@byloth/micro-ecs/src/system.ts

A simple & lightweight ECS (Entity Component System) library for JavaScript and TypeScript. 🕹

import { ReferenceException, RuntimeException } from "@byloth/core";

import μObject from "./core.js";
import type World from "./world.js";

export default class System<W extends World = World> extends μObject
{
    public static Sort(a: System, b: System): number
    {
        return a.priority - b.priority;
    }

    public readonly priority: number;

    private _isEnabled: boolean;
    public get isEnabled(): boolean { return this._isEnabled; }

    private _world: W | null;
    public get world(): W | null { return this._world; }

    public constructor(priority = 0, enabled = true)
    {
        super();

        this.priority = priority;

        this._isEnabled = enabled;
        this._world = null;
    }

    public enable(): void
    {
        if (this._isEnabled) { throw new RuntimeException("The system is already enabled."); }
        this._isEnabled = true;

        this._world?.["_enableSystem"](this);
    }
    public disable(): void
    {
        if (!(this._isEnabled)) { throw new RuntimeException("The system is already disabled."); }
        this._isEnabled = false;

        this._world?.["_disableSystem"](this);
    }

    public onAttach(world: W): void
    {
        if (this._world) { throw new ReferenceException("The system is already attached to a world."); }
        this._world = world;
    }
    public onDetach(): void
    {
        if (!(this._world)) { throw new ReferenceException("The system isn't attached to any world."); }
        this._world = null;
    }

    public update(deltaTime: number): void { /* ... */ }

    public dispose(): void
    {
        if (this._world)
        {
            throw new RuntimeException("The system must be detached from the world before disposing it.");
        }
    }
}