import {EntityPacket} from '@avocado/entity';

export class EntityPacketSynchronizer {

  constructor() {
    this.packetsToSynchronize = new Map();
    this.trackedEntities = new Map();
  }

  acceptPacket(packet) {
    if (!(packet instanceof EntityPacket)) {
      return;
    }
    for (let i = 0; i < packet.data.length; i++) {
      const data = packet.data[i];
      const packetEntity = this.trackedEntities.get(data.uuid);
      if (!packetEntity) {
        continue;
      }
      const Packet = packet.constructor;
      packetEntity.acceptPacket(new Packet([data]));
    }
  }

  flushPackets(flusher) {
    for (const [entity, packets] of this.packetsToSynchronize.entries()) {
      const mergedPackets = this._mergePackets(packets);
      flusher(entity, Array.from(mergedPackets.values()));
    }
    this.packetsToSynchronize = new Map();
  }

  _mergePackets(packets) {
    const mergedPackets = new Map();
    for (let i = 0; i < packets.length; i++) {
      const packet = packets[i];
      const Packet = packet.constructor;
      if (!mergedPackets.has(Packet)) {
        mergedPackets.set(Packet, packet);
      }
      else {
        mergedPackets.get(Packet).mergeWith(packet);
      }
    }
    return mergedPackets;
  }

  _queuePacketFor(entity, packet) {
    if (!this.packetsToSynchronize.has(entity)) {
      this.packetsToSynchronize.set(entity, []);
    }
    this.packetsToSynchronize.get(entity).push(packet);
  }

  trackEntity(entity) {
    this.trackedEntities.set(entity.instanceUuid, entity);
    entity.once('destroy', () => {
      this.trackedEntities.delete(entity.instanceUuid);
    });
    this._watchEntityPackets(entity);
  }

  _watchEntityPackets(entity) {
    const onSendPacket = (packet) => {
      this._queuePacketFor(entity, packet);
    };
    entity.on('sendPacket', onSendPacket);
    entity.once('destroy', () => {
      this.packetsToSynchronize.delete(entity);
      entity.off('sendPacket', onSendPacket);
    });
  }

}