import CryptoKit
import ExpoModulesCore

internal struct SealedDataConfig: Record {
  @Field
  var ivLength: Int = DEFAULT_IV_LENGTH

  @Field
  var tagLength: Int = DEFAULT_TAG_LENGTH
}

final class SealedData: SharedObject {
  private var inner: AES.GCM.SealedBox

  init(sealedBox: AES.GCM.SealedBox) {
    inner = sealedBox
  }

  init(ivLength: Int, tagLength: Int, content: Data) throws {
    // SealedBox(combined:) works only if IV length is 12 (default)
    // otherwise this needs to be done manually
    if ivLength == DEFAULT_IV_LENGTH {
      inner = try AES.GCM.SealedBox(combined: content)
    } else {
      let nonce = try AES.GCM.Nonce(data: content.prefix(ivLength))
      inner = try AES.GCM.SealedBox(
        nonce: nonce,
        ciphertext: content.dropFirst(ivLength).dropLast(tagLength),
        tag: content.suffix(tagLength)
      )
    }
  }

  init(iv: Data, ciphertext: Data, tag: Data) throws {
    let nonce = try AES.GCM.Nonce(data: iv)
    inner = try AES.GCM.SealedBox(
      nonce: nonce,
      ciphertext: ciphertext,
      tag: tag
    )
  }

  convenience init(iv: Data, ciphertextWithTag: Data, tagLength: Int) throws {
    try self.init(
      iv: iv,
      ciphertext: ciphertextWithTag.dropLast(tagLength),
      tag: ciphertextWithTag.suffix(tagLength)
    )
  }

  var combined: Data {
    // combined works only if IV length is 12 bytes
    if let combined = inner.combined {
      return combined
    }

    return self.iv + inner.ciphertext + self.tag
  }

  var iv: Data {
    Data(inner.nonce)
  }

  var tag: Data {
    inner.tag
  }

  func ciphertext(withTag: Bool) -> Data {
    if withTag {
      return inner.ciphertext + inner.tag
    }
    return inner.ciphertext
  }

  var nativeValue: AES.GCM.SealedBox { inner }

  override func getAdditionalMemoryPressure() -> Int {
    self.combined.count
  }
}