import logger from 'log'
import SecretBox from './secret-box'
import {DHusage, ecdh} from './kdf'
import {pubkey_fromString, pubkey_toString, Usage} from './misc'
import * as consts from './const'

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

export default class PrivateBox {
  private constructor(
    private readonly pubkey: CryptoKey,
    private readonly box: SecretBox
  ) {}

  public static gen(extractable: boolean = true): Promise<CryptoKeyPair> {
    log.trace('generate keypair')
    log.trace('Extractable :', extractable)
    try {
      return crypto.subtle.generateKey(consts.ECDH, extractable, ['deriveKey']) as Promise<CryptoKeyPair>
    } catch (e) {
      log.warn('Failed to generate a key')
      log.debug('Error :', e)
      throw e
    }
  }

  public static async encrypt(data: Uint8Array, pubkey: CryptoKey): Promise<PrivateBox> {
    log.trace('encrypt')
    const tmp_pair = await PrivateBox.gen(false)
    const key = await ecdh(tmp_pair.privateKey, pubkey, DHusage.box)
    const box = await SecretBox.encrypt(data, key)
    return new this(tmp_pair.publicKey, box)
  }
  public async decrypt(privkey: CryptoKey): Promise<Uint8Array | null> {
    log.trace('decrypt')
    const key = await ecdh(privkey, this.pubkey, DHusage.box)
    return this.box.decrypt(key)
  }

  public async toString(): Promise<string> {
    log.trace('toString')
    const pubkey = await pubkey_toString(this.pubkey)
    const box = this.box.toString()
    return `${pubkey}.${box}`
  }
  public static async fromString(data: string): Promise<PrivateBox | null> {
    log.trace('fromString')

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

    const pubkey = await pubkey_fromString(parts[0], Usage.ecdh)
    if (pubkey === null) return null
    const box = SecretBox.fromString(parts.slice(1).join('.'))
    if (box === null) return null

    return new PrivateBox(pubkey, box)
  }
}