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

export default class Colliders 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) {
        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 (!entity.Collider) {
      return;
    }
    entity.Collider.recalculateAabbs();
    this.hash.update(entity.Collider.aabb, entity.id);
  }

  tick() {
    const seen = {};
    for (const entity of this.ecs.changed(['Position'])) {
      if (seen[entity.id]) {
        continue;
      }
      seen[entity.id] = true;
      if (!entity.Collider) {
        continue;
      }
      this.updateHash(entity);
      for (const other of this.within(entity.Collider.aabb)) {
        if (seen[other.id]) {
          continue;
        }
        seen[other.id] = true;
        if (!other.Collider) {
          continue;
        }
        if (entity.Collider.isCollidingWith(other.Collider)) {
          console.log('collide', entity, other);
        }
      }
    }
  }

  within(query) {
    const {x0, x1, y0, y1} = query;
    const [cx0, cy0] = this.hash.chunkIndex(x0, y0);
    const [cx1, cy1] = this.hash.chunkIndex(x1, y1);
    const seen = {};
    const within = new Set();
    for (let cy = cy0; cy <= cy1; ++cy) {
      for (let cx = cx0; cx <= cx1; ++cx) {
        for (const id of this.hash.chunks[cx][cy]) {
          if (seen[id]) {
            continue;
          }
          seen[id] = true;
          const entity = this.ecs.get(id);
          if (entity.Collider.isWithin(query)) {
            within.add(entity);
          }
        }
      }
    }
    return within;
  }

}