require "thread"

module HTTP_Spew::ClassMethods
  def error_all(requests, error) # :nodoc:
    requests.each { |req| req.error ||= error }
  end

  def done_early(ready, failed, requests) # :nodoc:
    ready.concat(failed)
    pending = requests - ready
    unless pending.empty?
      error = HTTP_Spew::ConnectionReset.new("prematurely terminated")
      ready.concat(error_all(pending, error))
    end
    ready.uniq!
    ready
  end

  # Returns an array of requests that are complete, including those
  # that have errored out.  Incomplete requests remain in +requests+
  # If +need+ is fullfilled, it closes all incomplete requests and
  # returns all requests.
  def wait_nonblock!(need, requests)
    ready, failed = [], []
    requests.delete_if do |req|
      begin
        case req.resume
        when Symbol # :wait_writable, :wait_readable
          false
        else
          (ready << req).size == need and
            return done_early(ready, failed, requests)
          true
        end
      rescue => e
        req.error = e
        failed << req
      end
    end
    ready.concat(failed).empty? ? nil : ready
  end

  def with_timeout(t)
    t0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    yield
  ensure
    t[0] -= Process.clock_gettime(Process::CLOCK_MONOTONIC) - t0
    t[0] = 0.0 if t[0] < 0
  end

  # Returns an array of requests that are complete, including those
  # that have errored out.
  # If +need+ is fullfilled, it closes all incomplete requests.
  def wait_mt(need, requests, timeout)
    ready, failed = [], []
    r, w = IO.pipe
    active = []
    t = [ timeout ]
    requests.each_with_index do |req, i|
      active << Thread.new do
        begin
          rv = req.run(timeout)
          w.write([ i ].pack("v".freeze))
          rv
        rescue => err
          err
        end
      end
    end
    begin
      with_timeout(t) { r.wait_readable(t[0]) }
      req_idx = r.read(2).unpack("v".freeze)[0]
      thr = active[req_idx]
      with_timeout(t) { thr.join(t[0]) }
      rv = thr.value
      (Array === rv ? ready : failed) << requests[req_idx]
      ready.size == need and return done_early(ready, failed, requests)
    end until t[0] < 0.0 || (ready.size + failed.size) == requests.size

    ready.concat(failed)
    pending = requests - ready
    error = HTTP_Spew::TimeoutError.new("request timed out")
    ready.concat(error_all(pending, error))
  ensure
    w.close
    r.close
  end

  def wait(need, requests, timeout)
    ready, failed = [], []
    pollset = {}
    t = [ timeout ]
    begin
      requests.each do |req|
        begin
          case rv = req.resume
          when Symbol # :wait_writable, :wait_readable
            pollset[req] = rv
          else
            (ready << req).size == need and
              return done_early(ready, failed, requests)
            pollset.delete(req)
          end
        rescue => e
          req.error = e
          failed << req
          pollset.delete(req)
        end
      end
      break if pollset.empty?

      busy = pollset.keys
      rv = with_timeout(t) { do_poll(pollset, t[0]) } or break
    end while t[0] > 0.0 && requests = rv.keys.concat(busy).uniq!

    ready.concat(failed)
    unless requests.empty?
      error = HTTP_Spew::TimeoutError.new("request timed out")
      ready.concat(error_all(requests, error))
      ready.uniq!
    end
    ready
  end

  begin
    require 'kgio'
    def do_poll(pollset, sec) # :nodoc:
      Kgio.poll(pollset, (sec * 1000).to_i)
    end
  rescue LoadError
    # emulate Kgio.poll with IO.select
    def do_poll(pollset, sec) # :nodoc:
      rd = []
      wr = []
      pollset.each do |io, events|
        case events
        when :wait_readable
          rd << io
        when :wait_writable
          wr << io
        else
          raise "BUG: unsupported event #{event.inspect} for #{io.inspect}"
        end
      end
      ready = IO.select(rd, wr, nil, sec) or return
      pollset.clear
      ready[0].each { |io| pollset[io] = 1 } # POLLIN
      ready[1].each { |io| pollset[io] = 4 } # POLLOUT
      pollset
    end
  end
end