rpclibrary/src/Backend.ts

'use strict'

import http = require('http');
import bsock = require('bsock');
import * as T from './Types';
import * as U from './Utils';
import * as I from './Interfaces';


/**
 * A Websocket-server-on-steroids with built-in RPC capabilities
 */
export class RPCServer<
    InterfaceT extends T.RPCInterface = T.RPCInterface,
> implements I.Destroyable {

    private ws = http.createServer()
    private io = bsock.createServer()
    private visibility: T.Visibility
    private closeHandler: T.CloseHandler
    private errorHandler: T.ErrorHandler
    private connectionHandler: T.ConnectionHandler
    private sesame?: T.SesameFunction
    private accessFilter: T.AccessFilter<InterfaceT>

    /**
     * @throws On RPC with no name
     * @param port The port to listen on
     * @param exporters A list of {@link RPCExporter} to publish
     * @param conf A {@link SocketConf} object with optional settings
     */
    constructor(
        private port: number,
        private exporters: T.ExporterArray<InterfaceT> = [],
        conf: T.ServerConf<InterfaceT> = {}
    ) {
        if (!conf.visibility) this.visibility = "0.0.0.0"

        if (conf.sesame) {
            this.sesame = U.makeSesameFunction(conf.sesame)
        }

        this.accessFilter = conf.accessFilter || (async (sesame) => {
            if (!this.sesame) return true
            return this.sesame!(sesame!)
        })


        this.errorHandler = (socket: I.Socket) => (error: any, rpcName: string, args: any[]) => {
            if (conf.errorHandler) conf.errorHandler(socket, error, rpcName, args)
            else throw error
        }

        this.closeHandler = (socket: I.Socket) => {
            if (conf.closeHandler) conf.closeHandler(socket)
        }

        this.connectionHandler = (socket: I.Socket) => {
            if (conf.connectionHandler) conf.connectionHandler(socket)
        }

        exporters.forEach(U.fixNames) //TSC for some reason doesn't preserve name properties of methods

        let badRPC = exporters.flatMap(ex => ex.exportRPCs()).find(rpc => !rpc.name)
        if (badRPC) {
            throw new Error(`
            RPC did not provide a name. 
            \nUse 'funtion name(..){ .. }' syntax instead.
            \n
            \n<------------OFFENDING RPC:
            \n`+ badRPC.toString() + `
            \n>------------OFFENDING RPC`)
        }
        this.startWebsocket()
    }

    private startWebsocket() {
        try {
            this.io.attach(this.ws)
            this.io.on('socket', (socket: I.Socket) => {
                socket.on('error', (err) => this.errorHandler(socket, err, "system", []))
                socket.on('close', () => this.closeHandler(socket))
                this.connectionHandler(socket)
                this.initRPCs(socket)
            })
            this.ws = this.ws.listen(this.port, this.visibility)
        } catch (e) {
            this.errorHandler(this.io, e, 'system', [])
        }
    }

    protected initRPCs(socket: I.Socket) {
        socket.hook('info', async (sesame?: string) => {
            const rpcs = await Promise.all(this.exporters.map(async exp => {
                const allowed = await this.accessFilter(sesame, exp)
                if (!allowed) return []
                return U.rpcHooker(socket, exp, this.errorHandler, this.sesame)
            }))
            return rpcs.flat()
        })
    }

    /**
     * Publishes a new list of Exporters. This destroys and restarts the socket
     * @param exporters the exporters to publish
    public setExporters(exporters: T.ExporterArray<InterfaceT>): any {
        exporters.forEach(U.fixNames)
        this.destroy()
        this.ws = http.createServer()
        this.io = bsock.createServer()
        this.exporters = exporters
        this.startWebsocket()
    }
    */


    destroy(): void {
        this.io.close()
        this.ws.close()
    }
}