package monitor

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

// R-82 Slice C — tier-aware thresholds.
//
// The whole point: a healthy WEEKLY offsite snapshot is >26h old six days in seven, so the merged
// threshold would cry wolf on it — exactly what `backupStaleAfter`'s comment predicted. Each tier is
// now judged against its own limit, and R-81's structure (three verdicts, anchored absence, one
// distinct reason per failure mode) is preserved intact.

func tieredReport(pbsAge time.Duration, verify string, hostAge time.Duration, now time.Time) string {
	at := func(d time.Duration) string { return now.Add(-d).Format(time.RFC3339) }
	return `{
	  "storage_targets":[
	    {"name":"local","type":"local","content":"backup,iso"},
	    {"name":"felhom-pbs","type":"pbs","content":"backup"}
	  ],
	  "pbs_snapshots":[{"backup_time":"` + at(pbsAge) + `","verify_state":"` + verify + `"}],
	  "backups":[{"target_id":"local","started_at":"` + at(hostAge) + `","success":true}]
	}`
}

func freshEv(now time.Time, hostAge, offAge time.Duration) backupEvidence {
	return backupEvidence{
		newestHost: now.Add(-hostAge), haveHost: true,
		newestOffsite: now.Add(-offAge), haveOffsite: true,
		firstReportAt: now.Add(-60 * 24 * time.Hour),
	}
}

// ── THE SCENARIO ─────────────────────────────────────────────────────────────────────────────
//
// A 6-day-old offsite snapshot with a fresh host backup is SILENT; the same snapshot at 9 days
// ALARMS.
//
// COMPANION RED-PROOF (observed): give tierOffsite the host threshold
// (`tierOffsite = backupTier{name:"offsite", staleWhen: backupStaleAfter}`) — i.e. restore the
// single merged threshold — and the 6-day case fails with
//
//	6-day-old offsite snapshot is HEALTHY under a weekly cadence and must be SILENT;
//	got verdict=2 reason="offsite tier: newest backup is 144h0m0s old (limit 26h0m0s)"
//
// which is verbatim the cry-wolf this slice exists to remove. Restored.
func TestTierAware_SixDayOffsiteSilent_NineDayAlarms(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)

	t.Run("6 days offsite + fresh host → SILENT", func(t *testing.T) {
		got := assessBackupFreshness(tieredReport(6*24*time.Hour, "ok", 2*time.Hour, now),
			freshEv(now, 2*time.Hour, 6*24*time.Hour), now)
		if got.missed() {
			t.Fatalf("6-day-old offsite snapshot is HEALTHY under a weekly cadence and must be SILENT; got verdict=%d reason=%q",
				got.verdict, got.reason)
		}
		if got.verdict != verdictOK {
			t.Fatalf("both tiers have evidence inside their limits → OK, not a deferred UNKNOWN; got verdict=%d reason=%q", got.verdict, got.reason)
		}
	})

	t.Run("9 days offsite + fresh host → ALARMS, naming the offsite tier", func(t *testing.T) {
		got := assessBackupFreshness(tieredReport(9*24*time.Hour, "ok", 2*time.Hour, now),
			freshEv(now, 2*time.Hour, 9*24*time.Hour), now)
		if !got.missed() {
			t.Fatalf("9-day-old offsite snapshot is past the 8-day limit and MUST alarm; got verdict=%d reason=%q",
				got.verdict, got.reason)
		}
		if !strings.HasPrefix(got.reason, "offsite tier:") {
			t.Fatalf("the reason must name the OFFSITE tier — a merged message would have made the R-80 diagnosis impossible; got %q", got.reason)
		}
		if strings.Contains(got.reason, "host tier") {
			t.Fatalf("the host tier is fresh and must not appear in the reason; got %q", got.reason)
		}
	})
}

// Neither tier rescues the other. This is the merged-threshold bug in both directions.
func TestTierAware_TiersDoNotRescueEachOther(t *testing.T) {
	now := time.Date(2026, 7, 26, 3, 0, 0, 0, time.UTC)

	t.Run("fresh host does not rescue a stale offsite tier", func(t *testing.T) {
		got := assessBackupFreshness(tieredReport(9*24*time.Hour, "ok", time.Hour, now),
			freshEv(now, time.Hour, 9*24*time.Hour), now)
		if !got.missed() {
			t.Fatalf("a fresh DAILY backup must not satisfy the WEEKLY tier; got %q", got.reason)
		}
	})

	t.Run("fresh offsite does not rescue a stale host tier", func(t *testing.T) {
		got := assessBackupFreshness(tieredReport(time.Hour, "ok", 30*time.Hour, now),
			freshEv(now, 30*time.Hour, time.Hour), now)
		if !got.missed() {
			t.Fatalf("a fresh WEEKLY snapshot must not satisfy the DAILY tier; got %q", got.reason)
		}
		if !strings.Contains(got.reason, "host tier") {
			t.Fatalf("the reason must name the HOST tier; got %q", got.reason)
		}
	})

	t.Run("both stale → BOTH named", func(t *testing.T) {
		got := assessBackupFreshness(tieredReport(9*24*time.Hour, "ok", 30*time.Hour, now),
			freshEv(now, 30*time.Hour, 9*24*time.Hour), now)
		if !got.missed() {
			t.Fatalf("both tiers stale must alarm; got %q", got.reason)
		}
		if !strings.Contains(got.reason, "host tier") || !strings.Contains(got.reason, "offsite tier") {
			t.Fatalf("a box with TWO broken tiers must not report only one; got %q", got.reason)
		}
	})
}

// ── The A.4 rule: classify by TARGET TYPE, never by array membership ─────────────────────────
//
// A PBS-targeted vzdump appears in BOTH arrays. Treating every `backups[]` entry as the host tier
// would let a PBS backup make a STALE HOST TIER LOOK FRESH — silently losing the daily tier's alarm.
func TestTierAware_PBSTargetedVzdumpIsNotHostEvidence(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) }

	// The host tier's own backup is 40h old (stale). A FRESH PBS-targeted vzdump sits in the same
	// array — exactly the double-appearance Slice A.4 recorded.
	report := `{
	  "storage_targets":[
	    {"name":"local","type":"local","content":"backup"},
	    {"name":"felhom-pbs","type":"pbs","content":"backup"}
	  ],
	  "pbs_snapshots":[{"backup_time":"` + at(time.Hour) + `","verify_state":"ok"}],
	  "backups":[
	    {"target_id":"local","started_at":"` + at(40*time.Hour) + `","success":true},
	    {"target_id":"felhom-pbs","started_at":"` + at(time.Hour) + `","success":true}
	  ]
	}`
	ev := backupEvidence{
		newestHost: now.Add(-40 * time.Hour), haveHost: true,
		newestOffsite: now.Add(-time.Hour), haveOffsite: true,
		firstReportAt: now.Add(-60 * 24 * time.Hour),
	}
	got := assessBackupFreshness(report, ev, now)
	if !got.missed() {
		t.Fatalf("a PBS-targeted vzdump must NOT count as host-tier evidence — the host tier is 40h stale; got verdict=%d reason=%q",
			got.verdict, got.reason)
	}
	if !strings.Contains(got.reason, "host tier") {
		t.Fatalf("the stale HOST tier must be named; got %q", got.reason)
	}
}

// splitTiers is the classifier the whole slice rests on.
func TestSplitTiers_Classification(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) }

	t.Run("no storage_targets and no evidence → neither tier expected (old-agent fallback)", func(t *testing.T) {
		var hr hostReportBackups
		mustUnmarshal(t, `{"pbs_snapshots":[],"backups":[]}`, &hr)
		h, o := splitTiers(hr)
		if h.expected || o.expected {
			t.Fatalf("nothing identifiable must leave BOTH tiers unexpected so the pre-Slice-C path runs; got host=%v offsite=%v", h.expected, o.expected)
		}
	})

	t.Run("a PBS storage alone makes the offsite tier expected", func(t *testing.T) {
		var hr hostReportBackups
		mustUnmarshal(t, `{"storage_targets":[{"name":"felhom-pbs","type":"pbs","content":"backup"}]}`, &hr)
		_, o := splitTiers(hr)
		if !o.expected || o.have {
			t.Fatalf("a configured-but-empty offsite tier is EXPECTED with no evidence — that is the R-82 fault; got %+v", o)
		}
	})

	t.Run("verify_state failed is carried on the newest offsite snapshot only", func(t *testing.T) {
		var hr hostReportBackups
		mustUnmarshal(t, `{"pbs_snapshots":[
		  {"backup_time":"`+at(48*time.Hour)+`","verify_state":"failed"},
		  {"backup_time":"`+at(time.Hour)+`","verify_state":"ok"}]}`, &hr)
		_, o := splitTiers(hr)
		if o.failed {
			t.Fatalf("an OLDER failed snapshot must not condemn a newer good one; got %+v", o)
		}
	})
}

func mustUnmarshal(t *testing.T, s string, v any) {
	t.Helper()
	if err := json.Unmarshal([]byte(s), v); err != nil {
		t.Fatal(err)
	}
}