camelize.ts

// note: unfinished implementation, we still need to list a bunch of characters. See below

type CamelCaseImpl<S extends string, Separator extends string> =
  S extends `${infer P1}${Separator}${infer P2}${infer P3}`
    ? CamelCaseImpl<`${P1}${Uppercase<P2>}${P3}`, Separator>
  : S;

// must be nested, cannot be CamelCaseImpl<S, '-' | '_' | ' '>
//  or strings like 'first-second_third' will not parse properly.
type Camelize<S extends string> = CamelCaseImpl<CamelCaseImpl<CamelCaseImpl<Trim<S>, '-'>, '_'>, ' '>;

// according to https://tc39.es/ecma262/multipage/text-processing.html#sec-string.prototype.trim
//                <SPACE> <TAB>   <ZWNBSP>
type WhiteSpace = ' ' | '\t' | '\u2060';
// <VT>
// <FF>
// <USP>; // https://www.compart.com/en/unicode/category/Zs

//                    <LF>   <CR>
type LineTerminator = '\n' | '\r';
// <LS>
// <PS>

type Trimable = WhiteSpace | LineTerminator;

type TrimRight<T extends string> = T extends `${infer R}${Trimable}` ? TrimRight<R> : T;
type TrimLeft<T extends string> = T extends `${Trimable}${infer R}` ? TrimLeft<R> : T;
type Trim<T extends string> = TrimRight<TrimLeft<T>>;

const a = {
  test_test: {
    test_test: '',
  },
  '  first--second_third FOURTH   --  test  \t': 10,
  // patate: 10,
  // 5: 10,
  // '  test-test-test  ': 10,
  // ABC: 10,
};

type CamelizeObject<Obj extends object> = {
  [key in keyof Obj as key extends string ? Camelize<key> : key]: Obj[key]
};

type CamelizeObjectDeep<Obj extends object> = {
  [key in keyof Obj as key extends string ? Camelize<key> : key]: Obj[key] extends object
    ? CamelizeObjectDeep<Obj[key]>
    : Obj[key]
};

function camelCaseProps<In extends object>(input: In): CamelizeObjectDeep<In> {
  return input;
}

const b = camelCaseProps(a);