package main

import (
	"bufio"
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"text/tabwriter"
	"time"

	"github.com/spf13/cobra"
	"golang.org/x/term"

	"jarl/internal/auth"
	"jarl/internal/backup"
	"jarl/internal/config"
	"jarl/internal/store"
)

func backupCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "backup [FILE]",
		Short: "Back up the database (safe while jarld runs)",
		Long: `Writes a consistent copy of Jarl's database and checks it.

Without FILE the copy goes into backup.dir from jarl.yaml (/var/backups/jarl),
named jarl-<UTC time>.db (plus stats-<UTC time>.db with backup.stats), and
older backups there are deleted as backup.retention and backup.keep_at_least
say. This is what the jarl-backup.timer systemd timer runs every day.

With FILE it writes a single copy there, which is never deleted
automatically.

Every backup is recorded in the database, and the dashboard shows the newest.
Restore one with 'jarld restore'.`,
		Example: `  sudo -u jarl jarld backup
  sudo -u jarl jarld backup /root/jarl-before-upgrade.db`,
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := config.Load(configPath, true)
			if err != nil {
				return fmt.Errorf("loading configuration: %w", err)
			}
			if _, err := os.Stat(cfg.Database); err != nil {
				return fmt.Errorf("no database at %s to back up (create it with 'jarld init')", cfg.Database)
			}
			// Not store.Open: a backup must never create or upgrade the
			// database a running jarld uses.
			st, err := store.OpenExisting(cfg.Database)
			if err != nil {
				return fmt.Errorf("opening %s: %w", cfg.Database, err)
			}
			defer st.Close()
			// Run as root, leave no root-owned files behind for jarld.
			defer newDirOwner(filepath.Dir(cfg.Database)).fix(filepath.Dir(cfg.Database))
			ctx := context.Background()
			now := time.Now()
			fail := func(err error) error {
				if rerr := st.RecordBackup(ctx, store.BackupRecord{At: now, Error: err.Error()}); rerr != nil {
					fmt.Fprintln(os.Stderr, "warning: couldn't record the failure in the database:", rerr)
				}
				return err
			}
			if len(args) == 1 {
				dst := args[0]
				if _, err := os.Lstat(dst); err == nil {
					return fmt.Errorf("%s already exists", dst)
				}
				if err := backup.Copy(ctx, cfg.Database, dst); err != nil {
					os.Remove(dst)
					return fail(fmt.Errorf("backing up %s: %w", cfg.Database, err))
				}
				if err := backup.Verify(ctx, dst); err != nil {
					os.Remove(dst)
					return fail(fmt.Errorf("the backup failed its check: %w", err))
				}
				fi, _ := os.Stat(dst)
				st.RecordBackup(ctx, store.BackupRecord{At: now, File: dst, Size: fi.Size()})
				fmt.Printf("Database backed up to %s (%s)\n", dst, size(fi.Size()))
				return nil
			}

			dir := cfg.Backup.Dir
			defer newDirOwner(dir).fix(dir)
			f, err := backup.Write(ctx, cfg.Database, dir, backup.KindJarl, now)
			if err != nil {
				return fail(fmt.Errorf("backing up %s: %w", cfg.Database, err))
			}
			fmt.Printf("Database backed up to %s (%s)\n", f.Path, size(f.Size))
			kinds := []string{backup.KindJarl}
			if cfg.Backup.Stats {
				if _, err := os.Stat(cfg.Stats.Database); err == nil {
					sf, err := backup.Write(ctx, cfg.Stats.Database, dir, backup.KindStats, now)
					if err != nil {
						return fail(fmt.Errorf("backing up the statistics database %s: %w", cfg.Stats.Database, err))
					}
					fmt.Printf("Statistics backed up to %s (%s)\n", sf.Path, size(sf.Size))
				}
				kinds = append(kinds, backup.KindStats)
			}
			for _, kind := range kinds {
				removed, err := backup.Prune(dir, kind, now, time.Duration(cfg.Backup.Retention), cfg.Backup.KeepAtLeast)
				for _, r := range removed {
					fmt.Printf("Deleted %s (older than %s)\n", r.Path, fmtDuration(time.Duration(cfg.Backup.Retention)))
				}
				if err != nil {
					return fail(fmt.Errorf("deleting old backups: %w", err))
				}
			}
			if err := st.RecordBackup(ctx, store.BackupRecord{At: now, File: f.Path, Size: f.Size}); err != nil {
				fmt.Fprintln(os.Stderr, "warning: couldn't record the backup in the database:", err)
			}
			return nil
		},
	}
}

func restoreCmd() *cobra.Command {
	var yes bool
	cmd := &cobra.Command{
		Use:   "restore [FILE | latest]",
		Short: "Replace the database with a backup (jarld must be stopped)",
		Long: `Without arguments, lists the backups in backup.dir.

With FILE, or "latest" for the newest backup in backup.dir, it checks the
backup, shows what it holds next to the current database, and after you
confirm replaces the database with it. jarld must be stopped first. The
current database is kept as DATABASE.before-restore-<UTC time>, and the
restore is recorded in the restored database's audit log.

Then start jarld and bring named's files in line with the restored database:

  systemctl start jarl
  jarl resync --dry-run     # what differs
  jarl resync --force       # write everything and reload named

See "Restoring" in docs/operations.md, also for zone serials and secondaries.`,
		Example: `  sudo jarld restore
  sudo systemctl stop jarl
  sudo jarld restore latest
  sudo jarld restore /var/backups/jarl/jarl-20261008T031512Z.db`,
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			cfg, err := config.Load(configPath, true)
			if err != nil {
				return fmt.Errorf("loading configuration: %w", err)
			}
			ctx := context.Background()
			if len(args) == 0 {
				return listBackups(cfg.Backup.Dir)
			}
			src := args[0]
			if src == "latest" {
				files, err := backup.List(cfg.Backup.Dir)
				if err != nil {
					return err
				}
				src = ""
				for _, f := range files {
					if f.Kind == backup.KindJarl {
						src = f.Path
						break
					}
				}
				if src == "" {
					return fmt.Errorf("no backups in %s", cfg.Backup.Dir)
				}
			}
			if err := backup.Verify(ctx, src); err != nil {
				return fmt.Errorf("%s can't be restored: %w", src, err)
			}
			info, err := backup.Inspect(ctx, src)
			if err != nil {
				return err
			}
			if info.Schema > store.SchemaVersion() {
				return fmt.Errorf("%s was made by a newer Jarl (schema %d, this one knows %d); install that version to restore it", src, info.Schema, store.SchemaVersion())
			}
			unlock, err := lockDatabase(cfg.Database)
			if errors.Is(err, errInUse) {
				return fmt.Errorf("jarld is running; stop it first (systemctl stop jarl), then run this again")
			}
			if err != nil {
				return err
			}
			defer unlock()

			w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
			fmt.Fprintf(w, "Backup:\t%s\n", src)
			describe(w, info, backupTime(src))
			if cur, err := backup.Inspect(ctx, cfg.Database); err == nil {
				fmt.Fprintf(w, "\nCurrent database:\t%s\n", cfg.Database)
				describe(w, cur, time.Time{})
			} else if !errors.Is(err, os.ErrNotExist) {
				fmt.Fprintf(w, "\nCurrent database:\t%s (unreadable: %v)\n", cfg.Database, err)
			}
			w.Flush()
			if !yes {
				if !term.IsTerminal(int(os.Stdin.Fd())) {
					return fmt.Errorf("add --yes to restore without being asked")
				}
				fmt.Print("\nReplace the current database with this backup? [y/N] ")
				line, _ := bufio.NewReader(os.Stdin).ReadString('\n')
				if a := strings.ToLower(strings.TrimSpace(line)); a != "y" && a != "yes" {
					return fmt.Errorf("nothing changed")
				}
			}

			db := cfg.Database
			defer newDirOwner(filepath.Dir(db)).fix(filepath.Dir(db))
			aside := db + ".before-restore-" + time.Now().UTC().Format("20060102T150405Z")
			// The database's WAL and shared-memory files belong to it:
			// they move with it, and the restored copy starts without.
			moved := false
			for _, suffix := range []string{"", "-wal", "-shm"} {
				if _, err := os.Lstat(db + suffix); err == nil {
					if err := os.Rename(db+suffix, aside+suffix); err != nil {
						return err
					}
					moved = true
				}
			}
			if err := copyFile(src, db, 0o640); err != nil {
				if moved {
					os.Rename(aside, db)
					os.Rename(aside+"-wal", db+"-wal")
					os.Rename(aside+"-shm", db+"-shm")
				}
				return fmt.Errorf("restoring: %w (the current database was left in place)", err)
			}
			// Open it as jarld will: an older backup gets the current
			// schema now, and the restore goes into its audit log.
			a, err := openApp(true)
			if err != nil {
				return fmt.Errorf("the backup was copied to %s but doesn't open: %w", db, err)
			}
			p := &auth.Principal{Method: "local"}
			if lp, err := a.localPrincipal(ctx, ""); err == nil {
				p = lp
			}
			a.eng.Audit(ctx, p, "system.restore", "", 0, "", "success", "database restored from "+src)
			a.close()

			fmt.Printf("\nRestored %s from %s.\n", db, src)
			if moved {
				fmt.Printf("The previous database is in %s.\n", aside)
			}
			fmt.Print(`
Next:
  systemctl start jarl
  jarl resync --dry-run     # what differs between the restored database and named's files
  jarl resync --force       # write them and reload named

If you have secondary servers, zone serials older than what they last saw
are ignored by them: raise them with 'jarl zone update ZONE --serial N'
(see "Restoring" in docs/operations.md).
`)
			return nil
		},
	}
	cmd.Flags().BoolVarP(&yes, "yes", "y", false, "don't ask for confirmation")
	return cmd
}

func listBackups(dir string) error {
	files, err := backup.List(dir)
	if err != nil {
		return err
	}
	if len(files) == 0 {
		fmt.Printf("No backups in %s.\n", dir)
		return nil
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintln(w, "MADE\tAGE\tKIND\tSIZE\tFILE")
	for _, f := range files {
		fmt.Fprintf(w, "%s\t%s\t%s\t%s\t%s\n", f.Time.Local().Format("2006-01-02 15:04:05"), fmtDuration(time.Since(f.Time)), f.Kind, size(f.Size), f.Path)
	}
	w.Flush()
	fmt.Println("\nRestore one with: jarld restore FILE   (or: jarld restore latest)")
	return nil
}

func describe(w io.Writer, in *backup.Info, made time.Time) {
	if !made.IsZero() {
		fmt.Fprintf(w, "  made\t%s (%s ago)\n", made.Local().Format("2006-01-02 15:04:05"), fmtDuration(time.Since(made)))
	}
	fmt.Fprintf(w, "  contents\t%s, %s, %s (schema %d)\n", plural(in.Zones, "zone"), plural(in.Records, "record"), plural(in.Users, "user"), in.Schema)
	if in.LastChange != nil {
		fmt.Fprintf(w, "  last change\t%s\n", in.LastChange.Local().Format("2006-01-02 15:04:05"))
	}
}

// backupTime is when a backup was made: from its name if it has a
// backup's name, otherwise its modification time.
func backupTime(path string) time.Time {
	for _, f := range mustList(filepath.Dir(path)) {
		if f.Path == filepath.Clean(path) {
			return f.Time
		}
	}
	if fi, err := os.Stat(path); err == nil {
		return fi.ModTime()
	}
	return time.Time{}
}

func mustList(dir string) []backup.File {
	files, _ := backup.List(dir)
	return files
}

// copyFile copies src to dst through a temporary file, so dst is either
// complete or absent.
func copyFile(src, dst string, mode os.FileMode) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()
	tmp := dst + ".restore-tmp"
	out, err := os.OpenFile(tmp, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, mode)
	if err != nil {
		return err
	}
	if _, err := io.Copy(out, in); err != nil {
		out.Close()
		os.Remove(tmp)
		return err
	}
	if err := out.Sync(); err != nil {
		out.Close()
		os.Remove(tmp)
		return err
	}
	if err := out.Close(); err != nil {
		os.Remove(tmp)
		return err
	}
	return os.Rename(tmp, dst)
}

func size(n int64) string {
	switch {
	case n >= 1<<20:
		return fmt.Sprintf("%.1f MB", float64(n)/(1<<20))
	case n >= 1<<10:
		return fmt.Sprintf("%.0f KB", float64(n)/(1<<10))
	}
	return fmt.Sprintf("%d bytes", n)
}

func fmtDuration(d time.Duration) string {
	switch {
	case d >= 48*time.Hour:
		return fmt.Sprintf("%d days", int(d/(24*time.Hour)))
	case d >= 2*time.Hour:
		return fmt.Sprintf("%d hours", int(d/time.Hour))
	case d >= 2*time.Minute:
		return fmt.Sprintf("%d minutes", int(d/time.Minute))
	}
	return "under 2 minutes"
}

func plural(n int, word string) string {
	if n == 1 {
		return "1 " + word
	}
	return fmt.Sprintf("%d %ss", n, word)
}