const spawn = require('child_process').spawn
const fs = require('fs')
const youtubedl = require('youtube-dl-exec')
const tmp = require('tmp')

const STREAM_URL = "https://www.youtube.com/henrikomagnifico/live"

function readText(tmpfile, charWhitelist) {
	return new Promise((resolve, reject) => {
		const tesseract = charWhitelist ? spawn('tesseract', [tmpfile.name, '-', '-c', `tessedit_char_whitelist="${charWhitelist}`]) : spawn('tesseract', [tmpfile.name, '-'])
		let recognizedString = ''

		tesseract.stdout.on('data', (data) => {
			recognizedString += data;
		})

		tesseract.on('exit', (code) => {
			tmpfile.removeCallback()
			if (code !== 0) {
				reject()
			} else {
				resolve(recognizedString)
			}
		})
	})
}

function thresholdImage(image, threshold) {

}

function getRegion(frame, x, y, width, height) { // Returns Promise<Buffer>
    console.log("retrieving region")
	const threshold = "15%"
	return new Promise(function (resolve, reject) {
		const tmpFile = tmp.fileSync()
		const convert = spawn('convert', [`png:${frame.name}`, '-negate', '-crop', `${width}x${height}+${x}+${y}`, '-white-threshold', threshold, `png:${tmpFile.name}`])

		convert.stderr.on('data', data => console.error(data.toString()))

		convert.on('exit', (code) => {
			if (code !== 0) {
				reject()
			} else {
				console.log("got region", tmpFile.name)
				resolve(tmpFile);
			}
		});
	});
}

function getFrame(url) {
	return new Promise((resolve, reject) => { // Returns Promise<Buffer>
	    const frameFile = tmp.fileSync()
		const ffmpeg = spawn('ffmpeg', ['-i', url, '-y', '-f', 'image2', '-c:v', 'png', '-frames:v', '1', frameFile.name])

		ffmpeg.stderr.on('data', data => console.error(data.toString()))

		ffmpeg.on('exit', (code) => {
			if (code !== 0) {
				reject()
			} else {
				console.log("got frame", frameFile.name)
				resolve(frameFile)
			}
		})
	});
}

function getYoutubeStream() {
	return new Promise((resolve, reject) => {
		youtubedl(STREAM_URL, {
			dumpJson: true,
			format: "best"
		}).then(output => resolve(output.url))
			.catch(err => reject(err))
	})
}

getYoutubeStream()
	.then(url => getFrame(url))
	.then(frame => {
		let title = '',
			album = '',
			duration = ''

		const titlePromise = getRegion(frame, 432, 906, 1487, 54).then(titleRegion => readText(titleRegion))
		const albumPromise = getRegion(frame, 440, 957, 1487, 32).then(albumRegion => readText(albumRegion))
		const durationPromise = getRegion(frame, 0, 1028, 235, 34).then(durationRegion => readText(durationRegion, "1234567890:/"))

		console.log("waiting for processors")
		Promise.all([titlePromise, albumPromise, durationPromise]).then(values => {
			frame.removeCallback()
			title = values[0].trim()
			album = values[1].trim()
			duration = values[2].trim()

			console.log(`${album}: ${title} (${duration})`)
		}).catch(err => console.error(err))
	}).catch(err => console.error(err))