import { Observable } from "rxjs";
import { useObservableInternal } from "./internal/use-observable-internal";
import { useEffect } from "react";

/**
 * Accepts a function that returns an Observable.
 * Optionally accepts an array of dependencies which
 * will be turned into Observable and be passed to the
 * `init` function.
 *
 * React functional components are called many times during their lifecycle.
 * Create or transform Observables in `init` function so that the operations
 * won't be repeatedly performed.
 *
 * ⚠ **Note:** `useObservable` will call `init` once and always return
 * the same Observable. It is not safe to access closure (except other Observables)
 * directly inside `init`.
 * You should use ref or pass them as dependencies through the second argument.
 *
 * ⚠ **Note:** Due to rules of hooks you can either offer or omit the
 * dependencies array but do not change to one another during Component's life cycle.
 * The length of the dependencies array must also be fixed.
 *
 * @template TOutput Output value in Observable
 *
 * @param init A pure function that, when applied to an Observable,
 * returns an Observable.
 */
export function useObservable<
  TOutput,
  TObservable extends Observable<TOutput> = Observable<TOutput>
>(init: () => TObservable): TObservable;
/**
 * @template TOutput Output value within Observable.
 * @template TInputs A readonly tuple of all dependencies.
 *
 * @param init A pure function that, when applied to an Observable,
 * returns an Observable.
 * @param inputs An dependency array with fixed length. When one of the dependencies
 * changes the Observable in `init` will emit an array of all the dependencies.
 */
export function useObservable<
  TOutput,
  TInputs extends Readonly<any[]>,
  TObservable extends Observable<TOutput> = Observable<TOutput>
>(
  init: (inputs$: Observable<[...TInputs]>) => TObservable,
  inputs: [...TInputs]
): TObservable;
export function useObservable<TOutput, TInputs extends Readonly<any[]>>(
  init:
    | (() => Observable<TOutput>)
    | ((inputs$: Observable<[...TInputs]>) => Observable<TOutput>),
  inputs?: [...TInputs]
): Observable<TOutput> {
  return useObservableInternal(useEffect, init, inputs);
}