import type { DocumentNode, IntrospectionQuery } from 'graphql';
import type { Client, ClientOptions } from 'graphql-ws';
import type { SubscriptionClient } from 'subscriptions-transport-ws';

export type Observable<T> = {
  subscribe(opts: {
    next: (value: T) => void;
    error: (error: any) => void;
    complete: () => void;
  }): Unsubscribable;
  subscribe(
    next: (value: T) => void,
    error: null | undefined,
    complete: () => void,
  ): Unsubscribable;
  subscribe(
    next?: (value: T) => void,
    error?: (error: any) => void,
    complete?: () => void,
  ): Unsubscribable;
};

// These type just taken from https://github.com/ReactiveX/rxjs/blob/master/src/internal/types.ts#L41
export type Unsubscribable = {
  unsubscribe: () => void;
};

export type FetcherParams = {
  query: string;
  operationName: string;
  variables?: any;
};

export type FetcherOpts = {
  headers?: { [key: string]: any };
  shouldPersistHeaders?: boolean;
  documentAST?: DocumentNode;
};

export type FetcherResultPayload =
  | {
      data: IntrospectionQuery;
      errors?: Array<any>;
    }
  // normal result payloads
  | { data?: any; errors?: Array<any> }
  // for the initial Stream/Defer payload
  | { data?: any; errors?: Array<any>; hasNext: boolean }
  // for successive Stream/Defer payloads
  | {
      data?: any;
      errors?: any[];
      path: (string | number)[];
      hasNext: boolean;
    };

export type FetcherResult = FetcherResultPayload | string;

export type MaybePromise<T> = T | Promise<T>;

export type SyncFetcherResult =
  | FetcherResult
  | Observable<FetcherResult>
  | AsyncIterable<FetcherResult>;

export type FetcherReturnType = MaybePromise<SyncFetcherResult>;

export type Fetcher = (
  graphQLParams: FetcherParams,
  opts?: FetcherOpts,
) => FetcherReturnType;

export type WebsocketsClient = Client | SubscriptionClient;

/**
 * Options for creating a simple, spec-compliant GraphiQL fetcher
 */
export interface CreateFetcherOptions {
  /**
   * url for HTTP(S) requests. required!
   */
  url: string;
  /**
   * url for websocket subscription requests
   */
  subscriptionUrl?: string;
  /**
   * `wsClient` implementation that matches `ws-graphql` signature,
   * whether via `createClient()` itself or another client.
   */
  wsClient?: Client;
  /**
   * `legacyClient` implementation that matches `subscriptions-transport-ws` signature,
   * whether via `new SubcriptionsClient()` itself or another client with a similar signature.
   */
  legacyClient?: SubscriptionClient;
  /**
   * Headers you can provide statically.
   *
   * If you enable the headers editor and the user provides
   * A header you set statically here, it will be overriden by their value.
   */
  headers?: Record<string, string>;
  /**
   * Websockets connection params used when you provide subscriptionUrl. graphql-ws `ClientOptions.connectionParams`
   */
  wsConnectionParams?: ClientOptions['connectionParams'];
  /**
   * You can disable the usage of the `fetch-multipart-graphql` library
   * entirely, defaulting to a simple fetch POST implementation.
   */
  enableIncrementalDelivery?: boolean;
  /**
   * The fetch implementation, in case the user needs to override this for SSR
   * or other purposes. this does not override the `fetch-multipart-graphql`
   * default fetch behavior yet.
   */
  fetch?: typeof fetch;
  /**
   * An optional custom fetcher specifically for your schema. For most cases
   * the `url` and `headers` property should have you covered.
   */
  schemaFetcher?: Fetcher;
}