651 - Length of String 2

[so11y]

type GetHaveString<A, B> = A extends "" ? B : A;
type Build<
  T extends number,
  Result extends Array<never> = []
> = Result["length"] extends T ? Result : Build<T, [...Result, never]>;

type Add<A extends number, B extends number> = [
  ...Build<A>,
  ...Build<B>
]["length"];
type stringToNumber<T> = `${T & string}` extends `${infer A extends number}`
  ? A
  : never;
type Add2<A extends number, B extends number> = `${Add<A, B> &
  number}` extends `1${infer G extends number}`
  ? {
      overflow: 1;
      value: G;
    }
  : {
      overflow: 0;
      value: Add<A, B>;
    };
type Reverse<T extends string | number | bigint> =
  `${T}` extends `${infer A}${infer B}` ? `${Reverse<B>}${A}` : T;

type GetSLast1<T extends string | number | bigint> =
  `${T}` extends `${infer A}${infer B}` ? stringToNumber<A> : "";

type GetSLast<
  T extends string | number | bigint,
  B extends string | number | bigint
> = [GetSLast1<T>, GetSLast1<B>];
type GetSOther<T extends string | number | bigint> =
  `${T}` extends `${infer A}${infer B}` ? B : "";
type Sum1<
  A extends string | number | bigint,
  B extends string | number | bigint,
  Overflow extends number = 0,
  Result extends string = ""
> = [""] extends [A | B]
  ? [A, B] extends ["", ""]
    ? `${Result}${Overflow extends 0 ? "" : Overflow}`
    : GetHaveString<A, B> extends `${infer Z}`
    ? Z extends ""
      ? Result
      : Sum1<Z, Overflow, 0, Result>
    : never
  : GetSLast<A, B> extends [infer A1 extends number, infer B1 extends number]
  ? Add2<Add<A1, Overflow> & number, B1> extends {
      overflow: infer O extends number;
      value: infer V;
    }
    ? Sum1<GetSOther<A>, GetSOther<B>, O, `${Result}${V & number}`>
    : never
  : Result;

type Sum<
  A extends string | number | bigint,
  B extends string | number | bigint
> = Reverse<Sum1<Reverse<A>, Reverse<B>>>;
type parseNum<T> = T extends `${infer C extends number}` ? C : never;

type LengthOfString<
  S extends string,
  V extends number = 0
> = S extends `${infer A}${infer B}`
  ? LengthOfString<B, parseNum<Sum<V, 1>>>
  : V;