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import type {JSONValue} from './json';import type {ReadTransaction} from './transactions';import * as db from './db/mod';import type * as sync from './sync/mod';
export type ScanSubscriptionInfo = {  options: db.ScanOptions;  inclusiveLimitKey?: string;};
export type Subscription<R extends JSONValue | undefined, E> = {  body: (tx: ReadTransaction) => Promise<R>;  onData: (r: R) => void;  onError?: (e: E) => void;  onDone?: () => void;  lastValue?: R;  keys: ReadonlySet<string>;  scans: ReadonlyArray<Readonly<ScanSubscriptionInfo>>;};
function keyMatchesSubscription<V, E>(  subscription: Subscription<V, E>,  indexName: string,  changedKey: string,) {  // subscription.keys contains the primary index keys. If we are passing in an  // indexName there was a change to the index map, in which case the changedKey  // is an encoded index key. We could skip checking the indexName here since  // the set would never contain encoded index keys but we do the check for  // clarity.  if (indexName === '' && subscription.keys.has(changedKey)) {    return true;  }
  for (const scanInfo of subscription.scans) {    if (scanInfoMatchesKey(scanInfo, indexName, changedKey)) {      return true;    }  }
  return false;}
export function scanInfoMatchesKey(  scanInfo: ScanSubscriptionInfo,  changeIndexName: string,  changedKey: string,): boolean {  const {indexName, prefix, startKey, startExclusive, startSecondaryKey} =    scanInfo.options;
  if (!indexName) {    if (changeIndexName) {      return false;    }
    // A scan with limit <= 0 can have no matches    if (scanInfo.options.limit !== undefined && scanInfo.options.limit <= 0) {      return false;    }
    // No prefix and no start. Must recompute the subscription because all keys    // will have an effect on the subscription.    if (!prefix && !startKey) {      return true;    }
    if (      prefix &&      (!changedKey.startsWith(prefix) ||        isKeyPastInclusiveLimit(scanInfo, changedKey))    ) {      return false;    }
    if (      startKey &&      ((startExclusive && changedKey <= startKey) ||        changedKey < startKey ||        isKeyPastInclusiveLimit(scanInfo, changedKey))    ) {      return false;    }
    return true;  }
  if (changeIndexName !== indexName) {    return false;  }
  // No prefix and no start. Must recompute the subscription because all keys  // will have an effect on the subscription.  if (!prefix && !startKey && !startSecondaryKey) {    return true;  }
  const [changedKeySecondary, changedKeyPrimary] =    db.decodeIndexKey(changedKey);
  if (prefix) {    if (!changedKeySecondary.startsWith(prefix)) {      return false;    }  }
  if (    startSecondaryKey &&    ((startExclusive && changedKeySecondary <= startSecondaryKey) ||      changedKeySecondary < startSecondaryKey)  ) {    return false;  }
  if (    startKey &&    ((startExclusive && changedKeyPrimary <= startKey) ||      changedKeyPrimary < startKey)  ) {    return false;  }
  return true;}
function isKeyPastInclusiveLimit(  scanInfo: ScanSubscriptionInfo,  changedKey: string,): boolean {  const {inclusiveLimitKey} = scanInfo;  return (    scanInfo.options.limit !== undefined &&    inclusiveLimitKey !== undefined &&    changedKey > inclusiveLimitKey  );}
export function* subscriptionsForChangedKeys<V, E>(  subscriptions: Set<Subscription<V, E>>,  changedKeysMap: sync.ChangedKeysMap,): Generator<Subscription<V, E>> {  outer: for (const subscription of subscriptions) {    for (const [indexName, changedKeys] of changedKeysMap) {      for (const key of changedKeys) {        if (keyMatchesSubscription(subscription, indexName, key)) {          yield subscription;          continue outer;        }      }    }  }}
export function* subscriptionsForIndexDefinitionChanged<V, E>(  subscriptions: Set<Subscription<V, E>>,  name: string,): Generator<Subscription<V, E>> {  for (const subscription of subscriptions) {    if (      subscription.scans.some(scanInfo => scanInfo.options.indexName === name)    ) {      yield subscription;    }  }}