import {System} from '@/ecs/index.js';
import {intersects} from '@/util/math.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;
    }
    this.hash.update(entity.Collider.aabb, entity.id);
  }

  tick() {
    const collisions = new Map();
    for (const entity of this.ecs.changed(['Position'])) {
      this.updateHash(entity);
    }
    for (const entity of this.ecs.changed(['Position'])) {
      if (!entity.Collider) {
        continue;
      }
      collisions.set(entity, new Set());
      for (const other of this.within(entity.Collider.aabb)) {
        if (entity === other) {
          continue;
        }
        if (!collisions.has(other)) {
          collisions.set(other, new Set());
        }
        if (!other.Collider || collisions.get(other).has(entity)) {
          continue;
        }
        const intersections = entity.Collider.isCollidingWith(other.Collider);
        if (intersections.length > 0) {
          collisions.get(entity).add(other);
          if (!entity.Collider.collidingWith[other.id]) {
            entity.Collider.collidingWith[other.id] = true;
            other.Collider.collidingWith[entity.id] = true;
            if (entity.Collider.collisionStartScriptInstance) {
              const script = entity.Collider.collisionStartScriptInstance.clone();
              script.context.intersections = intersections;
              script.context.other = other;
              entity.Ticking.add(script.ticker());
            }
            if (other.Collider.collisionStartScriptInstance) {
              const script = other.Collider.collisionStartScriptInstance.clone();
              script.context.intersections = intersections
                .map(([l, r]) => [r, l]);
                script.context.other = entity;
              other.Ticking.add(script.ticker());
            }
          }
          for (const i in intersections) {
            const [body, otherBody] = intersections[i];
            const {impassable} = otherBody;
            if (impassable) {
              const j = entity.Collider.bodies.indexOf(body);
              const oj = other.Collider.bodies.indexOf(otherBody);
              const aabb = entity.Collider.$$aabbs[j];
              const otherAabb = other.Collider.aabbs[oj];
              if (!intersects(
                {
                  x0: aabb.x0 + entity.Position.lastX,
                  x1: aabb.x1 + entity.Position.lastX,
                  y0: aabb.y0 + entity.Position.y,
                  y1: aabb.y1 + entity.Position.y,
                },
                otherAabb,
              )) {
                entity.Position.x = entity.Position.lastX
              }
              else if (!intersects(
                {
                  x0: aabb.x0 + entity.Position.x,
                  x1: aabb.x1 + entity.Position.x,
                  y0: aabb.y0 + entity.Position.lastY,
                  y1: aabb.y1 + entity.Position.lastY,
                },
                otherAabb,
              )) {
                entity.Position.y = entity.Position.lastY
              }
              else {
                entity.Position.x = entity.Position.lastX
                entity.Position.y = entity.Position.lastY
              }
              break;
            }
          }
        }
        else {
          if (entity.Collider.collidingWith[other.id]) {
            if (entity.Collider.collisionEndScriptInstance) {
              const script = entity.Collider.collisionEndScriptInstance.clone();
              script.context.other = other;
              entity.Ticking.add(script.ticker());
            }
            if (other.Collider.collisionEndScriptInstance) {
              const script = other.Collider.collisionEndScriptInstance.clone();
              script.context.other = entity;
              other.Ticking.add(script.ticker());
            }
            delete entity.Collider.collidingWith[other.id];
            delete other.Collider.collidingWith[entity.id];
          }
        }
      }
    }
  }

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

}