r3x.ts

import { ServerResponse, IncomingMessage } from "http";
import { JSONHandler } from './src/handlers/JSONhandler';
import { ErrorHandler } from './src/error/ErrorHandler';
import { FuncSchema } from './src/schema/schemaHandler';
import { Context } from './src/context/Context';
import { join } from "path";

let http = require('http')

let errorRes = new ErrorHandler()

let schema = new FuncSchema()

const exceptionMessage = 'Function Exception'
const fs = require('fs');

/**
 * Function user is visible too
 * Triggers SDK
 * @param r3x {Function}
 */
export function execute(r3x: Function) {
    HTTPStream(r3x)
}

/**
 * Takes users function and handles requests and responses
 * @param r3x {Function}
 */
function HTTPStream(r3x: Function){
    let port = 8080

    if (port == null) {
        console.log("Error Configuration. Missing Port")
        process.exit(2)
    }
    /**
     * Handles function request and responses
     * @param req {IncomingMessage}
     * @param res {ServerResponse}
     */
    let functionHandler = (req: IncomingMessage, res: ServerResponse) => {
        //declare schema path and get if cors is to be enabled
        let schemaPath = join(__dirname, "schema.json")
        try {
            if (fs.existsSync(schemaPath)) {
                let cors = schema.getSchema(schemaPath).cors
                if (cors) {
                    //set cors headers
                    setCORS(res)
                }
            }
        } catch(err) {
            errorRes.sendJSONError(res, 502, {message: "No `schema.json` detected" , detail: err.message.toString()})
        }
        
        // declare JSON Handler
        let input = new JSONHandler()

        // Check only POST and OPTIONS request. OPTIONS is allowed for preflight requests
        if (req.method !== 'POST' && req.method !== 'OPTIONS'){
            errorRes.sendJSONError(res, 400, {message: "Invalid method", detail: `${req.method} ${req.url}`})
            return
        }

        // Handle request
        req.on('error', (err) => {
            errorRes.sendJSONError(res, 502, {message: exceptionMessage , detail: err.message.toString()})
        }).on('data', chunk => {
            // parse request body
            input.pushData(chunk)
        }).on('end', () => {
            let headers = {}
            
            let body = input.getBody()
            let cont = new Context(body, headers)

            cont.responseContentType = 'application/json'

            // handle user function execution
            new Promise(function (res, rej) {
                try {
                    return res(r3x(body))
                } catch (err) {
                    rej(err)
                } 
            }).then((result) => {
                return sendResponse(cont, res, result)
            }, (error) => {
                errorRes.sendJSONError(res, 502, {message: exceptionMessage , detail: error.message.toString()})

            }).then(() => {
                res.end()
                res.on('error', (err) => {
                    errorRes.sendJSONError(res, 502, {message: exceptionMessage , detail: err.message.toString()})
                })
            }).catch(err => errorRes.sendJSONError(res, 502, {message: exceptionMessage , detail: err.message.toString()}))
        })
    }

    /**
     * Creates HTTP server
     */
    http.createServer(functionHandler).listen(port)
    .on('error', (error : any) => {
        console.log(`Connection failed to port ${port}`, error)
        process.exit(2)
    })
} 


// handle response
function sendResponse(cont: Context, resp : ServerResponse, result : any){
    let headers = cont._responseHeaders
    for (let key in headers) {
        if (headers.hasOwnPropery(key)){
            resp.setHeader(key, headers[key])
        }
    }
    resp.removeHeader('Content-length')
    resp.writeHead(200, 'OK')

    console.log(result)
    let pro : Promise<any> | undefined
    if(result != null) {
        pro = Promise.resolve(resp.write(JSON.stringify(result)))
    }
    return pro
}

/**
 * Sets CORS headers
 * @param res {ServerResponse}
 */
function setCORS(res: ServerResponse) {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Request-Method', '*');
    res.setHeader('Access-Control-Allow-Methods', 'POST, OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', '*');
}