import type { WorkflowInfo } from './interfaces';

export type SdkFlag = {
  get id(): number;
  get default(): boolean;
  get alternativeConditions(): AltConditionFn[] | undefined;
};

const flagsRegistry: Map<number, SdkFlag> = new Map();

export const SdkFlags = {
  /**
   * This flag gates multiple fixes related to cancellation scopes and timers introduced in 1.10.2/1.11.0:
   * - Cancellation of a non-cancellable scope no longer propagates to children scopes
   *   (see https://github.com/temporalio/sdk-typescript/issues/1423).
   * - CancellationScope.withTimeout(fn) now cancel the timer if `fn` completes before expiration
   *   of the timeout, similar to how `condition(fn, timeout)` works.
   * - Timers created using setTimeout can now be intercepted.
   *
   * @since Introduced in 1.10.2/1.11.0. However, due to an SDK bug, SDKs v1.11.0 and v1.11.1 were not
   *        properly writing back the flags to history, possibly resulting in NDE on replay. We therefore
   *        consider that a WFT emitted by Worker v1.11.0 or v1.11.1 to implicitly have this flag on.
   */
  NonCancellableScopesAreShieldedFromPropagation: defineFlag(1, true, [buildIdSdkVersionMatches(/1\.11\.[01]/)]),

  /**
   * Prior to 1.11.0, when processing a Workflow activation, the SDK would execute `notifyHasPatch`
   * and `signalWorkflow` jobs in distinct phases, before other types of jobs. The primary reason
   * behind that multi-phase algorithm was to avoid the possibility that a Workflow execution might
   * complete before all incoming signals have been dispatched (at least to the point that the
   * _synchronous_ part of the handler function has been executed).
   *
   * This flag replaces that multi-phase algorithm with a simpler one where jobs are simply sorted as
   * `(signals and updates) -> others`, but without processing them as distinct batches (i.e. without
   * leaving/reentering the VM context between each group, which automatically triggers the execution
   * of all outstanding microtasks). That single-phase approach resolves a number of quirks of the
   * former algorithm, and yet still satisfies to the original requirement of ensuring that every
   * `signalWorkflow` jobs - and now `doUpdate` jobs as well - have been given a proper chance to
   * execute before the Workflow main function might completes.
   *
   * @since Introduced in 1.11.0. This change is not rollback-safe. However, due to an SDK bug, SDKs
   *        v1.11.0 and v1.11.1 were not properly writing back the flags to history, possibly resulting
   *        in NDE on replay. We therefore consider that a WFT emitted by Worker v1.11.0 or v1.11.1
   *        to implicitely have this flag on.
   */
  ProcessWorkflowActivationJobsAsSingleBatch: defineFlag(2, true, [buildIdSdkVersionMatches(/1\.11\.[01]/)]),
} as const;

function defineFlag(id: number, def: boolean, alternativeConditions?: AltConditionFn[]): SdkFlag {
  const flag = { id, default: def, alternativeConditions };
  flagsRegistry.set(id, flag);
  return flag;
}

export function assertValidFlag(id: number): void {
  if (!flagsRegistry.has(id)) throw new TypeError(`Unknown SDK flag: ${id}`);
}

/**
 * An SDK Flag Alternate Condition provides an alternative way of determining whether a flag
 * should be considered as enabled for the current WFT; e.g. by looking at the version of the SDK
 * that emitted a WFT. The main use case for this is to retroactively turn on some flags for WFT
 * emitted by previous SDKs that contained a bug.
 *
 * Note that conditions are only evaluated while replaying, and only if the corresponing flag is
 * not already set. Also, alternate conditions will not cause the flag to be persisted to the
 * "used flags" set, which means that further Workflow Tasks may not reflect this flag if the
 * condition no longer holds. This is so to avoid incorrect behaviors in case where a Workflow
 * Execution has gone through a newer SDK version then again through an older one.
 */
type AltConditionFn = (ctx: { info: WorkflowInfo }) => boolean;

function buildIdSdkVersionMatches(version: RegExp): AltConditionFn {
  const regex = new RegExp(`^@temporalio/worker@(${version.source})[+]`);
  return ({ info }) => info.currentBuildId != null && regex.test(info.currentBuildId);
}