use last-seen msgid to prevent duplicate messages in chathistory BATCH

modules/chathistory.py

@@ -0,0 +1,29 @@
+#--depends-on msgid
+
+from src import ModuleManager, utils
+
+TAG = utils.irc.MessageTag("msgid", "draft/msgid")
+
+class Module(ModuleManager.BaseModule):
+    @utils.hook("received.batch.end")
+    def batch_end(self, event):
+        if event["batch"].type == "chathistory":
+            target_name = event["batch"].args[0]
+            if target_name in event["server"].channels:
+                target = event["server"].channels.get(target_name)
+            else:
+                target = event["server"].get_user(target_name)
+
+            last_msgid = target.get_setting("last-msgid", None)
+            if not last_msgid == None:
+                lines = event["batch"].get_lines()
+                stop_index = -1
+
+                for i, line in enumerate(lines):
+                    msgid = TAG.get_value(line.tags)
+                    if msgid == last_msgid:
+                        stop_index = i
+                        break
+
+                if not stop_index == -1:
+                    return lines[stop_index+1:]