module Cryptology

# File lib/cryptology.rb, line 17
def self.decrypt(data:, key:, salt:, iter: 10_000, cipher: 'AES-256-CBC', iv:)
  base64_decoded = ::Base64.decode64(data.to_s)
  decrypt_data(base64_decoded, digest_key(key, salt, iter), cipher, iv)
    .force_encoding('UTF-8').encode
end

# File lib/cryptology.rb, line 23
def self.decryptable?(data:, key:, salt:, iter: 10_000, cipher: 'AES-256-CBC', iv:)
  return true if decrypt(data: data, key: key, salt: salt, iter: iter, cipher: cipher, iv: iv)
rescue OpenSSL::Cipher::CipherError
  false
end

# File lib/cryptology.rb, line 6
def self.encrypt(data:, key:, salt: nil, iter: 10_000, cipher: 'AES-256-CBC', iv: nil)
  salt ||= OpenSSL::Random.random_bytes(16)
  iv ||= OpenSSL::Cipher.new(cipher).random_iv
  encrypted = encrypt_data(data.to_s, digest_key(key, salt, iter), cipher, iv)
  { 'cipher' => cipher,
    'salt' => salt,
    'iter' => iter,
    'iv' => iv,
    'data' => ::Base64.encode64(encrypted) }
end

# File lib/cryptology.rb, line 37
def self.decrypt_data(data, key, cipher, iv)
  decipher = OpenSSL::Cipher.new(cipher)
  decipher.decrypt
  decipher.key = key
  decipher.iv  = iv unless iv.length != decipher.random_iv.length
  decipher.update(data) + decipher.final
end

# File lib/cryptology.rb, line 45
def self.digest_key(key, salt, iter)
  digest = OpenSSL::Digest::SHA256.new
  len = digest.digest_length
  OpenSSL::PKCS5.pbkdf2_hmac(key, salt, iter, len, digest)
end

# File lib/cryptology.rb, line 29
def self.encrypt_data(data, key, cipher, iv)
  c = OpenSSL::Cipher.new(cipher)
  c.encrypt
  c.key = key
  c.iv  = iv unless iv.length != c.random_iv.length
  c.update(data) + c.final
end