rpclibrary/src/Frontend.ts

'use strict'

import bsock = require('bsock');

import * as T from './Types'; 
import * as I from './Interfaces';

/**
 * Utility function to strip parameters like "a = 3" of their defaults
 * @param str The parameter to modify
 */
function stripAfterEquals(str:string):string{
    return str.split("=")[0]
}

/**
 * A websocket-on-steroids with built-in RPC capabilities
 */
export class RPCSocket implements I.Socket{
    static async makeSocket<T extends T.RPCInterface= T.RPCInterface>(port:number, server: string, tls: boolean = false): Promise<RPCSocket & T.RPCInterface<T>> {
        const socket = <RPCSocket & T> new RPCSocket(port, server, tls)
        return await socket.connect<T>()
    }

    private socket: I.Socket

    /**
     * 
     * @param port Port to connect to
     * @param server Server address
     * @param tls @default false use TLS
     */
    constructor(public port:number, private server: string, private tls: boolean = false){
        Object.defineProperty(this, 'socket', {value: undefined, writable: true})
    }

    /**
     * Hooks a handler to a function name. Use {@link call} to trigger it.
     * @param name The function name to listen on
     * @param handler The handler to attach
     */
    public hook(name: string, handler: (...args:any[]) => any | Promise<any>){
        return this.socket.hook(name, handler)
    }

    /**
     * Removes a {@link hook} listener by name.
     * @param name The function name 
     */
    public unhook(name: string){
        return this.socket.unhook(name)
    }

    /**
     * Attach a listener to error or close events
     * @param type 'error' or 'close'
     * @param f The listener to attach
     */
    public on(type: "error" | "close", f: (e?: any) => void){
        return this.socket.on(type, f)
    }

    /**
     * Destroys the socket
     */
    public destroy(){
        return this.socket.destroy()
    }

    /**
     * Closes the socket. It may attempt to reconnect.
     */
    public close(){
        return this.socket.close()
    }

    /**
     * Trigger a hooked handler on the server
     * @param rpcname The function to call
     * @param args other arguments
     */
    public async call (rpcname: string, ...args: any[]) : Promise<any>{
        return await this.socket.call.apply(this.socket, [rpcname, ...args])
    }

    /**
     * An alternative to call that does not wait for confirmation and doesn't return a value.
     * @param rpcname The function to call
     * @param args other arguments
     */
    public async fire(rpcname: string, ...args: any[]) : Promise<void>{
        await this.socket.fire.apply(this.socket, [rpcname, ...args])
    }
    
    /**
     * Connects to the server and attaches available RPCs to this object
     */
    public async connect<T extends T.RPCInterface= T.RPCInterface>() : Promise<RPCSocket & T.RPCInterface<T>>{
        this.socket = await bsock.connect(this.port, this.server, this.tls)

        const info:T.ExtendedRpcInfo[] = await this.info()
        info.forEach(i => {
            let f: any
            switch (i.type) {
                case 'Call':
                    f = this.callGenerator(i.uniqueName, i.argNames)    
                    break                
                case 'Hook':
                    f = this.hookGenerator(i.uniqueName, i.argNames)                    
                    break
            }
            if(this[i.owner] == null)
                this[i.owner] = {}
            this[i.owner][i.name] = f
            this[i.owner][i.name].bind(this)
        })
        return <RPCSocket & T.RPCInterface<T>> <any> this
    }

    /**
     * Get a list of available RPCs from the server
     */
    public async info(){
        return await this.socket.call('info')
    }

    /**
     * Utility {@link AsyncFunction} generator
     * @param fnName The function name
     * @param fnArgs A string-list of parameters
     */
    private callGenerator(fnName: string, fnArgs:string[]): T.AnyFunction{
        const headerArgs = fnArgs.join(",")
        const argParams = fnArgs.map(stripAfterEquals).join(",")
        return eval( '( () => async ('+headerArgs+') => { return await this.socket.call("'+fnName+'", '+argParams+')} )()' )
    }

    /**
     * Utility {@link HookFunction} generator
     * @param fnName The function name
     * @param fnArgs A string-list of parameters
     */
    private hookGenerator(fnName: string, fnArgs:string[]): T.HookFunction{
        const headerArgs = fnArgs.join(",")
        const argParams = fnArgs.map(stripAfterEquals).join(",")
        return eval( `( () => async (`+headerArgs+(headerArgs.length!==0?",":"")+` callback) => {
                            const r = await this.socket.call("`+fnName+`", `+argParams+`)
                            if(r.result === 'Success'){
                                this.socket.hook(r.uuid, callback)
                            }
                            return r
                        } )()` )
    }
}