/*
 * Copyright 2021 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Package xds contains functions, structs, and utilities for working with
// handshake cluster names, as well as shared components used by xds balancers
// and resolvers. It is separated from the top-level /internal package to
// avoid circular dependencies.
package xds

import (
	"fmt"

	"google.golang.org/grpc/attributes"
	"google.golang.org/grpc/internal"
	"google.golang.org/grpc/internal/xds/clients"
	"google.golang.org/grpc/resolver"
)

// handshakeClusterNameKey is the type used as the key to store cluster name in
// the Attributes field of resolver.Address.
type handshakeClusterNameKey struct{}

// SetXDSHandshakeClusterName returns a copy of addr in which the Attributes field
// is updated with the cluster name.
func SetXDSHandshakeClusterName(addr resolver.Address, clusterName string) resolver.Address {
	addr.Attributes = addr.Attributes.WithValue(handshakeClusterNameKey{}, clusterName)
	return addr
}

// GetXDSHandshakeClusterName returns cluster name stored in attr.
func GetXDSHandshakeClusterName(attr *attributes.Attributes) (string, bool) {
	v := attr.Value(handshakeClusterNameKey{})
	name, ok := v.(string)
	return name, ok
}

// addressToTelemetryLabels prepares a telemetry label map from resolver
// address attributes.
func addressToTelemetryLabels(addr resolver.Address) map[string]string {
	cluster, _ := GetXDSHandshakeClusterName(addr.Attributes)
	locality := LocalityString(GetLocalityID(addr))
	return map[string]string{
		"grpc.lb.locality":        locality,
		"grpc.lb.backend_service": cluster,
	}
}

// LocalityString generates a string representation of clients.Locality in the
// format specified in gRFC A76.
func LocalityString(l clients.Locality) string {
	return fmt.Sprintf("{region=%q, zone=%q, sub_zone=%q}", l.Region, l.Zone, l.SubZone)
}

// IsLocalityEqual allows the values to be compared by Attributes.Equal.
func IsLocalityEqual(l clients.Locality, o any) bool {
	ol, ok := o.(clients.Locality)
	if !ok {
		return false
	}
	return l.Region == ol.Region && l.Zone == ol.Zone && l.SubZone == ol.SubZone
}

// LocalityFromString converts a string representation of clients.locality as
// specified in gRFC A76, into a LocalityID struct.
func LocalityFromString(s string) (ret clients.Locality, _ error) {
	_, err := fmt.Sscanf(s, "{region=%q, zone=%q, sub_zone=%q}", &ret.Region, &ret.Zone, &ret.SubZone)
	if err != nil {
		return clients.Locality{}, fmt.Errorf("%s is not a well formatted locality ID, error: %v", s, err)
	}
	return ret, nil
}

type localityKeyType string

const localityKey = localityKeyType("grpc.xds.internal.address.locality")

// GetLocalityID returns the locality ID of addr.
func GetLocalityID(addr resolver.Address) clients.Locality {
	path, _ := addr.BalancerAttributes.Value(localityKey).(clients.Locality)
	return path
}

// SetLocalityID sets locality ID in addr to l.
func SetLocalityID(addr resolver.Address, l clients.Locality) resolver.Address {
	addr.BalancerAttributes = addr.BalancerAttributes.WithValue(localityKey, l)
	return addr
}

// SetLocalityIDInEndpoint sets locality ID in endpoint to l.
func SetLocalityIDInEndpoint(endpoint resolver.Endpoint, l clients.Locality) resolver.Endpoint {
	endpoint.Attributes = endpoint.Attributes.WithValue(localityKey, l)
	return endpoint
}

// UnknownCSMLabels are TelemetryLabels emitted from CDS if CSM Telemetry Label
// data is not present in the CDS Resource.
var UnknownCSMLabels = map[string]string{
	"csm.service_name":           "unknown",
	"csm.service_namespace_name": "unknown",
}

func init() {
	internal.AddressToTelemetryLabels = addressToTelemetryLabels
}
