class AssertionError < RuntimeError; end

class MustAssertions < ExtraBlankSlate
  def initialize obj
    @obj = obj
  end
  
  def == o
    @obj == o
  end
  
  def never_called
    false
  end
  
  def nil
    @obj.equal? nil
  end
    
  def a klass
    if klass.class == Array
      klass.any?{|k| @obj.is_a? k}
    else
      @obj.is_a? klass
    end
  end
  alias_method :an, :a
        
  # def be klass = nil
  #   if klass.class == Array
  #     klass.any?{|k| @obj.respond_to :is?, k}
  #   else
  #     @obj.respond_to :is?, klass
  #   end
  # end
    
  def include o
    @obj.include? o
  end
    
  def in *enum
    Array(enum).include? @obj
  end

  def true
    !!@obj
  end

  def false
    !@obj
  end

  def empty
    @obj.empty?
  end
  
  def blank
    @obj.blank?
  end
  
  def > o
    @obj > o
  end
  
  def < o
    @obj < o
  end
  
  def be
    @prefix = 'be'
    self
  end
  
  def have
    @prefix = 'have'
    self
  end
  
  def self.assertions
    special = %w{be have}
    instance_methods.select{|m| m !~ /^__/ and m != 'be'}
  end

  protected
    def method_missing m, *args, &b
      raise RuntimeError, "Assertion '#{m}' is unknown!", caller[1..-1]
    end
  
    def failed method, negative, *args
      unless args.empty?
        Kernel.raise AssertionError, "
  ASSERTION FAILED (#{caller[1]}):
  #{@obj.inspect} must #{'not ' if negative}#{"#{@prefix} " if @prefix}#{method} #{args.first}
        ", caller[3..-1]
      else
        Kernel.raise AssertionError, "
  ASSERTION FAILED (#{caller[1]}):
  #{@obj.inspect} must #{'not ' if negative}#{"#{@prefix} " if @prefix}#{method}
        ", caller[3..-1]
      end
    end
end

class Must < MustAssertions
  assertions.each do |m|
    desition = "_#{m}"
    alias_method desition, m
    define_method m do |*args|
      failed m, false, *args unless __send__(desition, *args)      
    end
  end
end

class MustNot < MustAssertions
  assertions.each do |m|
    desition = "_#{m}"
    alias_method desition, m
    define_method m do |*args|
      failed m, true, *args if __send__(desition, *args)      
    end
  end
end

Object.class_eval do
  
  def must
    Must.new self
  end
  
  def must_not
    MustNot.new self
  end
  
  def must_be
    must.be
  end
  
  def must_not_be
    must_not.be
  end
  
  # def must_have
  #   must.have
  # end
  # 
  # def must_not_have
  #   must_not.have
  # end
end