// Copyright 2024 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package conn

import (
	"time"

	"github.com/pingcap/ticdc/pkg/security"
	"google.golang.org/grpc"
	"google.golang.org/grpc/backoff"
	"google.golang.org/grpc/keepalive"
)

// A Conn is a grpc client connection.
type Conn struct {
	*grpc.ClientConn
}

const (
	grpcInitialWindowSize     = (1 << 16) - 1
	grpcInitialConnWindowSize = 1 << 23
	grpcMaxCallRecvMsgSize    = 1 << 28
)

// Connect returns a new grpc client connection to the target.
func Connect(target string, credential *security.Credential) (*grpc.ClientConn, error) {
	// If credential is nil, use an empty credential.
	if credential == nil {
		credential = &security.Credential{}
	}

	grpcTLSOption, err := credential.ToGRPCDialOption()
	if err != nil {
		return nil, err
	}

	dialOptions := []grpc.DialOption{
		grpcTLSOption,
		grpc.WithInitialWindowSize(grpcInitialWindowSize),
		grpc.WithInitialConnWindowSize(grpcInitialConnWindowSize),
		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(grpcMaxCallRecvMsgSize)),
		grpc.WithConnectParams(grpc.ConnectParams{
			Backoff: backoff.Config{
				BaseDelay:  time.Second,
				Multiplier: 1.1,
				Jitter:     0.1,
				MaxDelay:   3 * time.Second,
			},
			MinConnectTimeout: 3 * time.Second,
		}),
		grpc.WithKeepaliveParams(keepalive.ClientParameters{
			Time:                20 * time.Second,
			Timeout:             30 * time.Second,
			PermitWithoutStream: true,
		}),
	}

	return grpc.NewClient(target, dialOptions...)
}