import {System} from '@/ecs/index.js';
import {intersects} from '@/util/math.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) {
        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.VisibleAabb) {
      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) {
          const frame = Sprite.animation
            ? Sprite.$$sourceJson.animations[Sprite.animation][Sprite.frame]
            : '';
          size = Sprite.$$sourceJson.frames[frame].sourceSize;
        }
        /* 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 {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 (intersects(query, entity.VisibleAabb)) {
            within.add(entity);
          }
        }
      }
    }
    return within;
  }

}