rpclibrary/src/Frontend.ts

'use strict'

import { PromiseIOClient } from './PromiseIO/Client'
import * as T from './Types'; 
import * as I from './Interfaces';
import { stripAfterEquals, appendComma } from './Utils';


/**
 * A websocket-on-steroids with built-in RPC capabilities
 */
export class RPCSocket<Ifc extends T.RPCInterface = T.RPCInterface> implements I.Socket{

    static async makeSocket<T extends T.RPCInterface = T.RPCInterface>(port:number, server: string, sesame?:string, conf?:T.SocketConf): Promise<T.ConnectedSocket<T>> {
        const socket = new RPCSocket<T>(port, server, conf)
        return await socket.connect(sesame)
    }

    private protocol: 'http:' | 'https:'
    private socket: I.Socket
    private handlers : {
        [name in string]: T.AnyFunction[]
    } = {
        error: [],
        close: []
    }
    private hooks : {[name in string]: T.AnyFunction} = {} 

    /**
     * 
     * @param port Port to connect to
     * @param server Server address
     * @param tls @default false use TLS
     */
    constructor(public port:number, private server: string, private conf:T.SocketConf = { tls: false }){
        Object.defineProperty(this, 'socket', {value: undefined, writable: true})
        if(conf.tls){
            this.protocol = "https:"
        }else{
            this.protocol = "http:"
        }
    }

    /**
     * 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>){
        if(!this.socket){
            this.hooks[name] = handler
        }else{
            this.socket.hook(name, handler)
        }
    }

    /**
     * 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 bind(name: string, handler: (...args:any[]) => any | Promise<any>){
        if(!this.socket){
            this.hooks[name] = handler
        }else{
            this.socket.bind(name, handler)
        }
    }

    /**
     * Removes a {@link hook} listener by name.
     * @param name The function name 
     */
    public unhook(name: string){
        if(!this.socket){
            delete this.hooks[name]
        }else{
            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: string, f: T.AnyFunction){
        if(!this.socket){
            if(!this.handlers[type]) 
                this.handlers[type] = []

            this.handlers[type].push(f)
        }else{
            this.socket.on(type, f)
        }
    }

    /**
     * Emit a LOCAL event
     * @param eventName The event name to emit under
     * @param data The data the event carries
     */
    public emit(eventName:string, data:any){
        if(!this.socket) return
        this.socket.emit(eventName, data)
    }

    /**
     * Closes the socket. It may attempt to reconnect.
     */
    public close(){
        if(!this.socket) 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>{
        if(!this.socket) throw new Error("The socket is not connected! Use socket.connect() first")
        try{
            const val = await this.socket.call.apply(this.socket, [rpcname, ...args])
            return val
        }catch(e){
            this.emit('error', e)
            throw e
        }
    }

    /**
     * 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>{
        if(!this.socket) throw new Error("The socket is not connected! Use socket.connect() first")
        await this.socket.fire.apply(this.socket, [rpcname, ...args])
    }
    
    /**
     * Connects to the server and attaches available RPCs to this object
     */
    public async connect( sesame?: string ) : Promise<T.ConnectedSocket<Ifc>> {

        try{
            this.socket = await PromiseIOClient.connect(this.port, this.server, this.protocol)
        }catch(e){
            this.handlers['error'].forEach(h => h(e))
            throw e
        }

        Object.entries(this.handlers).forEach(([k,v])=>{
            v.forEach(h => this.socket.on(k, h))
        })

        Object.entries(this.hooks).forEach((kv: [string, T.AnyFunction]) => {
            this.socket.hook(kv[0], kv[1])
        })
        const info:T.ExtendedRpcInfo[] = await this.info(sesame)

        info.forEach(i => {
            let f: any
            
            switch (i.type) {
                case 'Call':
                    f = this.callGenerator(i.uniqueName, i.argNames, sesame)    
                    break                
                case 'Hook':
                    f = this.frontEndHookGenerator(i.uniqueName, i.argNames, sesame)                    
                    break
            }
            if(this[i.owner] == null)
                this[i.owner] = {}
            this[i.owner][i.name] = f
            this[i.owner][i.name].bind(this)
        })
        
        
        return <T.ConnectedSocket<Ifc>> (this as any) 
    }

    /**
     * Get a list of available RPCs from the server
     */
    public async info(sesame?:string){
        if(!this.socket) throw new Error("The socket is not connected! Use socket.connect() first")
        return await this.socket.call('info', sesame)
    }

    /**
     * Utility {@link AsyncFunction} generator
     * @param fnName The function name
     * @param fnArgs A string-list of parameters
     */
    private callGenerator(fnName: string, fnArgs:string[], sesame?:string): T.AnyFunction{
        const headerArgs = fnArgs.join(",")
        const argParams = fnArgs.map(stripAfterEquals).join(",")
        sesame = appendComma(sesame)

        return eval(`async (${headerArgs}) => { 
            return await this.call("${fnName}", ${sesame} ${argParams})
        }`)
    }

    /**
     * Utility {@link HookFunction} generator
     * @param fnName The function name
     * @param fnArgs A string-list of parameters
     */
    private frontEndHookGenerator(fnName: string, fnArgs:string[], sesame?:string): T.HookFunction{
        
        if(sesame)
            fnArgs.shift()

        let headerArgs = fnArgs.join(",")
        const argParams = fnArgs.map(stripAfterEquals).join(",")
        sesame = appendComma(sesame, true)
        headerArgs = fnArgs.length>0?headerArgs+",":headerArgs 

        return eval( `
        async (${headerArgs} callback) => {
            const r = await this.call("${fnName}", ${sesame} ${argParams})
            try{
                if(r){
                    if(r.uuid){
                        callback['destroy'] = () => { this.socket.unhook(r.uuid) }
                        this.socket.hook(r.uuid, callback)
                    }
                    return r.return
                }else{
                    throw new Error("Empty response")
                }
            }catch(e){
                throw e
            }
        }`)
    }
}