package backup

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"

	"gitea.dooplex.hu/admin/felhom-controller/internal/infra"
)

// Shares restore — R-7b Part 4. A SIBLING of the per-app scratch/place flow in offbox_restore.go,
// mirroring its shape (restore to an on-data-drive scratch first, then a separate, deliberate
// place-to-live merge) without touching it.
//
// Three things come back, in this order of importance:
//  1. the FILES — placed missing-only into each share's live folder, never overwriting;
//  2. the DEFINITIONS — merged into the share registry so the „Megosztás" page is whole again;
//  3. the CREDENTIAL — best-effort, into the samba named volume, so the household need not re-set it.
//
// The load-bearing guard is the PREFIX ASSERT: a destination is only written when it resolves
// strictly inside a REGISTERED, LIVE storage root. A snapshot is untrusted input for this purpose —
// it was written by an older version of this box, possibly with a different drive layout — so a path
// that no longer sits under a live root is refused rather than created.

// SetSharesReconciler wires the post-restore samba re-render (main.go → stacks.ReconcileSamba).
func (m *Manager) SetSharesReconciler(fn func() error) { m.sharesReconcile = fn }

// SetSharesPassdbRestorer overrides the passdb restore exec (tests).
func (m *Manager) SetSharesPassdbRestorer(fn func(tar []byte) error) { m.sharesPassdbRestore = fn }

func (m *Manager) sharesPassdbRestorer() func([]byte) error {
	if m.sharesPassdbRestore != nil {
		return m.sharesPassdbRestore
	}
	return defaultSharesPassdbRestore
}

// defaultSharesPassdbRestore untars a captured passdb archive back into the samba named volume. It
// writes ONLY into infra.SambaPassdbMount inside the samba container — never onto the host — so a
// malformed archive cannot reach anything outside the volume it came from.
func defaultSharesPassdbRestore(tar []byte) error {
	cmd := exec.Command("docker", "exec", "-i", infra.SambaContainerName,
		"tar", "xf", "-", "-C", infra.SambaPassdbMount)
	cmd.Stdin = bytes.NewReader(tar)
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("passdb restore: %s: %w", truncate(out), err)
	}
	return nil
}

// sharesRestoreScratchDir returns the on-DATA-DRIVE scratch for the shares restore. Never the
// controller data dir (the F-A1 rootfs-filler lesson) and never network storage when a local drive
// exists (the F-6C-1 ownership-fidelity lesson).
func (m *Manager) sharesRestoreScratchDir() (scratch, nsRoot string, err error) {
	if m.settings == nil {
		return "", "", fmt.Errorf("nincs elérhető adatmeghajtó a visszaállításhoz")
	}
	pick := func(networkOK bool) (string, string, bool) {
		for _, sp := range m.settings.GetSchedulableStoragePaths() {
			if strings.TrimSpace(sp.Path) == "" || (!networkOK && sp.IsNetwork()) {
				continue
			}
			nr := m.namespaceRoot(sp.Path)
			return filepath.Join(nr, "backups", "offsite-restore", SharesPseudoStack), nr, true
		}
		return "", "", false
	}
	if s, nr, ok := pick(false); ok {
		return s, nr, nil
	}
	if s, nr, ok := pick(true); ok {
		m.logger.Printf("[WARN] [shares] restore scratch on network storage — ownership fidelity not guaranteed under squash")
		return s, nr, nil
	}
	return "", "", fmt.Errorf("nincs elérhető adatmeghajtó a visszaállításhoz")
}

// RestoreSharesScratch restores the latest `_shares` snapshot into the scratch dir. Non-destructive:
// it never touches a live share folder, the registry, or the credential — PlaceSharesRestore is the
// deliberate second action that does.
func (m *Manager) RestoreSharesScratch(ctx context.Context) error {
	if !m.OffboxConfigured() {
		return fmt.Errorf("a távoli mentés nincs beállítva")
	}
	scratch, nsRoot, err := m.sharesRestoreScratchDir()
	if err != nil {
		return err
	}
	if free := m.offboxFree()(nsRoot); free > 0 && free < offboxUnitOnlyFreeFloor {
		return fmt.Errorf("Nincs elég szabad hely a visszaállításhoz (%s szükséges, %s szabad).",
			humanizeBytes(offboxUnitOnlyFreeFloor), humanizeBytes(free))
	}
	id, _, err := m.offboxLatestSnapshot(ctx, SharesPseudoStack)
	if err != nil {
		return fmt.Errorf("nincs visszaállítható megosztás-mentés: %w", err)
	}
	if err := os.MkdirAll(scratch, 0o755); err != nil {
		return fmt.Errorf("restore dir: %w", err)
	}
	t := m.settings.GetOffboxTarget()
	base, env := m.offboxBaseArgs(t)
	rctx, cancel := context.WithTimeout(ctx, offboxBackupTimeout)
	defer cancel()
	m.unlockStale(rctx, base, env)
	out, rerr := m.resticStep(rctx, env, base, "restore:"+SharesPseudoStack, "restore", id, "--target", scratch)
	if rerr != nil {
		return fmt.Errorf("a megosztások visszaállítása sikertelen: %w: %s", rerr, truncate(out))
	}
	m.logger.Printf("[INFO] [shares] restored snapshot %s → %s", id, scratch)
	return nil
}

// SharesScratchReady reports whether a completed shares scratch exists (gates the place action).
func (m *Manager) SharesScratchReady() bool {
	scratch, _, err := m.sharesRestoreScratchDir()
	if err != nil {
		return false
	}
	entries, rErr := os.ReadDir(scratch)
	return rErr == nil && len(entries) > 0
}

// SharesRestoreResult is what the flash message reports back to the customer.
type SharesRestoreResult struct {
	FilesRestored    int      // files merged into live share folders
	SharesPlaced     []string // share folders whose files were merged
	DefinitionsAdded []string // share definitions re-added to the registry
	DefinitionsKept  []string // definitions skipped because a live share already owns the name
	Refused          []string // definitions refused: destination is not under a live storage root
	PasswordRestored bool     // the household SMB credential was put back
}

// liveShareRootOK prefix-asserts a destination against the REGISTERED, LIVE storage roots. It
// requires a STRICT descendant: equal-to-the-root is refused too, because placing a share's contents
// at a drive root would scatter restored files across the whole drive. A `..` segment is refused
// outright rather than relying on Clean, so a traversal attempt is visible in the logs.
func (m *Manager) liveShareRootOK(dst string) bool {
	if m.settings == nil || strings.TrimSpace(dst) == "" {
		return false
	}
	clean := filepath.Clean(dst)
	for _, seg := range strings.Split(filepath.ToSlash(dst), "/") {
		if seg == ".." {
			return false
		}
	}
	p := filepath.ToSlash(clean)
	for _, sp := range m.settings.GetStoragePaths() {
		if sp.Decommissioned || sp.Disconnected {
			continue
		}
		root := filepath.ToSlash(filepath.Clean(sp.Path))
		if root == "" || root == "/" {
			continue
		}
		if strings.HasPrefix(p, root+"/") {
			return true
		}
	}
	return false
}

// scratchJoin reconstructs an absolute captured path UNDER a restore scratch — restic restores with
// the absolute source structure preserved, so /mnt/hdd_1/dokumentumok lands at
// <scratch>/mnt/hdd_1/dokumentumok. The volume name and leading separator are stripped explicitly
// rather than relying on filepath.Join, which on a non-POSIX host would splice a drive letter into
// the middle of the path and produce an unopenable name.
func scratchJoin(scratch, abs string) string {
	rel := abs
	if vol := filepath.VolumeName(rel); vol != "" {
		rel = rel[len(vol):]
	}
	rel = strings.TrimLeft(filepath.ToSlash(rel), "/")
	return filepath.Join(scratch, filepath.FromSlash(rel))
}

// readSharesManifestFrom reads the manifest out of a restored scratch tree.
func (m *Manager) readSharesManifestFrom(scratch string) (SharesManifest, error) {
	var mf SharesManifest
	p := filepath.Join(scratchJoin(scratch, m.sharesPayloadDir()), sharesManifestName)
	blob, err := os.ReadFile(p)
	if err != nil {
		return mf, fmt.Errorf("a mentésben nincs megosztás-leíró: %w", err)
	}
	if err := json.Unmarshal(blob, &mf); err != nil {
		return mf, fmt.Errorf("a megosztás-leíró olvashatatlan: %w", err)
	}
	return mf, nil
}

// PlaceSharesRestore places a completed shares scratch into live locations: files first (missing-only
// merge, never overwriting), then the definitions (existing live definitions WIN on a name conflict —
// a restore must not silently flip a live share's read-only or cloud setting), then the samba
// re-render, then the credential. Single-flight.
func (m *Manager) PlaceSharesRestore(ctx context.Context) (SharesRestoreResult, error) {
	var res SharesRestoreResult
	if err := m.acquireRunning(); err != nil {
		return res, fmt.Errorf("egy másik mentési/visszaállítási művelet már fut")
	}
	defer m.releaseRunning()

	scratch, _, err := m.sharesRestoreScratchDir()
	if err != nil {
		return res, err
	}
	if _, sErr := os.Stat(scratch); sErr != nil {
		return res, fmt.Errorf("nincs előkészített visszaállítás — futtass előbb egy megosztás-visszaállítást")
	}
	mf, err := m.readSharesManifestFrom(scratch)
	if err != nil {
		return res, err
	}

	// Live registry, indexed case-insensitively (AddSMBShare's own collision rule).
	live := map[string]bool{}
	if m.settings != nil {
		for _, sh := range m.settings.GetSMBShares() {
			live[strings.ToLower(sh.Name)] = true
		}
	}
	copier := m.placeCopier()
	for _, sh := range mf.Shares {
		// THE PREFIX ASSERT. The snapshot's path is untrusted layout input; a destination that is not
		// strictly inside a live registered root is refused, never created.
		if !m.liveShareRootOK(sh.Path) {
			m.logger.Printf("[WARN] [shares] restore refused for %s — destination is not under a live storage root", sh.Name)
			res.Refused = append(res.Refused, sh.Name)
			continue
		}
		src := scratchJoin(scratch, sh.Path)
		if _, sErr := os.Stat(src); sErr == nil {
			n, cErr := copier(src, sh.Path)
			if cErr != nil {
				return res, fmt.Errorf("a(z) „%s” megosztás fájljainak visszaállítása sikertelen: %w", sh.Name, cErr)
			}
			res.FilesRestored += n
			res.SharesPlaced = append(res.SharesPlaced, sh.Name)
		} else {
			// A definitions-only snapshot (the quota-degraded shape) legitimately has no file tree.
			m.logger.Printf("[DEBUG] [shares] no restored file tree for %s — definitions-only snapshot", sh.Name)
		}
		// Definitions: existing live share WINS. Restoring must never silently change a share the
		// household is using right now.
		if live[strings.ToLower(sh.Name)] {
			res.DefinitionsKept = append(res.DefinitionsKept, sh.Name)
			continue
		}
		if m.settings != nil {
			if aErr := m.settings.AddSMBShare(sh); aErr != nil {
				m.logger.Printf("[WARN] [shares] could not re-add definition %s: %v", sh.Name, aErr)
				continue
			}
			res.DefinitionsAdded = append(res.DefinitionsAdded, sh.Name)
		}
	}

	// Re-render smb.conf so the restored definitions are actually exported.
	if len(res.DefinitionsAdded) > 0 {
		if m.sharesReconcile == nil {
			m.logger.Printf("[WARN] [shares] no samba reconciler wired — smb.conf will catch up on the next health tick")
		} else if rErr := m.sharesReconcile(); rErr != nil {
			m.logger.Printf("[WARN] [shares] samba re-render after restore failed: %v", rErr)
		}
	}

	// Credential, best-effort and last: the files and definitions are the load-bearing parts, and
	// re-setting an SMB password is a cheap, well-signposted UX step.
	passdb := filepath.Join(scratchJoin(scratch, m.sharesPayloadDir()), sharesPassdbName)
	if blob, rErr := os.ReadFile(passdb); rErr == nil && len(blob) > 0 {
		if pErr := m.sharesPassdbRestorer()(blob); pErr != nil {
			m.logger.Printf("[WARN] [shares] credential restore failed — the SMB password must be re-set: %v", pErr)
		} else {
			res.PasswordRestored = true
			if m.settings != nil {
				if sErr := m.settings.SetSMBUserSet(true); sErr != nil {
					m.logger.Printf("[WARN] [shares] persist user-set flag after credential restore failed: %v", sErr)
				}
			}
			m.logger.Printf("[INFO] [shares] household credential restored into the sharing service")
		}
	}

	if rmErr := os.RemoveAll(scratch); rmErr != nil {
		m.logger.Printf("[WARN] [shares] scratch cleanup failed (harmless): %v", rmErr)
	}
	m.logger.Printf("[INFO] [shares] restore placed: %d file(s), %d definition(s) re-added, %d kept, %d refused, credential=%v",
		res.FilesRestored, len(res.DefinitionsAdded), len(res.DefinitionsKept), len(res.Refused), res.PasswordRestored)
	return res, nil
}

// FlashMessage renders the Hungarian summary the „Megosztások visszaállítása" action flashes back.
func (r SharesRestoreResult) FlashMessage() string {
	var parts []string
	parts = append(parts, fmt.Sprintf("%s visszaállítva: %d fájl, %d megosztás-beállítás.",
		SharesDisplayName, r.FilesRestored, len(r.DefinitionsAdded)))
	for _, n := range r.DefinitionsKept {
		parts = append(parts, fmt.Sprintf("A(z) %s megosztás beállítása már létezik — a meglévő maradt.", n))
	}
	if len(r.Refused) > 0 {
		parts = append(parts, fmt.Sprintf("Nem állítható vissza (a mappa nincs élő adatmeghajtón): %s.",
			strings.Join(r.Refused, ", ")))
	}
	if !r.PasswordRestored {
		parts = append(parts, "A megosztás jelszavát újra meg kell adni.")
	}
	return strings.Join(parts, " ")
}

// SharesRegistryCount is a small helper for the page (how many shares the registry holds).
func (m *Manager) SharesRegistryCount() int {
	if m.settings == nil {
		return 0
	}
	return len(m.settings.GetSMBShares())
}