import {
  assertValidStoragePolicy,
  isValidByteLength,
  type BrowserDataFailureCode,
  type BrowserDataOperation,
  type BrowserStoragePolicy,
} from "../../../application/ports/browser-file-storage/shared.ts";
import type { OpfsStorageScope } from "../../../application/ports/browser-file-storage/opfs-ports.ts";

export type OpfsRuntimePolicy = Readonly<{
  rootDirectoryName: string;
  mutationLockName: string;
  chunkSizeBytes: number;
  maxObjectBytes: number;
  maxChunkCount: number;
  rpcTimeoutMs: number;
  reconciliationBudgetMs: number;
  reconciliationBatchSize: number;
  orphanGracePeriodMs: number;
  orphanGcBatchSize: number;
  maxCancellationTombstones: number;
  allowAsyncWritableChunkFallback: boolean;
  isObjectIdAllowed: (objectId: string) => boolean;
  isMediaTypeAllowed: (mediaType: string) => boolean;
}>;

export type OpfsSafeObservation = Readonly<{
  operation: BrowserDataOperation;
  /**
   * NS-04. `DEGRADED` is a committed effect whose bookkeeping is unsettled:
   * the payload is durable but a reconciler still owns the transaction.
   */
  outcome: "STARTED" | "SUCCEEDED" | "FAILED" | "DEGRADED";
  failureCode?: BrowserDataFailureCode;
  byteBucket?: "0" | "1B_1MiB" | "1MiB_16MiB" | "16MiB_256MiB" | "GT_256MiB";
  transactionBucket?: "0" | "1_10" | "11_100" | "GT_100";
}>;

export type OpfsSafeObserver = (observation: OpfsSafeObservation) => void;

const SAFE_SEGMENT = /^[a-z0-9][a-z0-9._-]{0,63}$/u;
const OPAQUE_OBJECT_ID = /^[A-Za-z0-9_-]{8,128}$/u;
const MEDIA_TYPE = /^[a-z0-9!#$&^_.+-]+\/[a-z0-9!#$&^_.+-]+(?:\s*;.*)?$/iu;

export const DEFAULT_OPFS_RUNTIME_POLICY: OpfsRuntimePolicy = Object.freeze({
  rootDirectoryName: "ca-frontend-opfs-v1",
  mutationLockName: "ca-frontend-opfs-v1:mutation",
  chunkSizeBytes: 4 * 1024 * 1024,
  maxObjectBytes: 2 * 1024 * 1024 * 1024,
  maxChunkCount: 512,
  rpcTimeoutMs: 60_000,
  reconciliationBudgetMs: 5_000,
  reconciliationBatchSize: 100,
  orphanGracePeriodMs: 24 * 60 * 60 * 1_000,
  orphanGcBatchSize: 100,
  maxCancellationTombstones: 1_024,
  allowAsyncWritableChunkFallback: true,
  isObjectIdAllowed: (objectId) => OPAQUE_OBJECT_ID.test(objectId),
  isMediaTypeAllowed: (mediaType) => MEDIA_TYPE.test(mediaType),
});

export function resolveOpfsRuntimePolicy(
  policy: Partial<OpfsRuntimePolicy> = {},
): OpfsRuntimePolicy {
  const resolved: OpfsRuntimePolicy = Object.freeze({
    ...DEFAULT_OPFS_RUNTIME_POLICY,
    ...policy,
  });
  assertOpfsRuntimePolicy(resolved);
  return resolved;
}

export function assertOpfsRuntimePolicy(policy: OpfsRuntimePolicy): void {
  if (
    !SAFE_SEGMENT.test(policy.rootDirectoryName) ||
    policy.mutationLockName.length === 0 ||
    !Number.isSafeInteger(policy.chunkSizeBytes) ||
    policy.chunkSizeBytes < 64 * 1024 ||
    policy.chunkSizeBytes > 64 * 1024 * 1024 ||
    !isValidByteLength(policy.maxObjectBytes) ||
    policy.maxObjectBytes < policy.chunkSizeBytes ||
    !Number.isSafeInteger(policy.maxChunkCount) ||
    policy.maxChunkCount < 1 ||
    policy.maxObjectBytes > policy.chunkSizeBytes * policy.maxChunkCount ||
    !Number.isSafeInteger(policy.rpcTimeoutMs) ||
    policy.rpcTimeoutMs < 1_000 ||
    !Number.isSafeInteger(policy.reconciliationBudgetMs) ||
    policy.reconciliationBudgetMs < 1 ||
    policy.reconciliationBudgetMs > 60_000 ||
    !Number.isSafeInteger(policy.reconciliationBatchSize) ||
    policy.reconciliationBatchSize < 1 ||
    policy.reconciliationBatchSize > 1_000 ||
    !Number.isSafeInteger(policy.orphanGracePeriodMs) ||
    policy.orphanGracePeriodMs < 60_000 ||
    !Number.isSafeInteger(policy.orphanGcBatchSize) ||
    policy.orphanGcBatchSize < 1 ||
    policy.orphanGcBatchSize > 1_000 ||
    !Number.isSafeInteger(policy.maxCancellationTombstones) ||
    policy.maxCancellationTombstones < 16 ||
    policy.maxCancellationTombstones > 10_000 ||
    typeof policy.isObjectIdAllowed !== "function" ||
    typeof policy.isMediaTypeAllowed !== "function"
  ) {
    throw new TypeError("OPFS runtime policy is invalid.");
  }
}

export function validateObjectWriteInput(
  input: Readonly<{
    scope: OpfsStorageScope;
    objectId: string;
    expectedGeneration: number | null;
    mediaType: string;
    byteLength: number | null;
    storagePolicy: Parameters<typeof assertValidStoragePolicy>[0];
  }>,
  policy: OpfsRuntimePolicy,
): boolean {
  try {
    assertValidStoragePolicy(input.storagePolicy);
  } catch {
    return false;
  }

  return (
    isValidOpfsStorageScope(input.scope) &&
    input.scope.namespace === input.storagePolicy.namespace &&
    policy.isObjectIdAllowed(input.objectId) &&
    policy.isMediaTypeAllowed(input.mediaType) &&
    (input.expectedGeneration === null ||
      (Number.isSafeInteger(input.expectedGeneration) &&
        input.expectedGeneration > 0)) &&
    input.byteLength !== null &&
    isValidByteLength(input.byteLength) &&
    input.byteLength <= policy.maxObjectBytes &&
    Math.ceil(input.byteLength / policy.chunkSizeBytes) <=
      policy.maxChunkCount
  );
}

export function isValidOpfsStorageScope(
  scope: OpfsStorageScope,
): boolean {
  return (
    scope.namespace.length > 0 &&
    scope.namespace.length <= 64 &&
    OPAQUE_OBJECT_ID.test(scope.authorityToken) &&
    OPAQUE_OBJECT_ID.test(scope.namespaceToken) &&
    OPAQUE_OBJECT_ID.test(scope.partitionToken)
  );
}

/**
 * Captures the registry binding at composition time. Callers may own mutable
 * config objects, so no OPFS operation is allowed to retain those references.
 */
export function snapshotOpfsStorageScope(
  input: OpfsStorageScope,
): OpfsStorageScope {
  try {
    const snapshot: OpfsStorageScope = Object.freeze({
      namespace: input.namespace,
      authorityToken: input.authorityToken,
      namespaceToken: input.namespaceToken,
      partitionToken: input.partitionToken,
    });
    if (!isValidOpfsStorageScope(snapshot)) throw new TypeError();
    return snapshot;
  } catch {
    throw new TypeError("OPFS storage scope is invalid.");
  }
}

/**
 * Deep enough for the closed BrowserStoragePolicy contract: retention is the
 * only nested value. Fields are copied explicitly so later caller mutation or
 * extension properties cannot alter the bound policy fingerprint.
 */
export function snapshotOpfsStoragePolicy(
  input: BrowserStoragePolicy,
): BrowserStoragePolicy {
  try {
    const retention: BrowserStoragePolicy["retention"] =
      input.retention.kind === "TTL"
        ? Object.freeze({
            kind: "TTL",
            maxAgeMs: input.retention.maxAgeMs,
          })
        : Object.freeze({ kind: input.retention.kind });
    const snapshot: BrowserStoragePolicy = Object.freeze({
      owner: input.owner,
      namespace: input.namespace,
      classification: input.classification,
      authority: input.authority,
      accountScope: input.accountScope,
      retention,
      softBudgetBytes: input.softBudgetBytes,
      hardBudgetBytes: input.hardBudgetBytes,
      evictionPriority: input.evictionPriority,
      logoutAction: input.logoutAction,
      accountDeletionAction: input.accountDeletionAction,
      pressureAction: input.pressureAction,
      unavailableFallback: input.unavailableFallback,
    });
    assertValidStoragePolicy(snapshot);
    return snapshot;
  } catch {
    throw new TypeError("OPFS storage policy is invalid.");
  }
}

export function byteBucket(
  byteLength: number,
): NonNullable<OpfsSafeObservation["byteBucket"]> {
  if (byteLength === 0) return "0";
  if (byteLength <= 1024 * 1024) return "1B_1MiB";
  if (byteLength <= 16 * 1024 * 1024) return "1MiB_16MiB";
  if (byteLength <= 256 * 1024 * 1024) return "16MiB_256MiB";
  return "GT_256MiB";
}

export function transactionBucket(
  count: number,
): NonNullable<OpfsSafeObservation["transactionBucket"]> {
  if (count === 0) return "0";
  if (count <= 10) return "1_10";
  if (count <= 100) return "11_100";
  return "GT_100";
}

export function observeOpfsSafely(
  observer: OpfsSafeObserver | undefined,
  observation: OpfsSafeObservation,
): void {
  try {
    observer?.(Object.freeze({ ...observation }));
  } catch {
    // Persistence behavior never depends on observability.
  }
}