# From http://burgestrand.se/code/ruby-thread-pool/
#
# Copyright © 2012, Kim Burgestrand kim@burgestrand.se
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

# Class that creates a thread safe pool.
class Pool
  def initialize(size)
    @size = size
    @jobs = Queue.new
    @pool = Array.new(@size) do |i|
      Thread.new do
        Thread.current[:id] = i
        catch(:exit) do
          loop do
            job, args = @jobs.pop
            job.call(*args)
          end
        end
      end
    end
  end

  def schedule(*args, &block)
    @jobs << [block, args]
  end

  def shutdown
    @size.times do
      schedule { throw :exit }
    end
    @pool.map(&:join)
  end
end

if $PROGRAM_NAME == __FILE__
  p = Pool.new(10)

  20.times do |i|
    p.schedule do
      sleep rand(2..5)
      warn "Job #{i} finished by thread #{Thread.current[:id]}\n"
    end
  end
  at_exit { p.shutdown }
end