import {Cryptor} from './Cryptor'
import {Awaitable, DecodedValue, EncodedValue} from '../types'
import * as crypto from 'crypto'
import { Buffer } from 'buffer'

/**
 * AES 256 implementation of a Cryptor.
 */
export class AES256Cryptor extends Cryptor {
    encode(value: DecodedValue): Awaitable<EncodedValue> {
        const hash = crypto.createHash('sha256')
        hash.update(this.key)

        const vector = crypto.randomBytes(16)
        const cipher = crypto.createCipheriv('aes-256-ctr', hash.digest(), vector)
        const input = Buffer.from(value)
        const cipherText = cipher.update(input)

        const encoded = Buffer.concat([vector, cipherText, cipher.final()])
        return encoded.toString('base64')
    }

    decode(payload: EncodedValue): Awaitable<DecodedValue> {
        const hash = crypto.createHash('sha256')
        hash.update(this.key)

        const input = Buffer.from(payload, 'base64')
        const vector = input.slice(0, 16)
        const decipher = crypto.createDecipheriv('aes-256-ctr', hash.digest(), vector)
        const cipherText = input.slice(16)

        const decoded = Buffer.concat([decipher.update(cipherText), decipher.final()])
        return decoded.toString()
    }
}