# Licensed under the MIT license
# http://opensource.org/licenses/mit-license.php

# (c) 2005, Tim Potter <tpot@samba.org>

#
# Implementation of SSDP server under Twisted Python.
#

import string

from twisted.python import log
from twisted.internet.protocol import DatagramProtocol

# TODO: Is there a better way of hooking the SSDPServer into a reactor
# without having to know the default SSDP port and multicast address?
# There must be a twisted idiom for doing this.

SSDP_PORT = 1900
SSDP_ADDR = '239.255.255.250'

# TODO: Break out into a HTTPOverUDP class and implement
# process_SEARCH(), process_NOTIFY() methods.  Create UPNP specific
# class to handle services etc.

class SSDPServer(DatagramProtocol):
    """A class implementing a SSDP server.  The notifyReceived and
    searchReceived methods are called when the appropriate type of
    datagram is received by the server."""
    
    elements = {}
    known = {}

    def datagramReceived(self, data, (host, port)):
        """Handle a received multicast datagram."""

        # Break up message in to command and headers

        data = string.replace(data, '\r', '')
        data = string.replace(data, ': ', ':')
        lines = string.split(data, '\n')
        lines = filter(lambda x: len(x) > 0, lines)
        cmd = string.split(lines[0], ' ')

        headers = dict([string.split(x, ':', 1) for x in lines[1:]])

        # TODO: datagram may contain a payload, i.e Content-Length
        # header is > 0.  Maybe use some twisted HTTP object to do the
        # parsing for us.

        # SSDP discovery

        if cmd[0] == 'M-SEARCH' and cmd[1] == '*':
            self.discoveryRequest(headers, (host, port))

        # SSDP presence

        if cmd[0] == 'NOTIFY' and cmd[1] == '*':
            self.notifyReceived(headers, (host, port))

    def discoveryRequest(self, headers, (host, port)):
        """Process a discovery request.  The response must be sent to
        the address specified by (host, port)."""

        log.msg('Discovery request for %s' % headers['ST'])

        # Do we know about this service?

        if not self.known.has_key(headers['ST']):
            return

        # Generate a response

        response = []
        response.append('HTTP/1.1 200 OK')

        for k, v in self.known[headers['ST']].items():
            response.append('%s: %s' % (k, v))

        log.msg('responding with: %s' % response)

        self.transport.write(
            string.join(response, '\r\n') + '\r\n\r\n', (host, port))

    def register(self, usn, st, location):
        """Register a service or device that this SSDP server will
        respond to."""

        log.msg('Registering %s' % st)
        
        self.known[st] = {}
        self.known[st]['USN'] = usn
        self.known[st]['LOCATION'] = location
        self.known[st]['ST'] = st
        self.known[st]['EXT'] = ''
        self.known[st]['SERVER'] = 'Twisted, UPnP/1.0, python-upnp'
        self.known[st]['CACHE-CONTROL'] = 'max-age=1800'

    def notifyReceived(self, headers, (host, port)):
        """Process a presence announcement.  We just remember the
        details of the SSDP service announced."""

        if headers['NTS'] == 'ssdp:alive':

            if not self.elements.has_key(headers['NT']):

                # Register device/service

                self.elements[headers['NT']] = {}
                self.elements[headers['NT']]['USN'] = headers['USN']
                self.elements[headers['NT']]['host'] = (host, port)

                log.msg('Detected presence for %s' % headers['NT'])

        elif headers['NTS'] == 'ssdp:byebye':

            if self.elements.has_key(headers['NT']):

                # Unregister device/service
                
                del(self.elements[headers['NT']])

                log.msg('Detected absence for %s' % headers['NT'])
                
        else:
            log.msg('Unknown subtype %s for notification type %s' %
                    (headers['NTS'], headers['NT']))

    def findService(self, name):
        """Return information about a service registered over SSDP."""

        # TODO: Implement me.

        # TODO: Send out a discovery request if we haven't registered
        # a presence announcement.

    def findDevice(self, name):
        """Return information about a device registered over SSDP."""

        # TODO: Implement me.

        # TODO: Send out a discovery request if we haven't registered
        # a presence announcement.