Creating t.or()

import { TCustomType, customType } from "encodexx";

// Extract the type from TCustomType. For example, TCustomType<number | string> -> number | string
type ExtractCustomType<T extends TCustomType> = T extends TCustomType<infer R> ? R : never;

export function myOr<T extends TCustomType[]>(...types: T) {
  if (types.length > 255) throw new Error("Too many types provided: Maximum allowed is 255");

  return customType<ExtractCustomType<T[number]>>({
    decode(buff) {
      // Read the tag and use it to determine the type
      const index = buff.readUint8();
      return types[index].decode(buff);
    },
    encode(val, buffer) {
      // Find the corresponding type among the provided types
      const typeIndex = types.findIndex((el) => el.guard(val));
      if (typeIndex === -1) throw new Error("No matching type found among the provided types");

      buffer.writeUint8(typeIndex);
      types[typeIndex].encode(buffer, val);
    },
    guard(data): data is ExtractCustomType<T[number]> {
      // t.or applies if at least one of the provided types matches
      return types.some((el) => el.guard(data));
    },
    name: `Or<${types.map((el) => el.name).join("|")}>`,
  });
}