// Package backup implementiert Backup + Restore für EdgeGuard.
//
// Backup-Inhalt (eg-<ts>.tar.gz):
//
//	dump.sql       — pg_dump --clean --if-exists --no-owner --no-acl
//	                  der edgeguard-DB (Schema + Daten). Restore via psql.
//	files/         — Verbatim-Kopie node-lokaler State-Dateien:
//	                  - setup.json          (Setup-Wizard-Ergebnis)
//	                  - license_key         (node-lokale Lizenz)
//	                  - .jwt_fingerprint    (Session-Signing-Secret)
//	                  - acme-account/       (LE-Account + Privkey)
//	manifest.json  — Metadaten: version, ts, hostname, sizes.
//
// Node-local: ein Backup deckt nur diesen Node ab. In Phase 3-Cluster
// machen alle Nodes ihre eigenen Backups; Konfig ist eh aus PG
// reproduzierbar.
package backup

import (
	"archive/tar"
	"compress/gzip"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
)

// DefaultDir ist der Speicherort der Backup-Archive auf der Box.
const DefaultDir = "/var/backups/edgeguard"

// DefaultStateDir ist /var/lib/edgeguard — alle node-lokalen State-
// Files leben darunter.
const DefaultStateDir = "/var/lib/edgeguard"

// DefaultKeepN ist die Retention für scheduled-Backups. Operator kann
// das in der UI noch nicht überschreiben — Konvention reicht für v1.
const DefaultKeepN = 14

// Kind unterscheidet den Trigger — manual aus UI vs. scheduled aus
// dem 24h-Tick im edgeguard-scheduler.
type Kind string

const (
	KindManual    Kind = "manual"
	KindScheduled Kind = "scheduled"
)

// Result kommt von Run() zurück und landet auch (success oder failed)
// als Row in der backups-Tabelle.
type Result struct {
	ID            int64
	File          string
	SizeBytes     int64
	SHA256        string
	DBDumpBytes   int64
	FilesBytes    int64
	StartedAt     time.Time
	FinishedAt    time.Time
	Error         error
}

// Manifest ist der content von manifest.json im tarball.
type Manifest struct {
	Version       string    `json:"version"`
	Kind          Kind      `json:"kind"`
	Hostname      string    `json:"hostname"`
	CreatedAt     time.Time `json:"created_at"`
	DBDumpBytes   int64     `json:"db_dump_bytes"`
	FilesBytes    int64     `json:"files_bytes"`
}

// Service bündelt Backup + Restore + Retention. Stateless — alle
// Konfig kommt als Konstruktor-Param + Methode-Param.
type Service struct {
	Pool      *pgxpool.Pool
	BackupDir string
	StateDir  string

	// PGDumpCmd ist normalerweise "pg_dump" — postinst whitelisted
	// `sudo -n -u postgres pg_dump …`. Mit dem Override-Hook können
	// Tests einen fake-binary einschleusen.
	PGDumpCmd  func(ctx context.Context, w io.Writer) (int64, error)
	NowFn      func() time.Time
}

func New(pool *pgxpool.Pool) *Service {
	return &Service{
		Pool:      pool,
		BackupDir: DefaultDir,
		StateDir:  DefaultStateDir,
		NowFn:     time.Now,
	}
}

// Run führt ein Backup aus. Bei Erfolg: tarball auf Disk + Row in DB.
// Bei Failure: tarball gelöscht, Row mit status=failed.
func (s *Service) Run(ctx context.Context, kind Kind, version string) (*Result, error) {
	now := s.NowFn().UTC()
	hostname, _ := os.Hostname()

	res := &Result{
		File:      fmt.Sprintf("eg-%s.tar.gz", now.Format("20060102-150405")),
		StartedAt: now,
	}

	if err := os.MkdirAll(s.BackupDir, 0o755); err != nil {
		return res, fmt.Errorf("mkdir: %w", err)
	}
	outPath := filepath.Join(s.BackupDir, res.File)

	// SHA256 berechnen wir während-write parallel via TeeWriter.
	f, err := os.OpenFile(outPath, os.O_CREATE|os.O_WRONLY|os.O_EXCL, 0o640)
	if err != nil {
		return res, fmt.Errorf("create %s: %w", outPath, err)
	}
	hasher := sha256.New()
	mw := io.MultiWriter(f, hasher)

	gz := gzip.NewWriter(mw)
	tw := tar.NewWriter(gz)

	// 1) dump.sql — pg_dump streamt direkt rein.
	dumpSize, dumpErr := s.writeDump(ctx, tw)
	if dumpErr != nil {
		_ = tw.Close()
		_ = gz.Close()
		_ = f.Close()
		_ = os.Remove(outPath)
		res.Error = dumpErr
		res.FinishedAt = s.NowFn().UTC()
		s.recordFailure(ctx, res, hostname, kind)
		return res, dumpErr
	}
	res.DBDumpBytes = dumpSize

	// 2) files/ — alles aus /var/lib/edgeguard außer Cache/Tmp.
	filesSize, filesErr := s.writeFiles(tw)
	if filesErr != nil {
		_ = tw.Close()
		_ = gz.Close()
		_ = f.Close()
		_ = os.Remove(outPath)
		res.Error = filesErr
		res.FinishedAt = s.NowFn().UTC()
		s.recordFailure(ctx, res, hostname, kind)
		return res, filesErr
	}
	res.FilesBytes = filesSize

	// 3) manifest.json
	man := Manifest{
		Version:     version,
		Kind:        kind,
		Hostname:    hostname,
		CreatedAt:   now,
		DBDumpBytes: dumpSize,
		FilesBytes:  filesSize,
	}
	manBytes, _ := json.MarshalIndent(man, "", "  ")
	if err := writeTarBlob(tw, "manifest.json", manBytes); err != nil {
		_ = tw.Close()
		_ = gz.Close()
		_ = f.Close()
		_ = os.Remove(outPath)
		res.Error = err
		res.FinishedAt = s.NowFn().UTC()
		s.recordFailure(ctx, res, hostname, kind)
		return res, err
	}

	if err := tw.Close(); err != nil {
		_ = gz.Close()
		_ = f.Close()
		_ = os.Remove(outPath)
		res.Error = err
		s.recordFailure(ctx, res, hostname, kind)
		return res, err
	}
	if err := gz.Close(); err != nil {
		_ = f.Close()
		_ = os.Remove(outPath)
		res.Error = err
		s.recordFailure(ctx, res, hostname, kind)
		return res, err
	}
	if err := f.Sync(); err != nil {
		// Nicht fatal — fsync-failure kann passieren bei tmpfs in
		// Dev, aber der File ist da.
	}
	if err := f.Close(); err != nil {
		s.recordFailure(ctx, res, hostname, kind)
		return res, err
	}

	stat, _ := os.Stat(outPath)
	if stat != nil {
		res.SizeBytes = stat.Size()
	}
	res.SHA256 = hex.EncodeToString(hasher.Sum(nil))
	res.FinishedAt = s.NowFn().UTC()

	if err := s.recordSuccess(ctx, res, hostname, kind); err != nil {
		// DB-Insert failed — File haben wir, aber Operator sieht
		// das Backup nicht in der UI. Lassen wir's stehen mit Log-
		// Warnung; nächster Scheduled-Run räumt es nicht ab (Retention
		// arbeitet nur über DB-Rows).
		return res, fmt.Errorf("db record: %w", err)
	}
	return res, nil
}

// writeDump pipet pg_dump direkt in den tar-Stream als file "dump.sql".
// pg_dump läuft via `sudo -n -u postgres pg_dump --clean --if-exists
// --no-owner --no-acl edgeguard`. Sudoers-Whitelist in postinst.
func (s *Service) writeDump(ctx context.Context, tw *tar.Writer) (int64, error) {
	if s.PGDumpCmd != nil {
		var buf bytes
		size, err := s.PGDumpCmd(ctx, &buf)
		if err != nil {
			return 0, err
		}
		if err := writeTarBlob(tw, "dump.sql", buf.b); err != nil {
			return 0, err
		}
		return size, nil
	}

	cmd := exec.CommandContext(ctx, "sudo", "-n", "-u", "postgres",
		"/usr/bin/pg_dump",
		"--clean", "--if-exists", "--no-owner", "--no-acl",
		"edgeguard")
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return 0, err
	}
	if err := cmd.Start(); err != nil {
		return 0, fmt.Errorf("pg_dump start: %w", err)
	}

	dump, err := io.ReadAll(stdout)
	if err != nil {
		_ = cmd.Wait()
		return 0, fmt.Errorf("pg_dump read: %w", err)
	}
	if err := cmd.Wait(); err != nil {
		return 0, fmt.Errorf("pg_dump: %w", err)
	}
	if err := writeTarBlob(tw, "dump.sql", dump); err != nil {
		return 0, err
	}
	return int64(len(dump)), nil
}

// writeFiles bringt alle relevanten /var/lib/edgeguard-Files unter
// files/<relpath> in den tar. Bewusste Liste statt rekursiv-everything,
// damit wir nicht aus Versehen den fs.cache oder Lockfiles backupen.
func (s *Service) writeFiles(tw *tar.Writer) (int64, error) {
	var total int64
	candidates := []string{
		"setup.json",
		"license_key",
		"license.cache",
		"trial.json",
		".jwt_fingerprint",
		"node.conf",
	}
	for _, rel := range candidates {
		path := filepath.Join(s.StateDir, rel)
		data, err := os.ReadFile(path)
		if err != nil {
			if errors.Is(err, os.ErrNotExist) {
				continue // optional-file, skip
			}
			return total, fmt.Errorf("read %s: %w", path, err)
		}
		if err := writeTarBlob(tw, "files/"+rel, data); err != nil {
			return total, err
		}
		total += int64(len(data))
	}
	// acme-account/ rekursiv (Multi-File-Dir mit LE-Privkey).
	acmeDir := filepath.Join(s.StateDir, "acme-account")
	if _, err := os.Stat(acmeDir); err == nil {
		err := filepath.Walk(acmeDir, func(p string, info os.FileInfo, werr error) error {
			if werr != nil {
				return werr
			}
			if info.IsDir() {
				return nil
			}
			rel, _ := filepath.Rel(s.StateDir, p)
			data, rerr := os.ReadFile(p)
			if rerr != nil {
				return rerr
			}
			if werr := writeTarBlob(tw, "files/"+rel, data); werr != nil {
				return werr
			}
			total += int64(len(data))
			return nil
		})
		if err != nil {
			return total, err
		}
	}
	return total, nil
}

func writeTarBlob(tw *tar.Writer, name string, data []byte) error {
	hdr := &tar.Header{
		Name:    name,
		Mode:    0o600,
		Size:    int64(len(data)),
		ModTime: time.Now(),
	}
	if err := tw.WriteHeader(hdr); err != nil {
		return err
	}
	_, err := tw.Write(data)
	return err
}

// recordSuccess + recordFailure schreiben einen Eintrag in backups.
func (s *Service) recordSuccess(ctx context.Context, r *Result, host string, kind Kind) error {
	if s.Pool == nil {
		return nil
	}
	row := s.Pool.QueryRow(ctx, `
INSERT INTO backups (file, size_bytes, sha256, db_dump_bytes, files_bytes,
                     kind, status, host, started_at, finished_at)
VALUES ($1, $2, $3, $4, $5, $6, 'success', $7, $8, $9)
RETURNING id`,
		r.File, r.SizeBytes, r.SHA256, r.DBDumpBytes, r.FilesBytes,
		string(kind), host, r.StartedAt, r.FinishedAt)
	return row.Scan(&r.ID)
}

func (s *Service) recordFailure(ctx context.Context, r *Result, host string, kind Kind) {
	if s.Pool == nil {
		return
	}
	errStr := ""
	if r.Error != nil {
		errStr = r.Error.Error()
	}
	_, _ = s.Pool.Exec(ctx, `
INSERT INTO backups (file, size_bytes, sha256, db_dump_bytes, files_bytes,
                     kind, status, error, host, started_at, finished_at)
VALUES ($1, 0, '', 0, 0, $2, 'failed', $3, $4, $5, $6)
ON CONFLICT (file) DO NOTHING`,
		r.File, string(kind), errStr, host, r.StartedAt, r.FinishedAt)
}

// Prune löscht erfolgreiche Backups älter als die letzten keepN. Wird
// nach jedem scheduled-Run aufgerufen. Failed-Rows bleiben für die
// History.
func (s *Service) Prune(ctx context.Context, keepN int) error {
	if keepN <= 0 {
		keepN = DefaultKeepN
	}
	if s.Pool == nil {
		return nil
	}
	rows, err := s.Pool.Query(ctx, `
SELECT id, file FROM backups
 WHERE status = 'success'
 ORDER BY started_at DESC`)
	if err != nil {
		return err
	}
	type row struct {
		id   int64
		file string
	}
	var all []row
	for rows.Next() {
		var r row
		if err := rows.Scan(&r.id, &r.file); err != nil {
			rows.Close()
			return err
		}
		all = append(all, r)
	}
	rows.Close()
	if len(all) <= keepN {
		return nil
	}
	expired := all[keepN:]
	for _, e := range expired {
		_ = os.Remove(filepath.Join(s.BackupDir, e.file))
		_, _ = s.Pool.Exec(ctx, `DELETE FROM backups WHERE id = $1`, e.id)
	}
	return nil
}

// List gibt alle Backup-Einträge zurück (newest first).
func (s *Service) List(ctx context.Context) ([]Entry, error) {
	if s.Pool == nil {
		return nil, nil
	}
	rows, err := s.Pool.Query(ctx, `
SELECT id, file, size_bytes, sha256, db_dump_bytes, files_bytes,
       kind, status, COALESCE(error, ''), COALESCE(host, ''),
       started_at, finished_at
FROM backups
ORDER BY started_at DESC
LIMIT 200`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []Entry{}
	for rows.Next() {
		var e Entry
		if err := rows.Scan(&e.ID, &e.File, &e.SizeBytes, &e.SHA256,
			&e.DBDumpBytes, &e.FilesBytes, &e.Kind, &e.Status,
			&e.Error, &e.Host, &e.StartedAt, &e.FinishedAt); err != nil {
			return nil, err
		}
		out = append(out, e)
	}
	return out, rows.Err()
}

// Entry mirrort einen DB-Row.
type Entry struct {
	ID          int64     `json:"id"`
	File        string    `json:"file"`
	SizeBytes   int64     `json:"size_bytes"`
	SHA256      string    `json:"sha256"`
	DBDumpBytes int64     `json:"db_dump_bytes"`
	FilesBytes  int64     `json:"files_bytes"`
	Kind        string    `json:"kind"`
	Status      string    `json:"status"`
	Error       string    `json:"error,omitempty"`
	Host        string    `json:"host,omitempty"`
	StartedAt   time.Time `json:"started_at"`
	FinishedAt  time.Time `json:"finished_at"`
}

// Get gibt einen einzelnen Eintrag + den File-Pfad zurück.
func (s *Service) Get(ctx context.Context, id int64) (*Entry, string, error) {
	if s.Pool == nil {
		return nil, "", errors.New("no pool")
	}
	var e Entry
	err := s.Pool.QueryRow(ctx, `
SELECT id, file, size_bytes, sha256, db_dump_bytes, files_bytes,
       kind, status, COALESCE(error, ''), COALESCE(host, ''),
       started_at, finished_at
FROM backups WHERE id = $1`, id).Scan(
		&e.ID, &e.File, &e.SizeBytes, &e.SHA256, &e.DBDumpBytes, &e.FilesBytes,
		&e.Kind, &e.Status, &e.Error, &e.Host, &e.StartedAt, &e.FinishedAt)
	if err != nil {
		return nil, "", err
	}
	return &e, filepath.Join(s.BackupDir, e.File), nil
}

// Restore startet einen full-system-restore aus einem vorhandenen
// Backup-Tarball. Läuft analog `/system/upgrade`-Pattern: wir
// schreiben /var/lib/edgeguard/restore.sh und dispatchen es per
// `sudo systemd-run --unit=edgeguard-restore.service`. Das Skript
// stoppt edgeguard-api+scheduler, kopiert die files/, restored den
// DB-Dump als postgres, re-rendert die Configs und startet die
// Services neu.
//
// Returnt sofort nach dem Dispatch (asynchron) — der eigentliche
// Restore läuft im Hintergrund. UI pollt /healthz für die
// Version-Flip-Detection (analog Upgrade).
func (s *Service) Restore(ctx context.Context, id int64) (*Entry, error) {
	e, path, err := s.Get(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("backup not found: %w", err)
	}
	if e.Status != "success" {
		return nil, fmt.Errorf("backup is in status %q — cannot restore", e.Status)
	}
	if _, err := os.Stat(path); err != nil {
		return nil, fmt.Errorf("backup file missing on disk: %w", err)
	}

	const scriptPath = "/var/lib/edgeguard/restore.sh"
	script := fmt.Sprintf(`#!/bin/bash
# Generated by edgeguard-api — restore from %s
set -e
sleep 2  # let API return 202 first
TARBALL=%q
TMP=/var/lib/edgeguard/restore-tmp
echo "[restore] extract $TARBALL → $TMP"
rm -rf "$TMP"
mkdir -p "$TMP"
tar -xzf "$TARBALL" -C "$TMP"

# 1) Restore node-local state files BEFORE the DB swap so a crash
#    mid-restore leaves the box in a state where the next API-start
#    sees the new keys/setup. DB will be partial but recoverable.
echo "[restore] state files"
for f in setup.json license_key license.cache trial.json .jwt_fingerprint node.conf; do
    if [ -f "$TMP/files/$f" ]; then
        cp -a "$TMP/files/$f" /var/lib/edgeguard/
    fi
done
if [ -d "$TMP/files/acme-account" ]; then
    mkdir -p /var/lib/edgeguard/acme-account
    cp -a "$TMP/files/acme-account/." /var/lib/edgeguard/acme-account/
fi
chown -R edgeguard:edgeguard /var/lib/edgeguard/setup.json \
    /var/lib/edgeguard/license_key /var/lib/edgeguard/license.cache \
    /var/lib/edgeguard/trial.json /var/lib/edgeguard/.jwt_fingerprint \
    /var/lib/edgeguard/node.conf /var/lib/edgeguard/acme-account 2>/dev/null || true

# 2) Stop API+scheduler so psql can DROP/CREATE tables without active
#    connections fighting the dump-restore.
echo "[restore] stop services"
systemctl stop edgeguard-api edgeguard-scheduler

# 3) Apply DB dump. pg_dump --clean emits DROP TABLE IF EXISTS so
#    we don't need to wipe the schema manually.
echo "[restore] psql -f dump.sql"
sudo -u postgres /usr/bin/psql --quiet -d edgeguard -f "$TMP/dump.sql"

# 4) Re-render configs from the freshly restored DB. Each renderer
#    triggers its own service reload — haproxy, nft, etc. so the
#    user-visible state matches DB-state immediately.
echo "[restore] render-config"
sudo -u edgeguard /usr/bin/edgeguard-ctl render-config || true

# 5) Restart edgeguard-api so the UI's /healthz poll sees version-
#    flip / fresh connection. Scheduler comes back automatically.
echo "[restore] start services"
systemctl start edgeguard-api edgeguard-scheduler

rm -rf "$TMP" "$0"
echo "[restore] complete"
`, e.File, path)

	if err := os.WriteFile(scriptPath, []byte(script), 0o755); err != nil {
		return nil, fmt.Errorf("write %s: %w", scriptPath, err)
	}

	const unitName = "edgeguard-restore.service"
	_ = exec.Command("sudo", "-n", "/usr/bin/systemctl",
		"reset-failed", unitName).Run()
	cmd := exec.Command("sudo", "-n", "/usr/bin/systemd-run",
		"--unit="+unitName,
		"--description=EdgeGuard self-restore",
		"--collect",
		"bash", scriptPath)
	if err := cmd.Run(); err != nil {
		return nil, fmt.Errorf("systemd-run: %w", err)
	}
	return e, nil
}

// Delete entfernt File + DB-Row.
func (s *Service) Delete(ctx context.Context, id int64) error {
	_, path, err := s.Get(ctx, id)
	if err != nil {
		return err
	}
	if err := os.Remove(path); err != nil && !errors.Is(err, os.ErrNotExist) {
		return err
	}
	_, err = s.Pool.Exec(ctx, `DELETE FROM backups WHERE id = $1`, id)
	return err
}

// bytes ist ein tiny io.Writer-Stand-in für den PGDumpCmd-Override
// (Tests). Stdlib bytes.Buffer hätte's auch getan, aber das Package
// hat einen anderen import-graph.
type bytes struct{ b []byte }

func (b *bytes) Write(p []byte) (int, error) {
	b.b = append(b.b, p...)
	return len(p), nil
}

// strFold ist ein utility nur zum Defensiv-Check, dass kind ein
// erlaubter Wert ist (für die DB-Constraint).
func strFold(s string) string { return strings.ToLower(strings.TrimSpace(s)) }

// SortByDate sortiert Entries newest-first. Wird nicht direkt benutzt
// (DB-Query macht's), aber praktisch wenn der Caller eine eigene
// Liste hat.
func SortByDate(es []Entry) {
	sort.Slice(es, func(i, j int) bool {
		return es[i].StartedAt.After(es[j].StartedAt)
	})
}