/*
	Created by: Greg Hacic
	Last Update: 28 January 2010 by Greg Hacic
	Questions?: greg@interactiveties.com
*/
trigger reassignRelatedContactsAndOpportunities on Account (after update) {
	try {
		Set<Id> accountIds = new Set<Id>(); //set for holding the Ids of all Accounts that have been assigned to new Owners
		Map<Id, String> oldOwnerIds = new Map<Id, String>(); //map for holding the old account ownerId
		Map<Id, String> newOwnerIds = new Map<Id, String>(); //map for holding the new account ownerId
		Contact[] contactUpdates = new Contact[0]; //Contact sObject to hold OwnerId updates
		
		for (Account a : Trigger.new) { //for all records
			if (a.OwnerId != Trigger.oldMap.get(a.Id).OwnerId) {
				oldOwnerIds.put(a.Id, Trigger.oldMap.get(a.Id).OwnerId); //put the old OwnerId value in a map
				newOwnerIds.put(a.Id, a.OwnerId); //put the new OwnerId value in a map
				accountIds.add(a.Id); //add the Account Id to the set
			}
		}
		
		if (!accountIds.isEmpty()) { //if the accountIds Set is not empty
			for (Account act : [SELECT Id, (SELECT Id, OwnerId FROM Contacts) FROM Account WHERE Id in :accountIds]) { //SOQL to get Contacts 
				String newOwnerId = newOwnerIds.get(act.Id); //get the new OwnerId value for the account
				String oldOwnerId = oldOwnerIds.get(act.Id); //get the old OwnerId value for the account
				for (Contact c : act.Contacts) { //for all contacts
					if (c.OwnerId == oldOwnerId) { //if the contact is assigned to the old account Owner
						Contact updatedContact = new Contact(Id = c.Id, OwnerId = newOwnerId); //create a new Contact sObject
						contactUpdates.add(updatedContact); //add the contact to our List of updates
					}
				}
				
			}
			update contactUpdates; //update the Contacts
		}
	} catch(Exception e) { //catch errors
		System.Debug('reassignRelatedContactsAndOpportunities failure: '+e.getMessage()); //write error to the debug log
	}
}