import { ISignal, Signal } from '@lumino/signaling';

import type { IAgent } from './agents';
import type { IAgentRegistry } from './tokens';

/**
 * The concrete {@link IAgentRegistry} the launcher plugin provides on the
 * `IAgentRegistry` token. Holds the active agent list and re-emits `changed`
 * whenever the launcher recomputes it (on a settings change). The launcher
 * is the only writer, so the write side ({@link setAgents}) is kept off the
 * shared token.
 */
export class AgentRegistry implements IAgentRegistry {
  get agents(): IAgent[] {
    return this._agents;
  }

  get changed(): ISignal<IAgentRegistry, void> {
    return this._changed;
  }

  /**
   * Replace the agent list and notify observers. Called by the launcher
   * after merging the user's settings and filtering by availability.
   */
  setAgents(agents: IAgent[]): void {
    this._agents = agents;
    this._changed.emit();
  }

  private _agents: IAgent[] = [];
  private _changed = new Signal<IAgentRegistry, void>(this);
}