general: add longpoll.py (glib/libsoup longpoll)

1 files changed, 70 insertions, 0 deletions

diff --git a/longpoll.py b/longpoll.py
new file mode 100644
index 0000000..a771e32
--- /dev/null
+++ b/longpoll.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+# vim: set expandtab ts=4:
+
+from gi.repository import GLib, Soup
+import json
+
+ml = GLib.MainLoop()
+
+def callback(new, old):
+    try:
+        import datadiff
+        if old is None:
+            return
+        print datadiff.diff(old, new)
+    except ImportError:
+        print 'received longpoll update, datadiff not available'
+
+prevjson = None
+
+LPURL = 'http://beaglebone.local.sublab.org/longpoll'
+uri = Soup.URI.new(LPURL)
+
+#
+# TODO: add timer that aborts/kills previous requests after a timeout
+#       for proper error recovery
+#
+# Note: message.status_code contains HTTP codes _or_ libsoup specific errors
+#       (status_code < 100 => libsoup)
+#
+
+def cb(session, message, cbarg):
+    global prevjson
+
+    def request_next():
+        uri.set_query(prevjson['ref'])
+        get = Soup.Message.new_from_uri("GET", uri)
+        ss.queue_message(get, cb, None)
+
+    if message.status_code != 200:
+        print 'cb error:', message.status_code
+        if prevjson is None:
+            print 'first request failed'
+            ml.quit()
+        request_next()
+        return
+
+    try:
+        rdata = message.response_body.flatten().get_data()
+        if rdata == '':
+            request_next()
+            return
+
+        njson = json.loads(rdata)
+        print 'CB OK', njson['ref']
+
+        if prevjson is None or njson['ref'] != prevjson['ref']:
+            callback(njson['data'],
+                prevjson['data'] if prevjson is not None else None)
+        prevjson = njson
+
+    finally:
+        request_next()
+
+ss = Soup.SessionAsync.new()
+get = Soup.Message.new_from_uri("GET", uri)
+ss.queue_message(get, cb, None)
+del get
+
+ml.run()
+