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/* An example of a rule that increments a counter value in the datastore */
rule incrementDS {
  select when test incrementDS
  pre {
    currentCounter = datastore:getItem(meta:rid, "counter")o.picolabs.wrangler.profile that selects on the initialization of the datastore 
    newValue = currentCounter.isnull() => 0 | currentCounter + 1
  }
  always {
    raise wrangler event "ds_update" attributes {
      "domain":meta:rid,	// The domain of the key-value pairings you want to manipulate
      "key":"counter",		// The key of the value you want to change
      "value":newValue		// The new value for the store
    }
  }
}

/* This rule reacts to wrangler:ds_updated to ensure that the counter we are incrementing 
	above is always even by checking if the new value in the store is divisible by 2 */
rule makeCounterEven {
  select when wrangler ds_updated
  pre {
    domain = event:attr("domain")
    key = event:attr("key")
    value = event:attr("value")
  }
  if domain == meta:rid && key == "counter" && value % 2 == 1 then
  noop()
  fired {
    raise wrangler event "ds_update" attributes event:attrs.put("value", value + 1)
  }
}