Moved to https://github.com/znck/promised | A utility to convert callbacks to promises.

promised.ts

import {promisify, CustomPromisify} from 'util'

export type FunctionProxy<T extends Function> = CustomPromisify<T>

export type PackageProxy<P extends { [key: string]: Function }> = {
  [K in keyof P]: FunctionProxy<P[K]>
}

export function promised<T extends { [key: string]: Function | any }>(target: T): PackageProxy<T> {
  return new Proxy(target, {
    get(target: T, key: string): any {
      const value: any = target[key]

      if (typeof value === 'function') {
        return promisedFunction(value)
      }

      return value
    }
  })
}

function promisedFunction<T extends Function>(fn: T): CustomPromisify<T> | T {
  return new Proxy(fn, {
    apply(target, _this, args) {
      if (target.length > args.length) {
        return promisify(fn).apply(_this, args)
      }

      return fn.apply(_this, args)
    }
  })
}