How would anyone have an Apex trigger that simply rolls up the Opporunty Primary partner name up to the Opportunity record in Salesforce?

trigger rollupopp on Opportunity (after delete,after update,after insert,after undelete) {

set<ID>AccIds = new set<ID>();

if(trigger.isinsert || trigger.isundelete){
for(opportunity opp : trigger.new){
AccIds.add(opp.AccountId);
}
}
if(trigger.isdelete){
for(opportunity opp : trigger.old){
AccIds.add(opp.AccountId);
}
}

if(trigger.isupdate){
for(opportunity opp:trigger.new){
AccIds.add(opp.AccountId);
if(trigger.oldmap.get(opp.id).AccountId != opp.AccountId && trigger.oldmap.get(opp.id).AccountId != null ){
AccIds.add(trigger.oldmap.get(opp.id).AccountId);
}
}
}
map<id,double> amtmap = new map<id,double>();
for(aggregateresult ag : [select AccountId ,SUM(Opty_Amount_C) SOA,count(id) cc from opportunity where AccountId in:AccIds AND RecordType.Name = 'Revenue Type' group by AccountId]){
amtmap.put((ID)ag.get('AccountId'), double.valueof(ag.get('SOA')));
// amtmap.put((ID)ag.get('AccountId'), double.valueof(ag.get('cc')));
}
list<account>acclist = new list<account>();

for(id iid : AccIds){
account acnt = new account(id=iid);
if(amtmap.containskey(iid)){
acnt.Total_Opty_Amount_C = amtmap.get(iid);
}else{
acnt.Total_Opty_Amount_C = 0;
}
acclist.add(acnt);
}

if(acclist.size()>0){
update acclist;
}

}