# File lib/net/flickr.rb, line 102
def initialize(api_key, api_secret = nil)
  @api_key    = api_key
  @api_secret = api_secret
  
  # Initialize dependent classes.

  @auth   = Auth.new(self)
  @people = People.new(self)
  @photos = Photos.new(self)
end

# File lib/net/flickr.rb, line 113
def auth
  @auth
end

# File lib/net/flickr.rb, line 120
def parse_response(response_xml)
  begin
    xml = Hpricot::XML(response_xml)
  rescue => e
    raise InvalidResponse, 'Invalid Flickr API response'
  end
  
  unless rsp = xml.at('/rsp')
    raise InvalidResponse, 'Invalid Flickr API response'
  end
  
  if rsp['stat'] == 'ok'
    return rsp
  elsif rsp['stat'] == 'fail'
    raise APIError, rsp.at('/err')['msg']
  else
    raise InvalidResponse, 'Invalid Flickr API response'
  end
end

# File lib/net/flickr.rb, line 141
def people
  @people
end

# File lib/net/flickr.rb, line 146
def photos
  @photos
end

# File lib/net/flickr.rb, line 153
def request(method, args = {})
  params  = args.merge({'method' => method, 'api_key' => @api_key})      
  url     = URI.parse(REST_ENDPOINT)
  http    = Net::HTTP.new(url.host, url.port)
  request = sign_request(Net::HTTP::Post.new(url.path), params)
  
  http.start do |http|
    if block_given?
      http.request(request) {|response| yield response }
    else
      response = http.request(request)
    
      # Raise a Net::HTTP error if the HTTP request failed.

      unless response.is_a?(Net::HTTPSuccess) || 
          response.is_a?(Net::HTTPRedirection)
        response.error!
      end
      
      # Return the parsed response.

      return parse_response(response.body)
    end
  end
end

# File lib/net/flickr.rb, line 178
def sign_request(request, params)
  # If the secret isn't set, we can't sign anything.

  if @api_secret.nil?
    request.set_form_data(params)
    return request
  end
  
  # Add auth_token to the param list if we're already authenticated.

  params['auth_token'] = @auth.token unless @auth.token.nil?
  
  # Build a sorted, concatenated parameter list as described at

  # http://flickr.com/services/api/auth.spec.html

  paramlist = ''
  params.keys.sort.each {|key| paramlist << key << 
      URI.escape(params[key].to_s) }
  
  # Sign the request with a hash of the secret key and the concatenated

  # parameter list.

  params['api_sig'] = Digest::MD5.hexdigest(@api_secret + paramlist)
  request.set_form_data(params)
  
  return request      
end

# File lib/net/flickr.rb, line 203
def sign_url(url)
  return url if @api_secret.nil?

  uri = URI.parse(url)

  params = uri.query.split('&')
  params << 'api_sig=' + Digest::MD5.hexdigest(@api_secret +
      params.sort.join('').gsub('=', ''))

  uri.query = params.join('&')

  return uri.to_s
end