add list-channels API to relay, use it in receiver

bin/receive_text.py

@@ -1,12 +1,14 @@
 from __future__ import print_function
 import time, json
-from wormhole.transcribe import Receiver
+from wormhole.transcribe import Receiver, list_channels
 from wormhole.codes import input_code_with_completion
 
 APPID = "lothar.com/wormhole/text-xfer"
 
 # we're receiving
-code = input_code_with_completion("Enter receive-text wormhole code: ", [])
+channel_ids = list_channels()
+code = input_code_with_completion("Enter receive-text wormhole code: ",
+                                  channel_ids)
 start = time.time()
 data = json.dumps({"message": "ok"}).encode("utf-8")
 r = Receiver(APPID, data, code)

src/wormhole/relay.py

@@ -68,6 +68,13 @@ class Allocated(resource.Resource):
         request.setHeader("content-type", "application/json; charset=utf-8")
         return json.dumps({"channel-id": self.channel_id})+"\n"
 
+class ChannelList(resource.Resource):
+    def __init__(self, channel_ids):
+        resource.Resource.__init__(self)
+        self.channel_ids = channel_ids
+    def render_GET(self, request):
+        request.setHeader("content-type", "application/json; charset=utf-8")
+        return json.dumps({"channel-ids": self.channel_ids})+"\n"
 
 class Relay(resource.Resource):
     def __init__(self):
@@ -85,6 +92,9 @@ class Relay(resource.Resource):
             log.msg("allocated %d, now have %d channels" %
                     (channel_id, len(self.channels)))
             return Allocated(channel_id)
+        if path == "list":
+            channel_ids = sorted(self.channels.keys())
+            return ChannelList(channel_ids)
         if not re.search(r'^\d+$', path):
             return resource.ErrorPage(http.BAD_REQUEST,
                                       "invalid channel id",

src/wormhole/transcribe.py

@@ -115,6 +115,13 @@ class Initiator(Common):
         self._deallocate()
         return inbound_data
 
+
+def list_channels(relay=RELAY):
+    r = requests.get(relay + "list")
+    r.raise_for_status()
+    channel_ids = r.json()["channel-ids"]
+    return channel_ids
+
 class Receiver(Common):
     def __init__(self, appid, data, code, relay=RELAY):
         self.appid = appid