Function orderByWithIndex

packages/db-ivm/src/operators/orderBy.ts:82–135

(
  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 orderByWithIndex<
  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<
    KeyValue<
      T extends KeyValue<infer K, unknown> ? K : never,
      [T extends KeyValue<unknown, infer V> ? V : never, number]
    >
  > => {
    type KeyType = T extends KeyValue<infer K, unknown> ? K : never
    type ValueType = T extends KeyValue<unknown, infer V> ? V : 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]>,
      ),
      topKWithIndex((a, b) => comparator(a[1], b[1]), { limit, offset }),
      map(([_, [[key], index]]) => [key, index] as KeyValue<KeyType, number>),
      innerJoin(stream),
      map(([key, [index, value]]) => {
        return [key, [value, index]] as KeyValue<KeyType, [ValueType, number]>
      }),
      consolidate(),
    )
  }
}

export function orderByWithFractionalIndexBase<
  T extends KeyValue<unknown, unknown>,