package backup

import (
	"context"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
	"testing"

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

// R-102 Group B — the Tier-2 route: the mirror on the SECOND DRIVE becomes a way back.
//
// The mirror in every test here is written by the PRODUCTION Tier-2 run (RunTier2 with copyTree
// standing in for rsync, the seam tier2_v2_test.go already uses), not by hand. That matters: the
// claim is "the copy Tier-2 actually writes is the copy this restore reads", and a hand-built
// fixture could only prove that the restore agrees with the test's idea of the layout.

// r102T2 is a fully-wired Tier-2 fixture: a live drive carrying the app's PRIMARY recovery unit, a
// second drive carrying the mirror Tier-2 just wrote, and a restore-side Manager with the Docker and
// DB seams injected so no daemon is touched.
type r102T2 struct {
	m           *Manager
	fake        *fakeRecoveryProvider
	liveDrive   string
	destDrive   string
	destBase    string
	primaryUnit string
	volDirs     *[]string
	dbPaths     *[]string
}

// r102Tier2Fixture captures a unit on the live drive, runs the REAL RunTier2 to mirror it onto the
// second drive, then returns a Manager ready to restore. The mirror's contents differ from the
// primary's afterwards when the caller mutates one of them — B1 and B2 both depend on being able to
// tell the two copies apart.
func r102Tier2Fixture(t *testing.T, volTars []string, dbDump string) *r102T2 {
	t.Helper()
	tmp := t.TempDir()
	live := filepath.Join(tmp, "usb")
	dest := filepath.Join(tmp, "flash")
	sys := filepath.Join(tmp, "sys")

	primaryUnit := r102UnitOnDrive(t, live, "primary", volTars, dbDump)

	sett, err := settings.Load(filepath.Join(tmp, "settings.json"), log.New(io.Discard, "", 0))
	if err != nil {
		t.Fatal(err)
	}
	if err := sett.AddStoragePath(settings.StoragePath{Path: dest, Label: "flash", Schedulable: true}); err != nil {
		t.Fatal(err)
	}
	fake := &fakeRecoveryProvider{hdd: live, running: true}
	cfg := &config.Config{}
	cfg.Paths.SystemDataPath = sys
	cfg.Paths.DataDir = filepath.Join(tmp, "data")
	m := NewManager(cfg, sett, log.New(io.Discard, "", 0))
	m.stackProvider = fake
	m.systemDataPath = sys
	m.tier2Mirror = copyTree
	m.tier2SSDFits = func(string, int64) bool { return true }
	m.samePhysicalDevice = oneDrivePerSubtree

	if err := m.RunTier2("app"); err != nil {
		t.Fatalf("RunTier2 (the code that writes the mirror this task reads): %v", err)
	}
	destBase := filepath.Join(dest, "backups", "secondary", "app")
	if _, sErr := os.Stat(UnitManifestFile(tier2UnitDir(destBase))); sErr != nil {
		t.Fatalf("Tier-2 did not mirror the unit — the fixture proves nothing: %v", sErr)
	}

	var vd, dp []string
	m.volumeReplayFrom = func(_, dumpDir string) (int, error) {
		vd = append(vd, dumpDir)
		entries, rErr := os.ReadDir(dumpDir)
		if rErr != nil {
			return 0, nil
		}
		n := 0
		for _, e := range entries {
			if strings.HasSuffix(e.Name(), ".tar") {
				n++
			}
		}
		return n, nil
	}
	m.discoverDBs = func(context.Context) ([]DiscoveredDB, error) {
		return []DiscoveredDB{{StackName: "app", ContainerName: "app-db", DBType: DBTypePostgres}}, nil
	}
	m.importDBDump = func(_ context.Context, _ DiscoveredDB, p string) error {
		dp = append(dp, p)
		return nil
	}
	return &r102T2{m: m, fake: fake, liveDrive: live, destDrive: dest, destBase: destBase,
		primaryUnit: primaryUnit, volDirs: &vd, dbPaths: &dp}
}

// markMirror rewrites the MIRROR's app.yaml so the two copies are distinguishable. It edits the copy,
// never the primary, so a restore that read the primary would return the pre-edit value.
func (f *r102T2) markMirror(t *testing.T, marker string) {
	t.Helper()
	p := filepath.Join(UnitComposeDir(tier2UnitDir(f.destBase)), "app.yaml")
	b, err := os.ReadFile(p)
	if err != nil {
		t.Fatal(err)
	}
	out := strings.Replace(string(b), "SUBDOMAIN: primary", "SUBDOMAIN: "+marker, 1)
	if out == string(b) {
		t.Fatalf("mirror app.yaml did not carry the expected marker; contents:\n%s", b)
	}
	mustWrite(t, p, out)
}

// B1 — TestR102_Tier2UnitRestoreReadsTheSecondaryMirror.
func TestR102_Tier2UnitRestoreReadsTheSecondaryMirror(t *testing.T) {
	f := r102Tier2Fixture(t, []string{"vol_a.tar"}, pgDump(1))
	f.markMirror(t, "from-the-mirror")

	res, err := f.m.RestoreTier2Unit("app")
	if err != nil {
		t.Fatalf("Tier-2 unit restore: %v", err)
	}
	if got := f.fake.gotEnv["SUBDOMAIN"]; got != "from-the-mirror" {
		t.Errorf("config came from the PRIMARY unit: SUBDOMAIN=%q", got)
	}
	wantVol := UnitVolumeDumpDir(tier2UnitDir(f.destBase))
	if len(*f.volDirs) != 1 || (*f.volDirs)[0] != wantVol {
		t.Errorf("volume tars read from %v, want the mirror's %q", *f.volDirs, wantVol)
	}
	wantDB := UnitDBDumpDir(tier2UnitDir(f.destBase))
	if len(*f.dbPaths) != 1 || filepath.Dir((*f.dbPaths)[0]) != wantDB {
		t.Errorf("DB dump read from %v, want a file under the mirror's %q", *f.dbPaths, wantDB)
	}
	if res.VolumesReplayed != 1 || res.DBsReplayed != 1 {
		t.Errorf("nothing came back: volumes=%d dbs=%d", res.VolumesReplayed, res.DBsReplayed)
	}
	if res.ManifestVolumes != 1 || res.ManifestDBs != 1 {
		t.Errorf("the mirror's manifest did not enumerate its dumps: %+v", res)
	}
}

// B2 — TestR102_Tier2UnitRestoreWorksWithThePrimaryUnitABSENT.
//
// THE ACCEPTANCE TEST. Tier-2 exists for the loss of the primary drive, and in that failure the
// primary recovery unit is GONE. A test that leaves the primary in place proves the code compiles,
// not that the mirror is a route (07-backup-architecture §7.2).
//
// The primary unit is not merely emptied — the whole `backups/` tree on the live drive is removed and
// then made unreadable, so any code that tried to fall back to it would error rather than silently
// find nothing.
//
// Red-proof (recorded in REPORT.md): point RestoreTier2Unit back at the primary unit path → this test
// fails with "no readable recovery unit ... falling back to volume-only restore" behaviour and the
// mirror's marker never reaching the redeploy.
func TestR102_Tier2UnitRestoreWorksWithThePrimaryUnitABSENT(t *testing.T) {
	f := r102Tier2Fixture(t, []string{"vol_a.tar", "vol_b.tar"}, pgDump(1))
	f.markMirror(t, "only-the-mirror-survives")

	// The primary drive's whole backup tree is destroyed, then the parent is made unreadable so a
	// fallback read cannot quietly return "nothing here".
	primaryBackups := filepath.Join(f.liveDrive, "backups")
	if err := os.RemoveAll(primaryBackups); err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(primaryBackups, 0o000); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = os.Chmod(primaryBackups, 0o755) })
	if _, err := os.Stat(f.primaryUnit); err == nil {
		t.Fatalf("the primary unit is still readable at %q — the test would prove nothing", f.primaryUnit)
	}

	res, err := f.m.RestoreTier2Unit("app")
	if err != nil {
		t.Fatalf("the restore must succeed from the mirror ALONE — this is the whole point of R-102: %v", err)
	}
	if got := f.fake.gotEnv["SUBDOMAIN"]; got != "only-the-mirror-survives" {
		t.Errorf("SUBDOMAIN=%q — the mirror was not the source", got)
	}
	if got := f.fake.gotEnv["SECRET_KEY"]; got != "key-primary" {
		t.Errorf("the data-encrypting key did not come back from the mirrored unit: %q", got)
	}
	if res.VolumesReplayed != 2 {
		t.Errorf("VolumesReplayed=%d, want 2 from the mirror", res.VolumesReplayed)
	}
	if res.DBsReplayed != 1 {
		t.Errorf("DBsReplayed=%d, want 1 from the mirror", res.DBsReplayed)
	}
	wantVol := UnitVolumeDumpDir(tier2UnitDir(f.destBase))
	if len(*f.volDirs) != 1 || (*f.volDirs)[0] != wantVol {
		t.Errorf("volume source = %v, want %q", *f.volDirs, wantVol)
	}
}

// B3 — TestR102_Tier2UnitRestoreTakesTheSingleWriterFlag. Every restore in this manager shares one
// running flag. The Tier-2 unit route must be inside it, not beside it (R-351b).
func TestR102_Tier2UnitRestoreTakesTheSingleWriterFlag(t *testing.T) {
	f := r102Tier2Fixture(t, []string{"vol_a.tar"}, "")

	// A backup/restore is already in flight.
	if err := f.m.acquireRunning(); err != nil {
		t.Fatal(err)
	}
	_, err := f.m.RestoreTier2Unit("app")
	if err == nil {
		t.Fatal("a second restore started while one was in flight")
	}
	if !strings.Contains(err.Error(), "already in progress") {
		t.Errorf("refusal = %v, want the single-writer refusal", err)
	}
	if f.fake.stopped {
		t.Error("the app was stopped by a restore that should never have started")
	}
	f.m.releaseRunning()

	// And the flag is RELEASED afterwards, or the next restore would be refused forever.
	if _, err := f.m.RestoreTier2Unit("app"); err != nil {
		t.Fatalf("restore after the flag cleared: %v", err)
	}
	if err := f.m.acquireRunning(); err != nil {
		t.Errorf("the running flag was not released after the Tier-2 unit restore: %v", err)
	}
	f.m.releaseRunning()
}

// B4 — TestR102_NoTier2CopyIsAnHonestRefusal. No recorded copy at all: refuse with the reason the
// file restore already uses, and take no outage.
func TestR102_NoTier2CopyIsAnHonestRefusal(t *testing.T) {
	f := r102Tier2Fixture(t, []string{"vol_a.tar"}, "")
	// Forget the recorded copy entirely — the "this app has never had a Tier-2 run" shape.
	if err := f.m.settings.SetCrossDriveConfig("app", &settings.CrossDriveBackup{}); err != nil {
		t.Fatal(err)
	}
	_, err := f.m.RestoreTier2Unit("app")
	if err == nil {
		t.Fatal("expected a refusal with no recorded copy")
	}
	if !strings.Contains(err.Error(), errNoTier2Copy.Error()) {
		t.Errorf("refusal = %v, want errNoTier2Copy", err)
	}
	if f.fake.stopped {
		t.Error("the app was stopped despite the refusal")
	}
}

// B5 — TestR102_CopyAgeIsCarriedToTheSurface. The action overwrites live data with a copy of a
// certain age, so the age has to reach the surface. R-101 governs WHICH date: the success anchor,
// never the attempt clock, and Tier2CopyDate says which one it returned.
func TestR102_CopyAgeIsCarriedToTheSurface(t *testing.T) {
	f := r102Tier2Fixture(t, []string{"vol_a.tar"}, "")

	cov, err := f.m.Tier2RestoreCoverage("app")
	if err != nil {
		t.Fatalf("coverage: %v", err)
	}
	if cov.CopyLastSuccess == "" {
		t.Fatal("the successful Tier-2 run left no LastSuccess for the surface to name")
	}
	date, proven := cov.Tier2CopyDate()
	if !proven || date != cov.CopyLastSuccess {
		t.Errorf("Tier2CopyDate() = (%q,%v), want the success anchor %q", date, proven, cov.CopyLastSuccess)
	}

	// R-101's other half: a later FAILED attempt must not become the date shown. LastRun advances,
	// LastSuccess does not, and the surface must keep naming the copy that actually exists.
	older := cov.CopyLastSuccess
	if err := f.m.settings.UpdateCrossDriveStatus("app", func(c *settings.CrossDriveBackup) {
		c.LastRun = "2099-01-01T00:00:00Z"
		c.LastStatus = "error"
	}); err != nil {
		t.Fatal(err)
	}
	cov2, err := f.m.Tier2RestoreCoverage("app")
	if err != nil {
		t.Fatalf("coverage after a failed attempt: %v", err)
	}
	date2, proven2 := cov2.Tier2CopyDate()
	if !proven2 || date2 != older {
		t.Errorf("after a failed attempt the surface would name %q (proven=%v); want the last SUCCESS %q", date2, proven2, older)
	}
}

// TestR102_Tier2UnitRestoreDoesNotWriteTheMirror — a restore reads its source. If the Tier-2 copy
// were mutated, the second drive would stop being a way back the moment it was used once.
func TestR102_Tier2UnitRestoreDoesNotWriteTheMirror(t *testing.T) {
	f := r102Tier2Fixture(t, []string{"vol_a.tar"}, pgDump(1))
	before := fingerprintTree(t, f.destBase)
	if _, err := f.m.RestoreTier2Unit("app"); err != nil {
		t.Fatalf("restore: %v", err)
	}
	if after := fingerprintTree(t, f.destBase); after != before {
		t.Error("the Tier-2 copy was written to by a restore that only reads it")
	}
}