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 {Ticking} = this.ecs.get(1);
    const seen = {};
    for (const entity of this.ecs.changed(['Position'])) {
      if (seen[entity.id]) {
        continue;
      }
      seen[entity.id] = true;
      if (!entity.Collider) {
        continue;
      }
      const {collidingWith: wasCollidingWith} = entity.Collider;
      entity.Collider.collidingWith = {};
      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;
        }
        delete other.Collider.collidingWith[entity.id];
        const intersections = entity.Collider.isCollidingWith(other.Collider);
        if (intersections.length > 0) {
          entity.Collider.collidingWith[other.id] = true;
          other.Collider.collidingWith[entity.id] = true;
          if (!wasCollidingWith[other.id]) {
            if (entity.Collider.collisionStartScriptInstance) {
              entity.Collider.collisionStartScriptInstance.context.intersections = intersections;
              entity.Collider.collisionStartScriptInstance.context.other = other;
              Ticking.addTickingPromise(entity.Collider.collisionStartScriptInstance.tickingPromise());
            }
            if (other.Collider.collisionStartScriptInstance) {
              other.Collider.collisionStartScriptInstance.context.intersections = intersections
                .map(([l, r]) => [r, l]);
              other.Collider.collisionStartScriptInstance.context.other = entity;
              Ticking.addTickingPromise(other.Collider.collisionStartScriptInstance.tickingPromise());
            }
          }
          for (const [, {impassable}] of intersections) {
            if (impassable) {
              entity.Position.x = entity.Position.lastX
              entity.Position.y = entity.Position.lastY
              break;
            }
          }
        }
      }
      for (const otherId in wasCollidingWith) {
        if (!entity.Collider.collidingWith[otherId]) {
          const other = this.ecs.get(otherId);
          if (!other || !other.Collider) {
            continue;
          }
          if (entity.Collider.collisionEndScriptInstance) {
            entity.Collider.collisionEndScriptInstance.context.other = other;
            Ticking.addTickingPromise(entity.Collider.collisionEndScriptInstance.tickingPromise());
          }
          if (other.Collider.collisionEndScriptInstance) {
            other.Collider.collisionEndScriptInstance.context.other = entity;
            Ticking.addTickingPromise(other.Collider.collisionEndScriptInstance.tickingPromise());
          }
        }
      }
    }
  }

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

}