/**
 * §19. Offline Command and Background Sync contract.
 *
 * The product capability is `NOT_SELECTED` (§19.1). An operation only becomes
 * queueable when the external package contribution provides `KEYED` retry
 * semantics plus a non-null recovery descriptor (§19.3); the frontend never
 * defines server idempotency or an inspect protocol of its own.
 */

export const OFFLINE_COMMAND_BOUNDS = Object.freeze({
  operations: 64,
  defaultRequestBytes: 262_144,
  hardRequestBytes: 1_048_576,
  records: 1_000,
  datasetBytes: 50 * 1024 * 1024,
  senderLeaseMs: 30_000,
  leaseRenewMs: 10_000,
  batchCount: 10,
  batchWindowMs: 30_000,
  parallelSend: 1,
  retryBaseMs: 1_000,
  retryMaxMs: 300_000,
  attemptCap: 10,
  ordinaryRetentionMs: 7 * 24 * 60 * 60 * 1_000,
  conflictRetentionMs: 30 * 24 * 60 * 60 * 1_000,
  ackedSummaryRetentionMs: 24 * 60 * 60 * 1_000,
  syncReregisterMinimumMs: 60_000,
});

/** §19.18. Background Sync is a wake-up hint only; it never sends a command. */
export const OFFLINE_SYNC_TAG = "ca-outbox-v1" as const;

export interface InstalledOfflineOperation {
  readonly operationId: string;
  readonly contractPackageId: string;
  readonly maximumRequestBytes: number;
  readonly retentionClass: "STANDARD_7D";
}

export interface InstalledOfflineCommandContribution {
  readonly datasetId: "OFFLINE_COMMANDS_V1";
  readonly operations: readonly InstalledOfflineOperation[];
}

export type OfflineCommandState =
  | "PENDING"
  | "LEASED"
  | "FOREGROUND_REQUIRED"
  | "SENDING"
  | "RETRY_WAIT"
  | "ACKED"
  | "CONFLICT"
  | "EFFECT_UNKNOWN"
  | "EXPIRED";

export interface OfflineCommandRecordV1 {
  readonly recordVersion: 1;
  readonly commandId: string;
  readonly operationId: string;
  readonly contractPackageId: string;
  readonly contractPackageVersion: string;
  readonly contractPackageDigest: `sha256:${string}`;
  readonly scopePartition: string;
  readonly requestDigest: `sha256:${string}`;
  readonly requestPayload: Uint8Array;
  readonly idempotencyKey: string;
  readonly state: OfflineCommandState;
  readonly attempt: number;
  readonly createdAt: string;
  readonly updatedAt: string;
  readonly nextAttemptAt?: string;
  readonly leaseOwner?: string;
  readonly leaseExpiresAt?: string;
  readonly terminalCode?: string;
}

/**
 * §19.10. Anything not listed is corruption. In particular an expired
 * `SENDING` record is never reset to `PENDING`: it becomes `EFFECT_UNKNOWN`.
 */
const ALLOWED_TRANSITIONS = Object.freeze({
  PENDING: Object.freeze(["LEASED", "FOREGROUND_REQUIRED", "EXPIRED"]),
  LEASED: Object.freeze(["SENDING", "PENDING"]),
  SENDING: Object.freeze([
    "ACKED",
    "RETRY_WAIT",
    "CONFLICT",
    "EFFECT_UNKNOWN",
  ]),
  RETRY_WAIT: Object.freeze(["LEASED", "FOREGROUND_REQUIRED", "EXPIRED"]),
  FOREGROUND_REQUIRED: Object.freeze(["LEASED", "EXPIRED", "PENDING"]),
  ACKED: Object.freeze([]),
  CONFLICT: Object.freeze([]),
  EFFECT_UNKNOWN: Object.freeze(["ACKED", "PENDING"]),
  EXPIRED: Object.freeze([]),
} satisfies Readonly<Record<OfflineCommandState, readonly OfflineCommandState[]>>);

export function isAllowedOfflineTransition(
  from: OfflineCommandState,
  to: OfflineCommandState,
): boolean {
  const allowed: readonly OfflineCommandState[] = ALLOWED_TRANSITIONS[from];
  return allowed.includes(to);
}

/** §19.21. Nothing sensitive reaches the UI: no payload, key, digest or partition. */
export interface OfflineCommandSummary {
  readonly commandId: string;
  readonly operationLabelKey: string;
  readonly state: OfflineCommandState;
  readonly createdAt: string;
  readonly nextAction:
    | "WAIT"
    | "OPEN_APP"
    | "CHECK_STATUS"
    | "RESOLVE_CONFLICT"
    | "CONTACT_SUPPORT"
    | "DISMISS";
}

export function validateOfflineCommandContribution(
  contribution: InstalledOfflineCommandContribution,
): InstalledOfflineCommandContribution {
  if (contribution.datasetId !== "OFFLINE_COMMANDS_V1") {
    throw new TypeError("Offline command dataset identity is invalid.");
  }
  if (
    contribution.operations.length === 0 ||
    contribution.operations.length > OFFLINE_COMMAND_BOUNDS.operations
  ) {
    throw new TypeError("Offline command operation count is out of range.");
  }
  const seen = new Set<string>();
  for (const operation of contribution.operations) {
    if (!operation.operationId || seen.has(operation.operationId)) {
      throw new TypeError("Duplicate offline command operation.");
    }
    seen.add(operation.operationId);
    if (
      !Number.isSafeInteger(operation.maximumRequestBytes) ||
      operation.maximumRequestBytes < 1 ||
      operation.maximumRequestBytes > OFFLINE_COMMAND_BOUNDS.hardRequestBytes ||
      operation.retentionClass !== "STANDARD_7D"
    ) {
      throw new TypeError(
        `Offline command operation bounds invalid: ${operation.operationId}`,
      );
    }
  }
  return Object.freeze({
    datasetId: contribution.datasetId,
    operations: Object.freeze([...contribution.operations]),
  });
}