import logger from 'log'
const log = logger('crypto:kdf')

export enum Usage {
  sign,
  wrap
}
export async function hkdf(key: Uint8Array, usage: Usage): Promise<CryptoKey | Uint8Array> {
  log.trace('HKDF')
  log.trace(`usage : ${usage === Usage.sign ? 'sign' : 'wrap'}`)

  const material = await crypto.subtle.importKey('raw', key, 'HKDF', false, ['deriveKey', 'deriveBits'])

  if (usage === Usage.wrap) {
    return crypto.subtle.deriveKey(
      {
        name: 'HKDF',
        hash: 'SHA-512',
        salt: new Uint8Array(32),
        info: new TextEncoder().encode('wrap')
      },
      material,
      {name: 'AES-GCM', length: 256},
      false,
      ['wrapKey', 'unwrapKey']
    )
  } else if (usage === Usage.sign) {
    const buffer = await crypto.subtle.deriveBits(
      {
        name: 'HKDF',
        hash: 'SHA-512',
        salt: new Uint8Array(32),
        info: new TextEncoder().encode('sign')
      },
      material,
      512
    )
    return new Uint8Array(buffer)
  } else {
    log.warn(`Called HKDF with unknown enum value : ${usage}`)
    throw "I don't even know what to say."
  }
}

export async function pbkdf(salt: Uint8Array, password: string): Promise<Uint8Array> {
  log.trace('PBKDF')
  const material = await crypto.subtle.importKey('raw', new TextEncoder().encode(password), 'PBKDF2', false, [
    'deriveBits'
  ])

  const buffer = await crypto.subtle.deriveBits(
    {
      name: 'PBKDF2',
      salt,
      iterations: 250_000,
      hash: 'SHA-512'
    },
    material,
    256
  )

  return new Uint8Array(buffer)
}

export function ecdh(privkey: CryptoKey, pubkey: CryptoKey): Promise<CryptoKey> {
  log.trace('ECDH')
  return crypto.subtle.deriveKey(
    {
      name: 'ECDH',
      public: pubkey
    },
    privkey,
    {
      name: 'AES-GCM',
      length: 256
    },
    false,
    ['wrapKey', 'unwrapKey']
  )
}