require 'dionysus'
require 'dionysus/digest'
require 'dionysus/string'
require 'dionysus/security/password_salt'

##
# Adds String hashing and salting convenience methods.
#
#   require 'dionysus/security/string'
#
# The hash methods may be accessed by the <tt>digest</tt> method or by the 
# dynamic convenience methods.
#
# Examples:
# 
#     'my password'.digest(:sha1)
#     'my password'.sha1
class String
  ##
  # Generate a random, binary salt with the given length (default 16)
  def self.salt( length = 16 )
    PasswordSalt.generate(length, :binary).to_s
  end
  
  ##
  # Sanitize the String from memory.  This is non-reversible.  Runs 7 passes 
  # by default.
  #
  def sanitize( passes = 7 )
    passes.times do
      (0...self.length).each { |i| self[i] = rand(256) }
    end
    (0...self.length).each { |i| self[i] = 0 }
    self.delete!("\000")
  end
  
  ##
  # Generate the given digest hash.
  # 
  # Options:
  # [salt]      Salt to append to the string. (This may be a String or a 
  #             PasswordSalt object) Default: ''
  # [encoding]  Encoding for the hash: <tt>:binary</tt>, <tt>:hex</tt>, 
  #             <tt>:hexidecimal</tt>, <tt>:base64</tt>
  #             Default: <tt>:base64</tt>
  def digest( klass, options = {} )
    digest = Digest.digest(klass, _salted(options[:salt]))
    _encode(digest, options[:encoding] || :base64)
  end
  
  ##
  # Call the appropriate digest method.
  def method_missing( method, *args )
    super if block_given?
    
    if Digest.available_digests.include?(method)
      self.digest(method, *args)
    else
      super
    end
  end
  
  ##
  # Detect the digest of the string.  Returns nil if the digest cannot be 
  # determined.
  #
  # Example:
  #     "wxeCFXPVXePFcpwuFDjonyn1G/w=".detect_digest(:base64) #=> :sha1
  #     "foobar".detect_digest(:hex) #=> nil
  def detect_digest( encoding )
    Digest.detect_digest(self, encoding)
  end
  
  ##
  # Detect the digest of the string.  Raises "Unknown digest" if the digest
  # cannot be determined.
  #
  # Example:
  #     "wxeCFXPVXePFcpwuFDjonyn1G/w=".detect_digest!(:base64) #=> :sha1
  #     "foobar".detect_digest!(:hex) #=> RuntimeError
  def detect_digest!( encoding )
    Digest.detect_digest!(self, encoding)
  end
  
  private
  
  ##
  # Salt the string by appending it to the end or utilizing the 
  # PasswordSalt's salt_password method
  def _salted( salt )
    return self if salt.blank?
    
    unless salt.is_a?(PasswordSalt)
      salt = PasswordSalt.new(salt)
    end
    
    salt.salt_password(self)
  end
  
  ##
  # Encode the value to the given encoding
  def _encode( value, encoding )
    case encoding
    when :binary
      value
    when :base64
      value.encode64s
    when :hex, :hexidecimal
      value.encode_hex
    else
      raise ArgumentError, "Invalid encoding: #{encoding}"
    end
  end
end