summaryrefslogtreecommitdiff
path: root/lib/rbot/messagemapper.rb
blob: 3e877626d54289a47ed7134f314495e54a6e0790 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
# First of all we add a method to the Regexp class
class Regexp

  # a Regexp has captures when its source has open parenthesis which are
  # preceded by an even number of slashes and not followed by a question mark
  #
  def has_captures?
    self.source.match(/(?:^|[^\\])(?:\\\\)*\([^?]/)
  end

  # We may want to remove captures
  def remove_captures
    new = self.source.gsub(/(^|[^\\])((?:\\\\)*)\(([^?])/) {
      "%s%s(?:%s" % [$1, $2, $3]
    }
    Regexp.new(new, self.options)
  end

  # We may want to remove head and tail anchors
  def remove_head_tail
    new = self.source.sub(/^\^/,'').sub(/\$$/,'')
    Regexp.new(new, self.options)
  end

  # The MessageMapper cleanup method: does both remove_capture
  # and remove_head_tail
  def mm_cleanup
    new = self.source.gsub(/(^|[^\\])((?:\\\\)*)\(([^?])/) {
      "%s%s(?:%s" % [$1, $2, $3]
    }.sub(/^\^/,'').sub(/\$$/,'')
    Regexp.new(new, self.options)
  end
end

module Irc
class Bot

  # MessageMapper is a class designed to reduce the amount of regexps and
  # string parsing plugins and bot modules need to do, in order to process
  # and respond to messages.
  #
  # You add templates to the MessageMapper which are examined by the handle
  # method when handling a message. The templates tell the mapper which
  # method in its parent class (your class) to invoke for that message. The
  # string is split, optionally defaulted and validated before being passed
  # to the matched method.
  #
  # A template such as "foo :option :otheroption" will match the string "foo
  # bar baz" and, by default, result in method +foo+ being called, if
  # present, in the parent class. It will receive two parameters, the
  # message (derived from BasicUserMessage) and a Hash containing
  #   {:option => "bar", :otheroption => "baz"}
  # See the #map method for more details.
  class MessageMapper

    class Failure
      STRING   = "template %{template} failed to recognize message %{message}"
      FRIENDLY = "I failed to understand the command"
      attr_reader :template
      attr_reader :message
      def initialize(tmpl, msg)
        @template = tmpl
        @message = msg
      end

      def to_s
        STRING % {
          :template => template.template,
          :regexp => template.regexp,
          :message => message.message,
          :action => template.options[:action]
        }
      end
    end

    # failures with a friendly message
    class FriendlyFailure < Failure
      def friendly
        self.class::FRIENDLY rescue FRIENDLY
      end
    end

    class NotPrivateFailure < FriendlyFailure
      STRING   = "template %{template} is not configured for private messages"
      FRIENDLY = "the command must not be given in private"
    end

    class NotPublicFailure < FriendlyFailure
      STRING   = "template %{template} is not configured for public messages"
      FRIENDLY = "the command must not be given in public"
    end

    class NoMatchFailure < Failure
      STRING = "%{message} does not match %{template} (%{regex})"
    end

    class PartialMatchFailure < Failure
      STRING = "%{message} only matches %{template} (%{regex}) partially"
    end

    class NoActionFailure < FriendlyFailure
      STRING   = "%{template} calls undefined action %{action}"
      FRIENDLY = "uh-ho, somebody forgot to tell me how to do that ..."
    end

    # used to set the method name used as a fallback for unmatched messages.
    # The default fallback is a method called "usage".
    attr_writer :fallback

    # _parent_::   parent class which will receive mapped messages
    #
    # Create a new MessageMapper with parent class _parent_. This class will
    # receive messages from the mapper via the handle() method.
    def initialize(parent)
      @parent = parent
      @templates = Array.new
      @fallback = :usage
    end

    # call-seq: map(botmodule, template, options)
    #
    # _botmodule_:: the BotModule which will handle this map
    # _template_::  a String describing the messages to be matched
    # _options_::   a Hash holding variouns options
    #
    # This method is used to register a new MessageTemplate that will map any
    # BasicUserMessage matching the given _template_ to a corresponding action.
    # A simple example:
    #   plugin.map 'myplugin :parameter'
    # (other examples follow).
    #
    # By default, the action to which the messages are mapped is a method named
    # like the first word of the template. The
    #   :action => 'method_name'
    # option can be used to override this default behaviour. Example:
    #   plugin.map 'myplugin :parameter', :action => 'mymethod'
    #
    # By default whether a handler is fired depends on an auth check. In rbot
    # versions up to 0.9.10, the first component of the string was used for the
    # auth check, unless overridden via the :auth => 'auth_name' option. Since
    # version 0.9.11, a new auth method has been implemented. TODO document.
    #
    # Static parameters (not prefixed with ':' or '*') must match the
    # respective component of the message exactly. Example:
    #   plugin.map 'myplugin :foo is :bar'
    # will only match messages of the form "myplugin something is
    # somethingelse"
    #
    # Dynamic parameters can be specified by a colon ':' to match a single
    # component (whitespace separated), or a * to suck up all following
    # parameters into an array. Example:
    #   plugin.map 'myplugin :parameter1 *rest'
    #
    # You can provide defaults for dynamic components using the :defaults
    # parameter. If a component has a default, then it is optional. e.g:
    #   plugin.map 'myplugin :foo :bar', :defaults => {:bar => 'qux'}
    # would match 'myplugin param param2' and also 'myplugin param'. In the
    # latter case, :bar would be provided from the default.
    #
    # Static and dynamic parameters can also be made optional by wrapping them
    # in square brackets []. For example
    #   plugin.map 'myplugin :foo [is] :bar'
    # will match both 'myplugin something is somethingelse' and 'myplugin
    # something somethingelse'.
    #
    # Components can be validated before being allowed to match, for
    # example if you need a component to be a number:
    #   plugin.map 'myplugin :param', :requirements => {:param => /^\d+$/}
    # will only match strings of the form 'myplugin 1234' or some other
    # number.
    #
    # Templates can be set not to match public or private messages using the
    # :public or :private boolean options.
    #
    # Summary of recognized options:
    #
    # action::
    #   method to call when the template is matched
    # auth_path::
    #   TODO document
    # requirements::
    #   a Hash whose keys are names of dynamic parameters and whose values are
    #   regular expressions that the parameters must match
    # defaults::
    #   a Hash whose keys are names of dynamic parameters and whose values are
    #   the values to be assigned to those parameters when they are missing from
    #   the message. Any dynamic parameter appearing in the :defaults Hash is
    #   therefore optional
    # public::
    #   a boolean (defaults to true) that determines whether the template should
    #   match public (in channel) messages.
    # private::
    #   a boolean (defaults to true) that determines whether the template should
    #   match private (not in channel) messages.
    # threaded::
    #   a boolean (defaults to false) that determines whether the action should be
    #   called in a separate thread.
    #
    #
    # Further examples:
    #
    #   # match 'karmastats' and call my stats() method
    #   plugin.map 'karmastats', :action => 'stats'
    #   # match 'karma' with an optional 'key' and call my karma() method
    #   plugin.map 'karma :key', :defaults => {:key => false}
    #   # match 'karma for something' and call my karma() method
    #   plugin.map 'karma for :key'
    #
    #   # two matches, one for public messages in a channel, one for
    #   # private messages which therefore require a channel argument
    #   plugin.map 'urls search :channel :limit :string',
    #             :action => 'search',
    #             :defaults => {:limit => 4},
    #             :requirements => {:limit => /^\d+$/},
    #             :public => false
    #   plugin.map 'urls search :limit :string',
    #             :action => 'search',
    #             :defaults => {:limit => 4},
    #             :requirements => {:limit => /^\d+$/},
    #             :private => false
    #
    def map(botmodule, *args)
      @templates << MessageTemplate.new(botmodule, *args)
    end

    # Iterate over each MessageTemplate handled.
    def each
      @templates.each {|tmpl| yield tmpl}
    end

    # Return the last added MessageTemplate
    def last
      @templates.last
    end

    # _m_::  derived from BasicUserMessage
    #
    # Examine the message _m_, comparing it with each map()'d template to
    # find and process a match. Templates are examined in the order they
    # were map()'d - first match wins.
    #
    # Returns +true+ if a match is found including fallbacks, +false+
    # otherwise.
    def handle(m)
      return false if @templates.empty?
      failures = []
      @templates.each do |tmpl|
        params = tmpl.recognize(m)
        if params.kind_of? Failure
          failures << params
        else
          action = tmpl.options[:action]
          unless @parent.respond_to?(action)
            failures << NoActionFailure.new(tmpl, m)
            next
          end
          auth = tmpl.options[:full_auth_path]
          debug "checking auth for #{auth}"
          if m.bot.auth.allow?(auth, m.source, m.replyto)
            debug "template match found and auth'd: #{action.inspect} #{params.inspect}"
            if !m.in_thread and (tmpl.options[:thread] or tmpl.options[:threaded]) and
                (defined? WebServiceUser and not m.source.instance_of? WebServiceUser)
              # Web service: requests are handled threaded anyway and we want to 
              # wait for the responses.

              # since the message action is in a separate thread, the message may be
              # delegated to unreplied() before the thread has a chance to actually
              # mark it as replied. since threading is used mostly for commands that
              # are known to take some processing time (e.g. download a web page) before
              # giving an output, we just mark these as 'replied' here
              m.replied = true
              Thread.new do
                begin
                  @parent.send(action, m, params)
                rescue Exception => e
                  error "In threaded action: #{e.message}"
                  debug e.backtrace.join("\n")
                end
              end
            else
              @parent.send(action, m, params)
            end

            return true
          end
          debug "auth failed for #{auth}"
          # if it's just an auth failure but otherwise the match is good,
          # don't try any more handlers
          return false
        end
      end
      failures.each {|r|
        debug "#{r.template.inspect} => #{r}"
      }
      debug "no handler found, trying fallback"
      if @fallback && @parent.respond_to?(@fallback)
        if m.bot.auth.allow?(@fallback, m.source, m.replyto)
          @parent.send(@fallback, m, {:failures => failures})
          return true
        end
      end
      return false
    end

  end

  # MessageParameter is a class that collects all the necessary information
  # about a message (dynamic) parameter (the :param or *param that can be found
  # in a #map).
  #
  # It has a +name+ attribute, +multi+ and +optional+ booleans that tell if the
  # parameter collects more than one word, and if it's optional (respectively).
  # In the latter case, it can also have a default value.
  #
  # It is possible to assign a collector to a MessageParameter. This can be either
  # a Regexp with captures or an Array or a Hash. The collector defines what the
  # collect() method is supposed to return.
  class MessageParameter
    attr_reader :name
    attr_writer :multi
    attr_writer :optional
    attr_accessor :default

    def initialize(name)
      self.name = name
      @multi = false
      @optional = false
      @default = nil
      @regexp = nil
      @index = nil
    end

    def name=(val)
      @name = val.to_sym
    end

    def multi?
      @multi
    end

    def optional?
      @optional
    end

    # This method is used to turn a matched item into the actual parameter value.
    # It only does something when collector= set the @regexp to something. In
    # this case, _val_ is matched against @regexp and then the match result
    # specified in @index is selected. As a special case, when @index is nil
    # the first non-nil captured group is returned.
    def collect(val)
      return val unless @regexp
      mdata = @regexp.match(val)
      if @index
        return mdata[@index]
      else
        return mdata[1..-1].compact.first
      end
    end

    # This method allow the plugin programmer to choose to only pick a subset of the
    # string matched by a parameter. This is done by passing the collector=()
    # method either a Regexp with captures or an Array or a Hash.
    #
    # When the method is passed a Regexp with captures, the collect() method will
    # return the first non-nil captured group.
    #
    # When the method is passed an Array, it will grab a regexp from the first
    # element, and possibly an index from the second element. The index can
    # also be nil.
    #
    # When the method is passed a Hash, it will grab a regexp from the :regexp
    # element, and possibly an index from the :index element. The index can
    # also be nil.
    def collector=(val)
      return unless val
      case val
      when Regexp
        return unless val.has_captures?
        @regexp = val
      when Array
        warning "Collector #{val.inspect} is too long, ignoring extra entries" unless val.length <= 2
        @regexp = val[0]
        @index = val[1] rescue nil
      when Hash
        raise "Collector #{val.inspect} doesn't have a :regexp key" unless val.has_key?(:regexp)
        @regexp = val[:regexp]
        @index = val.fetch(:regexp, nil)
      end
      raise "The regexp of collector #{val.inspect} isn't a Regexp" unless @regexp.kind_of?(Regexp)
      raise "The index of collector #{val.inspect} is present but not an integer " if @index and not @index.kind_of?(Fixnum)
    end

    def inspect
      mul = multi? ? " multi" : " single"
      opt = optional? ? " optional" : " needed"
      if @regexp
        reg = " regexp=%s index=%s" % [@regexp, @index]
      else
        reg = nil
      end
      "<%s %s%s%s%s>" % [self.class, name, mul, opt, reg]
    end
  end

  # MessageTemplate is the class that holds the actual message template map()'d
  # by a BotModule and handled by a MessageMapper
  #
  class MessageTemplate
    attr_reader :defaults  # the defaults hash
    attr_reader :options   # the options hash
    attr_reader :template  # the actual template string
    attr_reader :items     # the collection of dynamic and static items in the template
    attr_reader :regexp    # the Regexp corresponding to the template
    attr_reader :botmodule # the BotModule that map()'d this MessageTemplate

    # call-seq: initialize(botmodule, template, opts={})
    #
    # Create a new MessageTemplate associated to BotModule _botmodule_, with
    # template _template_ and options _opts_
    #
    def initialize(botmodule, template, hash={})
      raise ArgumentError, "Third argument must be a hash!" unless hash.kind_of?(Hash)
      @defaults = hash[:defaults].kind_of?(Hash) ? hash.delete(:defaults) : {}
      @requirements = hash[:requirements].kind_of?(Hash) ? hash.delete(:requirements) : {}
      @template = template
      case botmodule
      when String
        @botmodule = botmodule
      when Plugins::BotModule
        @botmodule = botmodule.name
      else
        raise ArgumentError, "#{botmodule.inspect} is not a botmodule nor a botmodule name"
      end

      self.items = template
      # @dyn_items is an array of MessageParameters, except for the first entry
      # which is the template
      @dyn_items = @items.collect { |it|
        if it.kind_of?(Symbol)
          i = it.to_s
          opt = MessageParameter.new(i)
          if i.sub!(/^\*/,"")
            opt.name = i
            opt.multi = true
          end
          opt.default = @defaults[opt.name]
          opt.collector = @requirements[opt.name]
          opt
        else
          nil
        end
      }
      @dyn_items.unshift(template).compact!
      debug "Items: #{@items.inspect}; dyn items: #{@dyn_items.inspect}"

      self.regexp = template
      debug "Command #{template.inspect} in #{@botmodule} will match using #{@regexp}"

      set_auth_path(hash)

      unless hash.has_key?(:action)
        hash[:action] = items[0]
      end

      @options = hash

      # debug "Create template #{self.inspect}"
    end

    def set_auth_path(hash)
      if hash.has_key?(:auth)
        warning "Command #{@template.inspect} in #{@botmodule} uses old :auth syntax, please upgrade"
      end
      if hash.has_key?(:full_auth_path)
        warning "Command #{@template.inspect} in #{@botmodule} sets :full_auth_path, please don't do this"
      else
        pre = @botmodule
        words = items.reject{ |x|
          x == pre || x.kind_of?(Symbol) || x =~ /\[|\]/
        }
        if words.empty?
          post = nil
        else
          post = words.first
        end
        if hash.has_key?(:auth_path)
          extra = hash[:auth_path]
          if extra.sub!(/^:/, "")
            pre += "::" + post
            post = nil
          end
          if extra.sub!(/:$/, "")
            if words.length > 1
              post = [post,words[1]].compact.join("::")
            end
          end
          pre = nil if extra.sub!(/^!/, "")
          post = nil if extra.sub!(/!$/, "")
          extra = nil if extra.empty?
        else
          extra = nil
        end
        hash[:full_auth_path] = [pre,extra,post].compact.join("::")
        debug "Command #{@template} in #{botmodule} will use authPath #{hash[:full_auth_path]}"
        # TODO check if the full_auth_path is sane
      end
    end

    def items=(str)
      raise ArgumentError, "template #{str.inspect} should be a String" unless str.kind_of?(String)

      # split and convert ':xyz' to symbols
      items = str.strip.split(/\]?\s+\[?|\]?$/).collect { |c|
        # there might be extra (non-alphanumeric) stuff (e.g. punctuation) after the symbol name
        if /^(:|\*)(\w+)(.*)/ =~ c
          sym = ($1 == ':' ) ? $2.intern : "*#{$2}".intern
          if $3.empty?
            sym
          else
            [sym, $3]
          end
        else
          c
        end
      }.flatten
      @items = items

      raise ArgumentError, "Illegal template -- first component cannot be dynamic: #{str.inspect}" if @items.first.kind_of? Symbol

      raise ArgumentError, "Illegal template -- first component cannot be optional: #{str.inspect}" if @items.first =~ /\[|\]/

      # Verify uniqueness of each component.
      @items.inject({}) do |seen, item|
        if item.kind_of? Symbol
          # We must remove the initial * when present,
          # because the parameters hash will intern both :item and *item as :item
          it = item.to_s.sub(/^\*/,"").intern
          raise ArgumentError, "Illegal template -- duplicate item #{it} in #{str.inspect}" if seen.key? it
          seen[it] = true
        end
        seen
      end
    end

    def regexp=(str)
      # debug "Original string: #{str.inspect}"
      rx = Regexp.escape(str)
      # debug "Escaped: #{rx.inspect}"
      rx.gsub!(/((?:\\ )*)(:|\\\*)(\w+)/) { |m|
        whites = $1
        is_single = $2 == ":"
        name = $3.intern

        not_needed = @defaults.has_key?(name)

        has_req = @requirements[name]
        debug "Requirements for #{name}: #{has_req.inspect}"
        case has_req
        when nil
          sub = is_single ? "\\S+" : ".*?"
        when Regexp
          # Remove captures and the ^ and $ that are sometimes placed in requirement regexps
          sub = has_req.mm_cleanup
        when String
          sub = Regexp.escape(has_req)
        when Array
          sub = has_req[0].mm_cleanup
        when Hash
          sub = has_req[:regexp].mm_cleanup
        else
          warning "Odd requirement #{has_req.inspect} of class #{has_req.class} for parameter '#{name}'"
          sub = Regexp.escape(has_req.to_s) rescue "\\S+"
        end
        debug "Regexp for #{name}: #{sub.inspect}"
        s = "#{not_needed ? "(?:" : ""}#{whites}(#{sub})#{ not_needed ? ")?" : ""}"
      }
      # debug "Replaced dyns: #{rx.inspect}"
      rx.gsub!(/((?:\\ )*)((?:\\\[)+)/, '\2\1')
      # debug "Corrected optionals spacing: #{rx.inspect}"
      rx.gsub!(/\\\[/, "(?:")
      rx.gsub!(/\\\]/, ")?")
      # debug "Delimited optionals: #{rx.inspect}"
      rx.gsub!(/(?:\\ )+/, "\\s+")
      # debug "Corrected spaces: #{rx.inspect}"
      # Created message (such as by fake_message) can contain multiple lines
      @regexp = /\A#{rx}\z/m
    end

    # Recognize the provided string components, returning a hash of
    # recognized values, or [nil, reason] if the string isn't recognized.
    def recognize(m)

      debug "Testing #{m.message.inspect} against #{self.inspect}"

      matching = @regexp.match(m.message)
      return MessageMapper::NoMatchFailure.new(self, m) unless matching
      return MessageMapper::PartialMatchFailure.new(self, m) unless matching[0] == m.message

      return MessageMapper::NotPrivateFailure.new(self, m) if @options.has_key?(:private) && !@options[:private] && m.private?
      return MessageMapper::NotPublicFailure.new(self, m) if @options.has_key?(:public) && !@options[:public] && !m.private?

      debug_match = matching[1..-1].collect{ |d| d.inspect}.join(', ')
      debug "#{m.message.inspect} matched #{@regexp} with #{debug_match}"
      debug "Associating #{debug_match} with dyn items #{@dyn_items.join(', ')}"

      options = @defaults.dup

      @dyn_items.each_with_index { |it, i|
        next if i == 0
        item = it.name
        debug "dyn item #{item} (multi-word: #{it.multi?.inspect})"
        if it.multi?
          if matching[i].nil?
            default = it.default
            case default
            when Array
              value = default.clone
            when String
              value = default.strip.split
            when nil, false, []
              value = []
            else
              warning "Unmanageable default #{default} detected for :*#{item.to_s}, using []"
              value = []
            end
            case default
            when String
              value.instance_variable_set(:@string_value, default)
            else
              value.instance_variable_set(:@string_value, value.join(' '))
            end
          else
            value = matching[i].split
            value.instance_variable_set(:@string_value, matching[i])
          end
          def value.to_s
            @string_value
          end
        else
          if matching[i].nil?
            warning "No default value for option #{item.inspect} specified" unless @defaults.has_key?(item)
            value = it.default
          else
            value = it.collect(matching[i])
          end
        end
        options[item] = value
        debug "set #{item} to #{options[item].inspect}"
      }

      options.delete_if {|k, v| v.nil?} # Remove nil values.
      return options
    end

    def inspect
      when_str = @requirements.empty? ? "" : " when #{@requirements.inspect}"
      default_str = @defaults.empty? ? "" : " || #{@defaults.inspect}"
      "<#{self.class.to_s} #{@items.map { |c| c.inspect }.join(' ').inspect}#{default_str}#{when_str}>"
    end

    def requirements_for(name)
      name = name.to_s.sub(/^\*/,"").intern if (/^\*/ =~ name.inspect)
      presence = (@defaults.key?(name) && @defaults[name].nil?)
      requirement = case @requirements[name]
        when nil then nil
        when Regexp then "match #{@requirements[name].inspect}"
        else "be equal to #{@requirements[name].inspect}"
      end
      if presence && requirement then "#{name} must be present and #{requirement}"
      elsif presence || requirement then "#{name} must #{requirement || 'be present'}"
      else "#{name} has no requirements"
      end
    end
  end
end
end