discordeno/packages/utils/src/casing.ts

import type { Camelize, Snakelize } from '@discordeno/types';

export function camelize<T>(object: T): Camelize<T> {
  if (Array.isArray(object)) {
    return object.map((element) => camelize(element)) as Camelize<T>;
  }

  if (typeof object === 'object' && object !== null) {
    const obj = {} as Camelize<T>;
    (Object.keys(object) as Array<keyof T>).forEach((key) => {
      // @ts-expect-error js hack
      (obj[snakeToCamelCase(key)] as Camelize<(T & object)[keyof T]>) = camelize(object[key]);
    });
    return obj;
  }
  return object as Camelize<T>;
}

export function snakelize<T>(object: T): Snakelize<T> {
  if (Array.isArray(object)) {
    return object.map((element) => snakelize(element)) as Snakelize<T>;
  }

  if (typeof object === 'object' && object !== null) {
    const obj = {} as Snakelize<T>;
    (Object.keys(object) as Array<keyof T>).forEach((key) => {
      // @ts-expect-error js hack
      (obj[camelToSnakeCase(key)] as Snakelize<(T & object)[keyof T]>) = snakelize(object[key]);
    });
    return obj;
  }
  return object as Snakelize<T>;
}

export function snakeToCamelCase(str: string): string {
  if (!str.includes('_')) return str;

  let result = '';
  for (let i = 0, len = str.length; i < len; ++i) {
    if (str[i] === '_') {
      result += str[++i].toUpperCase();

      continue;
    }

    result += str[i];
  }

  return result;
}

export function camelToSnakeCase(str: string): string {
  let result = '';
  for (let i = 0, len = str.length; i < len; ++i) {
    if (str[i] >= 'A' && str[i] <= 'Z') {
      result += `_${str[i].toLowerCase()}`;

      continue;
    }

    result += str[i];
  }

  return result;
}