@woosh/meep-engine/src/engine/intelligence/behavior/ecs/WaitForEventBehavior.js

Pure JavaScript game engine. Fully featured and production ready.

import { assert } from "../../../../core/assert.js";
import { BehaviorStatus } from "../BehaviorStatus.js";
import { EntityBehavior } from "./EntityBehavior.js";

/**
 * Wait for a given entity event via {@link EntityComponentDataset#addEntityEventListener}
 * No failure condition, will wait forever until the event is detected.
 * @see SendEventBehavior
 * @author Alex Goldring
 * @copyright Company Named Limited (c) 2025
 */
export class WaitForEventBehavior extends EntityBehavior {

    /**
     * Event name
     * @type {string}
     */
    event = "";

    /**
     * Has the even occurred already?
     * @type {boolean}
     */
    detected = false;

    /**
     * Entity to listen event on
     * If value is negative - will assume value of the entity to which the behavior is bound
     * @type {number}
     */
    target = -1; // TODO replace target with an EntityReference instead for tighter binding

    fromJSON({ event, target = -1 }) {
        assert.isString(event, 'event');
        assert.isInteger(target, 'target');

        this.event = event;
        this.target = target;
    }

    /**
     *
     * @param json
     * @return {WaitForEventBehavior}
     */
    static fromJSON(json) {
        const r = new WaitForEventBehavior();

        r.fromJSON(json);

        return r;
    }

    tick(timeDelta) {
        if (this.detected) {
            return BehaviorStatus.Succeeded;
        }

        return BehaviorStatus.Running;
    }

    #listener() {
        this.detected = true;

        this.ecd.removeEntityEventListener(this.target, this.event, this.#listener, this);
    }

    initialize(context) {
        super.initialize(context);

        //reset detection flag
        this.detected = false;

        if (this.target < 0) {
            this.target = this.entity;
        }

        this.ecd.addEntityEventListener(this.target, this.event, this.#listener, this);
    }

    finalize() {
        super.finalize();

        this.ecd.removeEntityEventListener(this.target, this.event, this.#listener, this);
    }
}

/**
 * @readonly
 * @type {string}
 */
WaitForEventBehavior.typeName = "WaitForEventBehavior";