package backup

import (
	"os"
	"path/filepath"
	"strings"
	"time"
)

// RestorePoint describes one restorable keep-side backup for the /backups restore panel
// (GET /api/backup/snapshots). The field names/shape are the payload contract of the
// backups.html restore JS (formatSnapshot): time / short_id / tier / drive_label.
//
// The keep-side restore has exactly ONE restore point per app — the current recovery unit
// (RestoreFromRecoveryUnit reads "the unit", not a history; snapshot_id is logging-only).
// Tier is always 1: Tier-2 copies are NOT restorable through POST /backup/restore (it only
// reads the app's primary unit), so listing them would silently restore tier-1 data while
// claiming tier-2 — never emit them here.
type RestorePoint struct {
	Time       string `json:"time"`        // RFC3339 — newest artifact in the unit
	ShortID    string `json:"short_id"`    // opaque label; POST /backup/restore uses it for logging only
	Tier       int    `json:"tier"`        // always 1 (see above)
	DriveLabel string `json:"drive_label"` // registered storage label; empty for the SSD fallback
}

// restorePointShortID is the single keep-side restore point's identifier. Hungarian ("local"),
// because the JS renders it verbatim inside the snapshot dropdown label.
const restorePointShortID = "helyi"

// ListRestorePoints returns the app's restorable keep-side backups, and whether the stack is
// known at all (found=false → the caller should 404). A known stack with no recovery unit on
// disk returns an EMPTY list (a valid answer — "no backup yet"), not an error.
//
// The single point's Time is the unit's DATA time (unitNewestArtifact, v0.275.0 — R-696).
func (m *Manager) ListRestorePoints(stackName string) (points []RestorePoint, found bool) {
	if m.stackProvider == nil {
		return nil, false
	}
	// R-487: a removed app whose backups were kept is not deployed, but its unit is on a drive
	// and POST /backup/restore reinstalls from it. The picker used to be told 404 here while the
	// restore itself worked — the list is keyed on the drive now, the way R-237 keyed the
	// off-site list on the store.
	// R-690: "removed" is isStackDeployed, not GetStackComposePath — the latter is true for every
	// catalog app on a box, so the picker offered 0 copies for a removed app on a data drive.
	if !m.isStackDeployed(stackName) {
		if u, found := m.RemovedAppUnitFor(stackName); found {
			return []RestorePoint{{Time: u.Time, ShortID: restorePointShortID, Tier: 1, DriveLabel: u.DriveLabel}}, true
		}
	}
	if _, ok := m.stackProvider.GetStackComposePath(stackName); !ok {
		return nil, false
	}

	nsRoot := m.AppNamespaceRoot(stackName)
	if nsRoot == "" || !filepath.IsAbs(nsRoot) {
		// Stack is known but its backup location is unresolvable (e.g. systemDataPath unset in a
		// misconfigured environment) — honest empty list rather than a path walk from "".
		m.logger.Printf("[WARN] [backup] ListRestorePoints(%s): cannot resolve namespace root", stackName)
		return []RestorePoint{}, true
	}

	// v0.275.0 (R-696): the unit's DATA time (unitNewestArtifact), never the manifest's refresh time.
	newest, ok := unitNewestArtifact(RecoveryUnitPath(nsRoot, stackName))
	if !ok {
		return []RestorePoint{}, true // no recovery unit yet — "no backup" is a valid answer
	}

	return []RestorePoint{{
		Time:       newest.UTC().Format(time.RFC3339),
		ShortID:    restorePointShortID,
		Tier:       1,
		DriveLabel: m.sysDriveLabelFor(stackName),
	}}, true
}

// newestDataFile returns the newest mtime among cur and the DATA files with the given extension in dir
// (non-recursive; a missing dir contributes nothing). The undo copies (`pre-restore-*`) are not data of
// the unit (R-361) and never date it.
func newestDataFile(dir, ext string, cur time.Time) time.Time {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return cur
	}
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ext) || strings.HasPrefix(e.Name(), preRestoreDumpPrefix) {
			continue
		}
		if info, err := e.Info(); err == nil && info.ModTime().After(cur) {
			cur = info.ModTime()
		}
	}
	return cur
}