export declare namespace Effectify {
  interface Callback<E, A> {
    (err: E, a?: A): void
  }

  type ArgsWithCallback<Args extends Array<any>, E, A> = [...args: Args, cb: Callback<E, A>]

  type WithoutNull<A> = unknown extends A ? void : Exclude<A, null | undefined>

  /**
   * Converts a callback-based function type into an `Effect`-returning function type.
   *
   * @category effectify
   * @since 4.0.0
   */
  export type Effectify<T, E> = T extends {
    (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
    (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
    (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
    (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
    (...args: ArgsWithCallback<infer Args5, infer _E5, infer A5>): infer _R5
    (...args: ArgsWithCallback<infer Args6, infer _E6, infer A6>): infer _R6
    (...args: ArgsWithCallback<infer Args7, infer _E7, infer A7>): infer _R7
    (...args: ArgsWithCallback<infer Args8, infer _E8, infer A8>): infer _R8
    (...args: ArgsWithCallback<infer Args9, infer _E9, infer A9>): infer _R9
    (...args: ArgsWithCallback<infer Args10, infer _E10, infer A10>): infer _R10
  } ? {
      (...args: Args1): Effect<WithoutNull<A1>, E>
      (...args: Args2): Effect<WithoutNull<A2>, E>
      (...args: Args3): Effect<WithoutNull<A3>, E>
      (...args: Args4): Effect<WithoutNull<A4>, E>
      (...args: Args5): Effect<WithoutNull<A5>, E>
      (...args: Args6): Effect<WithoutNull<A6>, E>
      (...args: Args7): Effect<WithoutNull<A7>, E>
      (...args: Args8): Effect<WithoutNull<A8>, E>
      (...args: Args9): Effect<WithoutNull<A9>, E>
      (...args: Args10): Effect<WithoutNull<A10>, E>
    }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
      (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
      (...args: ArgsWithCallback<infer Args5, infer _E5, infer A5>): infer _R5
      (...args: ArgsWithCallback<infer Args6, infer _E6, infer A6>): infer _R6
      (...args: ArgsWithCallback<infer Args7, infer _E7, infer A7>): infer _R7
      (...args: ArgsWithCallback<infer Args8, infer _E8, infer A8>): infer _R8
      (...args: ArgsWithCallback<infer Args9, infer _E9, infer A9>): infer _R9
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
        (...args: Args4): Effect<WithoutNull<A4>, E>
        (...args: Args5): Effect<WithoutNull<A5>, E>
        (...args: Args6): Effect<WithoutNull<A6>, E>
        (...args: Args7): Effect<WithoutNull<A7>, E>
        (...args: Args8): Effect<WithoutNull<A8>, E>
        (...args: Args9): Effect<WithoutNull<A9>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
      (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
      (...args: ArgsWithCallback<infer Args5, infer _E5, infer A5>): infer _R5
      (...args: ArgsWithCallback<infer Args6, infer _E6, infer A6>): infer _R6
      (...args: ArgsWithCallback<infer Args7, infer _E7, infer A7>): infer _R7
      (...args: ArgsWithCallback<infer Args8, infer _E8, infer A8>): infer _R8
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
        (...args: Args4): Effect<WithoutNull<A4>, E>
        (...args: Args5): Effect<WithoutNull<A5>, E>
        (...args: Args6): Effect<WithoutNull<A6>, E>
        (...args: Args7): Effect<WithoutNull<A7>, E>
        (...args: Args8): Effect<WithoutNull<A8>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
      (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
      (...args: ArgsWithCallback<infer Args5, infer _E5, infer A5>): infer _R5
      (...args: ArgsWithCallback<infer Args6, infer _E6, infer A6>): infer _R6
      (...args: ArgsWithCallback<infer Args7, infer _E7, infer A7>): infer _R7
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
        (...args: Args4): Effect<WithoutNull<A4>, E>
        (...args: Args5): Effect<WithoutNull<A5>, E>
        (...args: Args6): Effect<WithoutNull<A6>, E>
        (...args: Args7): Effect<WithoutNull<A7>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
      (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
      (...args: ArgsWithCallback<infer Args5, infer _E5, infer A5>): infer _R5
      (...args: ArgsWithCallback<infer Args6, infer _E6, infer A6>): infer _R6
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
        (...args: Args4): Effect<WithoutNull<A4>, E>
        (...args: Args5): Effect<WithoutNull<A5>, E>
        (...args: Args6): Effect<WithoutNull<A6>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
      (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
      (...args: ArgsWithCallback<infer Args5, infer _E5, infer A5>): infer _R5
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
        (...args: Args4): Effect<WithoutNull<A4>, E>
        (...args: Args5): Effect<WithoutNull<A5>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
      (...args: ArgsWithCallback<infer Args4, infer _E4, infer A4>): infer _R4
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
        (...args: Args4): Effect<WithoutNull<A4>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
      (...args: ArgsWithCallback<infer Args3, infer _E3, infer A3>): infer _R3
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
        (...args: Args3): Effect<WithoutNull<A3>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
      (...args: ArgsWithCallback<infer Args2, infer _E2, infer A2>): infer _R2
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
        (...args: Args2): Effect<WithoutNull<A2>, E>
      }
    : T extends {
      (...args: ArgsWithCallback<infer Args1, infer _E1, infer A1>): infer _R1
    } ? {
        (...args: Args1): Effect<WithoutNull<A1>, E>
      }
    : never

  /**
   * Extracts the callback error type from a callback-based function type.
   *
   * @category effectify
   * @since 4.0.0
   */
  export type EffectifyError<T> = T extends {
    (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
    (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
    (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
    (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
    (...args: ArgsWithCallback<infer _Args5, infer E5, infer _A5>): infer _R5
    (...args: ArgsWithCallback<infer _Args6, infer E6, infer _A6>): infer _R6
    (...args: ArgsWithCallback<infer _Args7, infer E7, infer _A7>): infer _R7
    (...args: ArgsWithCallback<infer _Args8, infer E8, infer _A8>): infer _R8
    (...args: ArgsWithCallback<infer _Args9, infer E9, infer _A9>): infer _R9
    (...args: ArgsWithCallback<infer _Args10, infer E10, infer _A10>): infer _R10
  } ? NonNullable<E1 | E2 | E3 | E4 | E5 | E6 | E7 | E8 | E9 | E10>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
      (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
      (...args: ArgsWithCallback<infer _Args5, infer E5, infer _A5>): infer _R5
      (...args: ArgsWithCallback<infer _Args6, infer E6, infer _A6>): infer _R6
      (...args: ArgsWithCallback<infer _Args7, infer E7, infer _A7>): infer _R7
      (...args: ArgsWithCallback<infer _Args8, infer E8, infer _A8>): infer _R8
      (...args: ArgsWithCallback<infer _Args9, infer E9, infer _A9>): infer _R9
    } ? NonNullable<E1 | E2 | E3 | E4 | E5 | E6 | E7 | E8 | E9>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
      (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
      (...args: ArgsWithCallback<infer _Args5, infer E5, infer _A5>): infer _R5
      (...args: ArgsWithCallback<infer _Args6, infer E6, infer _A6>): infer _R6
      (...args: ArgsWithCallback<infer _Args7, infer E7, infer _A7>): infer _R7
      (...args: ArgsWithCallback<infer _Args8, infer E8, infer _A8>): infer _R8
    } ? NonNullable<E1 | E2 | E3 | E4 | E5 | E6 | E7 | E8>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
      (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
      (...args: ArgsWithCallback<infer _Args5, infer E5, infer _A5>): infer _R5
      (...args: ArgsWithCallback<infer _Args6, infer E6, infer _A6>): infer _R6
      (...args: ArgsWithCallback<infer _Args7, infer E7, infer _A7>): infer _R7
    } ? NonNullable<E1 | E2 | E3 | E4 | E5 | E6 | E7>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
      (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
      (...args: ArgsWithCallback<infer _Args5, infer E5, infer _A5>): infer _R5
      (...args: ArgsWithCallback<infer _Args6, infer E6, infer _A6>): infer _R6
    } ? NonNullable<E1 | E2 | E3 | E4 | E5 | E6>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
      (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
      (...args: ArgsWithCallback<infer _Args5, infer E5, infer _A5>): infer _R5
    } ? NonNullable<E1 | E2 | E3 | E4 | E5>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
      (...args: ArgsWithCallback<infer _Args4, infer E4, infer _A4>): infer _R4
    } ? NonNullable<E1 | E2 | E3 | E4>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
      (...args: ArgsWithCallback<infer _Args3, infer E3, infer _A3>): infer _R3
    } ? NonNullable<E1 | E2 | E3>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
      (...args: ArgsWithCallback<infer _Args2, infer E2, infer _A2>): infer _R2
    } ? NonNullable<E1 | E2>
    : T extends {
      (...args: ArgsWithCallback<infer _Args1, infer E1, infer _A1>): infer _R1
    } ? NonNullable<E1>
    : never
}