/*
 * Copyright 2016 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 internal contains gRPC-internal code, to avoid polluting
// the godoc of the top-level grpc package.  It must not import any grpc
// symbols to avoid circular dependencies.
package internal

import (
	"context"
	"time"

	"google.golang.org/grpc/connectivity"
	"google.golang.org/grpc/serviceconfig"
)

var (
	// WithHealthCheckFunc is set by dialoptions.go
	WithHealthCheckFunc interface{} // func (HealthChecker) DialOption
	// HealthCheckFunc is used to provide client-side LB channel health checking
	HealthCheckFunc HealthChecker
	// BalancerUnregister is exported by package balancer to unregister a balancer.
	BalancerUnregister func(name string)
	// KeepaliveMinPingTime is the minimum ping interval.  This must be 10s by
	// default, but tests may wish to set it lower for convenience.
	KeepaliveMinPingTime = 10 * time.Second
	// ParseServiceConfigForTesting is for creating a fake
	// ClientConn for resolver testing only
	ParseServiceConfigForTesting interface{} // func(string) *serviceconfig.ParseResult
	// EqualServiceConfigForTesting is for testing service config generation and
	// parsing. Both a and b should be returned by ParseServiceConfigForTesting.
	// This function compares the config without rawJSON stripped, in case the
	// there's difference in white space.
	EqualServiceConfigForTesting func(a, b serviceconfig.Config) bool
	// GetCertificateProviderBuilder returns the registered builder for the
	// given name. This is set by package certprovider for use from xDS
	// bootstrap code while parsing certificate provider configs in the
	// bootstrap file.
	GetCertificateProviderBuilder interface{} // func(string) certprovider.Builder
	// GetXDSHandshakeInfoForTesting returns a pointer to the xds.HandshakeInfo
	// stored in the passed in attributes. This is set by
	// credentials/xds/xds.go.
	GetXDSHandshakeInfoForTesting interface{} // func (*attributes.Attributes) *xds.HandshakeInfo
	// GetServerCredentials returns the transport credentials configured on a
	// gRPC server. An xDS-enabled server needs to know what type of credentials
	// is configured on the underlying gRPC server. This is set by server.go.
	GetServerCredentials interface{} // func (*grpc.Server) credentials.TransportCredentials
	// DrainServerTransports initiates a graceful close of existing connections
	// on a gRPC server accepted on the provided listener address. An
	// xDS-enabled server invokes this method on a grpc.Server when a particular
	// listener moves to "not-serving" mode.
	DrainServerTransports interface{} // func(*grpc.Server, string)
)

// HealthChecker defines the signature of the client-side LB channel health checking function.
//
// The implementation is expected to create a health checking RPC stream by
// calling newStream(), watch for the health status of serviceName, and report
// it's health back by calling setConnectivityState().
//
// The health checking protocol is defined at:
// https://github.com/grpc/grpc/blob/master/doc/health-checking.md
type HealthChecker func(ctx context.Context, newStream func(string) (interface{}, error), setConnectivityState func(connectivity.State, error), serviceName string) error

const (
	// CredsBundleModeFallback switches GoogleDefaultCreds to fallback mode.
	CredsBundleModeFallback = "fallback"
	// CredsBundleModeBalancer switches GoogleDefaultCreds to grpclb balancer
	// mode.
	CredsBundleModeBalancer = "balancer"
	// CredsBundleModeBackendFromBalancer switches GoogleDefaultCreds to mode
	// that supports backend returned by grpclb balancer.
	CredsBundleModeBackendFromBalancer = "backend-from-balancer"
)