import {Packet} from './packet';
import {idFromPacket, packetFromId} from './registry';

export class BundlePacket extends Packet {

  static pack(packet) {
    const packets = packet.data[1];
    // Pack up all the packets.
    const packedPackets = new Array(packets.length);
    for (let i = 0; i < packets.length; i++) {
      const packet = packets[i];
      const Packet_ = packet.constructor;
      const id = idFromPacket(Packet_);
      packedPackets[i] = Packet_.pack({
        data: [id, packet.data],
      });
    }
    // Calculate total length. All packed + 4 (int) for each.
    let length = 0;
    for (let i = 0; i < packedPackets.length; i++) {
      length += 4 + packedPackets[i].length;
    }
    // Allocate buffer.
    const buffer = Buffer.allocUnsafe(length);
    let caret = 0;
    for (let i = 0; i < packedPackets.length; i++) {
      const packedPacket = packedPackets[i];
      // Write packed length.
      buffer.writeUInt32LE(packedPacket.length, caret);
      caret += 4;
      // Write packed data.
      packedPacket.copy(buffer, caret, 0);
      caret += packedPacket.length;
    }
    return this.builder.encode({
      _id: packet.data[0],
      data: buffer,
    });
  }

  static get schema() {
    return {
      ...super.schema,
      data: 'buffer',
    };
  }

  static unpack(packet) {
    const {data} = this.builder.decode(packet);
    const packets = [];
    let caret = 0;
    while (caret < data.length) {
      // Read packed length.
      const length = data.readUInt32LE(caret);
      caret += 4;
      // Read packed data.
      const packedPacket = Buffer.from(data.buffer, caret, length);
      caret += length;
      // Lookup packet.
      const packetId = packedPacket.readUInt8(0);
      const Packet = packetFromId(packetId);
      // Unpack and instantiate the packet.
      const unpacked = Packet.unpack(packedPacket);
      packets.push(new Packet(unpacked));
    }
    return packets;
  }

}