package internal

import (
	"fmt"
	"net/url"

	gresolver "google.golang.org/grpc/resolver"

	"github.com/hashicorp/consul/agent/grpc-internal/balancer"
	"github.com/hashicorp/consul/agent/grpc-internal/resolver"
	"github.com/hashicorp/consul/agent/metadata"
	"github.com/hashicorp/consul/types"
)

// NewTracker returns an implementation of the router.ServerTracker interface
// backed by the given ServerResolverBuilder and Balancer.
func NewTracker(rb *resolver.ServerResolverBuilder, bb *balancer.Builder) *Tracker {
	return &Tracker{rb, bb}
}

// Tracker satisfies the ServerTracker interface the router manager uses to
// register/deregister servers and trigger rebalances.
type Tracker struct {
	rb *resolver.ServerResolverBuilder
	bb *balancer.Builder
}

// AddServer adds the given server to the resolver.
func (t *Tracker) AddServer(a types.AreaID, s *metadata.Server) { t.rb.AddServer(a, s) }

// RemoveServer removes the given server from the resolver.
func (t *Tracker) RemoveServer(a types.AreaID, s *metadata.Server) { t.rb.RemoveServer(a, s) }

// NewRebalancer returns a function that can be called to randomize the
// priority order of connections for the given datacenter.
func (t *Tracker) NewRebalancer(dc string) func() {
	return func() {
		t.bb.Rebalance(gresolver.Target{
			URL: url.URL{
				Scheme: "consul",
				Host:   t.rb.Authority(),
				Path:   fmt.Sprintf("server.%s", dc),
			},
		})
	}
}