feat(src): Allow listing devices of concrete types

Currently, the "list" command returns all discovered devices. This
includes also devices without host services like printers. That is a
problem for some API clients (i.e. gvfs). Let's add an optional
argument to specify concrete type.

Fixes: #178

man/wsdd.8

@@ -162,10 +162,12 @@ only. The following commands can be issued:
 Clears the list of all discovered devices. Use the \fBprobe\fR command to
 search for devices again. This command does not return any data and is only
 available in discover mode.
-.SS \fBlist\fR - List discovered devices
-Returns a tab-separated list of discovered devices with the following information.
-The possibly empty list of detected hosts is always terminated with a single
-dot ('.') in an otherwise empty line. This command is only available in discover mode.
+.SS \fBlist \fI[TYPE]\fR - List discovered devices
+Returns a tab-separated list of discovered devices of the provided TYPE (e.g.
+"pub:Computer") with the following information. If no type is provided, all
+discovered devices are listed. The possibly empty list of detected hosts is
+always terminated with a single dot ('.') in an otherwise empty line. This
+command is only available in discover mode.
 .TP
 UUID
 UUID of the discovered device. Note that a multi-homed device should appear

src/wsdd.py

@@ -680,7 +680,7 @@ def extract_wsdp_props(self, root: ElementTree.Element, dialect: str) -> None:
 
     def extract_host_props(self, root: ElementTree.Element) -> None:
         types = root.findtext('wsdp:Types', '', namespaces)
-        self.props['types'] = types.split(' ')[0]
+        self.props['types'] = types.split(' ')
         if types != PUB_COMPUTER:
             return
 
@@ -1162,7 +1162,8 @@ def handle_command(self, line: str, write_stream: asyncio.StreamWriter) -> None:
             logger.debug('clearing list of known devices')
             WSDDiscoveredDevice.instances.clear()
         elif command == 'list' and args.discovery:
-            write_stream.write(bytes(self.get_list_reply(), 'utf-8'))
+            wsd_type = command_args[0] if command_args else None
+            write_stream.write(bytes(self.get_list_reply(wsd_type), 'utf-8'))
         elif command == 'quit':
             write_stream.close()
         elif command == 'start':
@@ -1175,9 +1176,12 @@ def handle_command(self, line: str, write_stream: asyncio.StreamWriter) -> None:
     def get_clients_by_interface(self, interface: Optional[str]) -> List[WSDClient]:
         return [c for c in WSDClient.instances if c.mch.address.interface.name == interface or not interface]
 
-    def get_list_reply(self) -> str:
+    def get_list_reply(self, wsd_type: Optional[str]) -> str:
         retval = ''
         for dev_uuid, dev in WSDDiscoveredDevice.instances.items():
+            if wsd_type and (('types' not in dev.props) or (wsd_type not in dev.props['types'])):
+                continue
+
             addrs_str = []
             for addrs in dev.addresses.items():
                 addrs_str.append(', '.join(['{}'.format(a) for a in addrs]))