1 files changed, 124 insertions, 0 deletions
diff --git a/trigger.py b/trigger.py
new file mode 100644
index 0000000..7d2fdfd
--- /dev/null
+++ b/trigger.py
@@ -0,0 +1,124 @@
+from typing import Dict
+from pyparsing import alphanums, alphas, printables, pyparsing_common, pyparsing_common, Word, infix_notation, CaselessKeyword, opAssoc, ParserElement
+import logging
+import time
+
+import endpoint
+import misc
+
+'''
+Implementations of Trigger:
+
+MUST implement:
+  _evaluate(self, action: str) -> bool
+    evaluates the instace for action given by 'action'.
+    Provided configuration is stored in self._instances[action]['args']
+
+CAN implement:
+  _addInstance(self, action: str)
+    Called afer 'action' was added.
+
+SHOULDNT implement:
+  evaluate(self, action: str) -> bool
+    Only calls _evaluate(), if no check was performed in configured interval,
+    otherwise returns cached result
+  addInstance(self, action:str, interval=30, **kwargs)
+'''
+class Trigger:
+    NEEDS_CONTEXT = False
+
+    @staticmethod
+    def create(classname: str, **kwargs):
+        return misc.import_class(classname)(**kwargs)
+
+    def __init__(self):
+        self._instances = {}
+
+    def _addInstance(self, action: str):
+        pass
+
+    def addInstance(self, action: str, interval: int=30, **kwargs):
+        self._instances[action] = {'lastupdate':0,'interval':interval,'last':False,'args':kwargs}
+        self._addInstance(action)
+        logging.debug(f'Trigger: Action "{action}" registered.')
+
+    def _evaluate(self, action: str) -> bool:
+        raise NotImplemented
+
+    def _shouldReevaluate(self, action: str) -> bool:
+        return time.time() - self._instances[action]['lastupdate'] > self._instances[action]['interval']
+
+    def evaluate(self, action: str) -> bool:
+        if action not in self._instances:
+            logging.error(f'Trigger: Action "{action}" was not found. Evaluating to False.')
+            return False
+
+        if self._shouldReevaluate(action):
+            logging.debug(f'Re-evaluating trigger condition for action "{action}"')
+            result =  self._evaluate(action)
+
+            self._instances[action]['last'] = result
+            self._instances[action]['lastupdate'] = time.time()
+            return result
+
+        return self._instances[action]['last']
+
+'''
+```yaml
+conditional:
+  class: trigger.Conditional
+---
+- conditional:
+  interval: 30
+  when:
+    - host1.user.bob > 0
+```
+'''
+class ConditionalTrigger(Trigger):
+    NEEDS_CONTEXT = True
+
+    def __init__(self, endpoints: Dict[str, endpoint.Endpoint]):
+        super().__init__()
+
+        self._endpoints = endpoints
+        self._setup_parser()
+
+    def _setup_parser(self):
+        ParserElement.enable_packrat()
+
+        boolean = CaselessKeyword('True').setParseAction(lambda x: True) | CaselessKeyword('False').setParseAction(lambda x: False)
+        integer = pyparsing_common.integer
+        variable = Word(alphanums + '.').setParseAction(self._parseVariable)
+        operand = boolean | integer | variable
+
+        self._parser = infix_notation(
+                operand,
+                [
+                    ('not', 1, opAssoc.RIGHT, lambda a: not a[0][1]),
+                    ('and', 2, opAssoc.LEFT, lambda a: a[0][0] and a[0][2]),
+                    ('or', 2, opAssoc.LEFT, lambda a: a[0][0] or a[0][2]),
+                    ('==', 2, opAssoc.LEFT, lambda a: a[0][0] == a[0][2]),
+                    ('>', 2, opAssoc.LEFT, lambda a: a[0][0] > a[0][2]),
+                    ('>=', 2, opAssoc.LEFT, lambda a: a[0][0] >= a[0][2]),
+                    ('<', 2, opAssoc.LEFT, lambda a: a[0][0] < a[0][2]),
+                    ('<=', 2, opAssoc.LEFT, lambda a: a[0][0] <= a[0][2]),
+                    ('+', 2, opAssoc.LEFT, lambda a: a[0][0] + a[0][2]),
+                    ('-', 2, opAssoc.LEFT, lambda a: a[0][0] - a[0][2]),
+                    ('*', 2, opAssoc.LEFT, lambda a: a[0][0] * a[0][2]),
+                    ('/', 2, opAssoc.LEFT, lambda a: a[0][0] / a[0][2]),
+                ]
+            )
+
+    def _parseVariable(self, var):
+        logging.debug(f'Looking up variable "{var[0]}"')
+        endpoint, key = var[0].split('.',1)
+
+        if not endpoint in self._endpoints:
+            logging.error(f'Parser: Endpoint "{endpoint}" not found')
+            return None
+
+        return self._endpoints[endpoint].getState(key)
+
+    def _evaluate(self, action: str) -> bool:
+        return all(self._parser.parse_string(str(s)) for s in self._instances[action]['args']['when'])
+