trigger LAM_ChildCount on Account (after insert, after update, before delete, after undelete) {
   Set<Id> Ids= new Set<Id>();
    List<Account> acclist = new List<Account>();
    Integer count = 0;

    if(Trigger.isInsert || Trigger.isUpdate){
        for(Account acc: Trigger.new){
            if(acc.ParentId!=null)
                Ids.add(acc.ParentId);
            acclist.add(acc);
        }
    }

    if(Trigger.isUpdate){
        for(Account acc: Trigger.old){
            if(acc.ParentId!=null)
                Ids.add(acc.ParentId);
            acclist.add(acc);
        }
    }

    if(Ids.size()>0){
        List<Account> accChild = new List<Account>([SELECT Id,ParentId FROM Account WHERE ParentId IN: Trigger.newMap.keySet()]);
        List<Account> accParent = new List<Account>([SELECT Id, Retail_Child_Accounts__c FROM Account WHERE Id IN: Trigger.newMap.keySet()]);
        for(Account ac: accParent){
            count =0;
            for(Account acChild: accChild){
                if(acChild.ParentId == ac.Id)
                    count++;
            }
            ac.Retail_Child_Accounts__c = count;
        }
        try{
            upsert accParent;
        }catch(DMLException ex){
            System.debug('Exception is '+ex);
        }
    }
}

public class LAM_LRE_Rollup{

    /*
    First step is to create a context for LREngine, by specifying parent and child objects and
    lookup relationship field name
    */

    public static Id LAMCustomerRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('LAM Customer Account').getRecordTypeId();
    public static Id LAMDivisionRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('LAM Division Account').getRecordTypeId();
    public static Id LAMSiteRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('LAM Site Account').getRecordTypeId();
    public static Id LAMEnterpriseRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('LAM Enterprise Account').getRecordTypeId();
    //public static Id DukeEnergyStandardAccounts = Schema.SObjectType.Account.getRecordTypeInfosByName().get('DukeEnergyStandardAccounts').getRecordTypeId();

    //'012700000009H1Y'


    public static void rollupData(List<account> lstAcct)
    {
        List<Account> lstAccts = new List<account>();

        for(Account a : lstAcct)
        {
            if(a.recordtypeid != LAMEnterpriseRecordType && a.parent_Account_for_lam__c != null && (a.recordtypeid == LAMCustomerRecordType || a.recordtypeid == LAMSiteRecordType || a.RecordTypeId == LAMDivisionRecordType /*|| a.RecordTypeId == DukeEnergyStandardAccounts*/) && a.Account_Status__c == 'Active')  //put an and clause here with nested OR for Rollup. E.g. && (a.recordtypeid == enterprise || a.recordtypeid == site)
            {
                lstAccts.add(a);
                system.debug(a);
            }
        }
        LREngine.Context ctx = new LREngine.Context(Account.SobjectType, // parent object
                                                    Account.SobjectType,  // child object
                                                    Schema.SObjectType.Account.fields.Parent_Account_for_LAM__c// relationship field name
                                                   );
        /*
        Next, one can add multiple rollup fields on the above relationship.
        Here specify
        1. The field to aggregate in child object
        2. The field to which aggregated value will be saved in master/parent object
        3. The aggregate operation to be done i.e. SUM, AVG, COUNT, MIN/MAX
        */
        ctx.add(
            new LREngine.RollupSummaryField(
                Schema.SObjectType.Account.fields.AnnualRevenue,
                Schema.SObjectType.Account.fields.AnnualRevenue,
                LREngine.RollupOperation.Sum
            ));

        ctx.add(
            new LREngine.RollupSummaryField(
                Schema.SObjectType.Account.fields.Rolling_12_Month_Total_CCF__c,
                Schema.SObjectType.Account.fields.Rolling_12_Month_Total_CCF__c,
                LREngine.RollupOperation.Sum
            ));
        ctx.add(
            new LREngine.RollupSummaryField(
                Schema.SObjectType.Account.fields.Rolling_12_Month_Total_Usage_kWh__c,
                Schema.SObjectType.Account.fields.Rolling_12_Month_Total_Usage_kWh__c,
                LREngine.RollupOperation.Sum
            ));
        ctx.add(
            new LREngine.RollupSummaryField(
                Schema.SObjectType.Account.fields.Rolling_12_Month_Total_Revenue__c,
                Schema.SObjectType.Account.fields.Rolling_12_Month_Total_Revenue__c,
                LREngine.RollupOperation.Sum
            ));
        ctx.add(
            new LREngine.RollupSummaryField(
                Schema.SObjectType.Account.fields.Account_Max_Demand_kw__c,
                Schema.SObjectType.Account.fields.Account_Max_Demand_kw__c,
                LREngine.RollupOperation.Sum
            ));


        /*
        Calling rollup method returns in memory master objects with aggregated values in them.
        Please note these master records are not persisted back, so that client gets a chance
        to post process them after rollup
        */
        Sobject[] masters = LREngine.rollUp(ctx, lstAccts);


        // Push the changes in master

        update masters;
    }
}