Function orderBy

packages/db-ivm/src/operators/orderBy.ts:29–71

(
  valueExtractor: (
    value: T extends KeyValue<unknown, infer V> ? V : never,
  ) => Ve,
  options?: OrderByOptions<Ve>,
)

 * @returns A piped operator that orders the elements and limits the number of results
 */
export function orderBy<T extends KeyValue<unknown, unknown>, Ve = unknown>(
  valueExtractor: (
    value: T extends KeyValue<unknown, infer V> ? V : never,
  ) => Ve,
  options?: OrderByOptions<Ve>,
) {
  const limit = options?.limit ?? Infinity
  const offset = options?.offset ?? 0
  const comparator =
    options?.comparator ??
    ((a, b) => {
      // Default to JS like ordering
      if (a === b) return 0
      if (a < b) return -1
      return 1
    })

  return (stream: IStreamBuilder<T>): IStreamBuilder<T> => {
    type KeyType = T extends KeyValue<infer K, unknown> ? K : never

    return stream.pipe(
      map(
        ([key, value]) =>
          [
            null,
            [
              key,
              valueExtractor(
                value as T extends KeyValue<unknown, infer V> ? V : never,
              ),
            ],
          ] as KeyValue<null, [KeyType, Ve]>,
      ),
      topK((a, b) => comparator(a[1], b[1]), { limit, offset }),
      map(([_, [key]]) => [key, null] as KeyValue<KeyType, null>),
      innerJoin(stream),
      map(([key, value]) => {
        return [key, value[1]] as T
      }),
      consolidate(),
    )
  }
}

/**
 * Orders the elements and limits the number of results, with optional offset and