import tuntapAddon from './Tuntap2Addon';
import * as fs from 'fs';
import * as os from 'os';
import * as jmespath from 'jmespath';

/**
 *
 * @class TuntapBase
 */
export class TuntapBase {
    _deviceMode: 'tun' | 'tap';
    _fd: number;
    _ifName: string;
    _isUp: boolean = false;
    protected readonly readStream: fs.ReadStream;
    protected readonly writeStream: fs.WriteStream;

    /**
     * Creates an instance of TuntapBase.
     * @param {('tun' | 'tap')} mode
     * @memberof TuntapBase
     * @since 0.0.1
     */
    constructor(mode: 'tun' | 'tap') {
        this._deviceMode = mode;
        const fd = fs.openSync(`/dev/net/tun`, 'r+');
        this._fd = fd;
        this._ifName = tuntapAddon.tuntapInit(this._fd, mode == 'tap');
        this.readStream = fs.createReadStream('', {
            fd: this._fd,
            autoClose: true,
            emitClose: true
        } as any);
        this.writeStream = fs.createWriteStream('', {
            fd: this._fd,
            autoClose: true,
            emitClose: true,
            fs: {
                write: fs.write,
                open: () => { return fd },
                close: (fd: any, callback: () => void) => { callback() }
            }
        } as any);
        // const readStreamEvents = ['open', 'close', 'data', 'end', 'error', 'readable', 'pause', 'ready', 'resume']
        //transfer all events from writeStream to readStream
        //except open
        const writeStreamEvents = ['drain', 'error', 'finish', 'pipe', 'ready', 'unpipe', 'close', 'open']
        writeStreamEvents.forEach((event) => {
            this.writeStream.addListener(event, (...rests) => {
                this.readStream.emit(event, ...rests);
            })
        })

    }
    /**
     * release writeStreams, readStreams and the file descriptor.
     * @memberof TuntapBase
     */
    release(callback?: (err?: NodeJS.ErrnoException) => void) {
        this.writeStream.close(() => {
            //close two stream one by one
            this.readStream.close((error) => {
                if (callback) {
                    callback();
                }
            });
        });
    };
    /**
     * many get methods, like ipv4, ipv6 ... 
     * implemented via `os.networkInterfaces()`
     * The device needs to set 'up' to be visible in the `os.networkInterfaces()`
     * @private
     * @memberof TuntapBase
     */
    private makeSureIsUp() {
        if (!this.isUp) {
            throw `you must set isUp = true in order to access this method`;
        }
    }
    get name(): string {
        return this._ifName;
    }
    get isTap(): boolean {
        return this._deviceMode == 'tap';
    }
    get isTun(): boolean {
        return !this.isTap;
    }
    get isUp(): boolean {
        return this._isUp;
    }
    set isUp(activate: boolean) {
        if (activate) {
            tuntapAddon.tuntapSetUp(this._ifName);
        } else {
            tuntapAddon.tuntapSetDown(this._ifName);
        }
        this._isUp = activate;
    }
    get mac(): string {
        this.makeSureIsUp();
        const ifInfo = os.networkInterfaces();
        const mac: string = jmespath.search(
            ifInfo,
            `${this._ifName}[*].[mac]|[0]`,
        );
        return mac;
    }
    set mac(mac: string) {
        tuntapAddon.tuntapSetMac(this._ifName, mac);
    }
    get mtu(): number {
        return tuntapAddon.tuntapGetMtu(this._ifName);
    }
    set mtu(mtu: number) {
        tuntapAddon.tuntapSetMtu(this._ifName, mtu);
    }
    get ipv4(): string {
        this.makeSureIsUp();
        const ifInfo = os.networkInterfaces();
        return jmespath.search(
            ifInfo,
            `${this._ifName}[?family=='IPv4'].cidr|[0]`,
        );
    }
    set ipv4(ip: string) {
        const cirdArray = ip.split('/');
        if (cirdArray.length != 2) {
            throw `incorrect ip address: ${ip}`;
        }
        const ipv4Addr = cirdArray[0];
        const ipv4NetMask = Number.parseInt(cirdArray[1]);
        tuntapAddon.tuntapSetIpv4(this._ifName, ipv4Addr, ipv4NetMask);
    }
    get ipv6() {
        this.makeSureIsUp();
        const ifInfo = os.networkInterfaces();
        return jmespath.search(
            ifInfo,
            `${this._ifName}[?family=='IPv6'].cidr|[0]`,
        );
    }
    set ipv6(ip: string) {
        const cirdArray = ip.split('/');
        if (cirdArray.length != 2) {
            throw `incorrect ipv6 address: ${ip}`;
        }
        const addr = cirdArray[0];
        const prefix = Number.parseInt(cirdArray[1]);
        const ifIndex = tuntapAddon.tuntapGetIfIndex(this._ifName);
        tuntapAddon.tuntapSetIpv6(ifIndex, addr, prefix);
    }
    
    /**
     * @deprecated Please use on('data',callback);
     * @memberof TuntapBase
     */
    onReceive(){
    }

    /**
     * @deprecated Please use write(chunk,callback);
     * @memberof TuntapBase
     */
    writePacket(){
    }
}