#!/usr/bin/perl
# "HTTP Push" is not readily attainable, so instead we will simulate it using a
# long-pull, aka "Comet". The client browser simply opens an HTTP connection to
# the server and waits for a response. The server doesn't respond until there
# is some event (here a new message), giving the appearance of HTTP-push.
#
# Each user gets three continuations for these three cases:
#
# - Initial load or reload of the page
# - Sending a message (uses AJAX on the client)
# - Recieving messages (uses COMET on the client)
use strict;
use lib '../lib';
use Continuity;
my @messages; # Global (shared) list of messages
my $got_message; # Flag to indicate that there is a new message to display
my $server = Continuity->new(
port => 16001,
path_session => 1,
cookie_session => 'sid',
);
$server->loop;
# This is the main entrypoint. We are looking for one of three things -- a
# pushstream, a sent message, or a request for the main HTML. We delegate each
# of these cases, none of which will return (they all loop forever).
sub main {
my ($req) = @_;
my $path = $req->request->url->path;
print STDERR "Path: '$path'\n";
# If this is a request for the pushtream, then give them that
if($path =~ /pushstream/) {
pushstream($req);
}
# If they are sending us a message, we give them a thread for that too
if($path =~ /sendmessage/) {
send_message($req);
}
# Otherwise, lets give them the base page
send_base_page($req);
}
# Here we accept a connection to the browser, and keep it open. Meanwhile we
# watch the global $got_message variable, and when it gets touched we send off
# the list of messages through the held-open connection. Then we let the
# browser open a new connection and begin again.
sub pushstream {
my ($req) = @_;
# Set up watch event -- this will be triggered when $got_message is written
my $w = Coro::Event->var(var => \$got_message, poll => 'w');
while(1) {
print STDERR "**** GOT MESSAGE, SENDING ****\n";
my $log = join "
", @messages;
$req->print($log);
$req->next;
print STDERR "**** Waiting for got_message indicator ****\n";
$w->next;
}
}
# Watch for the user to send us a message. As soon as we get it, we add it to
# our list of messages and touch the $got_message flag to let all the
# pushstreams know.
sub send_message {
my ($req) = @_;
while(1) {
my $msg = $req->param('message');
my $name = $req->param('username');
if($msg) {
unshift @messages, "$name: $msg";
pop @messages if $#messages > 15; # Only keep the recent 15 messages
}
$got_message = 1;
$req->print("Got it!");
$req->next;
}
}
# This isn't a pushstream, nor a new message. It is just the main page. We loop
# in case they ask for it multiple times :)
sub send_base_page {
my ($req) = @_;
while(1) {
$req->print(qq{
Chat!
-- no messages yet --
});
$req->next;
}
}