--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/patchablegraph.py	Sun Jan 24 07:12:25 2016 -0800
@@ -0,0 +1,90 @@
+import sys, json
+import cyclone.sse
+sys.path.append("/my/proj/light9")
+from light9.rdfdb.grapheditapi import GraphEditApi
+from rdflib import ConjunctiveGraph
+from light9.rdfdb.rdflibpatch import patchQuads
+from rdflib_jsonld.serializer import from_rdf
+
+def writeGraphResponse(req, graph, acceptHeader):
+    if acceptHeader == 'application/nquads':
+        req.set_header('Content-type', 'application/nquads')
+        graph.serialize(req, format='nquads')
+    elif acceptHeader == 'application/ld+json':
+        req.set_header('Content-type', 'application/ld+json')
+        graph.serialize(req, format='json-ld', indent=2)
+    else:
+        req.set_header('Content-type', 'application/x-trig')
+        graph.serialize(req, format='trig')
+
+# forked from /my/proj/light9/light9/rdfdb/rdflibpatch.py
+def graphFromQuads2(q):
+    g = ConjunctiveGraph()
+    #g.addN(q) # no effect on nquad output
+    for s,p,o,c in q:
+        g.get_context(c).add((s,p,o)) # kind of works with broken rdflib nquad serializer code
+        #g.store.add((s,p,o), c) # no effect on nquad output
+    return g
+
+def patchAsJson(p):
+    return json.dumps({'patch': {
+        'adds': from_rdf(graphFromQuads2(p.addQuads)),
+        'deletes': from_rdf(graphFromQuads2(p.delQuads)),
+    }})
+
+class PatchableGraph(GraphEditApi):
+    """
+    Master graph that you modify with self.patch, and we get the
+    updates to all current listeners.
+    """
+    def __init__(self):
+        self._graph = ConjunctiveGraph()
+        self._observers = []
+
+    def serialize(self, to, **kw):
+        return self._graph.serialize(to, **kw)
+        
+    def patch(self, p):
+        if p.isNoop():
+            return
+        patchQuads(self._graph,
+                   deleteQuads=p.delQuads,
+                   addQuads=p.addQuads,
+                   perfect=False) # true?
+        for ob in self._observers:
+            ob(patchAsJson(p))
+
+    def addObserver(self, onPatch):
+        self._observers.append(onPatch)
+        
+    def removeObserver(self, onPatch):
+        try:
+            self._observers.remove(onPatch)
+        except ValueError:
+            pass
+        
+
+        
+class GraphEventsHandler(cyclone.sse.SSEHandler):
+    """
+    One session with one client.
+    
+    returns current graph plus future patches to keep remote version
+    in sync with ours.
+
+    intsead of turning off buffering all over, it may work for this
+    response to send 'x-accel-buffering: no', per
+    http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_buffering
+    """
+    def bind(self):
+        mg = self.settings.masterGraph
+        # todo: needs to be on one line, or else fix cyclone to stripe headers
+        self.sendEvent(message=mg.serialize(None, format='json-ld', indent=None), event='fullGraph')
+        mg.addObserver(self.onPatch)
+
+    def onPatch(self, patchJson):
+        self.sendEvent(message=patchJson, event='patch')
+               
+    def unbind(self):
+        self.settings.masterGraph.removeObserver(self.onPatch)
+