# Ruby Treasures 0.4
# Copyright (C) 2002 Paul Brannan <paul@atdesk.com>
# 
# You may distribute this software under the same terms as Ruby (see the file
# COPYING that was distributed with this library).
# 
##
# A class to redirect $stdout (or other IO object) to a StringIO object
# (or other object with a write() method).
#
# Example:
# <pre>
#   s = StringIO.new
#   r = Redirector.redirect($stdout, s) do
#     $stdout.puts "this is a test"
#   end
# </pre>
#
class Redirector
  ##
  # Start redirection from one IO object to any other object with a
  # write() method.
  # @param from the IO object to redirect from.
  # @param to the object to redirect to.
  #
  def initialize(from, to)
    @from = from
    @to = to
    start()
  end

  ##
  # Start redirection, if it has not already been started.
  #
  def start
    raise "Redirection already in progress" if @t
    tmp = @from.dup        
    r, w = IO.pipe
    @from.reopen(w)
    @t = Thread.new do
      begin
        loop do
          s = r.read(1) # TODO: can I make this buffered?
          @to.write(s)
        end
      ensure
        @from.reopen(tmp)
        @t = nil
      end
    end
  end

  ##
  # Stop redirection, if it is occurring.
  #
  def stop
    raise "Redirection already stopped" if not @t
    @t.kill
  end

  ##
  # An exception-safe class method for redirection.
  #
  def self.redirect(from, to)
    s = self.new(from, to)
    begin
      yield
    ensure
      s.stop
    end
  end
end

if __FILE__ == $0 then
  class SimpleStringIO
    attr_reader :str
    def initialize; @str = ''; end
    def write(str); @str << str; end
  end

  Thread.abort_on_exception = true
  s = SimpleStringIO.new
  r = Redirector.redirect($stdout, s) do
    $stdout.puts "this is a test"
    $stdout.puts "of the StringIO redirection system"
  end
  puts "Done redirecting."
  puts "Result:\n#{s.str}"
end