Node.js Queueing Tutorial

// Simple script to showcasing how to queue up and run multiple requests using the LEADTOOLS CloudServices.
// In order to run this script, the following changes will need to be added:
//	1) Place your Application ID in the user portion of the getRequestOptions method.
//	2) Place your Application Password in the password portion of the getRequestOptions method.
//
// The script will perform the following operations in order:
//	1)Perform an UploadFile request to the LEADTOOLS CloudServices.  A successfully made request will return a unique identifier.
//    We will use this identifier to queue up further methods.
//	2)We will queue up an ExtractText method using the identifier that was returned from the UploadFile method.
//	3)After we verify the ExtractText method was queued, we will then queue up a Conversion method to convert the file to TIFF.
//  4)Once the Conversion request has been queued, we will make a call to the Run method.  This will mark the file as ready to be processed.
//    **Note** Once a file has been marked for processing, or has finished processing, no further requests can be queued or run on that file.
//	5)We will then query the services using the GUID -- if the file is finished processing, the body will contain all the
//	  request data.
//  6)We will take the json data that was returned, parse it, and display all the information that was returned.

// This script makes use of the following NodeJS libraries:
//  1) Request - More information about this library can be found here: https://github.com/request/request
//  2) File System - More information about this library can be found here: https://nodejs.org/api/fs.html

const request = require('request');

//If uploading a file as multi-part content, we will need the file-system library installed.
//const fs = require('fs');

var servicesUrl = "https://azure.leadtools.com/api/";

//The first page in the file to mark for processing
var firstPage = 1;

//Sending a value of -1 will indicate to the services that the rest of the pages in the file should be processed.
var lastPage = -1;

//Enum corresponding to the output format for the file. For the purposes of this script, we will be converting to tif.
var fileFormat = 4;

//We will be uploading the file via a URl.  Files can also be passed by adding a PostFile to the request.  Only 1 file will be accepted per request.
//The services will use the following priority when determining what a request is trying to do GUID > URL > Request Body Content
var fileURL = 'http://demo.leadtools.com/images/cloud_samples/ocr1-4.tif';

var guid = '';

var uploadUrl = servicesUrl + "UploadFile?fileurl=" + fileURL;
request.post(getRequestOptions(uploadUrl), uploadCallback);

//If uploading a file as multi-part content:
//var uploadUrl = servicesUrl + "UploadFile";
//var req = request.post(getRequestOptions(uploadUrl), uploadCallback);
//var form = req.form();
//form.append('file', fs.createReadStream('path\to\inputFile'));

function uploadCallback(error, response, body) {
	if (!error && response.statusCode === 200) {
		guid = body;
		console.log("Unique ID returned by the Services: " + guid);

		checkVerification();
	}
}
function checkVerification(){
	var queryUrl = servicesUrl + "Query?id=" + guid;
	request.post(getRequestOptions(queryUrl), async function (error, response, body) {
		var results = JSON.parse(body);
		if (!error && results['FileStatus'] !== 123) {

			console.log("File finished processing with return code: " + response.statusCode);

			if(results['FileStatus'] == 122){
				var recognitionUrl = servicesUrl + 'Recognition/ExtractText?firstPage=' + firstPage + '&lastPage=' + lastPage + '&guid=' + guid;
				request.post(getRequestOptions(recognitionUrl), recognitionCallback);
			}else{
				console.log("File failed verification with File Status: " + results['FileStatus']);
			}

		} else {
			//The file has not yet finished processing.
			await function () {
				return new Promise(resolve => setTimeout(resolve, 5000)); //Sleep for 5 seconds before trying again
			};
			checkVerification(); //Call the method again.
		}
	});
}
function recognitionCallback(error, response, body) {
	if (!error && response.statusCode === 200) {
		console.log("ExtractText successfully queued");

		var conversionUrl = servicesUrl + 'Conversion/Convert?firstPage=' + firstPage + '&lastPage=' + lastPage + '&guid=' + guid + '&format=' + fileFormat;
		request.post(getRequestOptions(conversionUrl), conversionCallback);
	} else {
		console.log("ExtractText failed to queue with HTTP code: " + response.statusCode);
		console.log(body);
	}
}

function conversionCallback(error, response, body) {
	if (!error && response.statusCode === 200) {
		console.log("Conversion successfully queued");

		var runUrl = servicesUrl + 'Run?id=' + guid;
		request.post(getRequestOptions(runUrl), runCallback);
	} else {
		console.log("Conversion failed to queue with HTTP code: " + response.statusCode);
		console.log(body);
	}
}

function runCallback(error, response, body) {
	if (!error && response.statusCode === 200) {
		console.log("File has been successfully marked to run");
		queryServices();
	} else {
		console.log("Run failed with HTTP code: " + response.statusCode);
		console.log(body);
	}
}

function queryServices() {
	//Function to query the status of a request.  If the request has not yet finished, this function will recursively call itself until the file has finished.
	var queryUrl = servicesUrl + "Query?id=" + guid;
	request.post(getRequestOptions(queryUrl), async function (error, response, body) {
		var results = JSON.parse(body);
		if (!error && results['FileStatus'] !== 100) {

			console.log("File finished processing with return code: " + response.statusCode);
			if (results['FileStatus'] !== 200) {
				return;
			}
			console.log("Results: \n");
			parseJson(results['RequestData']);
		} else {
			//The file has not yet finished processing.
			await function () {
				return new Promise(resolve => setTimeout(resolve, 5000)); //Sleep for 5 seconds before trying again
			};
			queryServices(guid); //Call the method again.
		}
	});
}

function parseJson(jsonObject) {
	//Function to decode the JSON object that was returned by the LEADTOOLS CloudServices.
	for (let i = 0; i < jsonObject.length; i++) {
		var currentRequest = jsonObject[i];
		console.log("Service Type: " + currentRequest['ServiceType']);
		if (currentRequest['ServiceType'] === 'Recognition' && currentRequest['RecognitionType'] === 'ExtractText') {
			console.log("Recognition Method: " + currentRequest['RecognitionType']);
			console.log("Data:" + currentRequest['data']);
		} else if (currentRequest['ServiceType'] === 'Conversion') {
			console.log("Urls: ");
			currentRequest['urls'].forEach(url => {
				console.log(url);
			});
		} else {
			console.log("Unanticipated service type");
		}
	}
}

function getRequestOptions(url) {
	//Function to generate and return HTTP request  options.
	var requestOptions = {
		url: url,
		//If uploading a file as multi-part content, remove the Content-Length header.
		headers: {
			'Content-Length': 0
		},
		auth: {
			user: "Replace with Application ID",
			password: "Replace with Application Password"
		}
	};
	return requestOptions;
}