#!/usr/bin/perl
# file: web_fetch_p.pl
# Figure 13.9: The web_fetch script uses nonblocking connects to parallelize URL fetches

use strict;
use HTTPFetch;
use IO::Socket;
use IO::Select;

my %CONNECTIONS;  # map socket => object

# create two IO::Select objects to handle writing & reading
my $readers = IO::Select->new;
my $writers = IO::Select->new;

# create the connections from list of urls on command line
while (my $url = shift) {
  next unless my $object = HTTPFetch->new($url);
  $CONNECTIONS{$object->socket} = $object;  # remember its socket
  $writers->add($object->socket);           # monitor it for writing
}

while (my ($readable,$writable) = IO::Select->select($readers,$writers)) {

  foreach (@$writable) {        # handle is ready for writing
    my $obj = $CONNECTIONS{$_};       # recover the HTTP object
    my $result = $obj->send_request;  # try to send the request
    $readers->add($_) if $result;     # send successful, so monitor for reading
    $writers->remove($_);             # and remove from list monitored for writing
  }

  foreach (@$readable) {        # handle is ready for reading
    my $obj = $CONNECTIONS{$_};           # recover the HTTP object
    my $result = $obj->read;              # read some data
    unless ($result) {                    # remove if some error occurred
      $readers->remove($_);  
      delete $CONNECTIONS{$_};
    }
  }

  last unless $readers->count or $writers->count;  # quit when no more to do
}