package localapi

import (
	"context"
	"errors"
	"io"
	"log/slog"
	"testing"
	"time"

	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
)

// R-88 Part 2 — the agent gains a third state.
//
// `newestArchiveOn` promised in its own doc comment that "errors degrade to unknown, never to
// no-backup", while its `(time.Time, bool)` return made that impossible: an error and a genuine
// not-found both produced `(zero, false)`, so `/backup/due` answered a POSITIVE
// "no successful backup recorded yet" with a nil age. The controller read that as "never backed up"
// and fired its window-gate safety valve, quiescing customer app stacks outside the backup window.
//
// These tests assert the WIRE, because the wire is the contract another component reads.

// listerBackups is a fakeBackups that also implements BackupArchiveLister, with a controllable outcome.
type listerBackups struct {
	fakeBackups
	t     time.Time
	found bool
	err   error
}

func (l *listerBackups) NewestArchiveTime(context.Context, int) (time.Time, bool, error) {
	return l.t, l.found, l.err
}

// dueWithLister builds a server whose single tier's service is the given lister, and returns the
// /backup/due response.
// NOTE: the server must receive `lb` ITSELF, not its embedded fakeBackups — the tier's Service is
// type-asserted to BackupArchiveLister, and the embedded value does not satisfy it. Passing the
// inner struct silently routes every case to archiveUnknown, which looks like a code bug and is not.
func dueWithLister(t *testing.T, lb *listerBackups, store *fakeStore) BackupDueResponse {
	t.Helper()
	srv, err := NewServer(Options{
		ListenAddr:    "127.0.0.1:0",
		Guests:        &fakeGuests{},
		Backups:       lb,
		Store:         store,
		Storage:       fakeStorage{},
		Tokens:        staticTokens{"A": 8200, "B": 9300},
		BackupCadence: 24 * time.Hour,
		Logger:        slog.New(slog.NewTextHandler(io.Discard, nil)),
	})
	if err != nil {
		t.Fatalf("NewServer: %v", err)
	}
	srv.now = func() time.Time { return testNow }
	return dueOf(t, srv.Handler())
}

// ── SCENARIO A (agent half) — an unreadable storage is UNKNOWN, not "never" ──────────────────
//
// COMPANION RED-PROOF (observed): make newestArchiveOn return archiveAbsent on the error path (the
// pre-fix collapse) and this fails with
//
//	"an unreadable storage must report age_state=unknown, got \"absent\" — that is a POSITIVE claim
//	 of 'never backed up' built out of two absences"
//
// Restored.
func TestAgeState_UnreadableStorageIsUnknown(t *testing.T) {
	lb := &listerBackups{err: errors.New("proxmox: GET storage content: 500 connection refused")}
	got := dueWithLister(t, lb, &fakeStore{}) // empty store = cold in-memory record

	if got.AgeState != AgeStateUnknown {
		t.Fatalf("an unreadable storage must report age_state=%q, got %q — that is a POSITIVE claim of "+
			"'never backed up' built out of two absences", AgeStateUnknown, got.AgeState)
	}
	if !got.Due {
		t.Fatal("FAIL-SAFE DIRECTION: unknown must still be DUE — an unreadable storage must never suppress a backup")
	}
	if got.AgeSecs != nil {
		t.Fatalf("an unknown age must not invent a number; got %d", *got.AgeSecs)
	}
}

// ── SCENARIO B (agent half) — a genuine first-ever backup is ABSENT ──────────────────────────
//
// B is what makes A safe: an implementation that reported everything as "unknown" would pass A and
// silently starve a brand-new box, because the controller only fires the first-backup valve on ABSENT.
//
// COMPANION RED-PROOF (observed): make newestArchiveOn return archiveUnknown when !found and this
// fails with
//
//	"a genuine never-backed-up tier must report age_state=\"absent\", got \"unknown\" — the
//	 controller only licenses a first backup outside the window on ABSENT"
//
// Restored.
func TestAgeState_GenuinelyNeverIsAbsent(t *testing.T) {
	lb := &listerBackups{found: false} // read SUCCEEDED, nothing there
	got := dueWithLister(t, lb, &fakeStore{})

	if got.AgeState != AgeStateAbsent {
		t.Fatalf("a genuine never-backed-up tier must report age_state=%q, got %q — the controller only "+
			"licenses a first backup outside the window on ABSENT", AgeStateAbsent, got.AgeState)
	}
	if !got.Due {
		t.Fatal("a never-backed-up tier must be due")
	}
}

// A real archive → known, with a real age.
func TestAgeState_FoundIsKnown(t *testing.T) {
	lb := &listerBackups{t: testNow.Add(-2 * time.Hour), found: true}
	got := dueWithLister(t, lb, &fakeStore{})

	if got.AgeState != AgeStateKnown {
		t.Fatalf("a readable archive must report age_state=%q, got %q", AgeStateKnown, got.AgeState)
	}
	if got.AgeSecs == nil || *got.AgeSecs < 7100 || *got.AgeSecs > 7300 {
		t.Fatalf("expected ~7200s age, got %v", got.AgeSecs)
	}
	if got.Due {
		t.Fatal("2h old against a 24h cadence is not due")
	}
}

// An unparseable in-memory timestamp is UNKNOWN too — a backup DID happen, we just cannot date it.
// Reporting "absent" there would be the same false-positive claim in a different costume.
func TestAgeState_UnparseableTimestampIsUnknown(t *testing.T) {
	st := &fakeStore{backups: []hub.Backup{{VMID: 8200, Success: true, StartedAt: "not-a-timestamp"}}}
	lb := &listerBackups{err: errors.New("storage unreadable")}
	got := dueWithLister(t, lb, st)

	if got.AgeState != AgeStateUnknown {
		t.Fatalf("an unparseable backup time means we cannot DATE a backup that exists — want %q, got %q",
			AgeStateUnknown, got.AgeState)
	}
	if !got.Due {
		t.Fatal("still due — fail safe toward taking a backup")
	}
}

// ── SCENARIO D (agent half) — additive on the wire ───────────────────────────────────────────
//
// An OLD controller decodes into a struct without `age_state` and ignores it. What it MUST still see
// unchanged is every pre-existing field.
func TestAgeState_IsAdditive_PreExistingFieldsUnchanged(t *testing.T) {
	lb := &listerBackups{t: testNow.Add(-48 * time.Hour), found: true}
	got := dueWithLister(t, lb, &fakeStore{})

	if !got.Due || got.Reason != "older than cadence" {
		t.Fatalf("pre-existing due/reason semantics changed: due=%v reason=%q", got.Due, got.Reason)
	}
	if got.AgeSecs == nil {
		t.Fatal("age_seconds must still be present for a known age")
	}
	// And the state rides alongside rather than replacing anything.
	if got.AgeState != AgeStateKnown {
		t.Fatalf("age_state should be %q, got %q", AgeStateKnown, got.AgeState)
	}
}