package main

import (
	"flag"
	"fmt"
	"os"
	"runtime"
)

func main() {
	if len(os.Args) < 2 {
		usage()
		os.Exit(2)
	}

	var err error
	switch os.Args[1] {
	case "sync":
		err = cmdSync(os.Args[2:])
	case "agent":
		err = cmdAgent(os.Args[2:])
	case "version", "--version":
		fmt.Printf("clonetool %s/%s\n", runtime.GOOS, runtime.GOARCH)
		return
	case "-h", "--help", "help":
		usage()
		return
	default:
		usage()
		os.Exit(2)
	}
	if err != nil {
		fmt.Fprintln(os.Stderr, "clonetool: "+err.Error())
		os.Exit(1)
	}
}

func usage() {
	fmt.Fprint(os.Stderr, `clonetool - block-level file/device sync

Usage:
  clonetool sync --source LOC --dest LOC [options]
  clonetool version
  clonetool agent --role {control|sink|source-stream} ...   (internal, spawned automatically)

LOC is either a local path, or [user@]host:path for a path reached over SSH.
Source, destination, and the machine running "sync" (the manager) may all be
different machines: the manager only orchestrates, it never reads or writes
a single block itself.

clonetool keeps no state between runs: every sync re-reads and re-hashes both
the source and the destination and transfers only the blocks that differ.

Options for sync:
  --block-size SIZE       block size, e.g. 4M (default 4M)
  --job NAME             optional label shown in progress/log output
  --yes                   don't prompt before shrinking an existing destination file
  --sudo MODE             device-access privilege escalation: auto (escalate on a
                          permission error, default), always, or never
  --deploy               copy this binary to remote hosts that lack it
                          (default true; --deploy=false to disable)
  --connect-timeout SEC   ssh connect timeout for the push/pull direction probe (default 8)
  --ssh PATH              ssh binary to use (default "ssh")
  --ssh-opt OPT           extra "-o OPT" passed to ssh (repeatable)
  --remote-bin PATH       path to clonetool on remote hosts (default "clonetool")
  --manager-host HOST     address peers should use to reach this machine, when
                          source or dest has no host part (defaults to the local hostname)
`)
}

type stringSlice []string

func (s *stringSlice) String() string { return fmt.Sprint([]string(*s)) }
func (s *stringSlice) Set(v string) error {
	*s = append(*s, v)
	return nil
}

func cmdSync(args []string) error {
	fs := flag.NewFlagSet("sync", flag.ContinueOnError)
	job := fs.String("job", "", "optional label for progress/log output")
	source := fs.String("source", "", "source location (required)")
	dest := fs.String("dest", "", "destination location (required)")
	blockSizeStr := fs.String("block-size", "4M", "block size, e.g. 4M")
	yes := fs.Bool("yes", false, "don't prompt before shrinking destination")
	sudoMode := fs.String("sudo", "auto", "device-access privilege escalation: auto|always|never")
	deploy := fs.Bool("deploy", true, "copy this binary to remote hosts that lack it")
	connectTimeout := fs.Int("connect-timeout", defaultConnectTimeoutSec, "ssh connect timeout (seconds)")
	sshBin := fs.String("ssh", "ssh", "ssh binary")
	remoteBin := fs.String("remote-bin", "clonetool", "clonetool path on remote hosts")
	managerHost := fs.String("manager-host", "", "address peers use to reach this machine")
	var sshOpts stringSlice
	fs.Var(&sshOpts, "ssh-opt", `extra "-o OPT" passed to ssh (repeatable)`)
	if err := fs.Parse(args); err != nil {
		return err
	}

	if *source == "" || *dest == "" {
		fs.Usage()
		return fmt.Errorf("--source and --dest are required")
	}
	blockSize, err := parseSize(*blockSizeStr)
	if err != nil {
		return fmt.Errorf("--block-size: %w", err)
	}
	switch *sudoMode {
	case "auto", "always", "never":
	default:
		return fmt.Errorf("--sudo: want auto|always|never, got %q", *sudoMode)
	}

	return runSync(SyncConfig{
		Job: *job, Source: *source, Dest: *dest, BlockSize: blockSize,
		Yes: *yes, Sudo: *sudoMode, Deploy: *deploy, ConnectTimeoutSec: *connectTimeout,
		SSHBin: *sshBin, SSHOpts: sshOpts, RemoteBin: *remoteBin, ManagerHost: *managerHost,
	})
}

func parseSize(s string) (int64, error) {
	if s == "" {
		return 0, fmt.Errorf("empty size")
	}
	mult := int64(1)
	numPart := s
	switch s[len(s)-1] {
	case 'k', 'K':
		mult = 1024
		numPart = s[:len(s)-1]
	case 'm', 'M':
		mult = 1024 * 1024
		numPart = s[:len(s)-1]
	case 'g', 'G':
		mult = 1024 * 1024 * 1024
		numPart = s[:len(s)-1]
	}
	var n int64
	if _, err := fmt.Sscanf(numPart, "%d", &n); err != nil {
		return 0, fmt.Errorf("invalid size %q", s)
	}
	if n <= 0 {
		return 0, fmt.Errorf("size must be positive")
	}
	return n * mult, nil
}