pdfparser.js

'use strict';

let fs = require('fs'),
	stream = require('stream'),
	nodeUtil = require("util"),
    _ = require("lodash"),
    async = require("async"),
	PDFJS = require("./lib/pdf.js");

let PDFParser = (function () {
    // private static
    let _nextId = 1;
    let _name = 'PDFParser';

    let _binBuffer = {};
    let _maxBinBufferCount = 10;

	//private methods, needs to invoked by [funcName].call(this, ...)
	let _onPDFJSParseDataReady = function(data) {
		if (!data) { //v1.1.2: data===null means end of parsed data
			nodeUtil.p2jinfo("PDF parsing completed.");
			let output = {"formImage": this.data};
			this.emit("pdfParser_dataReady", output);
			if (typeof this.flushCallback === 'function') {
				this.push(output);
				this.flushCallback();
				this.flushCallback = null;
			}
		}
		else {
			Object.assign(this.data, data);
		}
	};

	let _onPDFJSParserDataError = function(data) {
		this.data = null;
		this.emit("pdfParser_dataError", {"parserError": data});
	};

	let _startParsingPDF = function(buffer) {
		this.data = {};

		this.PDFJS.on("pdfjs_parseDataReady", _onPDFJSParseDataReady.bind(this));
		this.PDFJS.on("pdfjs_parseDataError", _onPDFJSParserDataError.bind(this));

		this.PDFJS.parsePDFData(buffer || _binBuffer[this.pdfFilePath]);
	};

	let _processBinaryCache = function() {
		if (_.has(_binBuffer, this.pdfFilePath)) {
			_startParsingPDF.call(this);
			return true;
		}

		let allKeys = _.keys(_binBuffer);
		if (allKeys.length > _maxBinBufferCount) {
			let idx = this.get_id() % _maxBinBufferCount;
			let key = allKeys[idx];
			_binBuffer[key] = null;
			delete _binBuffer[key];

			nodeUtil.p2jinfo("re-cycled cache for " + key);
		}

		return false;
	};

	let _processPDFContent = function(err, data) {
		nodeUtil.p2jinfo("Load PDF file status:" + (!!err ? "Error!" : "Success!") );
		if (err) {
			this.data = err;
			this.emit("pdfParser_dataError", this);
		}
		else {
			_binBuffer[this.pdfFilePath] = data;
			_startParsingPDF.call(this);
		}
	};

	let _createContentStream = function(jsonObj) {
		let rStream = new stream.Readable({objectMode: true});
		rStream.push(jsonObj);
		rStream.push(null);
		return rStream;
	};

	// constructor
    function PdfParser(context, needRawText) {
		//call constructor for super class
	    stream.Transform.call(this, {objectMode: true, bufferSize: 64 * 1024});

        // private
        let _id = _nextId++;

        // public (every instance will have their own copy of these methods, needs to be lightweight)
        this.get_id = () => _id;
        this.get_name = () => _name + _id;

        // service context object, only used in Web Service project; null in command line
        this.context = context;

        this.pdfFilePath = null; //current PDF file to load and parse, null means loading/parsing not started
        this.data = null; //if file read success, data is PDF content; if failed, data is "err" object
        this.PDFJS = new PDFJS(needRawText);
        this.processFieldInfoXML = false;//disable additional _fieldInfo.xml parsing and merging

	    this.chunks = [];
	    this.flushCallback = null;
	}
	// inherit from event emitter
	nodeUtil.inherits(PdfParser, stream.Transform);

	//implements transform stream
	PdfParser.prototype._transform = function (chunk, enc, callback) {
		this.chunks.push(Buffer.isBuffer(chunk) ? chunk : new Buffer(chunk, enc));
		callback();
	};

	PdfParser.prototype._flush = function(callback) {
		this.flushCallback = callback;
		this.parseBuffer(Buffer.concat(this.chunks));
	};

	PdfParser.prototype.fq = async.queue( (task, callback) => {
		fs.readFile(task.path, callback);
	}, 100);

	//public APIs
	PdfParser.prototype.setVerbosity = function(verbosity) {
		nodeUtil.verbosity(verbosity || 0);
	};

	PdfParser.prototype.loadPDF = function(pdfFilePath, verbosity) {
		this.setVerbosity(verbosity);
		nodeUtil.p2jinfo("about to load PDF file " + pdfFilePath);

		this.pdfFilePath = pdfFilePath;
		if (this.processFieldInfoXML) {
			this.PDFJS.tryLoadFieldInfoXML(pdfFilePath);
		}

		if (_processBinaryCache.call(this))
			return;

		this.fq.push({path: pdfFilePath}, _processPDFContent.bind(this));
	};

	// Introduce a way to directly process buffers without the need to write it to a temporary file
	PdfParser.prototype.parseBuffer = function(pdfBuffer) {
		_startParsingPDF.call(this, pdfBuffer);
	};

	PdfParser.prototype.getRawTextContent = function() { return this.PDFJS.getRawTextContent(); };
	PdfParser.prototype.getRawTextContentStream = function() { return _createContentStream(this.getRawTextContent()); };

	PdfParser.prototype.getAllFieldsTypes = function() { return this.PDFJS.getAllFieldsTypes(); };
	PdfParser.prototype.getAllFieldsTypesStream = function() { return _createContentStream(this.getAllFieldsTypes()); };

	PdfParser.prototype.getMergedTextBlocksIfNeeded = function() { return {"formImage": this.PDFJS.getMergedTextBlocksIfNeeded()}; };
	PdfParser.prototype.getMergedTextBlocksStream = function() { return _createContentStream(this.getMergedTextBlocksIfNeeded()); };

	PdfParser.prototype.destroy = function() {
		this.removeAllListeners();

		//context object will be set in Web Service project, but not in command line utility
		if (this.context) {
			this.context.destroy();
			this.context = null;
		}

		this.pdfFilePath = null;
		this.data = null;
		this.chunks = null;

		this.PDFJS.destroy();
		this.PDFJS = null;
	};

	return PdfParser;
})();

module.exports = PDFParser;