package monitor

import (
	"encoding/json"
	"log"
	"strings"
	"testing"
	"time"

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

// R-81 — "no signal" is not "bad signal".
//
// Origin: 2026-07-26 03:00 UTC, expected_backup_missed fired on demo-felhom, demo-hp and
// drill-r50 at once. The agent's backup record store is IN-MEMORY
// (felhom-agent/internal/backup/store.go — "lost on restart; the cadence re-populates"), so
// the R-50 island migration's fleet restart at 12:44 UTC emptied the host-report `backups`
// array until the next backup at 07:03. The check read empty as "no backup exists". The
// vzdump had in fact run: three archives were on disk (07-24, 07-25, 07-26).
//
// The fix is an ANCHOR, not silence — the v0.73.0 offsite never-ran shape. These tests pin
// BOTH halves: absence must stop crying wolf (A, C) AND must still alarm when it is real (B).
// A test suite that only proved A would pass against an implementation that never alarms,
// which is strictly worse than the bug it replaces.

// evidenceAt builds a backupEvidence with hub-history evidence at `ago` before now, and a
// first-contact anchor `watched` before now.
func evidenceAt(now time.Time, ago, watched time.Duration) backupEvidence {
	return backupEvidence{
		newestSeen:    now.Add(-ago),
		haveSeen:      true,
		firstReportAt: now.Add(-watched),
	}
}

// noEvidence builds a backupEvidence with NO backup evidence, watched for `watched`.
func noEvidence(now time.Time, watched time.Duration) backupEvidence {
	return backupEvidence{firstReportAt: now.Add(-watched)}
}

// ── Scenario A — the 2026-07-26 case must NOT alarm ──────────────────────────────────────

// COMPANION RED-PROOF (observed): removing the ev.haveSeen fold-in from
// assessBackupFreshness (pre-R-81 shape: judge the latest report alone) makes this test fail
// with:
//
//	deadline_anchor_test.go: 07-26 shape must NOT alarm; got verdict=2 reason=
//	"newest backup is 176h0m0s old (limit 26h0m0s)"
//
// which is verbatim the message demo-felhom actually sent that morning. Restored after.
func TestBackupFreshness_AgentRestartBlindWindow_NoAlarm(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	// The real demo-felhom shape: backups:[] (agent forgot), pbs_snapshots:[one from 07-18].
	report := `{"pbs_snapshots":[{"backup_time":"2026-07-18T18:31:06Z","verify_state":"ok"}],"backups":[]}`
	// The hub's retained window still holds the 07-25 06:30 vzdump — ~20.5h before the check.
	ev := evidenceAt(now, 20*time.Hour+30*time.Minute, 8*24*time.Hour)

	got := assessBackupFreshness(report, ev, now)
	if got.missed() {
		t.Fatalf("07-26 shape must NOT alarm; got verdict=%d reason=%q", got.verdict, got.reason)
	}
	if got.verdict != verdictOK {
		t.Fatalf("evidence exists in the window → verdict must be OK, not a deferred UNKNOWN; got verdict=%d reason=%q", got.verdict, got.reason)
	}
}

// The demo-hp / drill-r50 shape: BOTH arrays empty, nothing in the window either, but the
// hub has been watching less than the threshold → UNKNOWN, not an alarm.
func TestBackupFreshness_EmptyArraysWithinGrace_Unknown(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	got := assessBackupFreshness(`{"pbs_snapshots":[],"backups":[]}`, noEvidence(now, 10*time.Hour), now)
	if got.missed() {
		t.Fatalf("absence inside the anchored grace must NOT alarm; got reason=%q", got.reason)
	}
	if got.verdict != verdictUnknown {
		t.Fatalf("want verdictUnknown, got verdict=%d reason=%q", got.verdict, got.reason)
	}
}

// ── Scenario B — a genuinely dead box MUST still alarm ───────────────────────────────────

// THE TEST THAT MAKES SCENARIO A SAFE. Without it, "return silent on absence" passes A and C.
//
// COMPANION RED-PROOF (observed): replacing the elapsed-anchor branch with an unconditional
// `return backupAssessment{verdict: verdictUnknown, ...}` (the naive over-suppression fix)
// makes this test fail with:
//
//	deadline_anchor_test.go: a box with NO backup evidence for 240h MUST alarm; got verdict=1
//	reason="no backup evidence yet, but only watching for 240h0m0s ..."
//
// Restored after.
func TestBackupFreshness_NoEvidenceBeyondAnchor_Alarms(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	got := assessBackupFreshness(`{"pbs_snapshots":[],"backups":[]}`, noEvidence(now, 240*time.Hour), now)
	if !got.missed() {
		t.Fatalf("a box with NO backup evidence for 240h MUST alarm; got verdict=%d reason=%q", got.verdict, got.reason)
	}
	// Scenario E: the reason must name absence-over-time, NOT bare absence and NOT staleness.
	if !strings.Contains(got.reason, "no backup evidence in any host-report for") {
		t.Fatalf("absence-over-time needs its own reason string; got %q", got.reason)
	}
	if strings.Contains(got.reason, "newest backup is") {
		t.Fatalf("absence must NOT reuse the stale-timestamp string; got %q", got.reason)
	}
}

// A zero anchor (hub holds no first-contact time) must fail toward VISIBILITY, not silence —
// the v0.73.0 legacy zero-anchor precedent.
func TestBackupFreshness_NoEvidenceNoAnchor_Alarms(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	got := assessBackupFreshness(`{"pbs_snapshots":[],"backups":[]}`, backupEvidence{}, now)
	if !got.missed() {
		t.Fatalf("unanchored absence must fail toward visibility; got verdict=%d reason=%q", got.verdict, got.reason)
	}
	if !strings.Contains(got.reason, "no first-contact anchor") {
		t.Fatalf("unanchored absence needs its own reason string; got %q", got.reason)
	}
}

// ── Scenario C — a fresh box is not born failing ─────────────────────────────────────────

// THE NAMED BOUNDARY CONTRACT (Part 2). "No evidence + no elapsed window → no alarm" is
// pinned here as a contract with an obvious name, so re-introducing the bug requires deleting
// a test that says what it is protecting. Exercises both sides of the boundary.
//
// COMPANION RED-PROOF (observed): pre-fix (`if !havePBS && !haveVzdump { return missed }`),
// the 1-minute-old newborn fails with:
//
//	deadline_anchor_test.go: CONTRACT VIOLATED: no evidence + no elapsed window must NOT
//	alarm (watched=1m0s, limit=26h0m0s); got reason="no PBS snapshot or successful backup in
//	the latest host-report"
//
// Restored after.
func TestBackupFreshness_Contract_AbsenceIsUnknownUntilAnchorElapses(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	empty := `{"pbs_snapshots":[],"backups":[]}`

	cases := []struct {
		name       string
		watched    time.Duration
		wantMissed bool
	}{
		{"newborn, 1 minute", time.Minute, false},
		{"newborn, 1 hour", time.Hour, false},
		{"just inside the window", backupStaleAfter - time.Minute, false},
		{"exactly at the window", backupStaleAfter, false}, // <= is grace, not fault
		{"just outside the window", backupStaleAfter + time.Minute, true},
		{"long past the window", 30 * 24 * time.Hour, true},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			got := assessBackupFreshness(empty, noEvidence(now, c.watched), now)
			if got.missed() != c.wantMissed {
				if c.wantMissed {
					t.Fatalf("CONTRACT VIOLATED: absence beyond the window MUST alarm (watched=%s, limit=%s); got verdict=%d reason=%q",
						c.watched, backupStaleAfter, got.verdict, got.reason)
				}
				t.Fatalf("CONTRACT VIOLATED: no evidence + no elapsed window must NOT alarm (watched=%s, limit=%s); got reason=%q",
					c.watched, backupStaleAfter, got.reason)
			}
			if !c.wantMissed && got.verdict != verdictUnknown {
				t.Fatalf("deferred absence must be UNKNOWN (not OK) so it stays visible; got verdict=%d", got.verdict)
			}
		})
	}
}

// ── Scenario D — the three existing behaviours are untouched ─────────────────────────────

// Pins the pre-R-81 outcomes byte-for-byte, INCLUDING the reason strings, under the new
// signature. Hub-history evidence is present and fresh in each case so it cannot be the
// thing producing the result — these must hold on the latest report's own merits.
func TestBackupFreshness_ExistingBehavioursUnchanged(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	at := func(d time.Duration) string { return now.Add(d).Format(time.RFC3339) }
	anchor := 30 * 24 * time.Hour

	t.Run("1 fresh verified PBS stays silent", func(t *testing.T) {
		r := `{"pbs_snapshots":[{"backup_time":"` + at(-3*time.Hour) + `","verify_state":"ok"}]}`
		got := assessBackupFreshness(r, evidenceAt(now, 3*time.Hour, anchor), now)
		if got.missed() || got.verdict != verdictOK {
			t.Fatalf("want silent OK; got verdict=%d reason=%q", got.verdict, got.reason)
		}
	})

	t.Run("2 a backup past its tier limit still alarms", func(t *testing.T) {
		// Slice C: the HOST tier keeps the 26h limit verbatim, so this is the same assertion the
		// merged code made — now scoped to the tier it actually belongs to.
		r := `{"backups":[{"target_id":"local","started_at":"` + at(-30*time.Hour) + `","success":true}]}`
		ev := backupEvidence{newestHost: now.Add(-30 * time.Hour), haveHost: true, firstReportAt: now.Add(-anchor)}
		got := assessBackupFreshness(r, ev, now)
		if !got.missed() {
			t.Fatalf("stale host backup must still alarm; got verdict=%d reason=%q", got.verdict, got.reason)
		}
		if got.reason != "host tier: newest backup is 30h0m0s old (limit 26h0m0s)" {
			t.Fatalf("stale reason string changed: %q", got.reason)
		}
	})

	t.Run("3 failed verify still alarms with the same string", func(t *testing.T) {
		r := `{"pbs_snapshots":[{"backup_time":"` + at(-2*time.Hour) + `","verify_state":"failed"}]}`
		got := assessBackupFreshness(r, evidenceAt(now, 2*time.Hour, anchor), now)
		if !got.missed() {
			t.Fatalf("failed verify must still alarm; got verdict=%d reason=%q", got.verdict, got.reason)
		}
		// Slice C prefixes the tier. The FAILURE MODE is unchanged and still has its own distinct
		// string; only the tier name was added, which is the point of tier-aware reasons.
		if got.reason != "offsite tier: newest PBS snapshot failed verification" {
			t.Fatalf("verify-failed reason string changed: %q", got.reason)
		}
	})

	t.Run("unparseable report still alarms", func(t *testing.T) {
		got := assessBackupFreshness(`not json`, evidenceAt(now, time.Hour, anchor), now)
		if !got.missed() || got.reason != "latest host-report could not be parsed" {
			t.Fatalf("unparseable behaviour changed: verdict=%d reason=%q", got.verdict, got.reason)
		}
	})
}

// Fresh hub-history evidence must NOT rescue a failed verify — behaviour 3 is about the
// snapshot's integrity, not its age, so the anchor has no business suppressing it.
func TestBackupFreshness_WindowEvidenceDoesNotRescueFailedVerify(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	r := `{"pbs_snapshots":[{"backup_time":"` + now.Add(-2*time.Hour).Format(time.RFC3339) + `","verify_state":"failed"}]}`
	got := assessBackupFreshness(r, evidenceAt(now, time.Minute, 30*24*time.Hour), now)
	if !got.missed() {
		t.Fatalf("fresh window evidence must not suppress a failed verify; got verdict=%d reason=%q", got.verdict, got.reason)
	}
}

// ── Scenario E — reason strings stay diagnostic ──────────────────────────────────────────

// Every failure mode must produce a DISTINCT message. The 2026-07-26 diagnosis turned
// entirely on reading the exact string; collapsing them would have made it impossible.
func TestBackupFreshness_ReasonStringsAreDistinct(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	at := func(d time.Duration) string { return now.Add(d).Format(time.RFC3339) }

	reasons := map[string]string{
		"unparseable":    assessBackupFreshness(`nope`, backupEvidence{}, now).reason,
		"stale":          assessBackupFreshness(`{"pbs_snapshots":[{"backup_time":"`+at(-9*24*time.Hour)+`","verify_state":"ok"}]}`, backupEvidence{}, now).reason,
		"verify failed":  assessBackupFreshness(`{"pbs_snapshots":[{"backup_time":"`+at(-2*time.Hour)+`","verify_state":"failed"}]}`, evidenceAt(now, 2*time.Hour, 30*24*time.Hour), now).reason,
		"absence timed":  assessBackupFreshness(`{"backups":[]}`, noEvidence(now, 240*time.Hour), now).reason,
		"absence unanch": assessBackupFreshness(`{"backups":[]}`, backupEvidence{}, now).reason,
		"absence grace":  assessBackupFreshness(`{"backups":[]}`, noEvidence(now, time.Hour), now).reason,
	}
	seen := map[string]string{}
	for name, r := range reasons {
		if r == "" {
			t.Fatalf("%s produced an empty reason", name)
		}
		if prev, dup := seen[r]; dup {
			t.Fatalf("reason strings collapsed: %q and %q both produce %q", prev, name, r)
		}
		seen[r] = name
	}
}

// ── newestBackupEvidence — the window scan ───────────────────────────────────────────────

func reportRow(t *testing.T, receivedAt time.Time, pbs []string, vzdump []struct {
	at string
	ok bool
}) store.HostReportRow {
	t.Helper()
	type snap struct {
		BackupTime  string `json:"backup_time"`
		VerifyState string `json:"verify_state"`
	}
	type bk struct {
		StartedAt string `json:"started_at"`
		Success   bool   `json:"success"`
	}
	p := struct {
		PBSSnapshots []snap `json:"pbs_snapshots"`
		Backups      []bk   `json:"backups"`
	}{}
	for _, s := range pbs {
		p.PBSSnapshots = append(p.PBSSnapshots, snap{BackupTime: s, VerifyState: "ok"})
	}
	for _, b := range vzdump {
		p.Backups = append(p.Backups, bk{StartedAt: b.at, Success: b.ok})
	}
	out, err := json.Marshal(p)
	if err != nil {
		t.Fatal(err)
	}
	return store.HostReportRow{ReceivedAt: receivedAt, ReportJSON: string(out)}
}

// The scan must reach PAST the empty reports the restart produced and find the vzdump that
// an older report still carries. This is the mechanism behind Scenario A.
func TestNewestBackupEvidence_ReachesPastEmptyReports(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	vz := func(at string, ok bool) []struct {
		at string
		ok bool
	} {
		return []struct {
			at string
			ok bool
		}{{at, ok}}
	}
	rows := []store.HostReportRow{
		// Newest first, as the store returns them. Post-restart reports carry nothing.
		reportRow(t, now.Add(-1*time.Minute), nil, nil),
		reportRow(t, now.Add(-1*time.Hour), nil, nil),
		reportRow(t, now.Add(-14*time.Hour), nil, nil),
		// The last pre-restart report still holds the 20.5h-old vzdump.
		reportRow(t, now.Add(-15*time.Hour), nil, vz(now.Add(-20*time.Hour-30*time.Minute).Format(time.RFC3339), true)),
		reportRow(t, now.Add(-40*time.Hour), nil, vz(now.Add(-44*time.Hour).Format(time.RFC3339), true)),
	}
	got, ok := newestBackupEvidence(rows, now)
	if !ok {
		t.Fatal("must find the vzdump carried by the pre-restart report")
	}
	if want := now.Add(-20*time.Hour - 30*time.Minute); !got.Equal(want) {
		t.Fatalf("newest evidence = %s, want %s", got, want)
	}
}

// A FAILED vzdump is not evidence of a backup.
func TestNewestBackupEvidence_IgnoresFailedVzdump(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	rows := []store.HostReportRow{
		reportRow(t, now.Add(-time.Hour), nil, []struct {
			at string
			ok bool
		}{{now.Add(-2 * time.Hour).Format(time.RFC3339), false}}),
	}
	if _, ok := newestBackupEvidence(rows, now); ok {
		t.Fatal("a failed vzdump must not count as evidence")
	}
}

// One malformed retained report must not blind the scan to the good ones behind it.
func TestNewestBackupEvidence_SkipsMalformedRows(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	rows := []store.HostReportRow{
		{ReceivedAt: now.Add(-time.Minute), ReportJSON: `{{{not json`},
		reportRow(t, now.Add(-2*time.Hour), []string{now.Add(-3 * time.Hour).Format(time.RFC3339)}, nil),
	}
	got, ok := newestBackupEvidence(rows, now)
	if !ok {
		t.Fatal("a malformed row must not blind the scan")
	}
	if want := now.Add(-3 * time.Hour); !got.Equal(want) {
		t.Fatalf("newest evidence = %s, want %s", got, want)
	}
}

// No rows at all → no evidence, and emphatically not a zero timestamp treated as evidence.
func TestNewestBackupEvidence_EmptyWindow(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)
	if _, ok := newestBackupEvidence(nil, now); ok {
		t.Fatal("an empty window must report no evidence")
	}
}

// ── End-to-end through CheckBackupDeadlines ──────────────────────────────────────────────

// The full 2026-07-26 replay against the real store: an agent restart empties the array, the
// hub's retained window still holds yesterday's vzdump → NO event.
func TestCheckBackupDeadlines_RestartBlindWindow_NoEvent(t *testing.T) {
	st := newDeadlineStore(t)
	if _, err := st.SaveEvent("c1", "db_dump_completed", "info", "", "{}", "controller"); err != nil {
		t.Fatal(err)
	}
	okVz := []struct {
		at string
		ok bool
	}{{rfc(-20 * time.Hour), true}}

	// Pre-restart report: carries the vzdump. Back-dated so it is not the latest.
	//
	// The offsite snapshot is RELATIVE and FRESH on purpose. It used to be the literal
	// `2026-07-18T18:31:06Z` from the incident, which was harmless while ONE 26h threshold covered
	// every tier — but Slice C gave the offsite tier its own 8-day limit, and this test compares
	// against the REAL clock (runDeadline uses time.Now). So the fixture quietly became a TIME BOMB:
	// it passed all day on 2026-07-26 and began failing at 18:31 UTC, exactly 8 days after the
	// hard-coded instant. A test that passes at commit time and fails hours later is worse than one
	// that fails immediately, because it lands on whoever is next in the file.
	//
	// This test is about the HOST tier's restart blind window; the offsite tier must be healthy so
	// it cannot contribute to the verdict.
	pre := hostReportJSON(t, [][2]string{{rfc(-2 * time.Hour), "ok"}}, okVz)
	if err := st.SaveHostReport("h1", "c1", []byte(pre), store.HostReportDenorm{}); err != nil {
		t.Fatal(err)
	}
	if err := st.SetHostReportsReceivedAtForTest("c1", sqliteAgo(15*time.Hour)); err != nil {
		t.Fatal(err)
	}
	// Post-restart report: offsite only (the agent's in-memory `backups` was wiped by the restart)
	// — demo-felhom's 07-26 shape, with the offsite snapshot kept fresh per the note above.
	post := hostReportJSON(t, [][2]string{{rfc(-2 * time.Hour), "ok"}}, nil)
	if err := st.SaveHostReport("h1", "c1", []byte(post), store.HostReportDenorm{}); err != nil {
		t.Fatal(err)
	}

	got := runDeadline(t, st)
	if has(got, "expected_backup_missed") {
		t.Fatalf("the 07-26 restart shape must NOT raise expected_backup_missed; got %v", got)
	}
}

// The counterpart end-to-end: a host that has been reporting for days and has NEVER produced
// a backup must still alarm through the real store path.
func TestCheckBackupDeadlines_NeverBackedUpBeyondAnchor_Alarms(t *testing.T) {
	st := newDeadlineStore(t)
	st.SaveEvent("c1", "db_dump_completed", "info", "", "{}", "controller")
	empty := hostReportJSON(t, nil, nil)
	if err := st.SaveHostReport("h1", "c1", []byte(empty), store.HostReportDenorm{}); err != nil {
		t.Fatal(err)
	}
	// Back-date first contact well beyond the 26h anchor.
	if err := st.SetHostReportsReceivedAtForTest("c1", sqliteAgo(120*time.Hour)); err != nil {
		t.Fatal(err)
	}
	if err := st.SaveHostReport("h1", "c1", []byte(empty), store.HostReportDenorm{}); err != nil {
		t.Fatal(err)
	}

	got := runDeadline(t, st)
	if !has(got, "expected_backup_missed") {
		t.Fatalf("a host with no backup for 120h MUST alarm; got %v", got)
	}
}

// A newborn host must not alarm on its first morning — end-to-end.
func TestCheckBackupDeadlines_NewbornHost_NoEvent(t *testing.T) {
	st := newDeadlineStore(t)
	st.SaveEvent("c1", "db_dump_completed", "info", "", "{}", "controller")
	empty := hostReportJSON(t, nil, nil)
	if err := st.SaveHostReport("h1", "c1", []byte(empty), store.HostReportDenorm{}); err != nil {
		t.Fatal(err)
	}
	var logged strings.Builder
	onEvent := func(customerID, eventType, severity, message, detailsJSON, source string) {
		if customerID == "c1" && eventType == "expected_backup_missed" {
			t.Fatalf("a newborn host must not alarm; got %q", message)
		}
	}
	CheckBackupDeadlines(st, nil, onEvent, log.New(&logged, "", 0))

	// The deferral must be VISIBLE — quiet must never look like "did not run".
	if !strings.Contains(logged.String(), "verdict UNKNOWN") {
		t.Fatalf("the deferred verdict must be logged; log was:\n%s", logged.String())
	}
}
