// @ts-ignore
import DhtNode from "@hyperswarm/dht-relay";
// @ts-ignore
import Stream from "@hyperswarm/dht-relay/ws";
// @ts-ignore
import createRoundRobin from "@derhuerst/round-robin-scheduler";
// @ts-ignore
// @ts-ignore
import { blake2b, errTuple, hexToBuf } from "libskynet";
// @ts-ignore
import { registryRead } from "libkmodule";

import { unpack } from "msgpackr";
import randomNumber from "random-number-csprng";

const REGISTRY_DHT_KEY = "lumeweb-dht-node";

export default class DHT {
  private _options: any;
  private _relays: Map<string, string> = new Map();
  private _activeRelays: Map<string, typeof DhtNode> = new Map();
  private _maxConnections = 10;
  private _inited = false;

  constructor(opts = {}) {
    // @ts-ignore
    opts.custodial = false;
    this._options = opts;
  }

  ready(): Promise<void> {
    if (this._inited) {
      return Promise.resolve();
    }

    this._inited = true;
    return this.fillConnections();
  }

  get relays(): string[] {
    return [...this._relays.keys()];
  }

  public async addRelay(pubkey: string): Promise<boolean> {
    let entry: errTuple = await registryRead(
      hexToBuf(pubkey).shift() as Uint8Array,
      hashDataKey(REGISTRY_DHT_KEY)
    );

    if (entry[1] || !entry[0]?.exists) {
      return false;
    }

    let host;

    try {
      host = unpack(entry[0].entryData);
    } catch (e) {
      return false;
    }

    const [domain, port] = host.split(":");

    if (isNaN(parseInt(port))) {
      return false;
    }

    this._relays.set(pubkey, `wss://${domain}:${port}/`);

    if (this._inited) {
      await this.fillConnections();
    }

    return true;
  }

  public removeRelay(pubkey: string): boolean {
    if (!this._relays.has(pubkey)) {
      return false;
    }

    if (this._activeRelays.has(pubkey)) {
      this._activeRelays.get(pubkey).destroy();
      this._activeRelays.delete(pubkey);
    }

    this._relays.delete(pubkey);

    return true;
  }

  public clearRelays(): void {
    [...this._relays.keys()].forEach(this.removeRelay);
  }

  private async isServerAvailable(connection: string): Promise<boolean> {
    return new Promise<boolean>((resolve) => {
      const ws = new WebSocket(connection);
      ws.addEventListener("open", () => {
        ws.close();
        resolve(true);
      });
      ws.addEventListener("error", () => {
        resolve(false);
      });
    });
  }

  async connect(pubkey: string, options = {}): Promise<DhtNode> {
    if (this._activeRelays.size === 0) {
      throw new Error("Failed to find an available relay");
    }

    let index = 0;

    if (this._activeRelays.size > 1) {
      index = await randomNumber(0, this._activeRelays.size - 1);
    }

    const node = this._activeRelays.get([...this._activeRelays.keys()][index]);

    return node.connect(pubkey, options);
  }

  private async fillConnections(): Promise<any> {
    let available: string[] = [];

    const updateAvailable = () => {
      available = [...this._relays.keys()].filter(
        (x) => ![...this._activeRelays.keys()].includes(x)
      );
    };
    updateAvailable();

    let relayPromises = [];
    while (
      this._activeRelays.size <=
      Math.min(this._maxConnections, available.length)
    ) {
      if (0 === available.length) {
        break;
      }

      let relayIndex = 0;

      if (available.length > 1) {
        relayIndex = await randomNumber(0, available.length - 1);
      }

      const connection = this._relays.get(available[relayIndex]) as string;

      if (!(await this.isServerAvailable(connection))) {
        available.splice(relayIndex, 1);
        this.removeRelay(available[relayIndex]);
        continue;
      }

      const node = new DhtNode(
        new Stream(true, new WebSocket(connection)),
        this._options
      );
      this._activeRelays.set(available[relayIndex], node);
      updateAvailable();

      relayPromises.push(node.ready());
    }

    return Promise.allSettled(relayPromises);
  }
}

export function hashDataKey(dataKey: string): Uint8Array {
  return blake2b(encodeUtf8String(dataKey));
}

function encodeUtf8String(str: string): Uint8Array {
  const byteArray = stringToUint8ArrayUtf8(str);
  const encoded = new Uint8Array(8 + byteArray.length);
  encoded.set(encodeNumber(byteArray.length));
  encoded.set(byteArray, 8);
  return encoded;
}

function stringToUint8ArrayUtf8(str: string): Uint8Array {
  return new TextEncoder().encode(str);
}

function encodeNumber(num: number): Uint8Array {
  const encoded = new Uint8Array(8);
  for (let index = 0; index < encoded.length; index++) {
    encoded[index] = num & 0xff;
    num = num >> 8;
  }
  return encoded;
}