import { isObject } from "./is-object"

export function pruneNullishValues<T>(input: T): PruneNullishValues<T> {
  if (Array.isArray(input)) {
    return input.filter(Boolean).map((item) => pruneNullishValues(item)) as any
  }

  if (!isObject(input)) {
    return input as any
  }

  const result: any = {}
  for (const [key, value] of Object.entries(input as any)) {
    if (value != undefined) {
      result[key] = pruneNullishValues(value)
    }
  }
  return result
}

export type PruneNullishValues<Input> = Input extends object
  ? OptionalKeys<
      { [Key in keyof Input]: NonNullable<PruneNullishValues<Input[Key]>> },
      KeysWithNullishValues<Input>
    >
  : Input

type OptionalKeys<Input, Keys extends keyof Input> = Omit<Input, Keys> & {
  [Key in Keys]?: Input[Key]
}

type KeysWithNullishValues<Input> = NonNullable<
  Values<{
    [Key in keyof Input]: null extends Input[Key]
      ? Key
      : undefined extends Input[Key]
      ? Key
      : never
  }>
>

type Values<Input> = Input[keyof Input]