HTTP User Agent Example

http.p6

#| Abstract representation of an HTTP connection
role HTTPConnection {
    method send(Buf $bytes) { ... }
}

# Stub classes that are HTTPConnections, just to illustrate the kind of things
# you could do.  They will probably wrap each other, something like this:
#
#    SSLConnection.new(ConnectProxyConnection.new(:host<...>, :port(...)));

#| Raw TCP connection; useful for direct http:// URLs
class RawConnection does HTTPConnection { ... }

#| HTTP over SSL; useful for https://
class SSLConnection does HTTPConnection { ... }

#| Useful if you need to go over a SOCKS proxy
class SOCKSConnection does HTTPConnection { ... }

#| Go over a network proxy using the CONNECT verb
class ConnectProxyConnection does HTTPConnection { ... }

#| Go over an HTTP proxy without using CONNECT
class ProxyConnection does HTTPConnection { ... }

class ConnectionManager {
    #| Returns an HTTPConnection object appropriate for C<$req>.
    method connect(Request $req) returns HTTPConnection {
        ...
    }
}

# The UserAgent itself
class UserAgent {
    has $.connection-manager is rw handles 'connect' = ConnectionManager.new; # this could be a different object (you could even provide a fake one for testing)

    method send-request(Request $req) {
        self.*before-request($req);

        my $conn = $.connect($req);
        my $res  = $conn.send($req.Buf);
           $res  = Response.parse($res);

        self.*after-request($req, $res);

        $res
    }

    method GET($url) {
        $.send-request(Request.new(:method<GET>, :$url))
    }
}

# An example middleware

role CookieBehavior {
    method before-request(Request $req) {
        # XXX insert cookies for domain
    }

    method after-request(Request $, Response $res) {
        # XXX store cookies for domain
    }
}

# Another middleware

role AuthBasicBehavior {
    method before-request(Request $req) {
        # XXX insert username/password into $req
    }
}

# Example:

my $ua = UserAgent.new does (CookieBehavior, AuthBasicBehavior); # there would probably be some internal sugar for this in UserAgent