Auto-assign tickets to team members by availability

Perhaps a particular issue I have or maybe there is already a solution for this. I am wanting to allocate a new ticket that comes in automatically to a member of staff (they would be in a group/role) but:

1. New ticket arrives for client A
2. system checks for what users are assigned to support client A
   • is the person available (set as profile field if they are off sick)
   • how many open or active tickets does each person have (who has the lowest workload currently)
3. allocate ticket to the member of staff selected.

If something like this does not exist I need to write it as it is kind of essential to reducing the workload of the person managing the team.

Hope that made sense