--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/backend/tools/trigger.py	Fri Jun 02 11:49:51 2023 +0200
@@ -0,0 +1,134 @@
+#!/usr/bin/env python3
+
+
+# SAT: a jabber client
+# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Misc usefull classes"""
+
+from libervia.backend.core.i18n import _
+from libervia.backend.core.log import getLogger
+
+log = getLogger(__name__)
+
+
+class TriggerException(Exception):
+    pass
+
+
+class SkipOtherTriggers(Exception):
+    """ Exception to raise if normal behaviour must be followed instead of following triggers list """
+
+    pass
+
+
+class TriggerManager(object):
+    """This class manage triggers: code which interact to change the behaviour of SàT"""
+
+    try:  # FIXME: to be removed when a better solution is found
+        MIN_PRIORITY = float("-inf")
+        MAX_PRIORITY = float("+inf")
+    except:  # XXX: Pyjamas will bug if you specify ValueError here
+        # Pyjamas uses the JS Float class
+        MIN_PRIORITY = Number.NEGATIVE_INFINITY
+        MAX_PRIORITY = Number.POSITIVE_INFINITY
+
+    def __init__(self):
+        self.__triggers = {}
+
+    def add(self, point_name, callback, priority=0):
+        """Add a trigger to a point
+
+        @param point_name: name of the point when the trigger should be run
+        @param callback: method to call at the trigger point
+        @param priority: callback will be called in priority order, biggest
+        first
+        """
+        if point_name not in self.__triggers:
+            self.__triggers[point_name] = []
+        if priority != 0 and priority in [
+            trigger_tuple[0] for trigger_tuple in self.__triggers[point_name]
+        ]:
+            if priority in (self.MIN_PRIORITY, self.MAX_PRIORITY):
+                log.warning(_("There is already a bound priority [%s]") % point_name)
+            else:
+                log.debug(
+                    _("There is already a trigger with the same priority [%s]")
+                    % point_name
+                )
+        self.__triggers[point_name].append((priority, callback))
+        self.__triggers[point_name].sort(
+            key=lambda trigger_tuple: trigger_tuple[0], reverse=True
+        )
+
+    def remove(self, point_name, callback):
+        """Remove a trigger from a point
+
+        @param point_name: name of the point when the trigger should be run
+        @param callback: method to remove, must exists in the trigger point
+        """
+        for trigger_tuple in self.__triggers[point_name]:
+            if trigger_tuple[1] == callback:
+                self.__triggers[point_name].remove(trigger_tuple)
+                return
+        raise TriggerException("Trying to remove an unexisting trigger")
+
+    def point(self, point_name, *args, **kwargs):
+        """This put a trigger point
+
+        All the triggers for that point will be run
+        @param point_name: name of the trigger point
+        @param *args: args to transmit to trigger
+        @param *kwargs: kwargs to transmit to trigger
+            if "triggers_no_cancel" is present, it will be popup out
+                when set to True, this argument don't let triggers stop
+                the workflow
+        @return: True if the action must be continued, False else
+        """
+        if point_name not in self.__triggers:
+            return True
+
+        can_cancel = not kwargs.pop('triggers_no_cancel', False)
+
+        for priority, trigger in self.__triggers[point_name]:
+            try:
+                if not trigger(*args, **kwargs) and can_cancel:
+                    return False
+            except SkipOtherTriggers:
+                break
+        return True
+
+    def return_point(self, point_name, *args, **kwargs):
+        """Like point but trigger must return (continue, return_value)
+
+        All triggers for that point must return a tuple with 2 values:
+            - continue, same as for point, if False action must be finished
+            - return_value: value to return ONLY IF CONTINUE IS FALSE
+        @param point_name: name of the trigger point
+        @return: True if the action must be continued, False else
+        """
+
+        if point_name not in self.__triggers:
+            return True
+
+        for priority, trigger in self.__triggers[point_name]:
+            try:
+                cont, ret_value = trigger(*args, **kwargs)
+                if not cont:
+                    return False, ret_value
+            except SkipOtherTriggers:
+                break
+        return True, None