require "random/secure"

module Cox
  class Error < ::Exception
    class VerificationFailed < Error
    end

    class DecryptionFailed < Error
    end
  end
end

require "./cox/**"

module Cox
  def self.encrypt(data, nonce : Nonce, recipient_public_key : CryptoBox::PublicKey, sender_secret_key : CryptoBox::SecretKey)
    data_buffer = data.to_slice
    data_size = data_buffer.bytesize
    output_buffer = Bytes.new(data_buffer.bytesize + LibSodium::MAC_SIZE)
    if LibSodium.crypto_box_easy(output_buffer.to_slice, data_buffer, data_size, nonce.to_slice, recipient_public_key.to_slice, sender_secret_key.to_slice) != 0
      raise Error.new("crypto_box_easy")
    end
    output_buffer
  end

  def self.encrypt(data, recipient_public_key : CryptoBox::PublicKey, sender_secret_key : CryptoBox::SecretKey)
    nonce = Nonce.new
    {nonce, encrypt(data, nonce, recipient_public_key, sender_secret_key)}
  end

  def self.decrypt(data, nonce : Nonce, sender_public_key : CryptoBox::PublicKey, recipient_secret_key : CryptoBox::SecretKey)
    data_buffer = data.to_slice
    data_size = data_buffer.bytesize
    output_buffer = Bytes.new(data_buffer.bytesize - LibSodium::MAC_SIZE)
    if LibSodium.crypto_box_open_easy(output_buffer.to_slice, data_buffer.to_slice, data_size, nonce.to_slice, sender_public_key.to_slice, recipient_secret_key.to_slice) != 0
      raise Error::DecryptionFailed.new("crypto_box_open_easy")
    end
    output_buffer
  end
end

if Cox::LibSodium.sodium_init == -1
  abort "Failed to init libsodium"
end