// Package sftp implements an SFTP server to serve an rclone VFS

//go:build !plan9
// +build !plan9

package sftp

import (
	"context"

	"github.com/rclone/rclone/cmd"
	"github.com/rclone/rclone/cmd/serve/proxy"
	"github.com/rclone/rclone/cmd/serve/proxy/proxyflags"
	"github.com/rclone/rclone/fs"
	"github.com/rclone/rclone/fs/config/flags"
	"github.com/rclone/rclone/fs/rc"
	"github.com/rclone/rclone/vfs"
	"github.com/rclone/rclone/vfs/vfsflags"
	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
)

// Options contains options for the http Server
type Options struct {
	ListenAddr     string   // Port to listen on
	HostKeys       []string // Paths to private host keys
	AuthorizedKeys string   // Path to authorized keys file
	User           string   // single username
	Pass           string   // password for user
	NoAuth         bool     // allow no authentication on connections
	Stdio          bool     // serve on stdio
}

// DefaultOpt is the default values used for Options
var DefaultOpt = Options{
	ListenAddr:     "localhost:2022",
	AuthorizedKeys: "~/.ssh/authorized_keys",
}

// Opt is options set by command line flags
var Opt = DefaultOpt

// AddFlags adds flags for the sftp
func AddFlags(flagSet *pflag.FlagSet, Opt *Options) {
	rc.AddOption("sftp", &Opt)
	flags.StringVarP(flagSet, &Opt.ListenAddr, "addr", "", Opt.ListenAddr, "IPaddress:Port or :Port to bind server to.")
	flags.StringArrayVarP(flagSet, &Opt.HostKeys, "key", "", Opt.HostKeys, "SSH private host key file (Can be multi-valued, leave blank to auto generate)")
	flags.StringVarP(flagSet, &Opt.AuthorizedKeys, "authorized-keys", "", Opt.AuthorizedKeys, "Authorized keys file")
	flags.StringVarP(flagSet, &Opt.User, "user", "", Opt.User, "User name for authentication.")
	flags.StringVarP(flagSet, &Opt.Pass, "pass", "", Opt.Pass, "Password for authentication.")
	flags.BoolVarP(flagSet, &Opt.NoAuth, "no-auth", "", Opt.NoAuth, "Allow connections with no authentication if set.")
	flags.BoolVarP(flagSet, &Opt.Stdio, "stdio", "", Opt.Stdio, "Run an sftp server on run stdin/stdout")
}

func init() {
	vfsflags.AddFlags(Command.Flags())
	proxyflags.AddFlags(Command.Flags())
	AddFlags(Command.Flags(), &Opt)
}

// Command definition for cobra
var Command = &cobra.Command{
	Use:   "sftp remote:path",
	Short: `Serve the remote over SFTP.`,
	Long: `rclone serve sftp implements an SFTP server to serve the remote
over SFTP.  This can be used with an SFTP client or you can make a
remote of type sftp to use with it.

You can use the filter flags (e.g. --include, --exclude) to control what
is served.

The server will log errors.  Use -v to see access logs.

--bwlimit will be respected for file transfers.  Use --stats to
control the stats printing.

You must provide some means of authentication, either with --user/--pass,
an authorized keys file (specify location with --authorized-keys - the
default is the same as ssh), an --auth-proxy, or set the --no-auth flag for no
authentication when logging in.

Note that this also implements a small number of shell commands so
that it can provide md5sum/sha1sum/df information for the rclone sftp
backend.  This means that is can support SHA1SUMs, MD5SUMs and the
about command when paired with the rclone sftp backend.

If you don't supply a host --key then rclone will generate rsa, ecdsa
and ed25519 variants, and cache them for later use in rclone's cache
directory (see "rclone help flags cache-dir") in the "serve-sftp"
directory.

By default the server binds to localhost:2022 - if you want it to be
reachable externally then supply "--addr :2022" for example.

Note that the default of "--vfs-cache-mode off" is fine for the rclone
sftp backend, but it may not be with other SFTP clients.

If --stdio is specified, rclone will serve SFTP over stdio, which can
be used with sshd via ~/.ssh/authorized_keys, for example:

    restrict,command="rclone serve sftp --stdio ./photos" ssh-rsa ...

` + vfs.Help + proxy.Help,
	Run: func(command *cobra.Command, args []string) {
		var f fs.Fs
		if proxyflags.Opt.AuthProxy == "" {
			cmd.CheckArgs(1, 1, command, args)
			f = cmd.NewFsSrc(args)
		} else {
			cmd.CheckArgs(0, 0, command, args)
		}
		cmd.Run(false, true, command, func() error {
			if Opt.Stdio {
				return serveStdio(f)
			}
			s := newServer(context.Background(), f, &Opt)
			err := s.Serve()
			if err != nil {
				return err
			}
			s.Wait()
			return nil
		})
	},
}