Conditions and Actions
Table of contents
Conditions
Condition is defined as a function,
type Condition func(*Event, *Context) bool
The function should return true is the condition encoded is satisfied based on the current event. Naturally, boolean connectives allow you to define more complex conditions,
Condition.And(Condition)
Condition.Or(Condition)
Condition.Not()
Other than boolean connective, some common conditions that you can use are,
IsMessageSend | true if the event type is MessageSendEventType |
IsMessageReceive | true if the event type is MessageReceiveEventType |
IsEventType(t) | true if the event type is GenericEventType with T parameter same as the argument t |
IsMessageType(t) | true if the event is a message send/receive with message type as t |
IsMessageFrom(from) | true if the event is a message send/receive with message.From == from |
IsMessageTo(to) | true if the event is a message send/receive with message.To == to |
Actions
Action should be used to determine the consequence of an If().Then() filter.
type Action func(*Event, *Context) []*Message
Default Actions are:
DeliverMessage | If the event is a message send, returns the respective message from the pool |
DropMessage | Returns an empty Message set. Should be used for better code expressivity |
RecordMessageAs(label) | If the event is a message send/receive, records the message in Context.VarSet with the specified label |
Message sets
The RecordMessageAs action indicates a need to record events which are messages and later use them. We abstract this concept to define MessageSet which can be used to store messages. Sets are referenced by a label and stored as part of Context.VarSet. To access MessageSet, a set of conditions and actions are provided:
Set(label).Store() | Actions to store the message. This is possible only if the event is message send/receive. label references the message set |
Set(label).DeliverAll() | Action that returns all the messages in the set referenced by label. It removes all the messages from the set |
Set(label).Contains() | Condition that returns true if the event is a message send/receive and the message is part of the set referenced by label |
Counters
Apart from storing messages in a set, counting common events is a common theme when describing filters. We define Counter which stores an integer counter as part of the Context.VarSet. Counter is also referenced by a label. One way to access counter is using Count(label), but in those circumstances when the label is dynamic, we allow you to specify a function which returns the label CountF(labelFunc) where labelFunc(*Event, *Context) string returns the label based on the current event.
Similar to message set, we provide conditions and actions to access and manipulate counter
Count(label).Incr() | Action to increment a counter referenced by label |
Count(label).LtF(valF), Count(label).Lt(val) | Condition functions to check if the counter is less than the value specified. LtF allows you to fetch the value based on the current event and context |
Count(label).GtF(valF), Count(label).Lt(val) | Condition that returns true if the counter is greater than value |
Count(label).GeqF(valF), .Geq(val), .LeqF(valF), .Leq(val) | Condition functions to assert the counter value |
Additionally, Set(label).Count() is a default counter available for every message set defined.