package backup

import (
	"context"
	"errors"
	"io"
	"log"
	"path/filepath"
	"strings"
	"testing"
)

// R-638 option A (09-update-architecture §3 decision 154) — a replay must meet the COPY's own schema.
//
// The loader overlays a copy on the live database: it only removes what the copy knows about. So a
// replay is only safe when the database it lands in holds the copy's own files, not a newer app's
// migrated schema. Measured 2026-10-06 on scratch 9202: the unit restore after a docmost 0.95 → 0.96
// migration put back exactly the copy's 42 tables — the main path is safe because it restores the
// volume FIRST and replays with ONLY the database up. These tests pin the two side paths that did not:
//
//   - Slice 1, the no-manifest fallback RestoreApp: it started the WHOLE stack at the CURRENT
//     definition before the replay, so a newer app could migrate the old data underneath it.
//   - Slice 2, the unit restore whose volume leg failed: it replayed anyway, over a database volume
//     that is not the copy's own.
//
// All Docker-reaching seams are injected (volumeReplayFrom, discoverDBs, importDBDump); no test here
// touches a daemon.

// r638FallbackFixture builds a Manager whose app "app" has NO recovery unit (so RestoreFromRecoveryUnit
// takes the RestoreApp fallback), a LIVE compose with the given body, and — optionally — a replayable
// dump at the app's on-drive dump path, which is where RestoreApp replays from.
func r638FallbackFixture(t *testing.T, compose string, withDump bool) (*Manager, *fakeRecoveryProvider, *[]string) {
	t.Helper()
	tmp := t.TempDir()
	drive := filepath.Join(tmp, "drive")
	stackDir := filepath.Join(tmp, "stack")
	mustWrite(t, filepath.Join(stackDir, "docker-compose.yml"), compose)
	if withDump {
		mustWrite(t, filepath.Join(AppDBDumpPath(drive, "app"), "app-postgres.sql"), pgDump(1))
	}
	prov := &fakeRecoveryProvider{hdd: drive, running: true, info: RecoveryInfo{StackDir: stackDir}}
	m := &Manager{
		logger:         log.New(io.Discard, "", 0),
		systemDataPath: filepath.Join(tmp, "sys"), // != drive ⇒ nsRoot = drive
		stackProvider:  prov,
	}
	// The volume leg is a seam here so the test can never reach Docker, even if a tar appears.
	m.volumeReplayFrom = func(string, string) (int, error) { return 0, nil }
	db := DiscoveredDB{StackName: "app", ContainerName: "immich-postgres", DBType: DBTypePostgres}
	m.discoverDBs = func(context.Context) ([]DiscoveredDB, error) { return []DiscoveredDB{db}, nil }
	var imported []string
	m.importDBDump = func(_ context.Context, _ DiscoveredDB, p string) error {
		imported = append(imported, p)
		return nil
	}
	return m, prov, &imported
}

// --- Slice 1: the no-manifest fallback ------------------------------------------------------------

// TestR638_FallbackReplaysBeforeTheAppStarts is the slice-1 assertion. It captures the provider's
// state AT THE MOMENT the importer fires: the database service must be up and the full stack must
// NOT be — a full start at the current definition is exactly the window in which a newer app
// migrates the restored data before the old copy is poured over it.
//
// COMPANION RED-PROOF: on the pre-fix RestoreApp (StartStack before reimportDBDumpsCtx) this fails on
// `the FULL stack was already up when the replay fired` — saved in
// audits/design-build-2026-10-06/B/red-slice1-fallback-order.txt.
func TestR638_FallbackReplaysBeforeTheAppStarts(t *testing.T) {
	m, prov, imported := r638FallbackFixture(t, immichLikeCompose, true)

	var dbUpAtReplay, fullUpAtReplay bool
	var callsAtReplay string
	m.importDBDump = func(_ context.Context, _ DiscoveredDB, p string) error {
		dbUpAtReplay = len(prov.gotServices) > 0
		fullUpAtReplay = prov.fullStarted
		callsAtReplay = strings.Join(prov.calls, ",")
		*imported = append(*imported, p)
		return nil
	}

	if err := m.RestoreApp("app", ""); err != nil {
		t.Fatalf("fallback restore: %v", err)
	}
	if len(*imported) != 1 {
		t.Fatalf("expected exactly one replay, got %v", *imported)
	}
	if fullUpAtReplay {
		t.Fatalf("the FULL stack was already up when the replay fired (calls before the replay: %q) — a newer app can migrate the restored data before the copy is loaded (R-638)", callsAtReplay)
	}
	if !dbUpAtReplay {
		t.Fatal("the database service was NOT started before the replay — the importer has no container to talk to")
	}
	if got := strings.Join(prov.gotServices, ","); got != "immich-postgres" {
		t.Fatalf("DB-only phase started %q, want only the database service immich-postgres", got)
	}
	if got := strings.Join(prov.calls, ","); got != "stop,startsvc:immich-postgres,start" {
		t.Fatalf("sequence = %q, want stop → volumes → db-only start → replay → full start", got)
	}
}

// TestR638_FallbackThroughUnitRestoreKeepsTheOrder reaches the fallback the way production does: a
// unit restore that finds no manifest. Same ordering, and the counts stay UNKNOWN (not zero).
func TestR638_FallbackThroughUnitRestoreKeepsTheOrder(t *testing.T) {
	m, prov, imported := r638FallbackFixture(t, immichLikeCompose, true)

	res, err := m.RestoreFromRecoveryUnit("app")
	if err != nil {
		t.Fatalf("restore: %v", err)
	}
	if !res.CountsUnknown {
		t.Error("the fallback's counts must stay UNKNOWN, not zero")
	}
	if len(*imported) != 1 {
		t.Fatalf("expected exactly one replay, got %v", *imported)
	}
	if got := strings.Join(prov.calls, ","); got != "stop,startsvc:immich-postgres,start" {
		t.Fatalf("sequence = %q, want stop → db-only start → replay → full start", got)
	}
}

// TestR638_FallbackNoDumpTakesOneFullStart is the negative: with nothing to replay there is no
// DB-only window, and the flow is the old stop → volumes → full start.
func TestR638_FallbackNoDumpTakesOneFullStart(t *testing.T) {
	m, prov, imported := r638FallbackFixture(t, immichLikeCompose, false)

	if err := m.RestoreApp("app", ""); err != nil {
		t.Fatalf("fallback restore: %v", err)
	}
	if len(prov.gotServices) != 0 {
		t.Fatalf("the DB-only phase ran with nothing to replay: %v", prov.gotServices)
	}
	if got := strings.Join(prov.calls, ","); got != "stop,start" {
		t.Fatalf("sequence = %q, want the unchanged stop → full start", got)
	}
	if len(*imported) != 0 {
		t.Fatalf("nothing should have been replayed, got %v", *imported)
	}
}

// TestR638_FallbackRefusesWhenNoDBServiceIdentifiable: a dump exists but the live compose names no
// database service that could be started alone. The only alternative is the old full start + replay
// — the R-638 shape — so it refuses, with ZERO mutations, exactly as the unit and off-site paths do.
func TestR638_FallbackRefusesWhenNoDBServiceIdentifiable(t *testing.T) {
	m, prov, imported := r638FallbackFixture(t, noDBCompose, true)
	volTouched := false
	m.volumeReplayFrom = func(string, string) (int, error) { volTouched = true; return 0, nil }

	err := m.RestoreApp("app", "")
	if err == nil {
		t.Fatal("expected a refusal: a dump exists but no database service can be started for it")
	}
	if !strings.Contains(err.Error(), "nem azonosítható") {
		t.Fatalf("refusal must say the database service could not be identified, got: %v", err)
	}
	if len(prov.calls) != 0 {
		t.Fatalf("ZERO mutations required, but the provider was called: %v", prov.calls)
	}
	if volTouched {
		t.Fatal("volumes were replaced despite the refusal")
	}
	if len(*imported) != 0 {
		t.Fatalf("a replay happened despite the refusal: %v", *imported)
	}
}

// TestR638_FallbackVolumeFailureSkipsTheReplay is slice 2's rule on the fallback path: when the
// volume leg failed, the database volume is not known to hold the copy's own files, so the copy is
// NOT poured over it. The failure is still returned and the app is still brought back up.
func TestR638_FallbackVolumeFailureSkipsTheReplay(t *testing.T) {
	m, prov, imported := r638FallbackFixture(t, immichLikeCompose, true)
	m.volumeReplayFrom = func(string, string) (int, error) {
		return 0, errors.New("failed to restore 1 volume(s): [app_db]")
	}

	err := m.RestoreApp("app", "")
	if err == nil || !strings.Contains(err.Error(), "completed with data errors") || !strings.Contains(err.Error(), "app_db") {
		t.Fatalf("the volume failure must surface as the data-error outcome naming the volume, got: %v", err)
	}
	if len(*imported) != 0 {
		t.Fatalf("the importer ran after a failed volume leg: %v", *imported)
	}
	if !prov.fullStarted {
		t.Fatal("the app was left down after the failure — today's failure path brings it back up")
	}
	if got := strings.Join(prov.calls, ","); got != "stop,start" {
		t.Fatalf("sequence = %q, want stop → full start (no DB-only window, no replay)", got)
	}
}

// --- Slice 2: unit restore with a failed volume leg -----------------------------------------------

// TestR638_UnitVolumeFailureNeverCallsTheImporter is the slice-2 assertion. A volume leg that errors
// means the database's volume may still be the LIVE (possibly newer, migrated) one, or a half-filled
// one — the copy overlays it and leaves whatever it does not know about. So the importer must not run.
//
// What must NOT change from today's failure path: the error reaches the caller as "completed with data
// errors" (no silent success), the definition is the unit's, and the app is brought back up.
//
// COMPANION RED-PROOF: on the pre-fix restore_unit.go (dataErr set, then fall through to the replay)
// this fails on `the importer ran after a failed volume leg` — saved in
// audits/design-build-2026-10-06/B/red-slice2-no-replay-after-volume-failure.txt.
func TestR638_UnitVolumeFailureNeverCallsTheImporter(t *testing.T) {
	m, prov, imported := r47UnitFixture(t, immichLikeCompose, true)
	m.volumeReplayFrom = func(string, string) (int, error) {
		return 1, errors.New("failed to restore 1 volume(s): [app_immich_postgres_data]")
	}

	res, err := m.RestoreFromRecoveryUnit("app")
	if len(*imported) != 0 {
		t.Fatalf("the importer ran after a failed volume leg: %v", *imported)
	}
	if err == nil {
		t.Fatal("a failed volume leg must be surfaced, not reported as success")
	}
	if !strings.Contains(err.Error(), "completed with data errors") || !strings.Contains(err.Error(), "app_immich_postgres_data") {
		t.Fatalf("the pre-existing outcome must be preserved and name the failed volume, got: %v", err)
	}
	if res.VolumesReplayed != 1 {
		t.Errorf("the partial volume count must still be reported, got %d", res.VolumesReplayed)
	}
	if res.DBsReplayed != 0 {
		t.Errorf("no database was replayed, but the result says %d", res.DBsReplayed)
	}
	if prov.gotEnv == nil {
		t.Error("the unit's definition must still be written, as on today's failure path")
	}
	if !prov.fullStarted {
		t.Fatal("the app was left down — today's failure path brings it back up")
	}
	if got := strings.Join(prov.calls, ","); got != "stop,recreate,start" {
		t.Fatalf("sequence = %q, want stop → recreate → full start (no DB-only window, no replay)", got)
	}
}

// TestR638_UnitVolumeSuccessStillReplays is the positive control for slice 2: the skip is keyed on the
// volume FAILURE, not on the presence of volumes — a clean volume leg still replays.
func TestR638_UnitVolumeSuccessStillReplays(t *testing.T) {
	m, prov, imported := r47UnitFixture(t, immichLikeCompose, true)
	m.volumeReplayFrom = func(string, string) (int, error) { return 1, nil }

	res, err := m.RestoreFromRecoveryUnit("app")
	if err != nil {
		t.Fatalf("restore: %v", err)
	}
	if len(*imported) != 1 || res.DBsReplayed != 1 {
		t.Fatalf("a clean volume leg must still replay: imported=%v replayed=%d", *imported, res.DBsReplayed)
	}
	if got := strings.Join(prov.calls, ","); got != "stop,recreate,startsvc:immich-postgres,start" {
		t.Fatalf("sequence = %q", got)
	}
}