fb-admin/src/backend/FrontblockAdmin.ts

'use strict'

import * as Logger from 'log4js'
import { Plugin, socketioRPC, ConfigLoader } from 'frontblock-generic/Plugin';
import { ErrorResponse, SuccessResponse } from 'frontblock-generic/Types';
import { PluginManagerPlugin } from './PluginManager/Plugin'
import express = require('express');
import http = require('http');
import bsock = require('bsock');
import { type } from 'os';

const kfs = require("key-file-storage").default('kfs')

Logger.configure({
    appenders: 
    {
    "frontblock-admin": { type: 'stdout' },
    //app: { type: 'file', filename: 'application.log' }
    },
    categories: 
    {
    default: { appenders: [ 'frontblock-admin' ], level: 'debug' }
    }
})
const logger = Logger.getLogger("frontblock-admin") 

type hookRPC = 
    { 
    type: 'hook', 
    generator: (socket) => Function, 
    unhook:(uid:string)=>Promise<ErrorResponse|SuccessResponse>
    }

type unhookRPC = 
    { 
    type: 'unhook', 
    fn: Function
    }

type callRPC = 
    { 
    type: 'call', 
    fn: Function
    }

export type rpcInfo = 
    {
    owner: string,
    name: string,
    args: string,
    info: hookRPC | unhookRPC | callRPC
    }

export type AdminConf = { httpPort: number}

/**
 * FrontblockAdmin
 * 
 * The customer-facing dynamic component of the customer backend
 * Supports (un)loading plugins which will be communicated to its library component (See FrontblockLib.ts and the info() RPC)
 * 
 * The list of available plugins is published via the frontblock API and downloaded via gitea-releases
 */
export class FrontblockAdmin extends ConfigLoader<AdminConf>{
    
    private hookToUids:{[hookName:string]:string[]} = {}
    private express
    private httpServer
    private io = bsock.createServer()
    private wsServer = http.createServer()
    private pm: PluginManagerPlugin

    constructor(){
        super("FrontblockAdmin")
        this.pm = new PluginManagerPlugin()

        this.initialize()
    }

    getDefaultConfig(): AdminConf {
        return {httpPort: 8080}
    }

    private async initialize(){
        this.startWebsocket()
        this.startWebserver()
    }

    private initApis(socket){
        //Declare own functions
        const rpcInfos:rpcInfo[] = [
            {
                owner: 'Admin',
                name: 'restartWebserver',
                args: 'port',
                info:{
                    type:'call', 
                    fn: (port:number) => { this.restartWebserver(port) } 
                }
            },{
                owner: 'Admin',
                name: 'info', 
                args: '',
                info:{
                    type:'call', 
                    fn: () => { return rpcInfos } 
                }
            }
        ]

        
        //translate RPCs to socket-bound function metadata
        const loadedPlugins = this.pm.getLoadedPlugins() 
        for(const name in loadedPlugins){
            loadedPlugins[name].exportRPCs().forEach(rpc => {
                const info = this.rpcToRpcInfo(name, rpc)
                rpcInfos.push(info)
            })
        }

        //Hook up all the functions
        for(const api of rpcInfos){
            switch(api.info.type){
                case 'call':
                    socket.hook(api.name, api.info.fn)
                break
                case 'hook':
                    const hook = api.info.generator(socket)
                    hook.bind(this)
                    socket.hook(api.name, hook)
                break
                case 'unhook':
                    socket.hook(api.name, api.info.fn)
                break
            }
        }

        //initialize the lists of open hooks
        rpcInfos
        .filter(rpc => rpc.info.type === "hook")
        .forEach(hook => { 
            this.hookToUids[hook.name] = []
         })

        //On close, unhook open hooks
        socket.on('close', () => {
            logger.info("Client disconnected")

            rpcInfos.forEach((rpc) => {
                if(this.hookToUids[rpc.name] == null)
                    return

                this.hookToUids[rpc.name].forEach((uid) => {
                    if(rpc.info.type === "hook"){
                        logger.info("Closing consumer `"+uid+"` owned by `"+rpc.name+"`")
                        rpc.info.unhook(uid)
                    }
                })
            })
        })
    }

    private startWebserver(){
        if(this.httpServer != null || this.express != null){
            logger.warn("Webserver is already running")
            return
        }
        
        let port:number = this.conf.httpPort
        this.express = express()
        this.express.use(express.static('static'))

        this.httpServer = new http.Server(this.express)
        this.httpServer.listen(port, () => {
            logger.info('Admin panel listening for HTTP on *'+port)
        })
    }

    private stopWebserver(){
        if(this.httpServer == null || this.express == null){
            logger.warn("Webserver is not running")
            return
        }
        this.httpServer.close()
        this.httpServer = null
        this.express = null
        logger.info("Webserver stopped")
    }

    private restartWebserver(port:number){
        this.stopWebserver()
        kfs[this.name+".conf"] = <AdminConf>{ httpPort: port }
        this.startWebserver()
    }

    private startWebsocket(){
        try{
            this.io.attach(this.wsServer)
            this.io.on('socket', (socket) => {
                logger.info("New Websocket connection on port", socket.port)

                const handleError = (e: any) => {
                    logger.info("Websocket closing", String(e))
                    socket.close()
                }
                
                socket.on('error', handleError)
                this.initApis(socket)
            })
            logger.info('Admin websocket listening on *20000')
            this.wsServer.listen(20000)
        }catch(e){
            logger.error(String(e))
        }
    }

    private rpcToRpcInfo(owner:string, rpc:socketioRPC):rpcInfo{
        switch(rpc.type){
            case 'hook':
                let f = this.hookGenerator(rpc)
                return {owner: owner, name: rpc.name, args: this.extractArgs(f(null)), info: { type: 'hook', generator: f, unhook: rpc.unhook } }
            case 'unhook':
                return {owner: owner, name: rpc.name, args: this.extractArgs(rpc.rpc), info: { type: 'unhook', fn: rpc.rpc } }
            case 'call':
                return {owner: owner, name: rpc.name, args: this.extractArgs(rpc.rpc), info: { type: 'call', fn: rpc.rpc } }
        }
    }

    /**
     * Generates RPC hooks which support a callback. 
     * 
     * Note callbacks *need* to accept a singular argument and they have to be the last parameter!
     */
    hookGenerator = (rpc:socketioRPC) => { 
        const argsArr = this.extractArgs(rpc.rpc).split(',')
        argsArr.pop()
        const args = argsArr.join(',')

        return eval(`(socket) => async (`+args+`) => { 
            const res = await rpc.rpc(`+args+(args.length!==0?',':'')+` (x) => {
                socket.call(res.uid, x).catch(e => {
                    logger.debug(String(e))
                })
            })
            if(res.uid != null){
                this.hookToUids[rpc.name].push(res.uid)
            }
            return res
        }`)
    }

    private extractArgs(f:Function):string{
        let fn = String(f)
        let args = fn.substr(0, fn.indexOf(")"))
        args = args.substr(fn.indexOf("(")+1)
        return args
    }
}

(async() => {
    new FrontblockAdmin()
})()