Refactor into submodules

Data models, events, errors, and stream handler are split from the
single module into submodules.

Change-Id: I03537c5e268135966c6b6e77ecaca1cb579a5fde

1 files changed, 108 insertions, 0 deletions

diff --git a/pygerrit/stream.py b/pygerrit/stream.py
new file mode 100644
index 0000000..97daca6
--- /dev/null
+++ b/pygerrit/stream.py
@@ -0,0 +1,108 @@
+""" Gerrit event stream interface.
+
+Class to listen to the Gerrit event stream and dispatch events.
+
+"""
+
+import json
+
+from events import PatchsetCreatedEvent, \
+    RefUpdatedEvent, ChangeMergedEvent, CommentAddedEvent, \
+    ChangeAbandonedEvent, ChangeRestoredEvent, \
+    DraftPublishedEvent
+
+
+# Event types
+CHANGE_MERGED = "change-merged"
+PATCHSET_CREATED = "patchset-created"
+DRAFT_PUBLISHED = "draft-published"
+COMMENT_ADDED = "comment-added"
+CHANGE_ABANDONED = "change-abandoned"
+CHANGE_RESTORED = "change-restored"
+REF_UPDATED = "ref-updated"
+
+
+class GerritStreamError(Exception):
+    ''' GerritStreamError is raised when an error occurs while
+    reading the Gerrit events stream.
+    '''
+
+
+class GerritStream(object):
+    ''' Gerrit stream handler.
+    '''
+
+    # Map the event types to class names.
+    _event_dict = {CHANGE_MERGED: "ChangeMergedEvent",
+                   PATCHSET_CREATED: "PatchsetCreatedEvent",
+                   DRAFT_PUBLISHED: "DraftPublishedEvent",
+                   COMMENT_ADDED: "CommentAddedEvent",
+                   CHANGE_ABANDONED: "ChangeAbandonedEvent",
+                   CHANGE_RESTORED: "ChangeRestoredEvent",
+                   REF_UPDATED: "RefUpdatedEvent"}
+
+    def __init__(self):
+        self.listeners = []
+
+    def attach(self, listener):
+        ''' Attach the `listener` to the list of listeners.
+        Raise GerritStreamError if the listener does not match the
+        expected signature, or if its event handler is not callable.
+        '''
+        if not hasattr(listener, "on_gerrit_event"):
+            raise GerritStreamError("Listener must have `on_gerrit_event` "
+                                    "event handler method")
+        if not callable(listener.on_gerrit_event):
+            raise GerritStreamError("`on_gerrit_event` must be callable")
+        if not listener.on_gerrit_event.func_code.co_argcount == 2:
+            raise GerritStreamError("`on_gerrit_event` must take 1 arg")
+        if not listener in self.listeners:
+            self.listeners.append(listener)
+
+    def detach(self, listener):
+        ''' Remove the `listener` from the list of listeners.
+        '''
+        if listener in self.listeners:
+            try:
+                self.listeners.remove(listener)
+            except ValueError:
+                pass
+
+    def _get_event(self, json_data):
+        ''' Create a new 'GerritEvent' from the JSON object
+        described in `json_data`.
+        Return an instance of one of the GerritEvent subclasses.
+        Raise GerritStreamError if any error occurs.
+        '''
+        event_type = json_data["type"]
+        if event_type in self._event_dict:
+            classname = self._event_dict[event_type]
+            try:
+                return globals()[classname](json_data)
+            except KeyError, e:
+                raise GerritStreamError("Error creating event: %s" % e)
+
+        raise GerritStreamError("Unexpected event type `%s`" % event_type)
+
+    def _dispatch_event(self, event):
+        ''' Dispatch the `event` to the listeners.
+        '''
+        for listener in self.listeners:
+            listener.on_gerrit_event(event)
+
+    def stream(self, inputstream):
+        ''' Listen to the `inputstream` and handle JSON objects.
+        '''
+        try:
+            done = 0
+            while not done:
+                line = inputstream.readline()
+                if line:
+                    data = json.loads(line)
+                    self._dispatch_event(self._get_event(data))
+                else:
+                    break
+        except IOError, e:
+            raise GerritStreamError("Error reading event stream: %s" % e)
+        except ValueError, e:
+            raise GerritStreamError("Invalid JSON data in event stream: %s" % e)