tesseract.js/src/index.js

const adapter = require('./node/index.js')
const circularize = require('./common/circularize.js')
const TesseractJob = require('./common/job');
const version = require('../package.json').version;

function create(workerOptions = {}){
	var worker = new TesseractWorker(Object.assign({}, adapter.defaultOptions, workerOptions));
	worker.create = create;
	worker.version = version;
	return worker;
}

class TesseractWorker {
	constructor(workerOptions){
		this.worker = null;
		this.workerOptions = workerOptions;
		this._currentJob = null;
		this._queue = [];
	}

	recognize(image, options = {}){
		return this._delay(job => {
			if (typeof options === 'string') options = {lang: options}
			options.lang = options.lang || 'eng';
			
			job._send('recognize', { image, options, workerOptions: this.workerOptions });
		})
	}
	detect(image, options = {}){
		return this._delay(job => {
			job._send('detect', { image, options, workerOptions: this.workerOptions });
		})
	}

	terminate(){ 
		if(this.worker) adapter.terminateWorker(this);
		this.worker = null;
	}

	_delay(fn){
		if(!this.worker) this.worker = adapter.spawnWorker(this, this.workerOptions);

		var job = new TesseractJob(this);
		this._queue.push(e => {
			this._queue.shift();
			this._currentJob = job;
			fn(job);
		});
		if(!this._currentJob) this._dequeue();
		return job;
	}

	_dequeue(){
		this._currentJob = null;
		if(this._queue.length){
			this._queue[0]();
		}
	}

	_recv(packet){
        if(packet.status === 'resolve' && packet.action === 'recognize'){
            packet.data = circularize(packet.data);
        }

		if(this._currentJob.id === packet.jobId){
			this._currentJob._handle(packet)
		} else {
			console.warn('Job ID ' + packet.jobId + ' not known.')
		}
	}
}

module.exports = create();