package shell

import (
	"context"
	"flag"
	"fmt"
	"github.com/chrislusf/seaweedfs/weed/filer"
	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
	"github.com/chrislusf/seaweedfs/weed/pb/remote_pb"
	"github.com/chrislusf/seaweedfs/weed/remote_storage"
	"github.com/chrislusf/seaweedfs/weed/util"
	"github.com/golang/protobuf/jsonpb"
	"github.com/golang/protobuf/proto"
	"io"
	"strings"
)

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

type commandRemoteMount struct {
}

func (c *commandRemoteMount) Name() string {
	return "remote.mount"
}

func (c *commandRemoteMount) Help() string {
	return `mount remote storage and pull its metadata

	# assume a remote storage is configured to name "cloud1"
	remote.configure -name=cloud1 -type=s3 -access_key=xxx -secret_key=yyy

	# mount and pull one bucket
	remote.mount -dir=/xxx -remote=cloud1/bucket
	# mount and pull one directory in the bucket
	remote.mount -dir=/xxx -remote=cloud1/bucket/dir1

	# after mount, start a separate process to write updates to remote storage
	weed filer.remote.sync -filer=<filerHost>:<filerPort> -dir=/xxx

`
}

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

	remoteMountCommand := flag.NewFlagSet(c.Name(), flag.ContinueOnError)

	dir := remoteMountCommand.String("dir", "", "a directory in filer")
	nonEmpty := remoteMountCommand.Bool("nonempty", false, "allows the mounting over a non-empty directory")
	remote := remoteMountCommand.String("remote", "", "a directory in remote storage, ex. <storageName>/<bucket>/path/to/dir")

	if err = remoteMountCommand.Parse(args); err != nil {
		return nil
	}

	if *dir == "" {
		_, err = listExistingRemoteStorageMounts(commandEnv, writer)
		return err
	}

	remoteStorageLocation := remote_storage.ParseLocation(*remote)

	// find configuration for remote storage
	// remotePath is /<bucket>/path/to/dir
	remoteConf, err := c.findRemoteStorageConfiguration(commandEnv, writer, remoteStorageLocation)
	if err != nil {
		return fmt.Errorf("find configuration for %s: %v", *remote, err)
	}

	// sync metadata from remote
	if err = c.syncMetadata(commandEnv, writer, *dir, *nonEmpty, remoteConf, remoteStorageLocation); err != nil {
		return fmt.Errorf("pull metadata: %v", err)
	}

	// store a mount configuration in filer
	if err = c.saveMountMapping(commandEnv, writer, *dir, remoteStorageLocation); err != nil {
		return fmt.Errorf("save mount mapping: %v", err)
	}

	return nil
}

func listExistingRemoteStorageMounts(commandEnv *CommandEnv, writer io.Writer) (mappings *remote_pb.RemoteStorageMapping, err error) {

	// read current mapping
	mappings, err = filer.ReadMountMappings(commandEnv.option.GrpcDialOption, commandEnv.option.FilerAddress)
	if err != nil {
		return mappings, err
	}

	jsonPrintln(writer, mappings)

	return

}

func jsonPrintln(writer io.Writer, message proto.Message) error {
	if message == nil {
		return nil
	}
	m := jsonpb.Marshaler{
		EmitDefaults: false,
		Indent:       "  ",
	}

	err := m.Marshal(writer, message)
	fmt.Fprintln(writer)
	return err
}

func (c *commandRemoteMount) findRemoteStorageConfiguration(commandEnv *CommandEnv, writer io.Writer, remote *remote_pb.RemoteStorageLocation) (conf *remote_pb.RemoteConf, err error) {

	return filer.ReadRemoteStorageConf(commandEnv.option.GrpcDialOption, commandEnv.option.FilerAddress, remote.Name)

}

func (c *commandRemoteMount) syncMetadata(commandEnv *CommandEnv, writer io.Writer, dir string, nonEmpty bool, remoteConf *remote_pb.RemoteConf, remote *remote_pb.RemoteStorageLocation) error {

	// find existing directory, and ensure the directory is empty
	err := commandEnv.WithFilerClient(func(client filer_pb.SeaweedFilerClient) error {
		parent, name := util.FullPath(dir).DirAndName()
		_, lookupErr := client.LookupDirectoryEntry(context.Background(), &filer_pb.LookupDirectoryEntryRequest{
			Directory: parent,
			Name:      name,
		})
		if lookupErr != nil {
			if !strings.Contains(lookupErr.Error(), filer_pb.ErrNotFound.Error()) {
				return fmt.Errorf("lookup %s: %v", dir, lookupErr)
			}
		}

		mountToDirIsEmpty := true
		listErr := filer_pb.SeaweedList(client, dir, "", func(entry *filer_pb.Entry, isLast bool) error {
			mountToDirIsEmpty = false
			return nil
		}, "", false, 1)

		if listErr != nil {
			return fmt.Errorf("list %s: %v", dir, listErr)
		}

		if !mountToDirIsEmpty {
			if !nonEmpty {
				return fmt.Errorf("dir %s is not empty", dir)
			}
		}

		return nil
	})
	if err != nil {
		return err
	}

	// pull metadata from remote
	if err = pullMetadata(commandEnv, writer, util.FullPath(dir), remote, util.FullPath(dir), remoteConf); err != nil {
		return fmt.Errorf("cache content data: %v", err)
	}

	return nil
}

func (c *commandRemoteMount) saveMountMapping(commandEnv *CommandEnv, writer io.Writer, dir string, remoteStorageLocation *remote_pb.RemoteStorageLocation) (err error) {

	// read current mapping
	var oldContent, newContent []byte
	err = commandEnv.WithFilerClient(func(client filer_pb.SeaweedFilerClient) error {
		oldContent, err = filer.ReadInsideFiler(client, filer.DirectoryEtcRemote, filer.REMOTE_STORAGE_MOUNT_FILE)
		return err
	})
	if err != nil {
		if err != filer_pb.ErrNotFound {
			return fmt.Errorf("read existing mapping: %v", err)
		}
	}

	// add new mapping
	newContent, err = filer.AddRemoteStorageMapping(oldContent, dir, remoteStorageLocation)
	if err != nil {
		return fmt.Errorf("add mapping %s~%s: %v", dir, remoteStorageLocation, err)
	}

	// save back
	err = commandEnv.WithFilerClient(func(client filer_pb.SeaweedFilerClient) error {
		return filer.SaveInsideFiler(client, filer.DirectoryEtcRemote, filer.REMOTE_STORAGE_MOUNT_FILE, newContent)
	})
	if err != nil {
		return fmt.Errorf("save mapping: %v", err)
	}

	return nil
}

// if an entry has synchronized metadata but has not synchronized content
//    entry.Attributes.FileSize == entry.RemoteEntry.RemoteSize
//    entry.Attributes.Mtime    == entry.RemoteEntry.RemoteMtime
//    entry.RemoteEntry.LastLocalSyncTsNs == 0
// if an entry has synchronized metadata but has synchronized content before
//    entry.Attributes.FileSize == entry.RemoteEntry.RemoteSize
//    entry.Attributes.Mtime    == entry.RemoteEntry.RemoteMtime
//    entry.RemoteEntry.LastLocalSyncTsNs > 0
// if an entry has synchronized metadata but has new updates
//    entry.Attributes.Mtime * 1,000,000,000    > entry.RemoteEntry.LastLocalSyncTsNs
func doSaveRemoteEntry(client filer_pb.SeaweedFilerClient, localDir string, existingEntry *filer_pb.Entry, remoteEntry *filer_pb.RemoteEntry) error {
	existingEntry.RemoteEntry = remoteEntry
	existingEntry.Attributes.FileSize = uint64(remoteEntry.RemoteSize)
	existingEntry.Attributes.Mtime = remoteEntry.RemoteMtime
	_, updateErr := client.UpdateEntry(context.Background(), &filer_pb.UpdateEntryRequest{
		Directory: localDir,
		Entry:     existingEntry,
	})
	if updateErr != nil {
		return updateErr
	}
	return nil
}