silphius/app/ecs/systems/visible-aabbs.js

import {System} from '@/ecs/index.js';
import SpatialHash from '@/util/spatial-hash.js';

export default class VisibleAabbs extends System {

  hash;

  deindex(entities) {
    super.deindex(entities);
    for (const id of entities) {
      this.hash.remove(id);
    }
  }

  static get priority() {
    return {
      after: 'IntegratePhysics',
    };
  }

  reindex(entities) {
    for (const id of entities) {
      if (1 === id) {
        const {AreaSize} = this.ecs.get(1)
        if (AreaSize) {
          const {x, y} = AreaSize;
          if (
            !this.hash ||
            (
              this.hash.area.x !== x
              || this.hash.area.y !== y
            )
          ) {
            this.hash = new SpatialHash(this.ecs.get(1).AreaSize);
          }
        }
      }
    }
    super.reindex(entities);
    for (const id of entities) {
      this.updateHash(this.ecs.get(id));
    }
  }

  updateHash(entity) {
    if (!this.hash) {
      return;
    }
    if (!entity.VisibleAabb) {
      this.hash.remove(entity.id);
      return;
    }
    this.hash.update(entity.VisibleAabb, entity.id);
  }

  tick() {
    for (const entity of this.ecs.changed(['Position'])) {
      const {Position: {x, y}, Sprite, VisibleAabb} = entity;
      if (VisibleAabb) {
        let size = undefined;
        if (Sprite) {
          size = Sprite.size;
        }
        /* v8 ignore next 3 */
        if (!size) {
          throw new Error(`no size for aabb for entity ${entity.id}(${JSON.stringify(entity.toJSON(), null, 2)})`);
        }
        VisibleAabb.x0 = x - Sprite.anchor.x * size.w;
        VisibleAabb.x1 = x + (1 - Sprite.anchor.x) * size.w;
        VisibleAabb.y0 = y - Sprite.anchor.y * size.h;
        VisibleAabb.y1 = y + (1 - Sprite.anchor.y) * size.h;
        this.updateHash(entity);
      }
    }
  }

  within(query) {
    const within = new Set();
    for (const id of this.hash.within(query)) {
      within.add(this.ecs.get(id));
    }
    return within;
  }

}