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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { mapEntries } from "./map_entries.ts";
/** * Applies the given aggregator to each group in the given Grouping, returning the results together with the respective group keys * * ```ts * import { aggregateGroups } from "https://deno.land/std@$STD_VERSION/collections/aggregate_groups.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * * const foodProperties = { *     'Curry': [ 'spicy', 'vegan' ], *     'Omelette': [ 'creamy', 'vegetarian' ], * } * const descriptions = aggregateGroups(foodProperties, *     (current, key, first, acc) => { *         if (first) *             return `${key} is ${current}` * *         return `${acc} and ${current}` *     }, * ) * * assertEquals(descriptions, { *     'Curry': 'Curry is spicy and vegan', *     'Omelette': 'Omelette is creamy and vegetarian', * }) * ``` */export function aggregateGroups<T, A>(  record: Readonly<Record<string, Array<T>>>,  aggregator: (current: T, key: string, first: boolean, accumulator?: A) => A,): Record<string, A> {  return mapEntries(    record,    ([key, values]) => [      key,      // Need the type assertions here because the reduce type does not support the type transition we need      values.reduce(        (accumulator, current, currentIndex) =>          aggregator(current, key, currentIndex === 0, accumulator),        undefined as A | undefined,      ) as A,    ],  );}