code-completer: re-fetch channelids upon TAB, if necessary

This fixes the situation where you start the receiver first, then start
the sender, then you hit TAB on the receiver.

This somewhat improves the situation where you start the receiver first,
hit TAB (getting nothing), then start the sender, then hit TAB on the
receiver again. The second TAB will list the channel-ids, but won't
insert the only one as it's supposed to. You must type something (which
you can erase) and then hit TAB again to get a unique channel-id
inserted. But at least you can tell which one to type.

The first TAB runs the completer with readline.get_completion_type()
equal to 9=TAB=try-to-insert. The second (and subsequent) TABs use
63=?=list-matches, and it won't go back to 9 until you type something.

src/wormhole/blocking/transcribe.py

@@ -223,8 +223,7 @@ class Receiver(Common):
         return channel_ids
 
     def input_code(self, prompt="Enter wormhole code: "):
-        channel_ids = self.list_channels()
-        code = codes.input_code_with_completion(prompt, channel_ids)
+        code = codes.input_code_with_completion(prompt, self.list_channels)
         return code
 
     def set_code(self, code):

src/wormhole/codes.py

@@ -16,8 +16,8 @@ import readline
 #import sys
 
 class CodeInputter:
-    def __init__(self, channel_ids):
-        self.channel_ids = channel_ids
+    def __init__(self, get_channel_ids):
+        self.get_channel_ids = get_channel_ids
         self.last_text = None # memoize for a speedup
         self.last_matches = None
 
@@ -31,15 +31,23 @@ class CodeInputter:
             raise e
 
     def completer(self, text, state):
-        #print("completer:", text, state, file=sys.stderr)
+        #if state == 0:
+        #    print("", file=sys.stderr)
+        #print("completer: '%s' %d '%d'" % (text, state,
+        #                                   readline.get_completion_type()),
+        #      file=sys.stderr)
+        #sys.stderr.flush()
         pieces = text.split("-")
         last = pieces[-1].lower()
-        if text == self.last_text:
+        if text == self.last_text and len(pieces) >= 2:
+            # if len(pieces) == 1, skip the cache, so we can re-fetch the
+            # channel_id list
             matches = self.last_matches
             #print(" old matches", len(matches), file=sys.stderr)
         else:
             if len(pieces) < 2:
-                matches = [str(channel_id) for channel_id in self.channel_ids
+                channel_ids = self.get_channel_ids()
+                matches = [str(channel_id) for channel_id in channel_ids
                            if str(channel_id).startswith(last)]
             else:
                 if len(pieces) % 2 == 0:
@@ -57,11 +65,13 @@ class CodeInputter:
         match = matches[state]
         if len(pieces) < 3:
             match += "-"
+        #print(" match: '%s'" % match, file=sys.stderr)
+        #sys.stderr.flush()
         return match
 
 
-def input_code_with_completion(prompt, channel_ids):
-    c = CodeInputter(channel_ids)
+def input_code_with_completion(prompt, get_channel_ids):
+    c = CodeInputter(get_channel_ids)
     readline.parse_and_bind("tab: complete")
     readline.set_completer(c.wrap_completer)
     readline.set_completer_delims("")
@@ -69,5 +79,5 @@ def input_code_with_completion(prompt, channel_ids):
     return code
 
 if __name__ == "__main__":
-    code = input_code_with_completion("Enter wormhole code: ", [])
+    code = input_code_with_completion("Enter wormhole code: ", lambda: [])
     print("code is:", code)