[SalesForce] Maximum stack depth reached: 12

My guess is that you're reaching a limit on nested groups in your regular expression.

You could try splitting it into two separate match patterns:

'/\\*([^*]|[\\r\\n]|(\\*+([^*/]|[\\r\\n])))*\\*+/'
'(//.*)|\'.*\''

And making two passes on sourceCode.

As for matching C-style comments, check out this Stack Overflow question.

I am confused as to what you are really trying to accomplish with this structure. You don't need to create any logic for the actual order of execution (which, correct me if I am wrong, it appears you are trying to do here). Triggers have a very specific order of execution. It will actually run through your trigger several times to hit before and after logic.

Wouldn't it be much easier to do something like:

trigger OpportunityTrigger on Opportunity (after insert, after update, before delete) {
    if(Trigger.isAfter && Trigger.isInsert){
        OpportunityHandler.createScheduleLines(Trigger.newMap);
    }

    if(Trigger.isAfter && Trigger.isUpdate){
        OpportunityHandler.adjustScheduleLines(Trigger.newMap, Trigger.oldMap);
    }

    if(Trigger.isBefore && Trigger.isDelete){
        OpportunityHandler.removeScheduleLines(Trigger.oldMap);
    }

}

public class OpportunityHandler{

    public static void createScheduleLines(Map<Id, Opportunity> newMap) {
        // logic
    }

    public static void adjustScheduleLines(Map<Id, Opportunity> newMap, Map<Id, Opportunity> oldMap) {
        // logic
    }

    public static void removeScheduleLines(Map<Id, Opportunity> oldMap) {
        // logic
    }

}

Let Salesforce worry about the order they are executed.