import {RESOLUTION} from '@/constants.js'
import {System} from '@/ecs/index.js';

class SpatialHash {

  constructor(area) {
    this.area = area;
    this.chunkSize = [RESOLUTION[0] / 2, RESOLUTION[1] / 2];
    this.chunks = [];
    const chunkCount = [
      Math.ceil(this.area[0] / this.chunkSize[0]),
      Math.ceil(this.area[1] / this.chunkSize[1]),
    ];
    this.chunks = Array(chunkCount[0])
      .fill(0)
      .map(() => (
        Array(chunkCount[1])
        .fill(0)
        .map(() => [])
      ));
    this.data = {};
  }

  clamp(x, y) {
    return [
      Math.max(0, Math.min(x, this.area[0] - 1)),
      Math.max(0, Math.min(y, this.area[1] - 1))
    ];
  }

  chunkIndex(x, y) {
    const [cx, cy] = this.clamp(x, y);
    return [
      Math.floor(cx / this.chunkSize[0]),
      Math.floor(cy / this.chunkSize[1]),
    ];
  }

  remove(datum) {
    if (datum in this.data) {
      for (const [cx, cy] of this.data[datum]) {
        const chunk = this.chunks[cx][cy];
        chunk.splice(chunk.indexOf(datum), 1);
      }
    }
    this.data[datum] = [];
  }

  update({x0, x1, y0, y1}, datum) {
    this.remove(datum);
    for (const [x, y] of [[x0, y0], [x0, y1], [x1, y0], [x1, y1]]) {
      const [cx, cy] = this.chunkIndex(x, y);
      this.data[datum].push([cx, cy]);
      this.chunks[cx][cy].push(datum);
    }
  }

}

export default class UpdateSpatialHash extends System {

  constructor(ecs) {
    super(ecs);
    const master = ecs.get(1);
    this.hash = new SpatialHash([master.AreaSize.x, master.AreaSize.y]);
  }

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

  reindex(entities) {
    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() {
    const {diff} = this.ecs;
    for (const id in diff) {
      if (diff[id].VisibleAabb) {
        this.updateHash(this.ecs.get(parseInt(id)));
      }
    }
  }

}