import { differenceBy as differenceBy$1 } from "../../array/differenceBy.mjs";
import { combineEagerAndLazyFunctions, createLazyFunction } from "../_internal/lazy.mjs";
//#region src/fp/array/differenceBy.ts
/**
* Creates a function that returns values whose mapped identity is absent from another array.
*
* The mapper is applied to values from both arrays. The returned function is
* lazy-capable inside {@link pipe}.
*
* @template T - The type of elements in the piped array.
* @template U - The type of elements in the configured array.
* @param secondArray - Values to exclude from the piped array after mapping.
* @param mapper - Maps values from both arrays to comparison keys.
* @returns A function that maps the piped array to its mapped difference.
*
* @example
* import { differenceBy, pipe } from 'es-toolkit/fp';
*
* pipe([{ id: 1 }, { id: 2 }], differenceBy([2], value => typeof value === 'number' ? value : value.id));
* // => [{ id: 1 }]
*/
function differenceBy(secondArray, mapper) {
	const mappedSecondSet = new Set(secondArray.map((item) => mapper(item)));
	function differenceByEager(array) {
		return differenceBy$1(array, secondArray, mapper);
	}
	return combineEagerAndLazyFunctions(differenceByEager, createLazyFunction((value, _index, emit) => {
		if (!mappedSecondSet.has(mapper(value))) emit(value);
	}));
}
//#endregion
export { differenceBy };
