// @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
import {Buffer} from "buffer";
// @ts-ignore
// @ts-ignore
import {blake2b, errTuple} 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(
            Uint8Array.from(Buffer.from(pubkey, "hex")),
            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[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");
        }

        const node = this._activeRelays.get([...this._activeRelays.keys()][await randomNumber(0, this._activeRelays.size - 1)]);

        return node.connect(pubkey, options)
    }

    private async fillConnections(): Promise<any> {
        let available = [...this._relays.keys()].filter(x => [...this._activeRelays.keys()].includes(x));
        let relayPromises = [];
        if (0 > available.length) {
            return;
        }
        while (this._activeRelays.size <= Math.min(this._maxConnections, available.length + this._activeRelays.size)) {
            const relayIndex = await randomNumber(0, available.length - 1);

            const connection = available[relayIndex];

            if (!this.isServerAvailable(connection)) {
                continue;
            }

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

            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 Uint8Array.from(Buffer.from(str, "utf-8"));
}

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;
}