/*
	Crypto String
		Securely Encrypts and decrypts a string using a password
*/


const IV_BYTE_SIZE = 100 // Size of initialization vector
const SALT_BYTE_SIZE = 900 // Size of salt
const KEY_BYTE_SIZE = 32 // size of cipher key
const AUTH_TAG_SIZE = 16  // Size of authentication tag


const crypto = require('crypto')

let CryptoString = module.exports = {}

CryptoString.encrypt = (password, salt64, rawText) => {

	const initializationVector = crypto.randomBytes(IV_BYTE_SIZE)
	const salt = Buffer.from(salt64, 'base64')
	const key = CryptoString.seasonedPassword(password, salt)

	const cipher = crypto.createCipheriv('aes-256-gcm', key, initializationVector, { 'authTagLength': AUTH_TAG_SIZE })
    let encryptedMessage = cipher.update(rawText)

    encryptedMessage = Buffer.concat([encryptedMessage, cipher.final()])
    return Buffer.concat([initializationVector, encryptedMessage, cipher.getAuthTag()]).toString('base64')

}

//Decrypt base64 string cipher text, 
CryptoString.decrypt = (password, salt64, cipherTextString) => {

	let cipherText = Buffer.from(cipherTextString, 'base64')
	const salt = Buffer.from(salt64, 'base64')

	const authTag = cipherText.slice(AUTH_TAG_SIZE*-1)
    const initializationVector = cipherText.slice(0, IV_BYTE_SIZE)
    const encryptedMessage = cipherText.slice(IV_BYTE_SIZE, AUTH_TAG_SIZE*-1)

    const key = CryptoString.seasonedPassword(password, salt)

    const decipher = crypto.createDecipheriv('aes-256-gcm', key, initializationVector, { 'authTagLength': AUTH_TAG_SIZE })

    try {
    	decipher.setAuthTag(authTag)

	    let messagetext = decipher.update(encryptedMessage)
	    messagetext = Buffer.concat([messagetext, decipher.final()]).toString('utf8')

	    return messagetext

    } catch(err) {

    	// console.log(err)
    	return null
    }
    
}

//Salt the password - return {buffer}
CryptoString.seasonedPassword = (password, salt) => {

	return crypto.scryptSync(password, salt, KEY_BYTE_SIZE)
}

//Create random salt - return {string}
CryptoString.createSalt = () => { 

	return crypto.randomBytes(SALT_BYTE_SIZE).toString('base64')
}
CryptoString.createSmallSalt = () => {

	return crypto.randomBytes(20).toString('base64')
}

CryptoString.hash = (hashString) => {

	return crypto.createHash('sha256').update(hashString).digest()
}

CryptoString.test = () => {

	const pp = (title, output) => {
		console.log('----------------'+title+'----------------')
		console.log(output)
	}

	const password = 'ItsMePasswordio123'
	const text = '<p>The genesis of&nbsp a new note. Very magical.<br></p><p>Quite a weonderful thing<br></p><p><br></p><p>Weonderful for sheore <br></p>'

	const hashTest = CryptoString.createSalt('password')

	const salt = CryptoString.createSalt()
	pp('salt',salt.length)

	const seasonPass = CryptoString.seasonedPassword(password, salt)

	const cipherText = CryptoString.encrypt(password, salt, text)

	const decipheredText = CryptoString.decrypt(password, salt, cipherText)
	pp('Success Decrypt', decipheredText == text ? 'Pass 😁':'Fail' )

	const wrongPass = CryptoString.decrypt('Wrong Password', salt, cipherText)
	pp('Wrong Password', wrongPass === null ? 'Pass':'Fail')

	const wrongSalt = CryptoString.decrypt(password, 'Wrong Salt', cipherText)
	pp('Wrong Salt', wrongSalt === null ? 'Pass':'Fail')

	const wrongCipher = CryptoString.decrypt(password, salt, Buffer.from('Hello there'))
	pp('Wrong Cipher Text', wrongCipher === null ? 'Pass':'Fail')

}