Factor out QT quoting specifics into the backend

piker/brokers/core.py

@@ -4,6 +4,7 @@ Core broker-daemon tasks and API.
 import time
 import inspect
 from types import ModuleType
+from typing import AsyncContextManager
 
 import trio
 
@@ -41,6 +42,7 @@ async def quote(brokermod: ModuleType, tickers: [str]) -> dict:
 
 async def poll_tickers(
     client: 'Client',
+    quoter: AsyncContextManager,
     tickers: [str],
     q: trio.Queue,
     rate: int = 3,  # delay between quote requests
@@ -49,25 +51,14 @@ async def poll_tickers(
     """Stream quotes for a sequence of tickers at the given ``rate``
     per second.
     """
-    t2ids = await client.tickers2ids(tickers)
-    ids = ','.join(map(str, t2ids.values()))
     sleeptime = round(1. / rate, 3)
     _cache = {}
 
+    async with quoter(client, tickers) as get_quotes:
         while True:  # use an event here to trigger exit?
             prequote_start = time.time()
-        try:
+            quotes = await get_quotes(tickers)
-            quotes_resp = await client.api.quotes(ids=ids)
-        except QuestradeError as qterr:
-            if "Access token is invalid" in str(qterr.args[0]):
-                # out-of-process piker may have renewed already
-                client._reload_config()
-                quotes_resp = await client.api.quotes(ids=ids)
-            else:
-                raise
-
             postquote_start = time.time()
-        quotes = quotes_resp['quotes']
             payload = []
             for quote in quotes:
 

piker/brokers/questrade.py

@@ -271,3 +271,26 @@ async def get_client() -> Client:
         yield client
     finally:
         write_conf(client)
+
+
+@asynccontextmanager
+async def quoter(client: Client, tickers: [str]):
+    t2ids = await client.tickers2ids(tickers)
+    ids = ','.join(map(str, t2ids.values()))
+
+    async def get_quote(tickers):
+        """Query for quotes using cached symbol ids.
+        """
+        try:
+            quotes_resp = await client.api.quotes(ids=ids)
+        except QuestradeError as qterr:
+            if "Access token is invalid" in str(qterr.args[0]):
+                # out-of-process piker may have renewed already
+                client._reload_config()
+                quotes_resp = await client.api.quotes(ids=ids)
+            else:
+                raise
+
+        return quotes_resp['quotes']
+
+    yield get_quote