From e629e40b4f95718e94de5c63180c38251c3c8e54 Mon Sep 17 00:00:00 2001
From: Jakub Trllo <jakub.trllo@gmail.com>
Date: Fri, 4 Mar 2022 18:58:33 +0100
Subject: [PATCH] created base of event system

---
 openpype/pipeline/__init__.py     |   8 ++
 openpype/pipeline/events.py       | 221 ++++++++++++++++++++++++++++++
 openpype/pipeline/lib/__init__.py |   8 --
 openpype/pipeline/lib/events.py   |  51 -------
 4 files changed, 229 insertions(+), 59 deletions(-)
 create mode 100644 openpype/pipeline/events.py
 delete mode 100644 openpype/pipeline/lib/events.py

diff --git a/openpype/pipeline/__init__.py b/openpype/pipeline/__init__.py
index e968df4011..673608bded 100644
--- a/openpype/pipeline/__init__.py
+++ b/openpype/pipeline/__init__.py
@@ -1,5 +1,10 @@
 from .lib import attribute_definitions
 
+from .events import (
+    emit_event,
+    register_event_callback
+)
+
 from .create import (
     BaseCreator,
     Creator,
@@ -17,6 +22,9 @@ from .publish import (
 __all__ = (
     "attribute_definitions",
 
+    "emit_event",
+    "register_event_callback",
+
     "BaseCreator",
     "Creator",
     "AutoCreator",
diff --git a/openpype/pipeline/events.py b/openpype/pipeline/events.py
new file mode 100644
index 0000000000..cae8b250f7
--- /dev/null
+++ b/openpype/pipeline/events.py
@@ -0,0 +1,221 @@
+"""Events holding data about specific event."""
+import os
+import re
+import inspect
+import logging
+import weakref
+from uuid import uuid4
+try:
+    from weakref import WeakMethod
+except Exception:
+    from .python_2_comp import WeakMethod
+
+
+class EventCallback(object):
+    def __init__(self, topic, func_ref, func_name, func_path):
+        self._topic = topic
+        # Replace '*' with any character regex and escape rest of text
+        #   - when callback is registered for '*' topic it will receive all
+        #       events
+        #   - it is possible to register to a partial topis 'my.event.*'
+        #       - it will receive all matching event topics
+        #           e.g. 'my.event.start' and 'my.event.end'
+        topic_regex_str = "^{}$".format(
+            ".+".join(
+                re.escape(part)
+                for part in topic.split("*")
+            )
+        )
+        topic_regex = re.compile(topic_regex_str)
+        self._topic_regex = topic_regex
+        self._func_ref = func_ref
+        self._func_name = func_name
+        self._func_path = func_path
+        self._ref_valid = True
+        self._enabled = True
+
+        self._log = None
+
+    def __repr__(self):
+        return "< {} - {} > {}".format(
+            self.__class__.__name__, self._func_name, self._func_path
+        )
+
+    @property
+    def log(self):
+        if self._log is None:
+            self._log = logging.getLogger(self.__class__.__name__)
+        return self._log
+
+    @property
+    def is_ref_valid(self):
+        return self._ref_valid
+
+    def validate_ref(self):
+        if not self._ref_valid:
+            return
+
+        callback = self._func_ref()
+        if not callback:
+            self._ref_valid = False
+
+    @property
+    def enabled(self):
+        """Is callback enabled."""
+        return self._enabled
+
+    def set_enabled(self, enabled):
+        """Change if callback is enabled."""
+        self._enabled = enabled
+
+    def deregister(self):
+        """Calling this funcion will cause that callback will be removed."""
+        # Fake reference
+        self._ref_valid = False
+
+    def topic_matches(self, topic):
+        """Check if event topic matches callback's topic."""
+        return self._topic_regex.match(topic)
+
+    def process_event(self, event):
+        """Process event.
+
+        Args:
+            event(Event): Event that was triggered.
+        """
+        # Skip if callback is not enabled or has invalid reference
+        if not self._ref_valid or not self._enabled:
+            return
+
+        # Get reference
+        callback = self._func_ref()
+        # Check if reference is valid or callback's topic matches the event
+        if not callback:
+            # Change state if is invalid so the callback is removed
+            self._ref_valid = False
+
+        elif self.topic_matches(event.topic):
+            # Try execute callback
+            sig = inspect.signature(callback)
+            try:
+                if len(sig.parameters) == 0:
+                    callback()
+                else:
+                    callback(event)
+            except Exception:
+                self.log.warning(
+                    "Failed to execute event callback {}".format(
+                        str(repr(self))
+                    ),
+                    exc_info=True
+                )
+
+
+# Inherit from 'object' for Python 2 hosts
+class Event(object):
+    """Base event object.
+
+    Can be used to anything because data are not much specific. Only required
+    argument is topic which defines why event is happening and may be used for
+    filtering.
+
+    Arg:
+        topic (str): Identifier of event.
+        data (Any): Data specific for event. Dictionary is recommended.
+    """
+    _data = {}
+
+    def __init__(self, topic, data=None, source=None):
+        self._id = str(uuid4())
+        self._topic = topic
+        if data is None:
+            data = {}
+        self._data = data
+        self._source = source
+
+    def __getitem__(self, key):
+        return self._data[key]
+
+    def get(self, key, *args, **kwargs):
+        return self._data.get(key, *args, **kwargs)
+
+    @property
+    def id(self):
+        return self._id
+
+    @property
+    def source(self):
+        return self._source
+
+    @property
+    def data(self):
+        return self._data
+
+    @property
+    def topic(self):
+        return self._topic
+
+    def emit(self):
+        """Emit event and trigger callbacks."""
+        StoredCallbacks.emit_event(self)
+
+
+class StoredCallbacks:
+    _registered_callbacks = []
+
+    @classmethod
+    def add_callback(cls, topic, callback):
+        # Convert callback into references
+        #   - deleted functions won't cause crashes
+        if inspect.ismethod(callback):
+            ref = WeakMethod(callback)
+        elif callable(callback):
+            ref = weakref.ref(callback)
+        else:
+            # TODO add logs
+            return
+
+        function_name = callback.__name__
+        function_path = os.path.abspath(inspect.getfile(callback))
+        callback = EventCallback(topic, ref, function_name, function_path)
+        cls._registered_callbacks.append(callback)
+        return callback
+
+    @classmethod
+    def validate(cls):
+        invalid_callbacks = []
+        for callbacks in cls._registered_callbacks:
+            for callback in tuple(callbacks):
+                callback.validate_ref()
+                if not callback.is_ref_valid:
+                    invalid_callbacks.append(callback)
+
+        for callback in invalid_callbacks:
+            cls._registered_callbacks.remove(callback)
+
+    @classmethod
+    def emit_event(cls, event):
+        invalid_callbacks = []
+        for callback in cls._registered_callbacks:
+            callback.process_event()
+            if not callback.is_ref_valid:
+                invalid_callbacks.append(callback)
+
+        for callback in invalid_callbacks:
+            cls._registered_callbacks.remove(callback)
+
+
+def register_event_callback(topic, callback):
+    """Add callback that will be executed on specific topic."""
+    return StoredCallbacks.add_callback(topic, callback)
+
+
+def emit_event(topic, data=None, source=None):
+    """Emit event with topic and data.
+
+    Returns:
+        Event: Object of event that was emitted.
+    """
+    event = Event(topic, data, source)
+    event.emit()
+    return event
diff --git a/openpype/pipeline/lib/__init__.py b/openpype/pipeline/lib/__init__.py
index ed38889c66..f762c4205d 100644
--- a/openpype/pipeline/lib/__init__.py
+++ b/openpype/pipeline/lib/__init__.py
@@ -1,8 +1,3 @@
-from .events import (
-    BaseEvent,
-    BeforeWorkfileSave
-)
-
 from .attribute_definitions import (
     AbtractAttrDef,
 
@@ -20,9 +15,6 @@ from .attribute_definitions import (
 
 
 __all__ = (
-    "BaseEvent",
-    "BeforeWorkfileSave",
-
     "AbtractAttrDef",
 
     "UIDef",
diff --git a/openpype/pipeline/lib/events.py b/openpype/pipeline/lib/events.py
deleted file mode 100644
index 05dea20e8c..0000000000
--- a/openpype/pipeline/lib/events.py
+++ /dev/null
@@ -1,51 +0,0 @@
-"""Events holding data about specific event."""
-
-
-# Inherit from 'object' for Python 2 hosts
-class BaseEvent(object):
-    """Base event object.
-
-    Can be used to anything because data are not much specific. Only required
-    argument is topic which defines why event is happening and may be used for
-    filtering.
-
-    Arg:
-        topic (str): Identifier of event.
-        data (Any): Data specific for event. Dictionary is recommended.
-    """
-    _data = {}
-
-    def __init__(self, topic, data=None):
-        self._topic = topic
-        if data is None:
-            data = {}
-        self._data = data
-
-    @property
-    def data(self):
-        return self._data
-
-    @property
-    def topic(self):
-        return self._topic
-
-    @classmethod
-    def emit(cls, *args, **kwargs):
-        """Create object of event and emit.
-
-        Args:
-            Same args as '__init__' expects which may be class specific.
-        """
-        from avalon import pipeline
-
-        obj = cls(*args, **kwargs)
-        pipeline.emit(obj.topic, [obj])
-        return obj
-
-
-class BeforeWorkfileSave(BaseEvent):
-    """Before workfile changes event data."""
-    def __init__(self, filename, workdir):
-        super(BeforeWorkfileSave, self).__init__("before.workfile.save")
-        self.filename = filename
-        self.workdir_path = workdir