@tanstack/db-ivm/src/operators/orderBy.ts

Incremental View Maintenance for TanStack DB based on Differential Dataflow

import { topK, topKWithIndex } from "./topK.js"
import { topKWithFractionalIndex } from "./topKWithFractionalIndex.js"
import { map } from "./map.js"
import { innerJoin } from "./join.js"
import { consolidate } from "./consolidate.js"
import type { KeyValue } from "../types.js"
import type { IStreamBuilder } from "../types"

export interface OrderByOptions<Ve> {
  comparator?: (a: Ve, b: Ve) => number
  limit?: number
  offset?: number
}

/**
 * Orders the elements and limits the number of results, with optional offset
 * This requires a keyed stream, and uses the `topK` operator to order all the elements.
 *
 * @param valueExtractor - A function that extracts the value to order by from the element
 * @param options - An optional object containing comparator, limit and offset properties
 * @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
 * annotates the value with the index.
 * This requires a keyed stream, and uses the `topKWithIndex` operator to order all the elements.
 *
 * @param valueExtractor - A function that extracts the value to order by from the element
 * @param options - An optional object containing comparator, limit and offset properties
 * @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>,
  Ve = unknown,
>(
  topKFunction: typeof topKWithFractionalIndex,
  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, string]
    >
  > => {
    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]>
      ),
      topKFunction((a, b) => comparator(a[1], b[1]), {
        limit,
        offset,
      }),
      map(([_, [[key], index]]) => [key, index] as KeyValue<KeyType, string>),
      innerJoin(stream),
      map(([key, [index, value]]) => {
        return [key, [value, index]] as KeyValue<KeyType, [ValueType, string]>
      }),
      consolidate()
    )
  }
}

/**
 * Orders the elements and limits the number of results, with optional offset and
 * annotates the value with a fractional index.
 * This requires a keyed stream, and uses the `topKWithFractionalIndex` operator to order all the elements.
 *
 * @param valueExtractor - A function that extracts the value to order by from the element
 * @param options - An optional object containing comparator, limit and offset properties
 * @returns A piped operator that orders the elements and limits the number of results
 */
export function orderByWithFractionalIndex<
  T extends KeyValue<unknown, unknown>,
  Ve = unknown,
>(
  valueExtractor: (
    value: T extends KeyValue<unknown, infer V> ? V : never
  ) => Ve,
  options?: OrderByOptions<Ve>
) {
  return orderByWithFractionalIndexBase(
    topKWithFractionalIndex,
    valueExtractor,
    options
  )
}