package backup

import (
	"context"
	"errors"
	"fmt"
	"path/filepath"
	"time"

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

// ── The backup side of the guarded update (update arc slice 4, controller v0.237.0) ─────────────
//
// 09-update-architecture.md §3 decision 1 (operator ruling 2026-09-02): the safety copy for an update
// is a VERIFIED RECENT BACKUP as a PRECONDITION — not a new copy mechanism invented for the update
// path. So everything in this file composes machinery that already exists and is proven live:
// the Tier-2 unit restore's own predicate (R-102/R-103), the nightly legs (DB dump, volume dump,
// unit capture, Tier-2 mirror), the pre-restore safety dump (R-361) and the R-379 hold.
//
// The stacks package cannot import this one, so the update job reaches all of it through the
// stacks.UpdateGuards interface, implemented by an adapter in cmd/controller/main.go.

// Tier2RestorePoint is the answer to "could this app be restored from its Tier-2 copy, and from
// when?" — the predicate the destructive „Teljes visszaállítás" action is gated on.
//
// EXTRACTED, NOT DUPLICATED (slice 4). Until v0.237.0 this computation lived inline in the backups
// page handler (buildAppBackupRows). The update path needs exactly the same question answered, and
// a second copy of a predicate is how this project's two copies of `namespaceRoot` came to differ
// (R-203). So there is one function, and the page and the update both call it.
type Tier2RestorePoint struct {
	// Restorable — the copy holds an OPENABLE recovery unit (Tier2Coverage.CanRestoreUnit).
	Restorable bool
	// CopyDate — the date the unit restore NAMES: the package's own manifest date, falling back to the
	// copy date (Tier2Coverage.UnitRestoreDate, R-403). RFC3339 as recorded, "" when unknown.
	CopyDate string
	// CopyDateProven — a copy actually SUCCEEDED (LastSuccess is set), never merely an attempt (R-101).
	CopyDateProven bool
	// PackagePreserved — the newest run PRESERVED an older package instead of refreshing it (R-403).
	PackagePreserved bool
	// CopyLastSuccess — the RFC3339 time of the last Tier-2 copy that succeeded.
	CopyLastSuccess string
}

// restorePointFromCoverage is the pure half of the predicate.
func restorePointFromCoverage(cov Tier2Coverage) Tier2RestorePoint {
	pkgDate, preserved := cov.UnitRestoreDate()
	return Tier2RestorePoint{
		Restorable:       cov.CanRestoreUnit(),
		CopyDate:         pkgDate,
		CopyDateProven:   cov.CopyLastSuccess != "",
		PackagePreserved: preserved,
		CopyLastSuccess:  cov.CopyLastSuccess,
	}
}

// Tier2UnitRestorePoint resolves the app's recorded Tier-2 copy and returns the restore point. The
// error is the same refusal Tier2RestoreCoverage raises (no copy, drive gone, pre-v2 layout).
func (m *Manager) Tier2UnitRestorePoint(stackName string) (Tier2RestorePoint, error) {
	cov, err := m.Tier2RestoreCoverage(stackName)
	if err != nil {
		return Tier2RestorePoint{}, err
	}
	return restorePointFromCoverage(cov), nil
}

// ProvenCopyTime returns WHEN the data this copy would restore was last proven copied, and false when
// there is no proven, restorable copy at all.
//
// WHY NOT CopyDate, measured rather than assumed. CopyDate is the unit MANIFEST's created_at, and a
// capture rewrites the manifest only when the app's DEFINITION changes (compose, app.yaml, controller
// version) — a nightly DB dump keeps the same file name, so it does not move it. Measured on demo-hp
// 2026-09-13: bookstack's Tier-2 mirror held `bookstack-mariadb.sql` written 2026-09-13T00:30Z while
// its manifest still read 2026-09-12T02:15:29Z. Judging "recent" by that date would call a fresh copy
// stale — and, worse, a "back up first" run would not move it either on a quiet app, so the update
// would be refused forever.
//
// So the age is the last SUCCESSFUL copy (LastSuccess), which the Tier-2 run records only when it
// actually mirrored the unit — EXCEPT when the run preserved an older package (R-403), in which case
// the package date is the honest one, because that is what the copy really holds.
func (p Tier2RestorePoint) ProvenCopyTime() (time.Time, bool) {
	if !p.Restorable || !p.CopyDateProven {
		return time.Time{}, false
	}
	src := p.CopyLastSuccess
	if p.PackagePreserved {
		src = p.CopyDate
	}
	t, err := time.Parse(time.RFC3339, src)
	if err != nil {
		return time.Time{}, false
	}
	return t, true
}

// UpdateBusy reports whether something else is ALREADY touching this app's data, which refuses an
// update before anything moves (slice 4 Scenario D). The reason is operator-English; the customer
// sentence is chosen by the caller.
//
// IsRunning is box-wide, deliberately: the backup/restore single-flight is box-wide, and an update's
// "back up first" leg needs that same flag — an update started beside a running backup would either
// wait on it invisibly or fail half-way.
func (m *Manager) UpdateBusy(stackName string) (bool, string) {
	if m == nil {
		return false, ""
	}
	if m.IsRunning() {
		return true, "a backup or restore is running (single-flight held)"
	}
	if st := m.RestoreStatus(); st.Running {
		return true, fmt.Sprintf("restore op %q is running for %q", st.Op, st.Stack)
	}
	for _, held := range m.appStop.HeldStacks() {
		if held == stackName {
			return true, "an app-data operation (volume dump / export / reconstitute) is holding it"
		}
	}
	return false, ""
}

// ErrUpdateBackupNoUnit is returned when a "back up first" run completed but the app still has no
// openable Tier-2 unit — typically Tier 2 is switched off for the app or has no second target.
var ErrUpdateBackupNoUnit = errors.New("a frissítés előtti mentés lefutott, de nem jött létre visszaállítható másolat")

// RunAppBackupNow runs THIS app's backup legs now, in the nightly order, and then its Tier-2 copy:
// database dump(s) → volume dump (if the app has named volumes) → recovery-unit capture → Tier-2
// mirror. It is the "back up first" of slice 4 Scenario B.
//
// Composed, not reinvented: every leg is the one runDBDumpsInternal and RunAllTier2 already run,
// including the R-181 reserve (admitApp) before the first write and the R-166 app-stop marker inside
// DumpAppVolumesSafe. What differs is only the scope — one app instead of all of them — because an
// update must not bounce every other app on the box to back up one.
func (m *Manager) RunAppBackupNow(ctx context.Context, stackName string) error {
	if m.stackProvider == nil {
		return fmt.Errorf("stack provider not configured")
	}
	if m.migrationActive() {
		return fmt.Errorf("adatáthelyezés folyamatban — a mentés most nem indítható")
	}
	if err := m.acquireRunning(); err != nil {
		return err
	}
	m.logger.Printf("[INFO] [backup] update pre-backup for %s: starting (DB dump → volume dump → unit capture → Tier 2)", stackName)
	start := time.Now()
	legErr := func() error {
		defer m.releaseRunning()
		defer m.beginAdmissionRun()()

		drivePath := m.GetAppDrivePath(stackName)
		if drivePath == "" || !filepath.IsAbs(drivePath) {
			return fmt.Errorf("az alkalmazás meghajtója nem határozható meg")
		}
		if m.settings != nil && (m.settings.IsDisconnected(drivePath) || m.settings.IsDecommissioned(drivePath)) {
			return fmt.Errorf("az alkalmazás meghajtója nem elérhető (%s)", drivePath)
		}
		if !m.admitApp(stackName) {
			return fmt.Errorf("nincs elég szabad hely a mentéshez a(z) %s meghajtón", drivePath)
		}
		nsRoot := m.namespaceRoot(drivePath)

		discover := m.discoverDBs
		if discover == nil {
			discover = func(ctx context.Context) ([]DiscoveredDB, error) {
				return DiscoverDatabases(ctx, m.logger, m.isDebug(), m.knownStackNames())
			}
		}
		dbs, err := discover(ctx)
		if err != nil {
			return fmt.Errorf("adatbázis-felderítés sikertelen: %w", err)
		}
		dumped := 0
		for _, db := range dbs {
			if db.StackName != stackName {
				continue
			}
			res := DumpOne(ctx, db, AppDBDumpPath(nsRoot, stackName), m.logger, m.isDebug())
			if res.Error != nil {
				return fmt.Errorf("adatbázis-mentés sikertelen (%s): %w", db.ContainerName, res.Error)
			}
			dumped++
			m.logger.Printf("[INFO] [backup] update pre-backup for %s: database dump OK (%s, %s)", stackName, db.ContainerName, humanizeBytes(res.Size))
		}

		if len(m.stackProvider.GetDockerVolumes(stackName)) > 0 {
			dump := m.dumpVolumesSafe
			if dump == nil {
				dump = m.DumpAppVolumesSafe
			}
			if err := dump(stackName); err != nil {
				return fmt.Errorf("kötetmentés sikertelen: %w", err)
			}
			m.logger.Printf("[INFO] [backup] update pre-backup for %s: volume dump OK", stackName)
		}

		if err := m.CaptureRecoveryUnit(stackName); err != nil {
			return fmt.Errorf("a mentési egység rögzítése sikertelen: %w", err)
		}
		m.logger.Printf("[INFO] [backup] update pre-backup for %s: recovery unit captured (%d database dump(s))", stackName, dumped)
		return nil
	}()
	if legErr != nil {
		m.logger.Printf("[ERROR] [backup] update pre-backup for %s FAILED after %s: %v", stackName, time.Since(start).Round(time.Millisecond), legErr)
		return legErr
	}

	runOne := m.perAppTier2
	if runOne == nil {
		runOne = m.RunTier2
	}
	if err := runOne(stackName); err != nil {
		m.logger.Printf("[ERROR] [backup] update pre-backup for %s: Tier 2 copy FAILED: %v", stackName, err)
		return fmt.Errorf("a másodlagos másolat elkészítése sikertelen: %w", err)
	}
	m.logger.Printf("[INFO] [backup] update pre-backup for %s: complete in %s", stackName, time.Since(start).Round(time.Millisecond))
	return nil
}

// WriteUpdateSafetyDump takes the last-minute database copy an update makes just before it moves the
// pin: "the state the customer was in a minute ago". It is writeSafetyDump (R-361) unchanged — the
// same `pre-restore-` undo naming, the same pruning to three, the same never-the-canonical-name rule
// — so it is also picked up by the same exclusions (it never enters a manifest's db_dumps).
//
// Returns the paths written; an app with no database returns (nil, nil), which is a no-op and never a
// failure (measured in writeSafetyDump: `len(mine) == 0` returns an empty set).
func (m *Manager) WriteUpdateSafetyDump(ctx context.Context, stackName string) ([]string, error) {
	nsRoot := m.AppNamespaceRoot(stackName)
	if nsRoot == "" {
		return nil, fmt.Errorf("az alkalmazás mentési helye nem határozható meg")
	}
	set, err := m.writeSafetyDump(ctx, stackName, nsRoot)
	if err != nil {
		return nil, err
	}
	var paths []string
	for _, f := range set.Files {
		paths = append(paths, f.Path)
	}
	if len(paths) == 0 {
		m.logger.Printf("[INFO] [backup] update safety dump for %s: the app has no database — nothing to copy (no-op)", stackName)
	} else {
		m.logger.Printf("[INFO] [backup] update safety dump for %s: %d file(s) %v", stackName, len(paths), paths)
	}
	return paths, nil
}

// UpdateHoldFmt is the customer sentence for an app held after a failed update. Arguments: the app,
// the time of the failure, and the PROVEN date of the copy it can be restored from. One named string so
// a test asserts it verbatim instead of retyping Hungarian (R-364).
const UpdateHoldFmt = "A(z) %s frissítése %s-kor nem sikerült, és az alkalmazás nem indult el az új verzióval. " +
	"Az alkalmazás biztonsági okból leállítva marad, hogy az adatai ne sérüljenek. " +
	"Visszaállítható a(z) %s-i biztonsági mentésből a Mentések oldalon."

// holdTimeZone is where the customer-facing hold sentence renders its times. The same zone the web
// layer renders the Mentések page's copy dates in (web.getTimezone), so the date in the hold text and
// the date on the page it points at are the same string.
func holdTimeZone() *time.Location {
	if loc, err := time.LoadLocation("Europe/Budapest"); err == nil {
		return loc
	}
	return time.UTC
}

func fmtHoldTime(rfc3339 string) string {
	t, err := time.Parse(time.RFC3339, rfc3339)
	if err != nil {
		return rfc3339
	}
	return t.In(holdTimeZone()).Format("2006-01-02 15:04")
}

// HoldAfterFailedUpdate records that an app is held stopped because its new version did not come up
// healthy. Same storage and same gate as the R-379 hold — every start path that already refuses a
// restore hold refuses this one without being touched.
//
// It returns the error rather than only logging it, unlike holdAppAfterFailedRollback: the update job
// has just stopped the app on the strength of this record, and an unrecorded hold is a stopped app
// that the next restart button will quietly start again. The caller logs it at ERROR and keeps the
// failure on the page.
func (m *Manager) HoldAfterFailedUpdate(stackName string, at time.Time, copyDate time.Time) error {
	if m == nil || m.settings == nil {
		return fmt.Errorf("no settings wired — the update hold for %s cannot be persisted", stackName)
	}
	h := settings.RestoreHold{
		Stack:  stackName,
		At:     at.UTC().Format(time.RFC3339),
		Reason: settings.HoldReasonUpdateFailed,
	}
	if !copyDate.IsZero() {
		h.CopyDate = copyDate.UTC().Format(time.RFC3339)
	}
	if err := m.settings.SetRestoreHold(h); err != nil {
		return fmt.Errorf("persisting the update hold for %s: %w", stackName, err)
	}
	m.logger.Printf("[WARN] [backup] %s is HELD STOPPED after a failed update (restore point: %s)", stackName, h.CopyDate)
	return nil
}

// isHeld reports whether an app carries ANY hold. Used by the nightly legs to leave a held app alone.
func (m *Manager) isHeld(stackName string) bool {
	held, _ := m.RestoreHoldFor(stackName)
	return held
}

// clearUpdateHoldAfterRestore lifts an UPDATE hold once a person has restored the app successfully.
//
// "A person clears it by restoring" — slice 4 Part 3. The restore just put the app back on the
// definition and data of its recovery unit and started it, which is the exact route back the hold
// text names; leaving the hold in place would refuse the next restart of an app that is now fine.
//
// A RESTORE hold (R-379) is deliberately NOT cleared here: that hold means a previous restore already
// left the database in an unknown state, and it stays operator-cleared (`-clear-restore-hold`).
func (m *Manager) clearUpdateHoldAfterRestore(stackName string) {
	if m.settings == nil {
		return
	}
	h, ok := m.settings.GetRestoreHold(stackName)
	if !ok || h.Reason != settings.HoldReasonUpdateFailed {
		return
	}
	if _, err := m.settings.ClearRestoreHold(stackName); err != nil {
		m.logger.Printf("[ERROR] [backup] %s was restored, but its update hold could not be cleared: %v", stackName, err)
		return
	}
	m.logger.Printf("[INFO] [backup] %s: restore completed — the update hold (set %s) is CLEARED", stackName, h.At)
}