package backup

import (
	"encoding/json"
	"os"
	"path/filepath"
	"sort"
	"time"
)

// R-1256 H8 (review round 2, HUNT-1): a restore copy (<namespace>/backups/restore-undo/<app>/<stamp>) that nothing
// will ever use again used to stay on the drive for good. A copy is KEPT on purpose in three states — a put-back that
// failed (the app is held, D20), a put-back waiting for its drive (the putback_pending hold, R-1251) and a restore cut
// by a power loss (the app-stop marker names it, D22) — and for 30 minutes after a restore while the box watches for a
// stable start (R-1270). Every one of those is still needed. A copy outside all of them — the app runs again, or was
// removed, and nothing names the copy — is disk the household cannot see or use.
//
// The rule (safest reading, decided in the 2026-10-28 night run; operator may change the age): a copy is removed only
// when ALL of these hold, and the sweep removes NOTHING when it cannot answer one of them:
//   - it is older than restoreCopyUnusedAge (its folder's stamp; the folder's time when the stamp does not parse);
//   - the app has no restore hold of any kind (held apps keep every copy — support decides);
//   - the app-stop marker does not name the app (a pending put-back), and the marker is readable;
//   - no restore op is in flight on the box (a new restore's copy and the stable-start watcher are left alone).
//
// Run every 6 hours from main.go (TestR1256_H8_TheSweepIsWiredAtStartup). Pinned by TestR1256_H8_*.

// restoreCopyUnusedAge is how long an unused copy stays for support after its restore.
const restoreCopyUnusedAge = 14 * 24 * time.Hour

// restoreCopyStampLayout is copyLiveVolumes' folder name.
const restoreCopyStampLayout = "20060102T150405Z"

// SweepUnusedRestoreCopies removes the restore copies no hold, no pending put-back and no running restore needs, and
// older than restoreCopyUnusedAge. Returns the folders removed.
func (m *Manager) SweepUnusedRestoreCopies(now time.Time) []string {
	if busy, _ := m.RestoreBusy(); busy == RestoreBusyRestore {
		m.logger.Printf("[INFO] [backup] restore-copy sweep skipped: a restore runs")
		return nil
	}
	named, ok := m.appStopNamedApps()
	if !ok {
		m.logger.Printf("[WARN] [backup] restore-copy sweep skipped: the app-stop marker cannot be read — a copy it names must not go")
		return nil
	}
	var removed []string
	for _, nsRoot := range m.primaryUnitRoots() {
		base := filepath.Join(nsRoot, "backups", "restore-undo")
		apps, err := os.ReadDir(base)
		if err != nil {
			continue
		}
		for _, a := range apps {
			if !a.IsDir() {
				continue
			}
			app := a.Name()
			if named[app] {
				continue
			}
			if m.settings == nil {
				return removed // no hold store: a held app cannot be told apart
			}
			if _, held := m.settings.GetRestoreHold(app); held {
				continue
			}
			appDir := filepath.Join(base, app)
			copies, err := os.ReadDir(appDir)
			if err != nil {
				continue
			}
			sort.Slice(copies, func(i, j int) bool { return copies[i].Name() < copies[j].Name() })
			for _, c := range copies {
				if !c.IsDir() {
					continue
				}
				dir := filepath.Join(appDir, c.Name())
				at, err := time.Parse(restoreCopyStampLayout, c.Name())
				if err != nil {
					fi, sErr := os.Stat(dir)
					if sErr != nil {
						continue
					}
					at = fi.ModTime()
				}
				if now.Sub(at) < restoreCopyUnusedAge {
					continue
				}
				if err := os.RemoveAll(dir); err != nil {
					m.logger.Printf("[WARN] [backup] %s: the unused restore copy %s could not be removed: %v", app, dir, err)
					continue
				}
				m.logger.Printf("[INFO] [backup] %s: the unused restore copy %s (from %s) is removed — no hold, no pending put-back, older than %s (R-1256)",
					app, dir, at.UTC().Format(time.RFC3339), restoreCopyUnusedAge)
				removed = append(removed, dir)
			}
			_ = os.Remove(appDir) // the per-app folder, when it is now empty
		}
	}
	return removed
}

// appStopNamedApps reads the app-stop marker without side effects: the apps of an ACTIVE marker and every app its Undo
// names. ok=false when the marker exists and cannot be read — the caller then touches nothing.
func (m *Manager) appStopNamedApps() (map[string]bool, bool) {
	named := map[string]bool{}
	if m.appStop == nil || m.appStop.path == "" {
		return named, true
	}
	data, err := os.ReadFile(m.appStop.path)
	if os.IsNotExist(err) {
		return named, true
	}
	if err != nil {
		return nil, false
	}
	var mk AppStopMarker
	if err := json.Unmarshal(data, &mk); err != nil {
		return nil, false
	}
	for app := range mk.Undo {
		named[app] = true
	}
	if mk.Active {
		for _, app := range mk.Stacks {
			named[app] = true
		}
	}
	return named, true
}