package backup

import (
	"errors"
	"fmt"
	"os"
)

// CLEARING AN OFF-SITE TARGET — R-729 / R-545 (the household's „Távoli mentési cél törlése" press).
//
// Before this, a target once saved could be edited or switched off but never removed: the page
// refuses an empty address, and the only other route (`/backup/offbox/reset`) means "start a new
// remote backup, set the old history aside", and only for an ORPHANED store. A household that tried
// its own NAS and gave up kept the host, user, path, SSH key and known-host line for ever.
//
// WHAT THE PRESS DOES: forgets the target (settings) and deletes the transport secrets (`ssh_key`,
// `known_hosts`) from `data/offbox/`. It NEVER touches the repository on the target — not one remote
// command runs (R-729: "never the repository").
//
// WHAT IT DOES WITH THE REPOSITORY PASSWORD — the one secret that is not transport:
// it is KEPT whenever anything could depend on it, and deleted only when nothing can:
//   - the hub holds a sealed recovery package for this box (the R-241 rule: a box without a password
//     and with a held package refuses to mint, so deleting the key here would strand the next target
//     in the „awaiting recovery key" holding state — and the history the package protects would lose
//     its on-box key);
//   - the escrow was confirmed (`escrowed`) — the hub's package seals exactly this key;
//   - the target ever completed a run or holds snapshots — history exists on the target that only
//     this key opens.
// Keeping it is harmless: a later target reuses it (WriteOffboxSecrets never re-mints over an
// existing file), and the escrow then matches by hash with nothing to redo.
//
// WHAT IT REFUSES (each leaves every file and setting untouched):
//   - the hub-provisioned Felhom tier (Transport rclone-pinned) — that target is Felhom's to remove,
//     not the page's; the hub would re-apply it anyway;
//   - while a backup/restore/check holds the single-flight — a run reading the key file mid-delete;
//   - while an abandonment countdown is running or awaiting the hub (R-241 / decision 74) — the
//     countdown's state lives on the target record, and clearing it would strand the scheduled
//     deletion of the set-aside history with nobody left to run or cancel it.
//
// Pinned by internal/backup/offbox_clear_r729_test.go.

// Refusal sentinels — the handler maps each to its own household sentence.
var (
	ErrOffboxClearNoTarget  = errors.New("offbox clear: no off-site target is configured")
	ErrOffboxClearHubTier   = errors.New("offbox clear: the Felhom-provided off-site tier cannot be removed from the box")
	ErrOffboxClearBusy      = errors.New("offbox clear: a backup operation is running")
	ErrOffboxClearAbandonOn = errors.New("offbox clear: a set-aside history deletion is scheduled")
)

// OffboxClearResult says what the press did with the one secret it may keep.
type OffboxClearResult struct {
	// KeptRepoPassword is true when the repository password stayed on disk (see the header for why).
	KeptRepoPassword bool
}

// offboxRepoPasswordNeeded reports whether anything could still depend on the on-box repository
// password. Fail-safe direction: every input that MIGHT mean "something depends on it" keeps it.
func (m *Manager) offboxRepoPasswordNeeded(escrowState, lastSuccess string, snapshots int) bool {
	return m.sealedPackageHeld() || escrowState == "escrowed" || lastSuccess != "" || snapshots > 0
}

// ClearOffboxTarget forgets the household's off-site target. See the file header.
func (m *Manager) ClearOffboxTarget() (OffboxClearResult, error) {
	var res OffboxClearResult
	t := m.settings.GetOffboxTarget()
	if t == nil {
		return res, ErrOffboxClearNoTarget
	}
	if t.Pinned() {
		return res, ErrOffboxClearHubTier
	}
	if ab := m.AbandonStatus(); ab.Active || ab.PurgeRequested || ab.HubPending {
		return res, ErrOffboxClearAbandonOn
	}
	// Hold the single-flight for the whole clear, so no run can start between the check and the delete.
	if err := m.acquireRunning(); err != nil {
		return res, ErrOffboxClearBusy
	}
	defer m.releaseRunning()

	res.KeptRepoPassword = m.offboxRepoPasswordNeeded(t.EscrowState, t.LastSuccess, t.SnapshotCount)

	// Files FIRST, settings LAST: a failure part-way leaves a target that is still listed (and no
	// longer runnable — OffboxConfigured needs the key file), so the press can simply be repeated.
	// The reverse order would leave secrets on disk with no target left to clear them through.
	files := []string{m.offboxKeyPath(), m.offboxKnownHosts()}
	if !res.KeptRepoPassword {
		files = append(files, m.offboxPwPath())
	}
	for _, f := range files {
		if err := os.Remove(f); err != nil && !os.IsNotExist(err) {
			return res, fmt.Errorf("offbox clear: remove %s: %w", f, err)
		}
	}
	if err := m.settings.SetOffboxTarget(nil); err != nil {
		return res, fmt.Errorf("offbox clear: save settings: %w", err)
	}
	m.logger.Printf("[INFO] [offbox] off-site target %s@%s:%s CLEARED by the household (transport secrets deleted; repository password kept=%v; nothing on the target was touched)",
		t.User, t.Host, t.RepoPath, res.KeptRepoPassword)
	return res, nil
}