import { Collab, CollabEventsRecord, InitToken } from "./collab";
import { CollabID } from "./collab_id";
import { EventEmitter, EventsRecord } from "./event_emitter";
import { IRuntime } from "./iruntime";
import { Parent } from "./parent";
import { MetaRequest } from "./updates";

/**
 * Skeletal implementation of [[IRuntime]] that uses
 * a root [[Collab]].
 */
export abstract class AbstractRuntime<Events extends EventsRecord>
  extends EventEmitter<Events>
  implements IRuntime
{
  readonly isRuntime: true = true;
  /**
   * A unique ID for this
   * [replica](https://collabs.readthedocs.io/en/latest/advanced/updates.html#terminology)
   * (copy of a Collabs document).
   */
  readonly replicaID: string;
  protected rootCollab!: Collab & Parent;

  /**
   * @param replicaID This replica's `replicaID`, usually
   * obtained from [[ReplicaIDs]]. Must not be `""`.
   */
  constructor(replicaID: string) {
    super();

    if (replicaID === "") {
      throw new Error('replicaID must not be ""');
    }
    this.replicaID = replicaID;
  }

  protected setRootCollab<C extends Collab & Parent>(
    rootCallback: (init: InitToken) => C
  ): C {
    const rootCollab = rootCallback(new InitToken("", this));
    this.rootCollab = rootCollab;
    return rootCollab;
  }

  idOf<C extends Collab<CollabEventsRecord>>(collab: C): CollabID<C> {
    if (collab.runtime !== this) {
      throw new Error("idOf called with Collab from different Runtime");
    }
    return this.rootCollab.idOf(collab);
  }

  fromID<C extends Collab<CollabEventsRecord>>(id: CollabID<C>): C | undefined {
    return this.rootCollab.fromID(id);
  }

  abstract childSend(
    child: Collab<CollabEventsRecord>,
    messageStack: (Uint8Array | string)[],
    metaRequests: MetaRequest[]
  ): void;
}