##
# Provides a single method +deprecate+ to be used to declare when
# something is going away.
#
#     class Legacy
#       def self.klass_method
#         # ...
#       end
#
#       def instance_method
#         # ...
#       end
#
#       extend Gem::Deprecate
#       deprecate :instance_method, "X.z", 2011, 4
#
#       class << self
#         extend Gem::Deprecate
#         deprecate :klass_method, :none, 2011, 4
#       end
#     end

module Gem
  module Deprecate

    def self.skip # :nodoc:
      @skip ||= false
    end

    def self.skip= v # :nodoc:
      @skip = v
    end

    ##
    # Temporarily turn off warnings. Intended for tests only.

    def skip_during
      Gem::Deprecate.skip, original = true, Gem::Deprecate.skip
      yield
    ensure
      Gem::Deprecate.skip = original
    end

    ##
    # Simple deprecation method that deprecates +name+ by wrapping it up
    # in a dummy method. It warns on each call to the dummy method
    # telling the user of +repl+ (unless +repl+ is :none) and the
    # year/month that it is planned to go away.

    def deprecate name, repl, year, month
      class_eval {
        old = "_deprecated_#{name}"
        alias_method old, name
        define_method name do |*args, &block| # TODO: really works on 1.8.7?
          klass = self.kind_of? Module
          target = klass ? "#{self}." : "#{self.class}#"
          msg = [ "NOTE: #{target}#{name} is deprecated",
            repl == :none ? " with no replacement" : ", use #{repl}",
            ". It will be removed on or after %4d-%02d-01." % [year, month],
            "\n#{target}#{name} called from #{Gem.location_of_caller.join(":")}",
          ]
          warn "#{msg.join}." unless Gem::Deprecate.skip
          send old, *args, &block
        end
      }
    end

    module_function :deprecate, :skip_during
  end
end