import type {
  DurableObjectDescriptor,
  DurableObjectMaintenancePort,
  DurableObjectStorePort,
  OpfsJournalPort,
  OpfsJournalTransaction,
  OpfsPolicyMaintenanceReport,
  OpfsPreparedObject,
  OpfsSensitiveMaintenanceReason,
  OpfsReconciliationReport,
  OpfsStorageScope,
  PutDurableObjectRequest,
  OpfsPhysicalGenerationId,
} from "../../../application/ports/browser-file-storage/opfs-ports.ts";
import {
  type BrowserDataFailure,
  type BrowserDataOperation,
  type BrowserDataResult,
  type BrowserStoragePolicy,
} from "../../../application/ports/browser-file-storage/shared.ts";
import {
  abortedResult,
  browserDataFailure,
  browserDataSuccess,
} from "../../browser-file-storage/result.ts";
import {
  byteBucket,
  observeOpfsSafely,
  resolveOpfsRuntimePolicy,
  transactionBucket,
  snapshotOpfsStoragePolicy,
  snapshotOpfsStorageScope,
  validateObjectWriteInput,
  type OpfsRuntimePolicy,
  type OpfsSafeObserver,
} from "./opfs-policy.ts";
import type { OpfsWorkerGateway } from "./opfs-worker-protocol.ts";

type BrowserFailureResult = Readonly<{
  ok: false;
  error: BrowserDataFailure;
}>;

export type OpfsByteStore = Readonly<{
  objects: DurableObjectStorePort;
  maintenance: DurableObjectMaintenancePort;
}>;

export type OpfsMaintenanceAuthorityRequest = Readonly<{
  reason: OpfsSensitiveMaintenanceReason;
  scope: OpfsStorageScope;
  storagePolicy: BrowserStoragePolicy;
  signal?: AbortSignal;
}>;

export type OpfsMaintenanceAuthorityDecision =
  | Readonly<{ authorized: false }>
  | Readonly<{
      authorized: true;
      /**
       * Opaque, short-lived proof issued for this exact action and scope.
       * It is passed directly to the composition-owned consumer and is never
       * persisted or returned through the application port.
       */
      proofToken: string;
      expiresAtEpochMs: number;
    }>;

export type OpfsMaintenanceAuthorityProvider = (
  request: OpfsMaintenanceAuthorityRequest,
) =>
  | OpfsMaintenanceAuthorityDecision
  | Promise<OpfsMaintenanceAuthorityDecision>;

export type OpfsMaintenanceAuthorityConsumer = (
  request: Readonly<{
    reason: OpfsSensitiveMaintenanceReason;
    proofToken: string;
    expiresAtEpochMs: number;
    scope: OpfsStorageScope;
    storagePolicy: BrowserStoragePolicy;
    signal?: AbortSignal;
  }>,
) => boolean | Promise<boolean>;

export type OpfsByteStoreDependencies = Readonly<{
  journal: OpfsJournalPort;
  worker: OpfsWorkerGateway;
  scope: OpfsStorageScope;
  storagePolicy: BrowserStoragePolicy;
  policy?: Partial<OpfsRuntimePolicy>;
  createTransactionId?: () => string;
  createPhysicalGenerationId?: () => OpfsPhysicalGenerationId;
  /**
   * Composition-owned bounded signal for compensating cleanup. It is
   * deliberately separate from any caller signal.
   */
  compensationSignal?: AbortSignal;
  now?: () => number;
  observer?: OpfsSafeObserver;
  /**
   * Obtains a new proof for every sensitive maintenance invocation. The
   * provider must bind it to the exact reason, scope and policy.
   */
  requestMaintenanceAuthority?: OpfsMaintenanceAuthorityProvider;
  /**
   * Atomically validates and consumes the issued proof. It must reject replay,
   * scope/action/policy mismatch and expiry. The runtime also performs shape
   * and short-expiry checks before invoking it.
   */
  consumeMaintenanceAuthority?: OpfsMaintenanceAuthorityConsumer;
}>;

export function createOpfsByteStoreAdapter(
  inputDependencies: OpfsByteStoreDependencies,
): OpfsByteStore {
  const policy = resolveOpfsRuntimePolicy(inputDependencies.policy);
  const scope = snapshotOpfsStorageScope(inputDependencies.scope);
  const storagePolicy = snapshotOpfsStoragePolicy(
    inputDependencies.storagePolicy,
  );
  if (
    storagePolicy.namespace !== scope.namespace
  ) {
    throw new TypeError(
      "OPFS storage policy must match the bound scope.",
    );
  }
  const dependencies: OpfsByteStoreDependencies = Object.freeze({
    ...inputDependencies,
    journal: snapshotOpfsJournal(inputDependencies.journal),
    worker: snapshotOpfsWorker(inputDependencies.worker),
    scope,
    storagePolicy,
    policy,
  });
  const createTransactionId =
    dependencies.createTransactionId ??
    (() => globalThis.crypto.randomUUID());
  const createPhysicalGenerationId =
    dependencies.createPhysicalGenerationId ??
    (() => {
      const bytes = new Uint8Array(16);
      globalThis.crypto.getRandomValues(bytes);
      let hex = "";
      for (const byte of bytes) hex += byte.toString(16).padStart(2, "0");
      return hex as OpfsPhysicalGenerationId;
    });
  /**
   * STO-01. Compensation must not inherit the caller's already aborted signal;
   * a cleanup that never starts cannot justify releasing the journal row.
   */
  const compensationSignal = dependencies.compensationSignal;
  const now = dependencies.now ?? Date.now;

  const objects: DurableObjectStorePort = Object.freeze({
    async capabilities() {
      return await dependencies.worker.capabilities();
    },

    async put(sourceRequest: PutDurableObjectRequest) {
      const requestSnapshot = snapshotPutRequest(sourceRequest);
      if (!requestSnapshot.ok) return requestSnapshot;
      const request = requestSnapshot.value;
      const earlyFailure = validatePut(
        request,
        policy,
        dependencies.scope,
        dependencies.storagePolicy,
      );
      if (earlyFailure) return earlyFailure;
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_WRITE",
        outcome: "STARTED",
        byteBucket: byteBucket(request.source.byteLength!),
      });
      notifyProgress(request, "VALIDATING", 0);

      const currentResult = await dependencies.journal.getCommittedObject(
        dependencies.scope,
        request.objectId,
      );
      if (!currentResult.ok) {
        return observeFailure(
          rebaseFailure(currentResult.error, "OBJECT_WRITE"),
          dependencies.observer,
          request.source.byteLength!,
        );
      }
      const current = currentResult.value;
      if (
        (current === null && request.expectedGeneration !== null) ||
        (current !== null &&
          request.expectedGeneration !== current.descriptor.generation)
      ) {
        return observeFailure(
          browserDataFailure("CONFLICT", "OBJECT_WRITE", {
            recovery: "REOPEN",
          }),
          dependencies.observer,
          request.source.byteLength!,
        );
      }
      const targetGeneration = (current?.descriptor.generation ?? 0) + 1;
      const transactionId = createTransactionId();
      // STO-01. The logical generation is reused across transactions; this
      // token makes the physical target unique so a late compensation can never
      // delete a newer transaction's directory.
      const physicalGenerationId = createPhysicalGenerationId();
      notifyProgress(request, "PREPARING", 0);
      const begun = await dependencies.journal.begin({
        transactionId,
        mutation: "PUT",
        scope: dependencies.scope,
        objectId: request.objectId,
        expectedGeneration: request.expectedGeneration,
        targetGeneration,
        targetByteLength: request.source.byteLength!,
        targetStoragePolicy: dependencies.storagePolicy,
        startedAtEpochMs: now(),
      });
      if (!begun.ok) {
        return observeFailure(
          rebaseFailure(begun.error, "OBJECT_WRITE"),
          dependencies.observer,
          request.source.byteLength!,
        );
      }

      const descriptor: Omit<DurableObjectDescriptor, "integrity"> =
        Object.freeze({
          objectId: request.objectId,
          scope: dependencies.scope,
          generation: targetGeneration,
          byteLength: request.source.byteLength!,
          mediaType: request.mediaType,
          createdAtEpochMs: now(),
          storagePolicy: dependencies.storagePolicy,
        });
      const prepared = await dependencies.worker.preparePut({
        transactionId,
        physicalGenerationId,
        descriptor,
        source: request.source,
        signal: request.signal,
        onProgress: request.onProgress,
      });
      if (!prepared.ok) {
        const compensated = await compensatePreparedPut(
          begun.value,
          physicalGenerationId,
        );
        if (!compensated.ok) {
          return observeFailure(
            compensated,
            dependencies.observer,
            request.source.byteLength!,
          );
        }
        return observeFailure(
          prepared,
          dependencies.observer,
          request.source.byteLength!,
        );
      }

      const filesReady = await dependencies.journal.markFilesReady(
        transactionId,
        begun.value.fencingToken,
        prepared.value,
      );
      if (!filesReady.ok) {
        const compensated = await compensatePreparedPut(
          begun.value,
          physicalGenerationId,
        );
        if (!compensated.ok) {
          return observeFailure(
            compensated,
            dependencies.observer,
            request.source.byteLength!,
          );
        }
        return observeFailure(
          rebaseFailure(filesReady.error, "OBJECT_WRITE"),
          dependencies.observer,
          request.source.byteLength!,
        );
      }

      const committed = await dependencies.journal.commitPut(
        transactionId,
        begun.value.fencingToken,
      );
      if (!committed.ok) {
        // The commit response can be lost after IndexedDB commits. Reconciliation
        // decides from the durable journal; rolling back here would be unsafe.
        return observeFailure(
          rebaseFailure(committed.error, "OBJECT_WRITE"),
          dependencies.observer,
          request.source.byteLength!,
        );
      }

      notifyProgress(
        request,
        "FINALIZING",
        prepared.value.descriptor.byteLength,
      );
      const finalized = await dependencies.worker.finalizePut(
        transactionId,
        prepared.value,
        request.signal,
      );
      if (!finalized.ok) {
        // STO-RR-01. The commit fence already passed, so the payload is durable
        // and the journal keeps its COMMITTED record for reconciliation to
        // settle. What did not happen is finalization: the previous generation
        // and the staging directory are still present. Reporting a plain
        // success here would claim a settled state nobody observed, so the
        // worker's own failure is surfaced and the record is left recoverable.
        return observeFailure(
          rebaseFailure(finalized.error, "OBJECT_WRITE"),
          dependencies.observer,
          request.source.byteLength!,
        );
      }
      await dependencies.journal.complete(
        transactionId,
        begun.value.fencingToken,
      );
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_WRITE",
        outcome: "SUCCEEDED",
        byteBucket: byteBucket(prepared.value.descriptor.byteLength),
      });
      return browserDataSuccess(prepared.value.descriptor);
    },

    async open(
      sourceRequest: Parameters<DurableObjectStorePort["open"]>[0],
    ) {
      const requestSnapshot = snapshotOpenRequest(sourceRequest);
      if (!requestSnapshot.ok) return requestSnapshot;
      const request = requestSnapshot.value;
      const aborted = abortedResult(request.signal, "OBJECT_READ");
      if (aborted) return aborted;
      if (
        !policy.isObjectIdAllowed(request.objectId) ||
        (request.generation !== undefined &&
          (!Number.isSafeInteger(request.generation) ||
            request.generation < 1))
      ) {
        return browserDataFailure("INVALID_INPUT", "OBJECT_READ");
      }
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_READ",
        outcome: "STARTED",
      });
      const committed = await dependencies.journal.getCommittedObject(
        dependencies.scope,
        request.objectId,
      );
      if (!committed.ok) {
        return observeFailure(
          rebaseFailure(committed.error, "OBJECT_READ"),
          dependencies.observer,
        );
      }
      if (
        !committed.value ||
        (request.generation !== undefined &&
          request.generation !== committed.value.descriptor.generation)
      ) {
        return observeFailure(
          browserDataFailure("NOT_FOUND", "OBJECT_READ", {
            recovery: "REHYDRATE",
          }),
          dependencies.observer,
        );
      }
      if (isExpired(committed.value.descriptor, now())) {
        await objects.remove({
          objectId: request.objectId,
          expectedGeneration: committed.value.descriptor.generation,
          signal: request.signal,
        });
        return observeFailure(
          browserDataFailure("EXPIRED_RESOURCE", "OBJECT_READ", {
            recovery: "REHYDRATE",
          }),
          dependencies.observer,
          committed.value.descriptor.byteLength,
        );
      }
      const opened = await dependencies.worker.openObject(
        committed.value,
        request.signal,
      );
      if (!opened.ok) {
        return observeFailure(
          opened,
          dependencies.observer,
          committed.value.descriptor.byteLength,
        );
      }
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_READ",
        outcome: "SUCCEEDED",
        byteBucket: byteBucket(committed.value.descriptor.byteLength),
      });
      return browserDataSuccess({
        descriptor: committed.value.descriptor,
        source: opened.value,
      });
    },

    async remove(
      sourceRequest: Parameters<DurableObjectStorePort["remove"]>[0],
    ) {
      const requestSnapshot = snapshotRemoveRequest(sourceRequest);
      if (!requestSnapshot.ok) return requestSnapshot;
      const request = requestSnapshot.value;
      const aborted = abortedResult(request.signal, "OBJECT_DELETE");
      if (aborted) return aborted;
      if (
        !policy.isObjectIdAllowed(request.objectId) ||
        !Number.isSafeInteger(request.expectedGeneration) ||
        request.expectedGeneration < 1
      ) {
        return browserDataFailure("INVALID_INPUT", "OBJECT_DELETE");
      }
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_DELETE",
        outcome: "STARTED",
      });
      const current = await dependencies.journal.getCommittedObject(
        dependencies.scope,
        request.objectId,
      );
      if (!current.ok) {
        return observeFailure(
          rebaseFailure(current.error, "OBJECT_DELETE"),
          dependencies.observer,
        );
      }
      if (!current.value) {
        return observeFailure(
          browserDataFailure("NOT_FOUND", "OBJECT_DELETE"),
          dependencies.observer,
        );
      }
      if (
        current.value.descriptor.generation !== request.expectedGeneration
      ) {
        return observeFailure(
          browserDataFailure("CONFLICT", "OBJECT_DELETE", {
            recovery: "REOPEN",
          }),
          dependencies.observer,
        );
      }

      const transactionId = createTransactionId();
      const begun = await dependencies.journal.begin({
        transactionId,
        mutation: "DELETE",
        scope: dependencies.scope,
        objectId: request.objectId,
        expectedGeneration: request.expectedGeneration,
        targetGeneration: request.expectedGeneration + 1,
        targetByteLength: 0,
        targetStoragePolicy: current.value.descriptor.storagePolicy,
        startedAtEpochMs: now(),
      });
      if (!begun.ok) {
        return observeFailure(
          rebaseFailure(begun.error, "OBJECT_DELETE"),
          dependencies.observer,
        );
      }
      const committed = await dependencies.journal.commitDelete(
        transactionId,
        begun.value.fencingToken,
      );
      if (!committed.ok) {
        return observeFailure(
          rebaseFailure(committed.error, "OBJECT_DELETE"),
          dependencies.observer,
        );
      }
      const removed = await dependencies.worker.removeObject(
        dependencies.scope,
        request.objectId,
        request.expectedGeneration,
        request.signal,
      );
      if (removed.ok) {
        await dependencies.journal.complete(
          transactionId,
          begun.value.fencingToken,
        );
      }
      // Logical deletion is already committed. Physical cleanup is retryable
      // maintenance and must not make the caller repeat a non-idempotent delete.
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_DELETE",
        outcome: "SUCCEEDED",
      });
      return browserDataSuccess(undefined);
    },
  });

  const maintenance: DurableObjectMaintenancePort = Object.freeze({
    async reconcile(
      sourceRequest: NonNullable<
        Parameters<DurableObjectMaintenancePort["reconcile"]>[0]
      > = {},
    ) {
      const requestSnapshot = snapshotReconciliationRequest(sourceRequest);
      if (!requestSnapshot.ok) return requestSnapshot;
      const request = requestSnapshot.value;
      const aborted = abortedResult(request.signal, "OBJECT_RECONCILE");
      if (aborted) return aborted;
      if (
        !isValidOptionalPositiveInteger(request.budgetMs) ||
        !isValidOptionalPositiveInteger(request.maxTransactions)
      ) {
        return browserDataFailure("INVALID_INPUT", "OBJECT_RECONCILE");
      }
      if (
        exceedsConfiguredCeiling(
          request.budgetMs,
          policy.reconciliationBudgetMs,
        ) ||
        exceedsConfiguredCeiling(
          request.maxTransactions,
          policy.reconciliationBatchSize,
        )
      ) {
        return browserDataFailure("LIMIT_EXCEEDED", "OBJECT_RECONCILE");
      }
      const budgetMs =
        request.budgetMs ?? policy.reconciliationBudgetMs;
      const maxTransactions =
        request.maxTransactions ?? policy.reconciliationBatchSize;
      const deadline = now() + budgetMs;
      const page = await dependencies.journal.listIncomplete(maxTransactions);
      if (!page.ok) {
        return rebaseFailure(page.error, "OBJECT_RECONCILE");
      }
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_RECONCILE",
        outcome: "STARTED",
        transactionBucket: transactionBucket(page.value.transactions.length),
      });

      const report: {
        inspectedTransactions: number;
        committedTransactions: number;
        rolledBackTransactions: number;
        cleanedTransactions: number;
        inspectedOrphanChunks: number;
        deletedOrphanChunks: number;
        orphanGcStatus:
          | "COMPLETED"
          | "DEADLINE_REACHED"
          | "STAGING_STATE_UNREADABLE";
        moreTransactionsAvailable: boolean;
        deadlineReached: boolean;
      } = {
        inspectedTransactions: 0,
        committedTransactions: 0,
        rolledBackTransactions: 0,
        cleanedTransactions: 0,
        inspectedOrphanChunks: 0,
        deletedOrphanChunks: 0,
        orphanGcStatus: "COMPLETED",
        moreTransactionsAvailable: page.value.moreAvailable,
        deadlineReached: false,
      };
      for (const transaction of page.value.transactions) {
        if (request.signal?.aborted) {
          return browserDataFailure("ABORTED", "OBJECT_RECONCILE");
        }
        if (now() >= deadline) {
          report.deadlineReached = true;
          report.moreTransactionsAvailable = true;
          break;
        }
        report.inspectedTransactions += 1;
        const reconciled = await reconcileTransaction(transaction, request.signal);
        if (!reconciled.ok) {
          return observeFailure(reconciled, dependencies.observer);
        }
        report.committedTransactions += reconciled.value.committed;
        report.rolledBackTransactions += reconciled.value.rolledBack;
        report.cleanedTransactions += reconciled.value.cleaned;
      }
      if (now() >= deadline) {
        report.deadlineReached = true;
        report.orphanGcStatus = "DEADLINE_REACHED";
      } else {
        const gc = await reconcileOrphanChunks(
          deadline,
          request.signal,
        );
        if (!gc.ok) return observeFailure(gc, dependencies.observer);
        report.inspectedOrphanChunks = gc.value.inspected;
        report.deletedOrphanChunks = gc.value.deleted;
        report.orphanGcStatus = gc.value.status;
        if (gc.value.status === "DEADLINE_REACHED") {
          report.deadlineReached = true;
        }
      }
      observeOpfsSafely(dependencies.observer, {
        operation: "OBJECT_RECONCILE",
        outcome: "SUCCEEDED",
        transactionBucket: transactionBucket(report.inspectedTransactions),
      });
      return browserDataSuccess<OpfsReconciliationReport>(
        Object.freeze({ ...report }),
      );
    },

    async enforcePolicies(
      sourceRequest: Parameters<
        DurableObjectMaintenancePort["enforcePolicies"]
      >[0],
    ) {
      const requestSnapshot = snapshotPolicyMaintenanceRequest(
        sourceRequest,
      );
      if (!requestSnapshot.ok) return requestSnapshot;
      const request = requestSnapshot.value;
      const aborted = abortedResult(request.signal, "OBJECT_RECONCILE");
      if (aborted) return aborted;
      if (
        !isValidOptionalPositiveInteger(request.budgetMs) ||
        !isValidOptionalPositiveInteger(request.maxObjects) ||
        (request.reason === "PRESSURE" &&
          (!Number.isSafeInteger(request.targetBytesToRelease) ||
            request.targetBytesToRelease < 1))
      ) {
        return browserDataFailure("INVALID_INPUT", "OBJECT_RECONCILE");
      }
      if (
        exceedsConfiguredCeiling(
          request.budgetMs,
          policy.reconciliationBudgetMs,
        ) ||
        exceedsConfiguredCeiling(
          request.maxObjects,
          policy.reconciliationBatchSize,
        )
      ) {
        return browserDataFailure("LIMIT_EXCEEDED", "OBJECT_RECONCILE");
      }
      if (
        !maintenanceReasonAllowed(
          request.reason,
          dependencies.storagePolicy,
        )
      ) {
        return browserDataFailure(
          "POLICY_REJECTED",
          "OBJECT_RECONCILE",
          { recovery: dependencies.storagePolicy.unavailableFallback },
        );
      }
      const budgetMs =
        request.budgetMs ?? policy.reconciliationBudgetMs;
      const maxObjects =
        request.maxObjects ?? policy.reconciliationBatchSize;
      const deadline = now() + budgetMs;
      const authorized = await authorizePolicyMaintenance(request);
      if (!authorized.ok) return authorized;
      if (request.signal?.aborted) {
        return browserDataFailure("ABORTED", "OBJECT_RECONCILE");
      }
      if (now() >= deadline) {
        // Authority acquisition is part of the maintenance budget. No journal
        // read is allowed after the deadline, so remaining work is reported
        // conservatively instead of implying that the partition was scanned.
        return browserDataSuccess<OpfsPolicyMaintenanceReport>(
          Object.freeze({
            inspectedObjects: 0,
            removedObjects: 0,
            releasedBytes: 0,
            moreObjectsAvailable: true,
            deadlineReached: true,
          }),
        );
      }
      let afterObjectId: string | undefined;
      let inspectedObjects = 0;
      let removedObjects = 0;
      let releasedBytes = 0;
      let moreObjectsAvailable = false;
      let deadlineReached = false;

      while (
        inspectedObjects < maxObjects &&
        now() < deadline
      ) {
        const page = await dependencies.journal.listCommittedObjects({
          scope: dependencies.scope,
          afterObjectId,
          limit: Math.min(
            policy.reconciliationBatchSize,
            maxObjects - inspectedObjects,
          ),
        });
        if (!page.ok) {
          return rebaseFailure(page.error, "OBJECT_RECONCILE");
        }
        const candidates = [...page.value.objects].sort(
          policyMaintenanceOrder,
        );
        for (const candidate of candidates) {
          if (
            request.signal?.aborted ||
            now() >= deadline ||
            inspectedObjects >= maxObjects
          ) {
            deadlineReached = now() >= deadline;
            moreObjectsAvailable = true;
            break;
          }
          inspectedObjects += 1;
          if (!shouldRemoveForPolicy(candidate, request, now())) continue;
          const removed = await objects.remove({
            objectId: candidate.descriptor.objectId,
            expectedGeneration: candidate.descriptor.generation,
            signal: request.signal,
          });
          if (!removed.ok) {
            if (removed.error.code === "CONFLICT" || removed.error.code === "NOT_FOUND") {
              continue;
            }
            return rebaseFailure(removed.error, "OBJECT_RECONCILE");
          }
          removedObjects += 1;
          releasedBytes += candidate.descriptor.byteLength;
          if (
            request.reason === "PRESSURE" &&
            releasedBytes >= request.targetBytesToRelease
          ) {
            moreObjectsAvailable = page.value.moreAvailable;
            break;
          }
        }
        if (
          deadlineReached ||
          (request.reason === "PRESSURE" &&
            releasedBytes >= request.targetBytesToRelease) ||
          !page.value.moreAvailable ||
          !page.value.nextObjectId
        ) {
          moreObjectsAvailable ||= page.value.moreAvailable;
          break;
        }
        afterObjectId = page.value.nextObjectId;
        moreObjectsAvailable = page.value.moreAvailable;
      }
      const report: OpfsPolicyMaintenanceReport = Object.freeze({
        inspectedObjects,
        removedObjects,
        releasedBytes,
        moreObjectsAvailable,
        deadlineReached,
      });
      return browserDataSuccess(report);
    },
  });

  async function authorizePolicyMaintenance(
    request: Parameters<
      DurableObjectMaintenancePort["enforcePolicies"]
    >[0],
  ): Promise<BrowserDataResult<void>> {
    if (!requiresMaintenanceAuthority(request)) {
      return browserDataSuccess(undefined);
    }
    const requestAuthority = dependencies.requestMaintenanceAuthority;
    const consumeAuthority = dependencies.consumeMaintenanceAuthority;
    if (!requestAuthority || !consumeAuthority) {
      return browserDataFailure(
        "POLICY_REJECTED",
        "OBJECT_RECONCILE",
        { recovery: "READ_ONLY" },
      );
    }

    let decision: OpfsMaintenanceAuthorityDecision;
    try {
      decision = await requestAuthority(
        Object.freeze({
          reason: request.reason,
          scope: dependencies.scope,
          storagePolicy: dependencies.storagePolicy,
          ...(request.signal ? { signal: request.signal } : {}),
        }),
      );
    } catch {
      return browserDataFailure(
        "POLICY_REJECTED",
        "OBJECT_RECONCILE",
        { recovery: "READ_ONLY" },
      );
    }
    if (request.signal?.aborted) {
      return browserDataFailure("ABORTED", "OBJECT_RECONCILE");
    }
    if (
      !decision ||
      decision.authorized !== true ||
      typeof decision.proofToken !== "string" ||
      !OPAQUE_AUTHORITY_PROOF.test(decision.proofToken) ||
      !Number.isSafeInteger(decision.expiresAtEpochMs)
    ) {
      return browserDataFailure(
        "POLICY_REJECTED",
        "OBJECT_RECONCILE",
        { recovery: "READ_ONLY" },
      );
    }

    let authorizationEpochMs: number;
    try {
      authorizationEpochMs = now();
    } catch {
      return browserDataFailure(
        "UNAVAILABLE",
        "OBJECT_RECONCILE",
        { retryable: true, recovery: "RETRY" },
      );
    }
    if (
      !Number.isSafeInteger(authorizationEpochMs) ||
      authorizationEpochMs < 0 ||
      decision.expiresAtEpochMs <= authorizationEpochMs ||
      decision.expiresAtEpochMs - authorizationEpochMs >
        MAX_AUTHORITY_PROOF_LIFETIME_MS
    ) {
      return browserDataFailure(
        "POLICY_REJECTED",
        "OBJECT_RECONCILE",
        { recovery: "READ_ONLY" },
      );
    }

    const proofToken = decision.proofToken;
    const expiresAtEpochMs = decision.expiresAtEpochMs;
    let consumed: boolean;
    try {
      consumed = await consumeAuthority(
        Object.freeze({
          reason: request.reason,
          proofToken,
          expiresAtEpochMs,
          scope: dependencies.scope,
          storagePolicy: dependencies.storagePolicy,
          ...(request.signal ? { signal: request.signal } : {}),
        }),
      );
    } catch {
      return browserDataFailure(
        "POLICY_REJECTED",
        "OBJECT_RECONCILE",
        { recovery: "READ_ONLY" },
      );
    }
    // The proof is intentionally not retained after this invocation. The
    // composition consumer owns atomic replay prevention across runtimes.
    if (request.signal?.aborted) {
      return browserDataFailure("ABORTED", "OBJECT_RECONCILE");
    }
    return consumed
      ? browserDataSuccess(undefined)
      : browserDataFailure(
          "POLICY_REJECTED",
          "OBJECT_RECONCILE",
          { recovery: "READ_ONLY" },
        );
  }

  return Object.freeze({ objects, maintenance });

  /**
   * STO-01. The compensating half of the put saga.
   *
   * The journal row and its budget reservation are the only durable evidence
   * that a physical staging generation may still exist, so they are released
   * exactly when the physical effect is confirmed `CLEANED` or
   * `ALREADY_CLEAN`. A timeout, crash, malformed response or `EFFECT_UNKNOWN`
   * keeps `PREPARING`/`FILES_READY` in place and asks for reconciliation.
   */
  async function compensatePreparedPut(
    transaction: OpfsJournalTransaction,
    physicalGenerationId: OpfsPhysicalGenerationId,
  ): Promise<BrowserDataResult<void>> {
    const cleanup = await dependencies.worker.abortPreparedPut({
      scope: transaction.scope,
      transactionId: transaction.transactionId,
      physicalGenerationId,
      ...(compensationSignal ? { signal: compensationSignal } : {}),
    });
    if (!cleanup.ok || cleanup.value.kind === "EFFECT_UNKNOWN") {
      return browserDataFailure("CONFLICT", "OBJECT_RECONCILE", {
        recovery: "RETRY",
      });
    }
    const rolledBack = await dependencies.journal.rollback(
      transaction.transactionId,
      transaction.fencingToken,
    );
    if (!rolledBack.ok) {
      return rebaseFailure(rolledBack.error, "OBJECT_RECONCILE");
    }
    return browserDataSuccess(undefined);
  }

  async function reconcileTransaction(
    transaction: OpfsJournalTransaction,
    signal: AbortSignal | undefined,
  ): Promise<
    BrowserDataResult<
      Readonly<{ committed: number; rolledBack: number; cleaned: number }>
    >
  > {
    if (transaction.phase === "PREPARING") {
      const cleaned = await dependencies.worker.cleanupTransaction(
        transaction.scope,
        transaction.transactionId,
        signal,
      );
      if (!cleaned.ok) return cleaned;
      if (cleaned.value.kind === "EFFECT_UNKNOWN") {
        return browserDataFailure("CONFLICT", "OBJECT_RECONCILE", {
          recovery: "RETRY",
        });
      }
      const rolledBack = await dependencies.journal.rollback(
        transaction.transactionId,
        transaction.fencingToken,
      );
      if (!rolledBack.ok) {
        return rebaseFailure(rolledBack.error, "OBJECT_RECONCILE");
      }
      return browserDataSuccess({ committed: 0, rolledBack: 1, cleaned: 1 });
    }

    if (transaction.phase === "FILES_READY") {
      if (
        transaction.mutation !== "PUT" ||
        !transaction.preparedObject
      ) {
        return browserDataFailure("CORRUPT_DATA", "OBJECT_RECONCILE", {
          recovery: "READ_ONLY",
        });
      }
      const verified = await dependencies.worker.verifyObject(
        transaction.preparedObject,
        signal,
      );
      if (!verified.ok) return verified;
      if (!verified.value) {
        const cleaned = await dependencies.worker.cleanupTransaction(
          transaction.scope,
          transaction.transactionId,
          signal,
        );
        if (!cleaned.ok) return cleaned;
        const rolledBack = await dependencies.journal.rollback(
          transaction.transactionId,
          transaction.fencingToken,
        );
        if (!rolledBack.ok) {
          return rebaseFailure(rolledBack.error, "OBJECT_RECONCILE");
        }
        return browserDataSuccess({
          committed: 0,
          rolledBack: 1,
          cleaned: 1,
        });
      }
      const committed = await dependencies.journal.commitPut(
        transaction.transactionId,
        transaction.fencingToken,
      );
      if (!committed.ok) {
        return rebaseFailure(committed.error, "OBJECT_RECONCILE");
      }
      const finalized = await dependencies.worker.finalizePut(
        transaction.transactionId,
        transaction.preparedObject,
        signal,
      );
      if (!finalized.ok) return finalized;
      const completed = await dependencies.journal.complete(
        transaction.transactionId,
        transaction.fencingToken,
      );
      if (!completed.ok) {
        return rebaseFailure(completed.error, "OBJECT_RECONCILE");
      }
      return browserDataSuccess({ committed: 1, rolledBack: 0, cleaned: 1 });
    }

    if (transaction.phase === "COMMITTED") {
      if (transaction.mutation === "PUT") {
        if (!transaction.preparedObject) {
          return browserDataFailure("CORRUPT_DATA", "OBJECT_RECONCILE", {
            recovery: "READ_ONLY",
          });
        }
        const finalized = await dependencies.worker.finalizePut(
          transaction.transactionId,
          transaction.preparedObject,
          signal,
        );
        if (!finalized.ok) return finalized;
      } else {
        const removed = await dependencies.worker.removeObject(
          transaction.scope,
          transaction.objectId,
          Math.max(1, transaction.targetGeneration - 1),
          signal,
        );
        if (!removed.ok) return removed;
      }
      const completed = await dependencies.journal.complete(
        transaction.transactionId,
        transaction.fencingToken,
      );
      if (!completed.ok) {
        return rebaseFailure(completed.error, "OBJECT_RECONCILE");
      }
      return browserDataSuccess({ committed: 0, rolledBack: 0, cleaned: 1 });
    }

    return browserDataFailure("CORRUPT_DATA", "OBJECT_RECONCILE", {
      recovery: "READ_ONLY",
    });
  }

  async function reconcileOrphanChunks(
    deadline: number,
    signal: AbortSignal | undefined,
  ): Promise<
    BrowserDataResult<
      Readonly<{
        inspected: number;
        deleted: number;
        status:
          | "COMPLETED"
          | "DEADLINE_REACHED"
          | "STAGING_STATE_UNREADABLE";
      }>
    >
  > {
    const olderThanEpochMs = Math.max(
      0,
      now() - policy.orphanGracePeriodMs,
    );
    const candidates = await dependencies.worker.listOrphanCandidates(
      dependencies.scope,
      olderThanEpochMs,
      policy.orphanGcBatchSize,
      signal,
    );
    if (!candidates.ok) return candidates;
    if (!candidates.value.safeToSweep) {
      return browserDataSuccess({
        inspected: 0,
        deleted: 0,
        status: "STAGING_STATE_UNREADABLE",
      });
    }
    let inspected = 0;
    let deleted = 0;
    for (const digestHex of candidates.value.digests) {
      if (signal?.aborted) {
        return browserDataFailure("ABORTED", "OBJECT_RECONCILE");
      }
      if (now() >= deadline) {
        return browserDataSuccess({
          inspected,
          deleted,
          status: "DEADLINE_REACHED",
        });
      }
      inspected += 1;
      const referenced = await dependencies.journal.isChunkReferenced(
        dependencies.scope,
        digestHex,
      );
      if (!referenced.ok) {
        return rebaseFailure(referenced.error, "OBJECT_RECONCILE");
      }
      if (referenced.value) continue;
      const removal = await dependencies.worker.deleteOrphanChunk(
        dependencies.scope,
        digestHex,
        olderThanEpochMs,
        signal,
      );
      if (!removal.ok) return removal;
      if (removal.value.skippedUnsafe) {
        return browserDataSuccess({
          inspected,
          deleted,
          status: "STAGING_STATE_UNREADABLE",
        });
      }
      if (removal.value.deleted) deleted += 1;
    }
    return browserDataSuccess({
      inspected,
      deleted,
      status:
        candidates.value.moreAvailable
          ? "DEADLINE_REACHED"
          : "COMPLETED",
    });
  }
}

function snapshotPutRequest(
  input: PutDurableObjectRequest,
): BrowserDataResult<PutDurableObjectRequest> {
  try {
    if (!input || typeof input !== "object") {
      return browserDataFailure("INVALID_INPUT", "OBJECT_WRITE");
    }
    const sourceInput = input.source;
    if (!sourceInput || typeof sourceInput !== "object") {
      return browserDataFailure("INVALID_INPUT", "OBJECT_WRITE");
    }
    const objectId = input.objectId;
    const expectedGeneration = input.expectedGeneration;
    const mediaType = input.mediaType;
    const signal = input.signal;
    const onProgress = input.onProgress;
    const byteLength = sourceInput.byteLength;
    const stream = sourceInput.stream;
    if (
      typeof stream !== "function" ||
      (onProgress !== undefined &&
        typeof onProgress !== "function")
    ) {
      return browserDataFailure("INVALID_INPUT", "OBJECT_WRITE");
    }
    const boundStream = stream.bind(sourceInput);
    const source = Object.freeze({
      byteLength,
      stream(signal: AbortSignal) {
        return boundStream(signal);
      },
    });
    return browserDataSuccess(
      Object.freeze({
        objectId,
        expectedGeneration,
        mediaType,
        source,
        ...(signal === undefined ? {} : { signal }),
        ...(onProgress === undefined
          ? {}
          : { onProgress }),
      }),
    );
  } catch {
    return browserDataFailure("INVALID_INPUT", "OBJECT_WRITE");
  }
}

function snapshotOpenRequest(
  input: Parameters<DurableObjectStorePort["open"]>[0],
): BrowserDataResult<
  Parameters<DurableObjectStorePort["open"]>[0]
> {
  try {
    if (!input || typeof input !== "object") {
      return browserDataFailure("INVALID_INPUT", "OBJECT_READ");
    }
    const objectId = input.objectId;
    const generation = input.generation;
    const signal = input.signal;
    return browserDataSuccess(
      Object.freeze({
        objectId,
        ...(generation === undefined
          ? {}
          : { generation }),
        ...(signal === undefined ? {} : { signal }),
      }),
    );
  } catch {
    return browserDataFailure("INVALID_INPUT", "OBJECT_READ");
  }
}

function snapshotRemoveRequest(
  input: Parameters<DurableObjectStorePort["remove"]>[0],
): BrowserDataResult<
  Parameters<DurableObjectStorePort["remove"]>[0]
> {
  try {
    if (!input || typeof input !== "object") {
      return browserDataFailure("INVALID_INPUT", "OBJECT_DELETE");
    }
    const objectId = input.objectId;
    const expectedGeneration = input.expectedGeneration;
    const signal = input.signal;
    return browserDataSuccess(
      Object.freeze({
        objectId,
        expectedGeneration,
        ...(signal === undefined ? {} : { signal }),
      }),
    );
  } catch {
    return browserDataFailure("INVALID_INPUT", "OBJECT_DELETE");
  }
}

function snapshotReconciliationRequest(
  input: NonNullable<
    Parameters<DurableObjectMaintenancePort["reconcile"]>[0]
  >,
): BrowserDataResult<
  NonNullable<
    Parameters<DurableObjectMaintenancePort["reconcile"]>[0]
  >
> {
  try {
    if (!input || typeof input !== "object") {
      return browserDataFailure("INVALID_INPUT", "OBJECT_RECONCILE");
    }
    const budgetMs = input.budgetMs;
    const maxTransactions = input.maxTransactions;
    const signal = input.signal;
    return browserDataSuccess(
      Object.freeze({
        ...(budgetMs === undefined
          ? {}
          : { budgetMs }),
        ...(maxTransactions === undefined
          ? {}
          : { maxTransactions }),
        ...(signal === undefined ? {} : { signal }),
      }),
    );
  } catch {
    return browserDataFailure("INVALID_INPUT", "OBJECT_RECONCILE");
  }
}

function snapshotPolicyMaintenanceRequest(
  input: Parameters<
    DurableObjectMaintenancePort["enforcePolicies"]
  >[0],
): BrowserDataResult<
  Parameters<DurableObjectMaintenancePort["enforcePolicies"]>[0]
> {
  try {
    if (!input || typeof input !== "object") {
      return browserDataFailure("INVALID_INPUT", "OBJECT_RECONCILE");
    }
    const reason = input.reason;
    const budgetMs = input.budgetMs;
    const maxObjects = input.maxObjects;
    const signal = input.signal;
    const common = {
      ...(budgetMs === undefined
        ? {}
        : { budgetMs }),
      ...(maxObjects === undefined
        ? {}
        : { maxObjects }),
      ...(signal === undefined ? {} : { signal }),
    };
    switch (reason) {
      case "TTL":
      case "LOGOUT":
      case "SESSION_END":
      case "UNTIL_SYNCED":
      case "ACCOUNT_DELETION":
        return browserDataSuccess(
          Object.freeze({ reason, ...common }),
        );
      case "PRESSURE": {
        const targetBytesToRelease = input.targetBytesToRelease;
        return browserDataSuccess(
          Object.freeze({
            reason: "PRESSURE",
            targetBytesToRelease,
            ...common,
          }),
        );
      }
      default:
        return browserDataFailure(
          "INVALID_INPUT",
          "OBJECT_RECONCILE",
        );
    }
  } catch {
    return browserDataFailure("INVALID_INPUT", "OBJECT_RECONCILE");
  }
}

function snapshotOpfsJournal(
  source: OpfsJournalPort,
): OpfsJournalPort {
  if (!source || typeof source !== "object") {
    throw new TypeError("OPFS journal dependency is invalid.");
  }
  const {
    getCommittedObject,
    begin,
    markFilesReady,
    commitPut,
    commitDelete,
    complete,
    rollback,
    listIncomplete,
    listCommittedObjects,
    isChunkReferenced,
  } = source;
  if (
    [
      getCommittedObject,
      begin,
      markFilesReady,
      commitPut,
      commitDelete,
      complete,
      rollback,
      listIncomplete,
      listCommittedObjects,
      isChunkReferenced,
    ].some((method) => typeof method !== "function")
  ) {
    throw new TypeError("OPFS journal dependency is invalid.");
  }
  return Object.freeze({
    getCommittedObject: getCommittedObject.bind(source),
    begin: begin.bind(source),
    markFilesReady: markFilesReady.bind(source),
    commitPut: commitPut.bind(source),
    commitDelete: commitDelete.bind(source),
    complete: complete.bind(source),
    rollback: rollback.bind(source),
    listIncomplete: listIncomplete.bind(source),
    listCommittedObjects: listCommittedObjects.bind(source),
    isChunkReferenced: isChunkReferenced.bind(source),
  });
}

function snapshotOpfsWorker(
  source: OpfsWorkerGateway,
): OpfsWorkerGateway {
  if (!source || typeof source !== "object") {
    throw new TypeError("OPFS worker dependency is invalid.");
  }
  const {
    capabilities,
    preparePut,
    verifyObject,
    openObject,
    removeObject,
    cleanupTransaction,
    abortPreparedPut,
    finalizePut,
    listOrphanCandidates,
    deleteOrphanChunk,
    close,
  } = source;
  if (
    [
      capabilities,
      preparePut,
      verifyObject,
      openObject,
      removeObject,
      cleanupTransaction,
      abortPreparedPut,
      finalizePut,
      listOrphanCandidates,
      deleteOrphanChunk,
      close,
    ].some((method) => typeof method !== "function")
  ) {
    throw new TypeError("OPFS worker dependency is invalid.");
  }
  return Object.freeze({
    capabilities: capabilities.bind(source),
    preparePut: preparePut.bind(source),
    verifyObject: verifyObject.bind(source),
    openObject: openObject.bind(source),
    removeObject: removeObject.bind(source),
    cleanupTransaction: cleanupTransaction.bind(source),
    abortPreparedPut: abortPreparedPut.bind(source),
    finalizePut: finalizePut.bind(source),
    listOrphanCandidates: listOrphanCandidates.bind(source),
    deleteOrphanChunk: deleteOrphanChunk.bind(source),
    close: close.bind(source),
  });
}

function validatePut(
  request: PutDurableObjectRequest,
  policy: OpfsRuntimePolicy,
  scope: OpfsStorageScope,
  storagePolicy: BrowserStoragePolicy,
): BrowserDataResult<never> | null {
  const aborted = abortedResult(request.signal, "OBJECT_WRITE");
  if (aborted) return aborted;
  if (
    !validateObjectWriteInput(
      {
        objectId: request.objectId,
        scope,
        expectedGeneration: request.expectedGeneration,
        mediaType: request.mediaType,
        byteLength: request.source.byteLength,
        storagePolicy,
      },
      policy,
    )
  ) {
    return browserDataFailure(
      request.source.byteLength !== null &&
        request.source.byteLength > policy.maxObjectBytes
        ? "LIMIT_EXCEEDED"
        : "INVALID_INPUT",
      "OBJECT_WRITE",
    );
  }
  return null;
}

function rebaseFailure(
  failure: BrowserDataFailure,
  operation: BrowserDataOperation,
): BrowserFailureResult {
  return {
    ok: false,
    error: Object.freeze({ ...failure, operation }),
  };
}

function observeFailure(
  failure: BrowserDataResult<unknown>,
  observer: OpfsSafeObserver | undefined,
  byteLength?: number,
): BrowserFailureResult {
  if (failure.ok) {
    throw new TypeError("Expected an OPFS failure result.");
  }
  observeOpfsSafely(observer, {
    operation: failure.error.operation,
    outcome: "FAILED",
    failureCode: failure.error.code,
    byteBucket:
      byteLength === undefined ? undefined : byteBucket(byteLength),
  });
  return failure;
}

function notifyProgress(
  request: PutDurableObjectRequest,
  phase: "VALIDATING" | "PREPARING" | "FINALIZING",
  transferredBytes: number,
): void {
  try {
    request.onProgress?.({
      phase,
      transferredBytes,
      totalBytes: request.source.byteLength,
    });
  } catch {
    // A UI callback cannot affect persistence.
  }
}

function exceedsConfiguredCeiling(
  requested: number | undefined,
  configured: number,
): boolean {
  return requested !== undefined && requested > configured;
}

function isValidOptionalPositiveInteger(
  value: number | undefined,
): boolean {
  return (
    value === undefined ||
    (Number.isSafeInteger(value) && value > 0)
  );
}

function isExpired(
  descriptor: DurableObjectDescriptor,
  nowEpochMs: number,
): boolean {
  const retention = descriptor.storagePolicy.retention;
  return (
    retention.kind === "TTL" &&
    descriptor.createdAtEpochMs + retention.maxAgeMs <= nowEpochMs
  );
}

function policyMaintenanceOrder(
  left: OpfsPreparedObject,
  right: OpfsPreparedObject,
): number {
  const priorities = {
    RECONSTRUCTABLE: 0,
    SYNCED_COPY: 1,
    USER_AUTHORED: 2,
  } as const;
  const priority =
    priorities[left.descriptor.storagePolicy.evictionPriority] -
    priorities[right.descriptor.storagePolicy.evictionPriority];
  return priority !== 0
    ? priority
    : left.descriptor.createdAtEpochMs -
        right.descriptor.createdAtEpochMs;
}

function shouldRemoveForPolicy(
  object: OpfsPreparedObject,
  request: Parameters<
    DurableObjectMaintenancePort["enforcePolicies"]
  >[0],
  nowEpochMs: number,
): boolean {
  if (request.reason === "TTL") {
    return isExpired(object.descriptor, nowEpochMs);
  }
  if (request.reason === "LOGOUT") {
    return (
      object.descriptor.storagePolicy.logoutAction ===
        "PURGE_PARTITION" ||
      object.descriptor.storagePolicy.logoutAction ===
        "EXPORT_THEN_PURGE"
    );
  }
  if (request.reason === "SESSION_END") {
    return object.descriptor.storagePolicy.retention.kind === "SESSION";
  }
  if (request.reason === "UNTIL_SYNCED") {
    return object.descriptor.storagePolicy.retention.kind === "UNTIL_SYNCED";
  }
  if (request.reason === "ACCOUNT_DELETION") {
    return (
      object.descriptor.storagePolicy.accountDeletionAction ===
      "PURGE_PARTITION"
    );
  }
  return (
    object.descriptor.storagePolicy.retention.kind !== "EXPLICIT_DELETE" &&
    object.descriptor.storagePolicy.pressureAction ===
      "EVICT_RECONSTRUCTABLE"
  );
}

function maintenanceReasonAllowed(
  reason: Parameters<
    DurableObjectMaintenancePort["enforcePolicies"]
  >[0]["reason"],
  policy: BrowserStoragePolicy,
): boolean {
  switch (reason) {
    case "TTL":
      return policy.retention.kind === "TTL";
    case "SESSION_END":
      return policy.retention.kind === "SESSION";
    case "UNTIL_SYNCED":
      return policy.retention.kind === "UNTIL_SYNCED";
    case "LOGOUT":
      return (
        policy.accountScope === "OPAQUE_PARTITION" &&
        (policy.logoutAction === "PURGE_PARTITION" ||
          policy.logoutAction === "EXPORT_THEN_PURGE")
      );
    case "ACCOUNT_DELETION":
      return (
        policy.accountScope === "OPAQUE_PARTITION" &&
        policy.accountDeletionAction === "PURGE_PARTITION"
      );
    case "PRESSURE":
      return policy.pressureAction === "EVICT_RECONSTRUCTABLE";
  }
}

function requiresMaintenanceAuthority(
  request: Parameters<
    DurableObjectMaintenancePort["enforcePolicies"]
  >[0],
): request is Extract<
  Parameters<DurableObjectMaintenancePort["enforcePolicies"]>[0],
  { reason: "LOGOUT" | "UNTIL_SYNCED" | "ACCOUNT_DELETION" }
> {
  return (
    request.reason === "LOGOUT" ||
    request.reason === "UNTIL_SYNCED" ||
    request.reason === "ACCOUNT_DELETION"
  );
}

const OPAQUE_AUTHORITY_PROOF = /^[A-Za-z0-9_-]{16,512}$/u;
const MAX_AUTHORITY_PROOF_LIFETIME_MS = 5 * 60 * 1_000;