class OauthUtil

def initialize
  @consumer_key = ''
  @consumer_secret = ''
  @token = ''
  @token_secret = ''
  @req_method = 'GET'
  @sig_method = 'HMAC-SHA1'
  @oauth_version = '1.0'
  @callback_url = ''
end

def nonce
  Array.new( 5 ) { rand(256) }.pack('C*').unpack('H*').first
end

def percent_encode( string )
  # ref http://snippets.dzone.com/posts/show/1260
  return URI.escape( string, Regexp.new("[^#{URI::PATTERN::UNRESERVED}]") ).gsub('*', '%2A')
end

def query_string
  pairs = []
  @params.sort.each { | key, val | 
    pairs.push( "#{ CGI.escape(key.to_s).gsub(/%(5B|5D)/n) { [$1].pack('H*') } }=#{ CGI.escape(val.to_s) }" )
  }
  pairs.join '&'
end

def sign( parsed_url )
  @params = {
    'oauth_consumer_key' => @consumer_key,
    'oauth_nonce' => nonce,
    'oauth_signature_method' => @sig_method,
    'oauth_timestamp' => Time.now.to_i.to_s,
    'oauth_version' => @oauth_version
  }
  # if url has query, merge key/values into params obj overwriting defaults
  if parsed_url.query
    CGI.parse( parsed_url.query ).each do |k,v|
      if v.is_a?(Array) && v.count == 1
        @params[k] = v.first
      else
        @params[k] = v
      end
    end
  end
  # @ref http://oauth.net/core/1.0/#rfc.section.9.1.2
  @req_url = parsed_url.scheme + '://' + parsed_url.host + parsed_url.path
  # create base str. make it an object attr for ez debugging
  # ref http://oauth.net/core/1.0/#anchor14
  @base_str = [ 
    @req_method, 
    percent_encode( req_url ), 
    # normalization is just x-www-form-urlencoded
    percent_encode( query_string ) 
  ].join( '&' )
  # add signature
  @params[ 'oauth_signature' ] = signature
  return self
end

def signature
  key = percent_encode( @consumer_secret ) + '&' + percent_encode( @token_secret )
  # ref: http://blog.nathanielbibler.com/post/63031273/openssl-hmac-vs-ruby-hmac-benchmarks
  digest = OpenSSL::Digest.new( 'sha1' )
  hmac = OpenSSL::HMAC.digest( digest, key, @base_str )
  # ref http://groups.google.com/group/oauth-ruby/browse_thread/thread/9110ed8c8f3cae81
  Base64.encode64( hmac ).chomp.gsub( /\n/, '' )
end