Booking2EditionTrigger

trigger Booking2EditionTrigger on Booking__c (after insert, after update, after delete) {
    
    // prepare set collection for bulk udpate at the end of the trigger
    List<Edition__c> editionsUpdate = new List<Edition__c>();
    Set<String> editionIds          = new Set<String>();
    editionIds.add('firstEdition');

    // loop the triggered booking
    for (Booking__c booking : Trigger.new){
        
        // find edition of the triggering booking
        Edition__c targetEdition = new Edition__c();
        targetEdition = [
            SELECT Id, ActualTotal__c, EstimateTotal__c, SuspendedTotal__c, CancelledTotal__c
            FROM   Edition__c
            WHERE  Id = :booking.Edition__c
            LIMIT  1
        ];

        // provide variables
        Decimal actual    = 0;
        Decimal estimate  = 0;
        Decimal suspended = 0;
        Decimal cancelled = 0;
            
        // if edition is already run the rollup process, then skip       
        If (!editionIds.contains(targetEdition.Id) && editionIds!=null) {
            editionIds.add(targetEdition.Id);
            
            // find all related bookings of the edition        
            List<Booking__c> relatedBookings = [
                SELECT NetCost__c,Edition__c,Status__c
                FROM   Booking__c
                WHERE  Edition__c = :targetEdition.Id
            ];
            
            //store the rolled-up values by booking status                
            for (Booking__c eachBooking : relatedBookings){
                if      (eachBooking.Status__c !=null && eachBooking.Status__c == 'Actual')    {actual    += eachBooking.NetCost__c;}
                else if (eachBooking.Status__c !=null && eachBooking.Status__c == 'Estimate')  {estimate  += eachBooking.NetCost__c;} 
                else if (eachBooking.Status__c !=null && eachBooking.Status__c == 'Suspended') {suspended += eachBooking.NetCost__c;}
                else if (eachBooking.Status__c !=null && eachBooking.Status__c == 'Cancelled') {cancelled += eachBooking.NetCost__c;}
            }

            // assign the rolled-up values to each field
            if(actual!=null)   {targetEdition.ActualTotal__c    = actual   ;}
            if(estimate!=null) {targetEdition.EstimateTotal__c  = estimate ;}
            if(suspended!=null){targetEdition.SuspendedTotal__c = suspended;}
            if(cancelled!=null){targetEdition.CancelledTotal__c = cancelled;}
             
            // add to the collection
            editionsUpdate.add(targetEdition);
        }
    }
    // bulk update
    update editionsUpdate;
}