# Simple RPC client on YAML
#
# Example usage:
#
#   yamlrpc = YamlRpc.new('http://rubyforge.org/projects/yamlrpc/')
#   yamlrpc.foo({
#     :bar => 'foo-bar'
#   )
#
# will HTTP POST
#
#   {
#     :bar => YAML::dump('foo-bar')
#   }
#
# to http://rubyforge.org/projects/yamlrpc/<b>foo</b>
#
# On the server side you can use (Ruby on Rails):
# 
#   YAML::load(params[:yamlrpc])[:foo]
#
# or in PHP:
#
#   $data = syck_load($_POST['yamlrpc']);
#   $data['foo']
#
# See examples in /examples directory
module YamlRpc
  
  class Client
    
    DEFAULT_FORM_DATA_ROOT = :yamlrpc
    DEFAULT_OPEN_TIMEOUT   = 10  # 10 seconds
    DEFAULT_READ_TIMEOUT   = 120 # 2 minutes
    
    attr_accessor :uri
    attr_accessor :form_data_root
    attr_accessor :open_timeout
    attr_accessor :read_timeout
    attr_accessor :user
    attr_accessor :password
    attr_accessor :permanent_data
    
    # * <tt>uri</tt> Root url, ie. "http://my.com/something/"; YamlRpc#some_method(:foo => 'bar') will POST to http://my.com/something/some_method with { :foo => 'bar' } params
    # * <tt>options</tt>
    #   * <tt>:form_data_root</tt> Default to :yamlrpc, meaning all params are passed inside :yamlrpc form field
    #   * <tt>:open_timeout</tt> Open timeout
    #   * <tt>:read_timeout</tt> Read timeout
    #   * <tt>:user</tt> Basic http auth, user name
    #   * <tt>:password</tt> Basic http auth, password
    def initialize(uri, options = {})
      @open_timeout   = options[:open_timeout]
      @read_timeout   = options[:read_timeout]
      @user           = options[:user]
      @password       = options[:password]
      @permanent_data = options[:permanent_data]
      @uri            = URI.parse(uri.to_s)
      @form_data_root = options[:form_data_root] || DEFAULT_FORM_DATA_ROOT
    end
    
    # * <tt>uri</tt> Method name (mainly) or full uri (to support redirects to other domains)
    # * <tt>args</tt> Arguments, nil or Hash of values
    def method_missing(uri, *args)
      args = args.first if args.size == 1 && args.first.is_a?(Hash)
      uri = URI.parse(uri.to_s)
      if uri.host.nil?
        uri.host = @uri.host
        uri.port = @uri.port
      end
      uri.path = "#{@uri.path}#{uri.path}" unless uri.path =~ /^\//
      post(uri, args)
    end

  protected

    # * <tt>uri</tt> URI instance
    # * <tt>args</tt> Optional data to be passed as POST fields, ie: { :status => 'SUCCESS', :message => 'All ok' }
    def post(uri, args = nil)
      req = Net::HTTP::Post.new(uri.path)
      req.set_form_data(args_to_form_data(args) || {}, ';')
      req.basic_auth @user, @password if @user && @password
      http = Net::HTTP.new(uri.host, uri.port)
      http.open_timeout = @open_timeout
      http.read_timeout = @read_timeout
      res = http.start { |http| http.request(req) }
      case res
        when Net::HTTPSuccess
          YAML::load(res.body)
        when Net::HTTPRedirection
          redirect_uri = URI.parse(res['location'])
          if redirect_uri.host.nil?
            redirect_uri.host = uri.host
            redirect_uri.port = uri.port
          end
          post(redirect_uri, args)
        else
          res.value # raises error if not kind of success
      end
    end
    
    # POST form data is always passed in YamlRpc#form_data_root variable name
    # * <tt>args</tt>
    def args_to_form_data(args = nil)
      args = @permanent_data if args.nil? # HACK: this is hack as hell but logically ok for merging to work for nil args
      unless @permanent_data.nil?
        if @permanent_data.respond_to?('merge')
          args = @permanent_data.merge(args)
        elsif @permanent_data.respond_to?('+')
          args = @permanent_data + args
        else
          raise ArgumentError.new("Can't merge #{@permanent_data.class} and #{args.class}")
        end
      end
      { @form_data_root.to_sym => YAML::dump(args) }
    end
  
  end

end