performActionPreNextAlarm.rule

// The follwing should be openHAB DSL, intended to be added as a new script with scripting method 'Rule DSL' selected 
// (https://demo.openhab.org/settings/scripts/add would be the link for this on the openHAB demo instance):

// A read only variable to store the amount of minutes we want to preschedule our action
val delta = 10

// A variable named alexaPreNextAlarmTimer will be initialized to null if it’s not already defined.
// If it is defined, it retains what ever value it was set to prior to the rule running.
// inspired by "Saving a variable" at https://community.openhab.org/t/oh-3-examples-writing-and-using-javascript-libraries-in-mainui-created-rules/108526
// and https://community.openhab.org/t/ternary-expression-error/91128/5
var alexaPreNextAlarmTimer = if (alexaPreNextAlarmTimer === undefined) null else alexaPreNextAlarmTimer

// rule inspired by example at https://www.openhab.org/docs/configuration/actions.html#timers
rule "Trigger command on alexa 10 minutes before NextAlarm"
when
    Item EchoDotG1_NextAlarm changed
then
    if (alexaPreNextAlarmTimer !== null) {
      // timer already active
      // we reschedule it to match new NextAlarm's time minus delta
      alexaPreNextAlarmTimer.reschedule(EchoDotG1_NextAlarm.minusMinutes(delta))
      logInfo("rules", "alexaPreNextAlarmTimer rescheduled")
    } else {
      // timer not defined yet 
      // (probably first change in EchoDotG1_NextAlarm received)
      // we create a new timer that gets activated 10 minutes prior to EchoDotG1_NextAlarm
      alexaPreNextAlarmTimer = createTimer(EchoDotG1_NextAlarm.minusMinutes(delta), [ |
                  logInfo("rules", "alexaPreNextAlarmTimer activated")
                  // this gets executed when the timer is finished at NextAlarm minus delta
                  EchoDotLivingroom_StartRoutine.sendCommand('Open the living room blinds') 
                  // ... (if more shall be executed, put it here)
                ])
      logInfo("rules", "alexaPreNextAlarmTimer created")
    }
end