module Dry::Core::Deprecations

def [](tag)
  Tagged.new(tag)
end

def announce(name, msg, tag: nil)
  warn(deprecation_message(name, msg), tag: tag)
end

def deprecated_name_message(old, new = nil, msg = nil)
  if new
    deprecation_message(old, <<-MSG)
      Please use #{new} instead.
      #{msg}
    MSG
  else
    deprecation_message(old, msg)
  end
end

def deprecation_message(name, msg)
  <<-MSG
    #{ name } is deprecated and will be removed in the next major version
    #{ msg }
  MSG
end

def logger(output = $stderr)
  if defined?(@logger)
    @logger
  else
    set_logger!(output)
  end
end

def set_logger!(output = $stderr)
  if output.respond_to?(:warn)
    @logger = output
  else
    @logger = Logger.new(output).tap do |logger|
      logger.formatter = proc { |_, _, _, msg| "#{ msg }\n" }
    end
  end
end

def warn(msg, tag: nil)
  tagged = "[#{tag || 'deprecated'}] #{msg.gsub(/^\s+/, '')}"
  logger.warn(tagged)
end