class ActiveSupport::EncryptedFile

def self.expected_key_length # :nodoc:

:nodoc: 
def self.expected_key_length # :nodoc:
  @expected_key_length ||= generate_key.length
end

def self.generate_key 

def self.generate_key
  SecureRandom.hex(ActiveSupport::MessageEncryptor.key_len(CIPHER))
end

def change(&block) 

def change(&block)
  writing read, &block
end

def check_key_length 

def check_key_length
  raise InvalidKeyLengthError if key&.length != self.class.expected_key_length
end

def decrypt(contents) 

def decrypt(contents)
  encryptor.decrypt_and_verify contents
end

def encrypt(contents) 

def encrypt(contents)
  check_key_length
  encryptor.encrypt_and_sign contents
end

def encryptor 

def encryptor
  @encryptor ||= ActiveSupport::MessageEncryptor.new([ key ].pack("H*"), cipher: CIPHER, serializer: Marshal)
end

def handle_missing_key 

def handle_missing_key
  raise MissingKeyError.new(key_path: key_path, env_key: env_key) if raise_if_missing_key
end

def initialize(content_path:, key_path:, env_key:, raise_if_missing_key:) 

def initialize(content_path:, key_path:, env_key:, raise_if_missing_key:)
  @content_path = Pathname.new(content_path).yield_self { |path| path.symlink? ? path.realpath : path }
  @key_path = Pathname.new(key_path)
  @env_key, @raise_if_missing_key = env_key, raise_if_missing_key
end

def key

environment variable is not set and the key file does not exist.
If +raise_if_missing_key+ is true, raises MissingKeyError if the
specified by +env_key+, then trying the key file specified by +key_path+.
Returns the encryption key, first trying the environment variable 
def key
  read_env_key || read_key_file || handle_missing_key
end

def key?

does not raise MissingKeyError when +raise_if_missing_key+ is true.
Returns truthy if #key is truthy. Returns falsy otherwise. Unlike #key, 
def key?
  read_env_key || read_key_file
end

def read

decrypted or verified.
- ActiveSupport::MessageEncryptor::InvalidMessage if the content cannot be
if the key is missing.
- MissingContentError if the encrypted file does not exist or otherwise
- MissingKeyError if the key is missing and +raise_if_missing_key+ is true.
Raises:

Reads the file and returns the decrypted content. 
def read
  if !key.nil? && content_path.exist?
    decrypt content_path.binread
  else
    raise MissingContentError, content_path
  end
end

def read_env_key 

def read_env_key
  ENV[env_key].presence
end

def read_key_file 

def read_key_file
  @key_file_contents ||= (key_path.binread.strip if key_path.exist?)
end

def write(contents) 

def write(contents)
  IO.binwrite "#{content_path}.tmp", encrypt(contents)
  FileUtils.mv "#{content_path}.tmp", content_path
end

def writing(contents) 

def writing(contents)
  Tempfile.create(["", "-" + content_path.basename.to_s.chomp(".enc")]) do |tmp_file|
    tmp_path = Pathname.new(tmp_file)
    tmp_path.binwrite contents
    yield tmp_path
    updated_contents = tmp_path.binread
    write(updated_contents) if updated_contents != contents
  end
end