Feature proposal: `keep` (opposite of `remove`) about json-query HOT 2 OPEN

import { beforeEach, describe, expect, it } from "bun:test";
import { get, set } from "@sagold/json-query";

// biome-ignore lint/suspicious/noExplicitAny: testing
let data: any;

beforeEach(() => {
	data = {
		a: {
			id: "a",
			needle: "needle-a",
		},
		b: {
			id: "b",
			needle: "needle-b",
			d: {
				id: "d",
				needle: "needle-d",
			},
		},
		c: {
			e: {
				f: {
					id: "f",
					needle: "needle-f",
				},
			},
		},
	};
});

describe("keep", () => {
	it("should keep any matches", () => {
		const kept = keep(data, "#/**/*/needle");

		expect(kept).toEqual({
			a: { needle: "needle-a" },
			b: { needle: "needle-b", d: { needle: "needle-d" } },
			c: { e: { f: { needle: "needle-f" } } },
		});
	});

	it("should keep any matches supporting filters", () => {
		const kept = keep(data, "#/**/*?needle:{needle-.*}");

		expect(kept).toEqual({
			a: { id: "a", needle: "needle-a" },
			b: { id: "b", needle: "needle-b", d: { id: "d", needle: "needle-d" } },
			c: { e: { f: { id: "f", needle: "needle-f" } } },
		});
	});

	it("should keep array indices", () => {
		const data = { array: [1, { keep: true }, { keep: true }, 2] };
		const result = keep(data, "#/array/*?keep:true");
		// @ts-expect-error
		expect(result.array).toHaveLength(3);
		// @ts-expect-error
		expect(result.array).toEqual([null, { keep: true }, { keep: true }]);
	});
});

function keep(data: Record<string, unknown> | unknown[], queries: string | string[]): unknown {
	if (typeof queries === "string") {
		queries = [queries];
	}

	let kept: Record<string, unknown> | unknown[] = Array.isArray(data) ? [] : {};
	for (const query of queries) {
		const ptrs: Record<string, unknown> = get(data, query, get.MAP);
		for (const ptr in ptrs) {
			kept = set(kept, ptr.substring(1), ptrs[ptr]);
		}
	}

	return kept;
}