rpclibrary/src/Utils.ts

import * as uuidv4 from "uuid/v4"

import * as T from "./Types";
import * as I from "./Interfaces";
import { Server as ioServer, Socket as ioSocket, Socket } from "socket.io"
import { Socket as ioClientSocket } from "socket.io-client"

/**
 * Translate an RPC to RPCInfo for serialization.
 * @param rpc The RPC to transform
 * @param owner The owning RPC group's name
 * @param errorHandler The error handler to invoke when  something goes wrong
 * @param sesame optional sesame phrase to prepend before all RPC arguments 
 * @throws Error on RPC without name property
 */
export const rpcToRpcinfo = (socket: I.Socket, rpc: T.RPC<any, any>, owner: string, errorHandler: T.ErrorHandler, sesame?: T.SesameFunction): T.RpcInfo => {
    switch (typeof rpc) {
        case "object":
            if (rpc['call']) {
                return {
                    owner: owner,
                    argNames: extractArgs(rpc['call']),
                    type: "Call",
                    name: rpc.name,
                    call: sesame ? async (_sesame, ...args) => { if (sesame(_sesame)) return await rpc['call'].apply({}, args); socket.close() } : rpc['call'], // check & remove sesame 
                }
            } else {
                const generator = hookGenerator(<T.HookRPC<any, any>>rpc, errorHandler, sesame)
                return {
                    owner: owner,
                    argNames: extractArgs(generator(undefined)),
                    type: "Hook",
                    name: rpc.name,
                    generator: generator,
                }
            }
        case "function":
            if (!rpc.name) throw new Error(`
RPC did not provide a name. 
\nUse 'funtion name(..){ .. }' syntax instead.
\n
\n<------------OFFENDING RPC:
\n${rpc.toString()}
\n>------------OFFENDING RPC`)
            return {
                owner: owner,
                argNames: extractArgs(rpc),
                type: "Call",
                name: rpc.name,
                call: sesame ? async (_sesame, ...args) => { if (sesame(_sesame)) return await rpc.apply({}, args); throw makeError(rpc.name) } : rpc, // check & remove sesame 
            }
    }
    throw new Error("Bad socketIORPC type " + typeof rpc)
}

/**
 * Utility function to apply the RPCs of an {@link RPCExporter}.
 * @param socket The websocket (implementation: bsock) to hook on
 * @param exporter The exporter
 * @param makeUnique @default true Attach a suffix to RPC names
 */
export function rpcHooker(socket: I.Socket, exporter: I.RPCExporter<any, any>, errorHandler: T.ErrorHandler, sesame?: T.SesameFunction, makeUnique = true): T.ExtendedRpcInfo[] {
    const owner = exporter.name
    const RPCs = typeof exporter.RPCs === "function" ? exporter.RPCs() : exporter.RPCs

    return RPCs.map(rpc => rpcToRpcinfo(socket, rpc, owner, errorHandler, sesame))
        .map(info => {
            const suffix = makeUnique ? "-" + uuidv4().substr(0, 4) : ""
            const ret: any = info
            ret.uniqueName = info.name + suffix
            let rpcFunction = info.type === 'Hook' ? info.generator(socket)
                : info.call

            socket.hook(ret.uniqueName, callGenerator(info.name, socket, rpcFunction, errorHandler))
            return ret
        })
}

/**
 * Decorate an RPC with the error handler
 * @param rpcFunction the function to decorate
 */
const callGenerator = (rpcName: string, socket: I.Socket, rpcFunction: T.AnyFunction, errorHandler: T.ErrorHandler): T.AnyFunction => {
    const argsArr = extractArgs(rpcFunction)
    const args = argsArr.join(',')
    const argsStr = argsArr.map(stripAfterEquals).join(',')

    return eval(`async (` + args + `) => {
        try{
            return await rpcFunction(`+ argsStr + `)
        }catch(e){
            errorHandler(socket)(e, rpcName, [`+ args + `])
        }
    }`)
}

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

/**
 * Utility function to generate {@link HookFunction} from a RPC for backend
 * @param rpc The RPC to transform
 * @returns A {@link HookFunction}
 */
const hookGenerator = (rpc: T.HookRPC<any, any>, /*not unused!*/ errorHandler: T.ErrorHandler, sesameFn?: T.SesameFunction): T.HookInfo['generator'] => {

    let argsArr = extractArgs(rpc.hook)
    argsArr.pop() //remove 'callback' from the end
    let callArgs = argsArr.join(',')

    const args = sesameFn ? (['sesame', ...argsArr].join(','))
        : callArgs

    callArgs = appendComma(callArgs, false)

    //note rpc.hook is the associated RPC, not a socket.hook
    return eval(`
    (clientSocket) => async (${args}) => {
        try{
            if(sesameFn && !sesameFn(sesame)) return
            const uuid = uuidv4()
            const res = await rpc.hook(${callArgs} (...cbargs) => {
                if(rpc.onCallback){
                    rpc.onCallback.apply({}, cbargs)
                }
                clientSocket.call.apply(clientSocket, [uuid, ...cbargs])
            })
            if(rpc.onClose){
                clientSocket.on('close', () => rpc.onClose(res, rpc))
            }
            return {'uuid': uuid, 'return': res}
        }catch(e){
            //can throw to pass exception to client or swallow to keep it local
            errorHandler(clientSocket)(e, ${rpc.name}, [${args}])
        }
    }`)
}

const makeError = (callName: string) => {
    return new Error("Call not found: " + callName + ". ; Zone: <root> ; Task: Promise.then ; Value: Error: Call not found: " + callName)
}

/**
 * Extract a string list of parameters from a function
 * @param f The source function
 */
const extractArgs = (f: Function): string[] => {
    let fn: string
    fn = (fn = String(f)).substr(0, fn.indexOf(")")).substr(fn.indexOf("(") + 1)
    return fn !== "" ? fn.split(',') : []
}


export function makeSesameFunction(sesame: T.SesameFunction | string): T.SesameFunction {
    if (typeof sesame === 'function') {
        return sesame
    }

    return (testSesame: string) => {
        return testSesame === sesame
    }
}


export function appendComma(s?: string, turnToString = true): string {
    if (turnToString)
        return s ? `'${s}',` : ""
    return s ? `${s},` : ""
}


/**
 * Typescript incorrectly omits the function.name attribute for MethodDeclaration.
 * This was supposedly fixed (https://github.com/microsoft/TypeScript/issues/5611) but it still is the case.
 * This function sets the name value for all object members that are functions.
*/
export function fixNames(o: Object): void {
    Object.keys(o).forEach(key => {
        if (typeof o[key] === 'function' && !o[key].name) {
            Object.defineProperty(o[key], 'name', {
                value: key
            })
        }
    })
}

export const makePioSocket = (socket: any): I.Socket => {
    return {
        bind: (name: string, listener: T.PioBindListener) => socket.on(name, (...args: any) => {
            const ack = args.pop()
            listener.apply(null, args)
            ack()
        }),

        hook: (name: string, listener: T.PioHookListener) => {
            const args = extractArgs(listener)
            let argNames
            let restParam = args.find(e => e.includes('...'))
            if(!restParam){
                argNames = [...args, '...__args__'].join(',')
                restParam = '__args__'
            }else{
                argNames = [...args].join(',')
                restParam = restParam.replace('...','')
            }

            const decoratedListener = eval(`(() => async (${argNames}) => {
                const __ack__ = ${restParam}.pop()
                try{
                    const response = await listener.apply(null, [${argNames}])
                    __ack__(response)
                }catch(e){
                    __ack__({
                        ...e,
                        stack: e.stack,
                        message: e.message,
                        name: e.name,
                    })
                }
            })()`)
            socket.on(name, decoratedListener)
        },

        call: (name: string, ...args: any) => {
            return new Promise((res, rej) => {
                const params: any = [name, ...args, (resp) => {
                    if(isError(resp)){
                        const err = new Error()
                        err.stack = resp.stack
                        err.name = resp.name
                        err.message = resp.message
                        return rej(err)
                    }
                    res(resp)
                }]
                socket.emit.apply(socket, params)                    
            })
        },

        fire: (name: string, ...args: any) => new Promise((res, rej) => {
            const params: any = [name, ...args]
            socket.emit.apply(socket, params)
            res()
        }),

        unhook: (name: string, listener?: T.AnyFunction) => {
            if (listener) {
                socket.removeListener(name, listener)
            } else {
                socket.removeAllListeners(name)
            }
        },

        id: socket.id,
        on: (...args) => socket.on.apply(socket, args),
        emit: (...args) => socket.emit.apply(socket, args),
        close: () => {
            socket
            socket.disconnect(true)
        }
    }
}

export const isError = function(e){
    return e && e.stack && e.message && typeof e.stack === 'string' 
           && typeof e.message === 'string';
   }