client) => client.id)),
          acknowledgedClientIds: new Set<string>(),
          resolve,
          timer,
        }),
      );
    });
    // SW-08. A client that cannot receive the drain request can never
    // acknowledge it, so it fails immediately instead of holding the pending
    // state until the timeout.
    for (const client of clients) {
      try {
        client.postMessage(
          createServiceWorkerMessage({
            kind: "CLIENT_DRAIN_REQUEST",
            sourceBuildId: config.identity.buildId,
            targetBuildId: requesterBuildId,
            nonce,
          }),
        );
      } catch {
        const pending = pendingActivations.get(nonce);
        if (pending) settlePendingActivation(nonce, pending, false);
        return await drained;
      }
    }
    return drained;
  }

  function onClientMessage(data: unknown, sourceClientId: string): void {
    const parsed = parseServiceWorkerMessage(data);
    if (!parsed.ok || !parsed.message.nonce) return;
    if (
      parsed.message.targetBuildId !== config.identity.buildId ||
      (parsed.message.kind !== "CLIENT_DRAINED" &&
        parsed.message.kind !== "ACTIVATE_REJECTED")
    ) {
      return;
    }
    const pending = pendingActivations.get(parsed.message.nonce);
    if (
      !pending ||
      parsed.message.sourceBuildId !== pending.requesterBuildId ||
      !pending.expectedClientIds.has(sourceClientId)
    ) {
      return;
    }
    if (parsed.message.kind === "ACTIVATE_REJECTED") {
      settlePendingActivation(parsed.message.nonce, pending, false);
      return;
    }
    pending.acknowledgedClientIds.add(sourceClientId);
    if (
      pending.acknowledgedClientIds.size === pending.expectedClientIds.size
    ) {
      settlePendingActivation(parsed.message.nonce, pending, true);
    }
  }

  async function onCacheResetRequest(
    data: unknown,
    source: WorkerClientLike,
  ): Promise<void> {
    const parsed = parseServiceWorkerMessage(data);
    if (
      !parsed.ok ||
      parsed.message.kind !== "CACHE_RESET_REQUEST" ||
      !parsed.message.nonce ||
      (parsed.message.targetBuildId !== undefined &&
        parsed.message.targetBuildId !== config.identity.buildId)
    ) {
      return;
    }
    let cachesDeleted = 0;
    const names = await scope.caches.keys();
    for (const name of names) {
      // SW-02. Exact ownership only: a prefix match would also delete
      // `ca-static-v1-not-owned` and any longer-suffixed foreign cache.
      if (!isOwnedStaticCacheName(name)) continue;
      try {
        if (await scope.caches.delete(name)) cachesDeleted += 1;
      } catch {
        return;
      }
    }
    source.postMessage(
      createServiceWorkerMessage({
        kind: "CACHE_RESET_RESULT",
        sourceBuildId: config.identity.buildId,
        targetBuildId: parsed.message.sourceBuildId,
        nonce: parsed.message.nonce,
        cachesDeleted,
      }),
    );
  }

  return Object.freeze({
    onInstall,
    onActivate,
    onFetch,
    onActivateRequest,
    onClientMessage,
    onCacheResetRequest,
    manifestUrls: manifestUrls as ReadonlySet<string>,
  });

  function settlePendingActivation(
    nonce: string,
    pending: PendingActivation,
    drained: boolean,
  ): void {
    clearTimeout(pending.timer);
    pendingActivations.delete(nonce);
    pending.resolve(drained);
  }
}

function isClientWithinRegistrationScope(
  clientUrl: string,
  registrationScope: string,
): boolean {
  try {
    const client = new URL(clientUrl);
    const scope = new URL(registrationScope);
    return client.origin === scope.origin && client.href.startsWith(scope.href);
  } catch {
    return false;
  }
}

/**
 * SW-RR-01. Reads at most one byte beyond the marker ceiling, cancels the
 * reader as soon as that byte arrives, and fails closed on invalid UTF-8. The
 * reader is also raced against a deadline so a stream that never produces a
 * chunk cannot hold `activate` open.
 */
const ACTIVATION_MARKER_READ_DEADLINE_MS = 5_000;

async function readBoundedMarkerText(
  response: Response,
): Promise<string | null> {
  if (!response.body) {
    try {
      const text = await response.text();
      return new TextEncoder().encode(text).byteLength >
        ACTIVATION_MARKER_MAX_BYTES
        ? null
        : text;
    } catch {
      return null;
    }
  }
  const reader = response.body.getReader();
  const chunks: Uint8Array[] = [];
  let total = 0;
  let timer: ReturnType<typeof setTimeout> | undefined;
  const deadline = new Promise<"DEADLINE">((resolve) => {
    timer = setTimeout(
      () => resolve("DEADLINE"),
      ACTIVATION_MARKER_READ_DEADLINE_MS,
    );
  });
  try {
    for (;;) {
      const next = await Promise.race([reader.read(), deadline]);
      if (next === "DEADLINE") return null;
      if (next.done) break;
      if (!next.value) continue;
      total += next.value.byteLength;
      if (total > ACTIVATION_MARKER_MAX_BYTES) return null;
      chunks.push(next.value);
    }
  } catch {
    return null;
  } finally {
    if (timer !== undefined) clearTimeout(timer);
    // Never awaited: cancelling a stream whose source ignores cancellation can
    // itself hang, and the marker read already has its answer.
    void reader.cancel().catch(() => {});
  }
  const bytes = new Uint8Array(total);
  let offset = 0;
  for (const chunk of chunks) {
    bytes.set(chunk, offset);
    offset += chunk.byteLength;
  }
  try {
    return new TextDecoder("utf-8", { fatal: true }).decode(bytes);
  } catch {
    return null;
  }
}

async function readActivationMarker(
  cache: Cache,
  expectedCacheName: string,
): Promise<ActivationMarker | null> {
  try {
    const response = await cache.match(ACTIVATION_MARKER_URL);
    if (!response || response.status !== 200) return null;
    const declaredLength = response.headers.get("content-length");
    if (
      declaredLength !== null &&
      (!/^\d+$/u.test(declaredLength) ||
        Number(declaredLength) > ACTIVATION_MARKER_MAX_BYTES)
    ) {
      return null;
    }
    // SW-RR-01. A Content-Length is a claim, not a bound. Without one the
    // previous `response.text()` read the whole body, so a large or
    // non-terminating stream could consume the activation step indefinitely.
    const text = await readBoundedMarkerText(response);
    if (text === null) return null;
    const value: unknown = JSON.parse(text);
    if (
      value === null ||
      typeof value !== "object" ||
      (value as { schemaVersion?: unknown }).schemaVersion !== 1 ||
      (value as { cacheName?: unknown }).cacheName !== expectedCacheName ||
      !Number.isSafeInteger(
        (value as { activationSequence?: unknown }).activationSequence,
      ) ||
      ((value as { activationSequence: number }).activationSequence ?? 0) < 1
    ) {
      return null;
    }
    return Object.freeze({
      cacheName: expectedCacheName,
      activationSequence: (value as { activationSequence: number })
        .activationSequence,
    });
  } catch {
    return null;
  }
}