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""" Gerrit event stream interface.
Class to listen to the Gerrit event stream and dispatch events.
"""
import json
from pygerrit.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):
""" Raised when an error occurs while reading the Gerrit events stream. """
pass
class GerritStream(object):
""" Gerrit events 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 event from `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)
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