package backup

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

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

// ── The backup's data and its version travel together (controller v0.275.0, R-696, `07` §6.6) ────────
//
// WHAT WENT WRONG. The recovery unit's DEFINITION (compose/, image_pins) was re-captured by the periodic
// status refresh as soon as the app's pin moved, while its DATA (db-dumps/, volume-dumps/) is written
// only by the backup legs. So for up to a day after an update the unit said "new version" and held the
// old version's data. Measured on 9202 2026-09-26 (`audits/version-travel-2026-09-26/A1/`): after a
// PostgreSQL 16 → 18 step the unit held the 18 definition over a 16 dump and a 16 datadir tar; a restore
// poured the 16 datadir back, `postgres:18` refused it and the app was left down. And Tier 1's "proven
// at" was the manifest's refresh time, so the kept pre-conversion copy was released on a backup taken
// BEFORE the conversion (demo-hp, 2026-09-26 night).
//
// THE SHAPE. Every data file a backup leg writes gets a STAMP beside it, at the moment it is written:
// its size and mtime (so a file rewritten by anything else is recognised as unstamped), the definition's
// image pins, and what each service was running (`installed_images`, ref@digest). The unit capture folds
// the stamps into the manifest's `data` block — the time of the unit's data (its OLDEST stamped file:
// the copy is as fresh as its stalest part) and the versions that wrote it — and KEEPS the definition
// the data belongs to: when the pins have moved since the data was written, compose/ is not rewritten
// until the next data run replaces the data. The manifest's `image_pins` stays the app's CURRENT pins,
// so it says both. Restores read `data` to start the data with its own definition (restore_unit.go),
// and the update/release read `data.at` as the unit's time (restore_points.go).
//
// UNKNOWN IS NEVER CURRENT. A unit whose data files are not all validly stamped (written before
// v0.275.0, or by a path that does not stamp) has NO `data` block, restores as before with a WARN, and
// its time is the newest DATA file's mtime — never the manifest's.

// dataStampsFile sits in the unit root, beside manifest.json, so it travels with every copy of the unit
// (the Tier-2 mirror copies the whole unit, the off-site snapshot includes it).
const dataStampsFile = "data-stamps.json"

// DataStamp is one data file's record, written by the leg that wrote the file.
type DataStamp struct {
	// At is the file's mtime when it was stamped, RFC3339Nano UTC — the stamp is valid only while the
	// file still has exactly this mtime and Size.
	At   string `json:"at"`
	Size int64  `json:"size"`
	// Pins are the definition's image pins (the compose `image:` lines) when the file was written.
	Pins []string `json:"pins"`
	// Images is service -> ref@digest running when the file was written. Empty when not observed.
	Images map[string]string `json:"images,omitempty"`
}

// UnitData is the manifest's account of the data the unit holds.
type UnitData struct {
	// At is RFC3339 UTC: the unit's data time — the oldest data file's stamp, or, for a unit with no data
	// files, the data run that confirmed it. This is the unit's "proven at", never the manifest's time.
	At string `json:"at"`
	// ImagePins are the definition pins the data belongs to — what compose/ holds. Empty when Mixed.
	ImagePins []string `json:"image_pins"`
	// Images is the running set (service -> ref@digest) when the oldest file was written.
	Images map[string]string `json:"images,omitempty"`
	// Files are the stamps, keyed by the path relative to the unit ("db-dumps/x.sql").
	Files map[string]DataStamp `json:"files,omitempty"`
	// Mixed: the files were written under DIFFERENT pins — no one definition fits all of them, so a
	// restore of this unit is refused (a restore never starts data with a definition it does not belong to).
	Mixed bool `json:"mixed,omitempty"`
}

// DataTime parses At. False when absent or unreadable.
func (d *UnitData) DataTime() (time.Time, bool) {
	if d == nil || d.At == "" {
		return time.Time{}, false
	}
	t, err := time.Parse(time.RFC3339, d.At)
	if err != nil {
		return time.Time{}, false
	}
	return t, true
}

func readDataStamps(unitDir string) map[string]DataStamp {
	data, err := os.ReadFile(filepath.Join(unitDir, dataStampsFile))
	if err != nil {
		return map[string]DataStamp{}
	}
	var out map[string]DataStamp
	if json.Unmarshal(data, &out) != nil || out == nil {
		return map[string]DataStamp{}
	}
	return out
}

// stampDataFile records the file at <unitDir>/<rel> as written NOW by the current definition and
// running images. Called by the legs right after a dump or a tar is promoted to its final name. A failure
// to stamp is a WARN and leaves the file unstamped — the unit then reads as "versions unknown", which is
// the pre-v0.275.0 behaviour, never a false claim.
func (m *Manager) stampDataFile(stackName, unitDir, rel string) {
	fi, err := os.Stat(filepath.Join(unitDir, rel))
	if err != nil {
		m.logger.Printf("[WARN] [backup] %s: cannot stamp %s (%v) — its versions will read as unknown", stackName, rel, err)
		return
	}
	var pins []string
	var images map[string]string
	if m.stackProvider != nil {
		if info, ok := m.stackProvider.GetStackRecoveryInfo(stackName); ok {
			pins, images = definitionPins(info), info.InstalledImages
		}
	}
	m.stampMu.Lock()
	defer m.stampMu.Unlock()
	stamps := readDataStamps(unitDir)
	stamps[rel] = DataStamp{At: fi.ModTime().UTC().Format(time.RFC3339Nano), Size: fi.Size(), Pins: pins, Images: images}
	// Entries whose file is gone (a volume the app no longer has) are dropped here, so the file stays small.
	for k := range stamps {
		if _, err := os.Stat(filepath.Join(unitDir, k)); err != nil {
			delete(stamps, k)
		}
	}
	body, err := json.MarshalIndent(stamps, "", "  ")
	if err == nil {
		err = atomicWrite(filepath.Join(unitDir, dataStampsFile), append(body, '\n'), 0644)
	}
	if err != nil {
		m.logger.Printf("[WARN] [backup] %s: writing the data stamp for %s failed (%v) — its versions will read as unknown", stackName, rel, err)
		return
	}
	if m.isDebug() {
		m.logger.Printf("[DEBUG] [backup] %s: stamped %s (%d B) with pins %v", stackName, rel, fi.Size(), pins)
	}
}

// foldUnitData builds the manifest's `data` block from the unit's data files and their stamps.
//
//   - no data files: a data run confirms the unit NOW under the current pins; a refresh keeps `prev`;
//   - every file validly stamped: the oldest stamp's time; its pins when all agree, else Mixed;
//   - any file unstamped or re-written since its stamp: nil — the versions are UNKNOWN.
func foldUnitData(unitDir string, dbDumps, volDumps []string, dataRun bool, now time.Time, pins []string, images map[string]string, prev *UnitData) *UnitData {
	var rels []string
	for _, n := range dbDumps {
		rels = append(rels, "db-dumps/"+n)
	}
	for _, n := range volDumps {
		rels = append(rels, "volume-dumps/"+n)
	}
	if len(rels) == 0 {
		if dataRun {
			return &UnitData{At: now.UTC().Format(time.RFC3339), ImagePins: pins, Images: images}
		}
		return prev
	}
	stamps := readDataStamps(unitDir)
	out := &UnitData{Files: map[string]DataStamp{}}
	var oldest time.Time
	for _, rel := range rels {
		st, ok := stamps[rel]
		if !ok {
			return nil
		}
		fi, err := os.Stat(filepath.Join(unitDir, rel))
		if err != nil || fi.Size() != st.Size || fi.ModTime().UTC().Format(time.RFC3339Nano) != st.At {
			return nil
		}
		t := fi.ModTime().UTC()
		if oldest.IsZero() || t.Before(oldest) {
			oldest = t
			out.ImagePins, out.Images = st.Pins, st.Images
		}
		out.Files[rel] = st
	}
	for _, st := range out.Files {
		if !samePins(st.Pins, out.ImagePins) {
			out.Mixed = true
		}
	}
	if out.Mixed {
		out.ImagePins, out.Images = nil, nil
	}
	out.At = oldest.Format(time.RFC3339)
	return out
}

// samePins compares two pin lists as SETS (compose order is file order on both sides, but a set compare
// cannot be fooled by it).
func samePins(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}
	x := append([]string(nil), a...)
	y := append([]string(nil), b...)
	sort.Strings(x)
	sort.Strings(y)
	return stringSliceEqual(x, y)
}

// unitDataEqual is the manifest-rewrite check's view of `data`.
func unitDataEqual(a, b *UnitData) bool {
	if a == nil || b == nil {
		return a == nil && b == nil
	}
	if a.At != b.At || a.Mixed != b.Mixed || !stringSliceEqual(a.ImagePins, b.ImagePins) || len(a.Files) != len(b.Files) {
		return false
	}
	for k, v := range a.Files {
		w, ok := b.Files[k]
		if !ok || v.At != w.At || v.Size != w.Size {
			return false
		}
	}
	return true
}

// PinsVersion is the household's name for a set of pins: every image as `name:tag`, registry path and
// digest stripped, in compose order ("docmost:0.96.0, postgres:16-alpine, redis:7-alpine"). All of them,
// because a version step can move ANY service — a PostgreSQL 16 → 18 step leaves the app's own tag as it
// was, and a label naming only the first image would read the same on both sides of it (seen on the
// first draft of the mismatch sentence: „(0.96.0) … (0.96.0)").
func PinsVersion(pins []string) string {
	out := make([]string, 0, len(pins))
	for _, ref := range pins {
		if i := strings.Index(ref, "@"); i >= 0 {
			ref = ref[:i]
		}
		if i := strings.LastIndex(ref, "/"); i >= 0 {
			ref = ref[i+1:]
		}
		out = append(out, ref)
	}
	return strings.Join(out, ", ")
}

// recordOffsiteDataAt remembers the data time of the unit just pushed off-site (v0.275.0, R-696).
func (m *Manager) recordOffsiteDataAt(stackName, unitDir string) {
	if m.settings == nil {
		return
	}
	t, ok := unitNewestArtifact(unitDir)
	if !ok {
		return
	}
	now := time.Now().UTC().Format(time.RFC3339)
	if err := m.settings.SetOffsiteDataAt(stackName, settings.OffsiteDataRecord{PushedAt: now, DataAt: t.UTC().Format(time.RFC3339)}); err != nil {
		m.logger.Printf("[WARN] [offbox] %s: recording the pushed copy's data time failed: %v — the off-site copy is dated by its snapshot", stackName, err)
	}
}

// offsiteDataTime caps an off-site snapshot's time with the data time this box recorded when it pushed
// it. A snapshot NEWER than the last recorded push (taken by another box, or a record lost) keeps its
// own time: the cap applies only to a copy this box knows the content of.
func (m *Manager) offsiteDataTime(stackName string, snapshotAt time.Time) time.Time {
	if m.settings == nil {
		return snapshotAt
	}
	rec, ok := m.settings.GetOffsiteDataAt(stackName)
	if !ok {
		return snapshotAt
	}
	pushed, perr := time.Parse(time.RFC3339, rec.PushedAt)
	data, derr := time.Parse(time.RFC3339, rec.DataAt)
	if perr != nil || derr != nil || snapshotAt.After(pushed) || !data.Before(snapshotAt) {
		return snapshotAt
	}
	return data
}

// UnitDumpStamp is one stamped database dump of an app's own unit (v0.275.0).
type UnitDumpStamp struct {
	File   string
	At     time.Time
	Images map[string]string
}

// UnitDumpStamps returns the app's OWN unit's database dumps as its manifest records them — only when
// the unit's data is known (a `data` block); an unstamped unit returns nothing, and a release that needs
// one waits (fail closed).
func (m *Manager) UnitDumpStamps(stackName string) []UnitDumpStamp {
	man := readManifest(UnitManifestFile(m.primaryUnitDirFor(stackName)))
	if man == nil || man.Data == nil {
		return nil
	}
	var out []UnitDumpStamp
	for rel, st := range man.Data.Files {
		if !strings.HasPrefix(rel, "db-dumps/") || !strings.HasSuffix(rel, ".sql") {
			continue
		}
		t, err := time.Parse(time.RFC3339Nano, st.At)
		if err != nil {
			continue
		}
		out = append(out, UnitDumpStamp{File: rel, At: t, Images: st.Images})
	}
	sort.Slice(out, func(i, j int) bool { return out[i].File < out[j].File })
	return out
}

// definitionPins are the pins of the definition a capture copies into compose/: the stack dir's own
// docker-compose.yml, parsed. ONE source for the stamps, the fold and the freeze, so "the data's pins"
// and "the pins compose/ holds" are read from the same file the restore will start (production's
// RecoveryInfo.ImagePins is that parse too; a provider that says otherwise cannot make them disagree).
func definitionPins(info RecoveryInfo) []string {
	if info.StackDir != "" {
		if p := ParseComposeImages(filepath.Join(info.StackDir, "docker-compose.yml")); len(p) > 0 {
			return p
		}
	}
	return info.ImagePins
}