/*
 * Adapted from @graphql-yoga/subscription
 * Original source: https://github.com/graphql-hive/graphql-yoga
 * License: MIT
 * 
 * Copyright (c) 2024 The Guild, GraphQL Yoga Contributors
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

import { Repeater } from "./repeater.js";
import type { TypedEventTarget, TypedEvent, EventEnvelope } from "./types.js";

export type PubSubEventMap = {
  [eventType: string]: unknown;
};

export type PubSubEvent<
  TEventMap extends PubSubEventMap,
  TType extends Extract<keyof TEventMap, string> = Extract<keyof TEventMap, string>,
> = TypedEvent<TType, EventEnvelope<TType, TEventMap[TType]>>;

export type PubSubEventTarget<TEventMap extends PubSubEventMap> =
  TypedEventTarget<
    PubSubEvent<TEventMap>
  >;

export type PubSubConfig<TEventMap extends PubSubEventMap> = {
  eventTarget?: PubSubEventTarget<TEventMap>;
};

export type PubSub<TEventMap extends PubSubEventMap> = {
  publish<TType extends Extract<keyof TEventMap, string>>(
    type: TType,
    id: string,
    payload: TEventMap[TType],
  ): void;
  subscribe<TType extends Extract<keyof TEventMap, string>>(
    type: TType,
    id: string,
  ): Repeater<EventEnvelope<TType, TEventMap[TType]>>;
};

export function createPubSub<TEventMap extends PubSubEventMap>(
  config?: PubSubConfig<TEventMap>,
): PubSub<TEventMap> {
  const target =
    config?.eventTarget ?? (new EventTarget() as PubSubEventTarget<TEventMap>);

  return {
    publish<TType extends Extract<keyof TEventMap, string>>(
      type: TType,
      id: string,
      payload: TEventMap[TType],
    ) {
      if (type.startsWith("__")) {
        throw new Error(
          `Event types starting with "__" are reserved for adapter control messages. Received: "${type}"`,
        );
      }
      const envelope: EventEnvelope<TType, TEventMap[TType]> = { type, id, payload };
      const topic = `${type}:${id}`;
      const event = new CustomEvent(topic, { detail: envelope }) as PubSubEvent<
        TEventMap,
        TType
      >;
      target.dispatchEvent(event);
    },
    subscribe<TType extends Extract<keyof TEventMap, string>>(
      type: TType,
      id: string,
    ): Repeater<EventEnvelope<TType, TEventMap[TType]>> {
      const topic = `${type}:${id}`;

      return new Repeater(function subscriptionRepeater(
        next: (value: unknown) => Promise<void>,
        stop: Promise<void>,
      ) {
        function pubsubEventListener(event: CustomEvent) {
          next(event.detail);
        }

        stop.then(function subscriptionRepeaterStopHandler() {
          target.removeEventListener(topic as TType, pubsubEventListener as EventListener);
        });

        target.addEventListener(topic as TType, pubsubEventListener as EventListener, undefined);
      }) as Repeater<EventEnvelope<TType, TEventMap[TType]>>;
    },
  };
}