package backup

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

	"gopkg.in/yaml.v3"
)

// ── Kept data: which copy can bring it back, and the load (`09` §3 decision 36) ───────────────────
//
// „Use my kept data" (at install) and „Load" (on the kept-data list) are the SAME act: the app's
// recovery unit (definition + database + volumes) is restored — through RestoreFromRecoveryUnitAt, the
// one body every unit restore uses (R-102) — while its files stay where they are on the drive. It is the
// removed-app restore (R-487) with the unit named explicitly.
//
// WHICH COPY. The newest unit that (1) opens (a readable manifest), (2) holds the app's data state (a
// database dump or a volume tar — a definition alone would install an empty app over the kept files), and
// (3) was taken of THIS drive's install: its app.yaml's HDD_PATH names this drive. Looked for in the
// app's own unit on the drive (Tier 1, R-487) and in every connected second-drive mirror (Tier 2). The
// off-site copy is NOT looked at here: its restore is a different operation (reconstitute) and it is
// not built into this choice yet — said on the page as "none" when it is the only one.

// KeptCopy is one database copy a kept folder can be loaded from.
type KeptCopy struct {
	UnitDir    string
	Tier       int // 1 own unit, 2 second drive
	Time       time.Time
	DriveLabel string
}

// unitHoldsData: a readable manifest that lists a database dump or a volume tar.
func unitHoldsData(unitDir string) (*RecoveryManifest, bool) {
	man := readManifest(UnitManifestFile(unitDir))
	if man == nil {
		return nil, false
	}
	return man, len(man.DBDumps)+len(man.VolumeDumps) > 0
}

// unitHDDPath reads the unit's own app.yaml env HDD_PATH (a plain, non-secret field). "" when absent.
func unitHDDPath(unitDir string) string {
	b, err := os.ReadFile(filepath.Join(unitDir, "compose", "app.yaml"))
	if err != nil {
		return ""
	}
	var doc struct {
		Env map[string]string `yaml:"env"`
	}
	if yaml.Unmarshal(b, &doc) != nil {
		return ""
	}
	return strings.TrimSpace(doc.Env["HDD_PATH"])
}

// KeptCopyAt judges one unit directory for drive: usable, and when it was taken.
func (m *Manager) KeptCopyAt(unitDir, drive string, tier int) (KeptCopy, bool) {
	if _, ok := unitHoldsData(unitDir); !ok {
		return KeptCopy{}, false
	}
	if h := unitHDDPath(unitDir); h != "" && filepath.Clean(h) != filepath.Clean(drive) {
		m.logger.Printf("[INFO] [backup] kept: unit %s was taken of %s, not %s — not offered", unitDir, h, drive)
		return KeptCopy{}, false
	}
	t, ok := unitNewestArtifact(unitDir)
	if !ok {
		return KeptCopy{}, false
	}
	return KeptCopy{UnitDir: unitDir, Tier: tier, Time: t}, true
}

// KeptDBCopy returns the NEWEST usable copy of app's data for kept files on drive: the app's own unit
// (Tier 1) and every connected second-drive mirror (Tier 2). Only for an app that is NOT installed — an
// installed app's unit is its live backup, never a kept-data offer.
func (m *Manager) KeptDBCopy(app, drive string) (KeptCopy, bool) {
	if app == "" || m.isStackDeployed(app) {
		return KeptCopy{}, false
	}
	var best KeptCopy
	found := false
	consider := func(c KeptCopy, ok bool) {
		if ok && (!found || c.Time.After(best.Time)) {
			best, found = c, true
		}
	}
	if u, ok := m.RemovedAppUnitFor(app); ok {
		c, ok := m.KeptCopyAt(u.UnitDir, drive, 1)
		c.DriveLabel = u.DriveLabel
		consider(c, ok)
	}
	for _, d := range m.Tier2MirrorDirsForApp(app) {
		consider(m.KeptCopyAt(tier2UnitDir(d), drive, 2))
	}
	return best, found
}

// RemovedUnitOnDrive is the start-fresh hook (stacks.SetKeptUnitFinder): the removed app's OWN unit when
// it sits on drive, so it moves into the kept folder with the files it belongs to. "" otherwise.
func (m *Manager) RemovedUnitOnDrive(app, drive string) string {
	if m.isStackDeployed(app) {
		return ""
	}
	u, ok := m.RemovedAppUnitFor(app)
	if !ok {
		return ""
	}
	if !strings.HasPrefix(filepath.Clean(u.UnitDir), filepath.Clean(drive)+string(filepath.Separator)) {
		return ""
	}
	return u.UnitDir
}

// PrimaryUnitHome is where app's own unit lives on drive (backups/primary/<app>).
func (m *Manager) PrimaryUnitHome(app, drive string) string {
	return RecoveryUnitPath(m.namespaceRoot(drive), app)
}

// LoadKeptApp runs the load as a restore operation the backup pages already follow (the poll banner):
// Begin → RestoreFromRecoveryUnitAt(app, unitDir) → End, then after(ok) in the same goroutine (the
// after_load command, the kept folder's tidy-up). The caller has checked RestoreStatus/IsRunning.
func (m *Manager) LoadKeptApp(app, unitDir string, okMsg, failMsg func(err error) string, after func(ok bool)) {
	m.BeginRestoreOp("restore", app)
	go func() {
		start := time.Now()
		res, err := m.RestoreFromRecoveryUnitAt(app, unitDir)
		if err != nil {
			m.logger.Printf("[ERROR] [backup] kept load %s from %s FAILED after %s: %v", app, unitDir, time.Since(start).Round(time.Second), err)
			m.EndRestoreOp(false, failMsg(err))
			if after != nil {
				after(false)
			}
			return
		}
		m.logger.Printf("[INFO] [backup] kept load %s from %s done in %s (volumes %d/%d, dbs %d/%d)", app, unitDir,
			time.Since(start).Round(time.Second), res.VolumesReplayed, res.ManifestVolumes, res.DBsReplayed, res.ManifestDBs)
		m.EndRestoreOp(true, okMsg(nil))
		if after != nil {
			after(true)
		}
	}()
}