rpclibrary/src/Frontend.ts

'use strict'

import { PromiseIOClient, defaultClientConfig } from './PromiseIO/Client'
import * as T from './Types';
import * as I from './Interfaces';
import { stripAfterEquals, appendComma } from './Utils';
import { CALLBACK_NAME, DESTROY_PREFIX, SOCKET_NOT_CONNECTED, UNKNOWN_RPC_IDENTIFIER, USER_DEFINED_TIMEOUT } from './Strings';


/**
 * 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.ClientConfig = defaultClientConfig): Promise<T.ConnectedSocket<T>> {
        const socket = new RPCSocket<T>(port, server, conf)
        return await socket.connect(sesame)
    }

    private socket: I.Socket
    private handlers: {
        [name in string]: T.GenericFunction[]
    } = {
            error: [],
            close: []
        }
    private hooks: { [name in string]: T.GenericFunction } = {}

    /**
     * 
     * @param port Port to connect to
     * @param server Server address
     * @param tls @default false use TLS
     */
    constructor(public port: number, public address: string, private conf: T.ClientConfig = defaultClientConfig) {
        Object.defineProperty(this, 'socket', { value: undefined, writable: true })
        this.hook(UNKNOWN_RPC_IDENTIFIER, (err) => this.handlers['error'].forEach(handler => handler(err)))
    }

    /**
     * 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.GenericFunction) {
        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(SOCKET_NOT_CONNECTED)

        try {
            if(!this.conf.callTimeoutMs || this.conf.callTimeoutMs <= 0)
                return await this.socket.call.apply(this.socket, [rpcname, ...args])
            else 
                if(this.conf.callTimeoutMs){
                    return await Promise.race([
                        this.socket.call.apply(this.socket, [rpcname, ...args]),
                        new Promise((_, rej) => {
                            setTimeout(_ => rej(USER_DEFINED_TIMEOUT(this.conf.callTimeoutMs)), this.conf.callTimeoutMs)
                        }) 
                    ])
                }else{
                    return await this.socket.call.apply(this.socket, [rpcname, ...args])
                }
                
        } 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(SOCKET_NOT_CONNECTED)
        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.address, this.conf)
        } 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.GenericFunction]) => {
            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(SOCKET_NOT_CONNECTED)
        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.GenericFunction {
        const headerArgs = fnArgs.join(",")
        const argParams = fnArgs.map(stripAfterEquals).join(",")
        sesame = appendComma(sesame)
        return eval(`async (${headerArgs}) => { 
            const returnvalue = await this.call("${fnName}", ${sesame} ${argParams})
            return returnvalue
        }`)
    }

    /**
     * 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.GenericFunction {

        if (sesame)
            fnArgs.shift()

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

        const frontendHookStr = `
        async (${CALLBACK_NAME}, ${headerArgs}) => {
            const r = await this.call("${fnName}", ${sesame} ${argParams})
            try{
                if(r){
                    if(r.uuid){
                        ${CALLBACK_NAME}['destroy'] = () => {
                            this.socket.fire(destroy_prefix+r.uuid)
                            this.socket.unhook(r.uuid) 
                        }
                        ${CALLBACK_NAME} = ${CALLBACK_NAME}.bind({
                            destroy: ${CALLBACK_NAME}['destroy']
                        })

                        this.socket.hook(r.uuid, (...args) => {
                            ${CALLBACK_NAME}.apply(${CALLBACK_NAME}, args)
                        })
                    }
                    return r.return
                }else{
                    throw new Error("Empty response")
                }
            }catch(e){
                throw e
            }
        }`
        return eval(frontendHookStr)
    }
}