silphius/app/ecs/system.js

import Query from './query.js';

export default class System {

  destroying = [];

  ecs;

  queries = {};

  constructor(ecs) {
    this.ecs = ecs;
    const queries = this.constructor.queries();
    for (const i in queries) {
      this.queries[i] = new Query(queries[i], ecs.Types);
    }
  }

  deindex(entities) {
    for (const i in this.queries) {
      this.queries[i].deindex(entities);
    }
  }

  destroyEntity(entity) {
    this.destroyManyEntities([entity]);
  }

  destroyManyEntities(entities) {
    for (let i = 0; i < entities.length; i++) {
      this.destroying.push(entities[i]);
    }
  }

  finalize() {}

  static normalize(SystemLike) {
    if (SystemLike.prototype instanceof System) {
      return SystemLike;
    }
    if ('function' === typeof SystemLike) {
      class TickingSystem extends System {}
      TickingSystem.prototype.tick = SystemLike;
      return TickingSystem;
    }
    /* v8 ignore next */
    throw new TypeError(`Couldn't normalize '${SystemLike}' as a system`);
  }

  static queries() {
    return {};
  }

  reindex(entities) {
    for (const i in this.queries) {
      this.queries[i].reindex(entities);
    }
  }

  select(query) {
    return this.queries[query].select();
  }

  tickDestruction() {
    this.deindex(this.destroying);
    this.destroying = [];
  }

  tick() {}

  static wrap(source, ecs) {
    class WrappedSystem extends System.normalize(source) {

      constructor() {
        super(ecs);
        this.reindex(ecs.entities);
      }

      createEntity(components) {
        return this.ecs.create(components);
      }

      createManyEntities(componentsList) {
        return this.ecs.createMany(componentsList);
      }

      get source() {
        return source;
      }

      insertComponents(entity, components) {
        this.ecs.insert(entity, components);
      }

      insertManyComponents(components) {
        this.ecs.insertMany(components);
      }

      removeComponents(entity, components) {
        this.ecs.remove(entity, components);
      }

      removeManyComponents(entities) {
        this.ecs.removeMany(entities);
      }

    };
    return new WrappedSystem();
  }

}