import logger from 'log'
import {hkdf, pbkdf, Usage} from './kdf'
import SecretBox from './secret-box'
import {a2b64, b642a} from 'misc'

const log = logger('crypto:pwd-box')

export default class PwdBox {
  private constructor(
    private readonly box: SecretBox,
    private readonly salt: Uint8Array
  ) {}

  private static async derive(pwd: string, salt: Uint8Array, context?: string): Promise<CryptoKey | null> {
    const k = await pbkdf(salt, pwd)
    if (k === null) return null
    return await hkdf(k, Usage.box, context) as CryptoKey
  }

  public static async encrypt(data: Uint8Array, pwd: string, context?: string): Promise<PwdBox | null> {
    log.trace('encrypt')

    const salt = crypto.getRandomValues(new Uint8Array(16))

    const k = await PwdBox.derive(pwd, salt, context)
    if (k === null) return null

    const box = await SecretBox.encrypt(data, k)
    if (box === null) return null

    return new PwdBox(box, salt)
  }
  public async decrypt(pwd: string, context?: string): Promise<Uint8Array | null> {
    log.trace('decrypt')

    const k = await PwdBox.derive(pwd, this.salt, context)
    if (k === null) return null

    return await this.box.decrypt(k)
  }

  public toString(): string {
    log.trace('toString')
    const salt = a2b64(this.salt)
    const box = this.box.toString()
    return `${salt}.${box}`
  }
  public static fromString(data: string): PwdBox | null {
    log.trace('fromString')

    const parts = data.split('.')
    if (parts.length < 2) return null

    const salt = b642a(parts[0])
    if (salt === null) return null
    const box = SecretBox.fromString(parts.slice(1).join('.'))
    if (box === null) return null

    return new PwdBox(box, salt)
  }
}