main.ts

type A = { v1: number, v2: number };

type X<K1 extends keyof any, K2 extends keyof any> = {
    [key in K1]: A | {
        [key in K2]: A
    }[]
} 

const f = <K1 extends keyof any, K2 extends keyof any>(
    obj: X<K1, K2>
): number => {
    return Object.keys(obj).reduce((acc: number, key: string) => {
        const item = obj[key];

        return (item['v1'] != undefined && item['v2'] != undefined) ?
            acc + culcA(item as A) :
                acc + f(item as any);
    }, 0);
}

const culcA = (a: A): number => a.v1 + a.v2;

const res =
    f({ a: { v1: 1, v2: 2 }, b: [{ c: { v1: 3, v2: 4 } }, { c: { v1: 5, v2: 6} }], d: { v1: 7, v2: 8 } });
console.log(res);