package app

import (
	"archive/tar"
	"compress/gzip"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"strings"
)

// Backup is an offline operation: Open has already acquired the exclusive service lock.
func (a *App) Backup(configPath, target string) error {
	abs, e := filepath.Abs(target)
	if e != nil {
		return e
	}
	data, e := filepath.Abs(a.cfg.DataDir)
	if e != nil {
		return e
	}
	if abs == data || strings.HasPrefix(abs, data+string(os.PathSeparator)) {
		return errors.New("备份目标必须在数据目录之外")
	}
	if e = a.db.Close(); e != nil {
		return e
	}
	a.db = nil
	out, e := os.OpenFile(abs, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
	if e != nil {
		return e
	}
	success := false
	defer func() {
		out.Close()
		if !success {
			os.Remove(abs)
		}
	}()
	gz := gzip.NewWriter(out)
	tw := tar.NewWriter(gz)
	write := func(name string, f *os.File, st os.FileInfo) error {
		h := &tar.Header{Name: name, Mode: 0600, Size: st.Size(), ModTime: st.ModTime(), Typeflag: tar.TypeReg}
		if e := tw.WriteHeader(h); e != nil {
			return e
		}
		_, e := io.Copy(tw, f)
		return e
	}
	cf, e := os.Open(configPath)
	if e != nil {
		return e
	}
	st, e := cf.Stat()
	if e == nil {
		e = write("config.toml", cf, st)
	}
	cf.Close()
	if e != nil {
		return e
	}
	e = fs.WalkDir(a.root.FS(), ".", func(path string, d fs.DirEntry, e error) error {
		if e != nil {
			return e
		}
		if d.Type()&os.ModeSymlink != 0 {
			return fmt.Errorf("拒绝备份符号链接: %s", path)
		}
		if d.IsDir() || path == "service.lock" {
			return nil
		}
		if strings.HasPrefix(path, "tmp/") {
			return nil
		}
		st, e := d.Info()
		if e != nil {
			return e
		}
		if !st.Mode().IsRegular() {
			return errors.New("数据目录包含特殊文件")
		}
		f, e := a.root.Open(path)
		if e != nil {
			return e
		}
		defer f.Close()
		return write("var/"+path, f, st)
	})
	if e != nil {
		return e
	}
	if e = tw.Close(); e != nil {
		return e
	}
	if e = gz.Close(); e != nil {
		return e
	}
	if e = out.Sync(); e != nil {
		return e
	}
	success = true
	return nil
}
func Restore(c Config, source string) error {
	if e := c.Validate(); e != nil {
		return e
	}
	if e := os.MkdirAll(c.DataDir, 0700); e != nil {
		return e
	}
	entries, e := os.ReadDir(c.DataDir)
	if e != nil {
		return e
	}
	if len(entries) != 0 {
		return errors.New("恢复数据目录必须为空")
	}
	root, e := os.OpenRoot(c.DataDir)
	if e != nil {
		return e
	}
	defer root.Close()
	if e = root.WriteFile("restore.incomplete", []byte("restoring"), 0600); e != nil {
		return e
	}
	input, e := os.Open(source)
	if e != nil {
		return e
	}
	defer input.Close()
	gz, e := gzip.NewReader(input)
	if e != nil {
		return e
	}
	defer gz.Close()
	tr := tar.NewReader(gz)
	var total int64
	var count int
	for {
		h, e := tr.Next()
		if errors.Is(e, io.EOF) {
			break
		}
		if e != nil {
			return e
		}
		if h.Typeflag != tar.TypeReg || !safeRelative(h.Name) {
			return errors.New("备份包含非法路径或文件类型")
		}
		count++
		if count > c.MaxRecords+32 {
			return errors.New("备份文件数量超出恢复限制")
		}
		name := ""
		if h.Name == "config.toml" {
			name = "restored-config.toml"
		} else if strings.HasPrefix(h.Name, "var/") {
			name = strings.TrimPrefix(h.Name, "var/")
		} else {
			return errors.New("未知备份路径")
		}
		if !safeRelative(name) || h.Size < 0 || h.Size > c.DataBudget || total > c.DataBudget-h.Size {
			return errors.New("备份超过恢复容量")
		}
		total += h.Size
		if e = root.MkdirAll(filepath.Dir(name), 0700); e != nil {
			return e
		}
		f, e := root.OpenFile(name, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0600)
		if e != nil {
			return e
		}
		_, e = io.CopyN(f, tr, h.Size)
		if e == nil {
			e = f.Sync()
		}
		ce := f.Close()
		if e == nil {
			e = ce
		}
		if e != nil {
			return e
		}
	}
	if _, e = io.Copy(io.Discard, gz); e != nil {
		return e
	}
	// Invalidate before Open runs lifecycle cleanup, leaving payloads retained for admin review.
	dbPath := filepath.Join(c.DataDir, "db", "bluebird.db")
	if _, e = os.Stat(dbPath); e != nil {
		return errors.New("备份缺少数据库")
	}
	a, e := OpenForRestore(c)
	if e != nil {
		return e
	}
	defer a.Close()
	if e = a.Check(); e != nil {
		return e
	}
	if e = a.InvalidateRestored(); e != nil {
		return e
	}
	if e = root.Remove("restore.incomplete"); e != nil {
		return e
	}
	return syncDir(root, ".")
}