class AWS::EC2::Subnet

def availability_zone
  AvailabilityZone.new(availability_zone_name, :config => config)
end

def delete
  client.delete_subnet(:subnet_id => subnet_id)
  nil
end

def initialize subnet_id, options = {}
  @subnet_id = subnet_id
  super
end

def instances
  InstanceCollection.new(:config => config).filter('subnet-id', id)
end

def network_acl
  network_acl_association.network_acl
end

def network_acl= network_acl
  network_acl_association.replace_network_acl(network_acl)
end

def network_acl_association
  associations = AWS.memoize { vpc.network_acls.map(&:associations) }.flatten
  associations.first{|a| a.subnet == self }
end

def network_interfaces
  NetworkInterfaceCollection.new(:config => config).filter('subnet-id', id)
end

def route_table
  route_table_association.route_table
end

def route_table_association
  assocs = AWS.memoize { vpc.route_tables.map(&:associations) }.flatten
  assocs.find{|a| a.subnet == self } || assocs.find{|a| a.main? }
end

def set_route_table route_table
  unless route_table.is_a?(RouteTable)
    route_table = RouteTable.new(route_table, :config => config)
  end
  client_opts = {}
  client_opts[:route_table_id] = route_table.id
  assoc = route_table_association
  if assoc.main?
    client_opts[:subnet_id] = subnet_id
    response = client.associate_route_table(client_opts)
    association_id = response.association_id 
  else
    client_opts[:association_id] = assoc.association_id
    resp = client.replace_route_table_association(client_opts)
    association_id = resp.new_association_id
  end
  RouteTable::Association.new(route_table, association_id, subnet_id)
end

def vpc
  VPC.new(vpc_id, :config => config)
end