module RSpec::Expectations::Syntax

def default_should_host
  @default_should_host ||= ::Object.ancestors.last
end

def disable_expect(syntax_host = ::RSpec::Matchers)
  return unless expect_enabled?(syntax_host)
  syntax_host.module_eval do
    undef expect
  end
  ::RSpec::Expectations::ExpectationTarget.disable_deprecated_should
end

def disable_should(syntax_host = default_should_host)
  return unless should_enabled?(syntax_host)
  syntax_host.module_eval do
    undef should
    undef should_not
  end
  ::RSpec::Expectations::ExpectationTarget.disable_deprecated_should
end

def enable_expect(syntax_host = ::RSpec::Matchers)
  return if expect_enabled?(syntax_host)
  syntax_host.module_exec do
    def expect(value=::RSpec::Expectations::ExpectationTarget::UndefinedValue, &block)
      ::RSpec::Expectations::ExpectationTarget.for(value, block)
    end
  end
  ::RSpec::Expectations::ExpectationTarget.enable_deprecated_should if should_enabled?
end

def enable_should(syntax_host = default_should_host)
  return if should_enabled?(syntax_host)
  syntax_host.module_eval do
    def should(matcher=nil, message=nil, &block)
      ::RSpec::Expectations::PositiveExpectationHandler.handle_matcher(self, matcher, message, &block)
    end
    def should_not(matcher=nil, message=nil, &block)
      ::RSpec::Expectations::NegativeExpectationHandler.handle_matcher(self, matcher, message, &block)
    end
  end
  ::RSpec::Expectations::ExpectationTarget.enable_deprecated_should if expect_enabled?
end

def expect(value=::RSpec::Expectations::ExpectationTarget::UndefinedValue, &block)
  ::RSpec::Expectations::ExpectationTarget.for(value, block)
end

def expect_enabled?(syntax_host = ::RSpec::Matchers)
  syntax_host.method_defined?(:expect)
end

def expression_generator
  if expect_enabled?
    ExpectExpressionGenerator
  else
    ShouldExpressionGenerator
  end
end

def negative_expression(target_expression, matcher_expression)
  expression_generator.negative_expression(target_expression, matcher_expression)
end

def positive_expression(target_expression, matcher_expression)
  expression_generator.positive_expression(target_expression, matcher_expression)
end

def should(matcher=nil, message=nil, &block)
  ::RSpec::Expectations::PositiveExpectationHandler.handle_matcher(self, matcher, message, &block)
end

def should_enabled?(syntax_host = default_should_host)
  syntax_host.method_defined?(:should)
end

def should_not(matcher=nil, message=nil, &block)
  ::RSpec::Expectations::NegativeExpectationHandler.handle_matcher(self, matcher, message, &block)
end