package shell

import (
	"context"
	"flag"
	"fmt"
	"io"
	"log"
	"time"

	"github.com/chrislusf/seaweedfs/weed/operation"
	"github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
	"github.com/chrislusf/seaweedfs/weed/storage/needle"
	"google.golang.org/grpc"
)

func init() {
	Commands = append(Commands, &commandVolumeMove{})
}

type commandVolumeMove struct {
}

func (c *commandVolumeMove) Name() string {
	return "volume.move"
}

func (c *commandVolumeMove) Help() string {
	return `move a live volume from one volume server to another volume server

	volume.move -source <source volume server host:port> -target <target volume server host:port> -volumeId <volume id>

	This command move a live volume from one volume server to another volume server. Here are the steps:

	1. This command asks the target volume server to copy the source volume from source volume server, remember the last entry's timestamp.
	2. This command asks the target volume server to mount the new volume
		Now the master will mark this volume id as readonly.
	3. This command asks the target volume server to tail the source volume for updates after the timestamp, for 1 minutes to drain the requests.
	4. This command asks the source volume server to unmount the source volume
		Now the master will mark this volume id as writable.
	5. This command asks the source volume server to delete the source volume

`
}

func (c *commandVolumeMove) Do(args []string, commandEnv *CommandEnv, writer io.Writer) (err error) {

	if err = commandEnv.confirmIsLocked(); err != nil {
		return
	}

	volMoveCommand := flag.NewFlagSet(c.Name(), flag.ContinueOnError)
	volumeIdInt := volMoveCommand.Int("volumeId", 0, "the volume id")
	sourceNodeStr := volMoveCommand.String("source", "", "the source volume server <host>:<port>")
	targetNodeStr := volMoveCommand.String("target", "", "the target volume server <host>:<port>")
	if err = volMoveCommand.Parse(args); err != nil {
		return nil
	}

	sourceVolumeServer, targetVolumeServer := *sourceNodeStr, *targetNodeStr

	volumeId := needle.VolumeId(*volumeIdInt)

	if sourceVolumeServer == targetVolumeServer {
		return fmt.Errorf("source and target volume servers are the same!")
	}

	return LiveMoveVolume(commandEnv.option.GrpcDialOption, volumeId, sourceVolumeServer, targetVolumeServer, 5*time.Second)
}

// LiveMoveVolume moves one volume from one source volume server to one target volume server, with idleTimeout to drain the incoming requests.
func LiveMoveVolume(grpcDialOption grpc.DialOption, volumeId needle.VolumeId, sourceVolumeServer, targetVolumeServer string, idleTimeout time.Duration) (err error) {

	log.Printf("copying volume %d from %s to %s", volumeId, sourceVolumeServer, targetVolumeServer)
	lastAppendAtNs, err := copyVolume(grpcDialOption, volumeId, sourceVolumeServer, targetVolumeServer)
	if err != nil {
		return fmt.Errorf("copy volume %d from %s to %s: %v", volumeId, sourceVolumeServer, targetVolumeServer, err)
	}

	log.Printf("tailing volume %d from %s to %s", volumeId, sourceVolumeServer, targetVolumeServer)
	if err = tailVolume(grpcDialOption, volumeId, sourceVolumeServer, targetVolumeServer, lastAppendAtNs, idleTimeout); err != nil {
		return fmt.Errorf("tail volume %d from %s to %s: %v", volumeId, sourceVolumeServer, targetVolumeServer, err)
	}

	log.Printf("deleting volume %d from %s", volumeId, sourceVolumeServer)
	if err = deleteVolume(grpcDialOption, volumeId, sourceVolumeServer); err != nil {
		return fmt.Errorf("delete volume %d from %s: %v", volumeId, sourceVolumeServer, err)
	}

	log.Printf("moved volume %d from %s to %s", volumeId, sourceVolumeServer, targetVolumeServer)
	return nil
}

func copyVolume(grpcDialOption grpc.DialOption, volumeId needle.VolumeId, sourceVolumeServer, targetVolumeServer string) (lastAppendAtNs uint64, err error) {

	// check to see if the volume is already read-only and if its not then we need
	// to mark it as read-only and then before we return we need to undo what we
	// did
	var shouldMarkWritable bool
	defer func() {
		if !shouldMarkWritable {
			return
		}

		clientErr := operation.WithVolumeServerClient(sourceVolumeServer, grpcDialOption, func(volumeServerClient volume_server_pb.VolumeServerClient) error {
			_, writableErr := volumeServerClient.VolumeMarkWritable(context.Background(), &volume_server_pb.VolumeMarkWritableRequest{
				VolumeId: uint32(volumeId),
			})
			return writableErr
		})
		if clientErr != nil {
			log.Printf("failed to mark volume %d as writable after copy from %s: %v", volumeId, sourceVolumeServer, clientErr)
		}
	}()

	err = operation.WithVolumeServerClient(sourceVolumeServer, grpcDialOption, func(volumeServerClient volume_server_pb.VolumeServerClient) error {
		resp, statusErr := volumeServerClient.VolumeStatus(context.Background(), &volume_server_pb.VolumeStatusRequest{
			VolumeId: uint32(volumeId),
		})
		if statusErr == nil && !resp.IsReadOnly {
			shouldMarkWritable = true
			_, readonlyErr := volumeServerClient.VolumeMarkReadonly(context.Background(), &volume_server_pb.VolumeMarkReadonlyRequest{
				VolumeId: uint32(volumeId),
			})
			return readonlyErr
		}
		return statusErr
	})
	if err != nil {
		return
	}

	err = operation.WithVolumeServerClient(targetVolumeServer, grpcDialOption, func(volumeServerClient volume_server_pb.VolumeServerClient) error {
		resp, replicateErr := volumeServerClient.VolumeCopy(context.Background(), &volume_server_pb.VolumeCopyRequest{
			VolumeId:       uint32(volumeId),
			SourceDataNode: sourceVolumeServer,
		})
		if replicateErr == nil {
			lastAppendAtNs = resp.LastAppendAtNs
		}
		return replicateErr
	})

	return
}

func tailVolume(grpcDialOption grpc.DialOption, volumeId needle.VolumeId, sourceVolumeServer, targetVolumeServer string, lastAppendAtNs uint64, idleTimeout time.Duration) (err error) {

	return operation.WithVolumeServerClient(targetVolumeServer, grpcDialOption, func(volumeServerClient volume_server_pb.VolumeServerClient) error {
		_, replicateErr := volumeServerClient.VolumeTailReceiver(context.Background(), &volume_server_pb.VolumeTailReceiverRequest{
			VolumeId:           uint32(volumeId),
			SinceNs:            lastAppendAtNs,
			IdleTimeoutSeconds: uint32(idleTimeout.Seconds()),
			SourceVolumeServer: sourceVolumeServer,
		})
		return replicateErr
	})

}

func deleteVolume(grpcDialOption grpc.DialOption, volumeId needle.VolumeId, sourceVolumeServer string) (err error) {
	return operation.WithVolumeServerClient(sourceVolumeServer, grpcDialOption, func(volumeServerClient volume_server_pb.VolumeServerClient) error {
		_, deleteErr := volumeServerClient.VolumeDelete(context.Background(), &volume_server_pb.VolumeDeleteRequest{
			VolumeId: uint32(volumeId),
		})
		return deleteErr
	})
}