fp-ts map map invert

MapInvert.ts

export const invert = <A,B,C>(ordA: Ord<A>, ordB:Ord<B>) => (map:Map<A,Map<B,C>>): Map<B,Map<A,C>> => {
    const arrayABC = pipe(
        map,
        M.toArray(ordA),
        Array.map(([a, mapBC]) => pipe(
            mapBC,
            M.toArray(ordB),
            Array.map(([b,c]) => [a,b,c] as const)
        )),
        Array.flatten
    )

    const monoidMapAC = M.getMonoid<A,C>(ordA, getMagmaRight());

    const mapBCA = pipe(
        arrayABC,
        Array.map(([a,b,c]) => pair(b, M.singleton(a,c))),
        M.fromFoldable(ordB, monoidMapAC, Array.array)
    )

    return mapBCA;
}