package agentapi

// DiskVerdict is the customer-facing disk-health verdict derived from a SmartSummary (v0.169.0).
// It is the SHARED source of truth for both the "Lemezek állapota" dashboard card and the periodic
// degradation check — one pure function so the chip and the alert can never disagree.
type DiskVerdict int

const (
	// DiskVerdictUnknown — no SMART data (nil / UNKNOWN / old agent). Renders "Nincs adat"; NEVER
	// alarms and NEVER participates in degradation transitions (excluded both directions).
	DiskVerdictUnknown DiskVerdict = iota
	DiskVerdictOK                  // "Rendben"        — clean
	DiskVerdictWarn                // "Figyelmeztetés" — a wear/relocation counter is non-zero, below the Hiba bar
	DiskVerdictFail                // "Hiba"           — FAILING, or failing-but-not-self-reported (v0.215.0)
)

// Thresholds. A number without a reason becomes permanent by default, so each carries its provenance.
// The evidence is committed at felhom.eu/documentation/audits/DIAG-smart-passed-trap-2026-08-14.md
// and its two fixtures (ST3000VX010 S/N Z6A07P2G, /dev/sdg on DooPlex, 11-13 Aug 2026).
const (
	// percentageUsedWarn / percentageUsedFail — NVMe wear (%). 100 means the vendor's rated endurance
	// is spent; that is a declaration, not a trend, so it is Hiba.
	percentageUsedWarn = 90
	percentageUsedFail = 100

	// uncorrectableFailCount — unreadable sectors too numerous to be a blip.
	//
	// PROVENANCE: on the one real failing drive observed, the benign excursion peaked at 16 and
	// cleared COMPLETELY within an hour (11 Aug 12:28 -> 13:28); the terminal run passed 64 at
	// 13 Aug 11:28 and never came back below it. 64 sits above the one observed transient and below
	// the observed terminal run. This is a judgement from ONE drive: it is a static BACKSTOP behind
	// the sustain rule, not the primary signal, and Phase 3 is expected to replace it with
	// growth-rate detection once the box keeps history.
	uncorrectableFailCount = 64

	// temperatureWarnC / TemperatureFailC — adopted UNCHANGED from the operator's existing Prometheus
	// bands on DooPlex, so the two systems cannot disagree about the same drive.
	temperatureWarnC = 55
	// TemperatureFailC is exported because the alert-copy layer must pick the "overheated" message
	// shape from the SAME number the verdict fired on. A second literal elsewhere would be free to
	// drift, and the drift would show up as a customer told the wrong reason.
	TemperatureFailC = 60
)

// DiskPrior is what the previous check observed for THIS SAME disk. It is the only history the
// verdict consults, and it is passed in rather than read so the function stays pure — the caller
// (internal/web) owns loading it from the persisted per-disk state.
//
// Plain value type: no methods, no I/O. A zero DiskPrior means "nothing known", which is the correct
// fail-safe — a first-ever observation can only reach Figyelmeztetés from counters, never Hiba.
type DiskPrior struct {
	// SawUncorrectable reports whether unreadable sectors (pending OR offline-uncorrectable) were
	// present at the previous check. It is what turns a one-off excursion into a sustained fault.
	SawUncorrectable bool
}

// DiskVerdictFor maps a SmartSummary plus the previous observation to a verdict. Rules are evaluated
// TOP-DOWN and the FIRST match wins (v0.215.0):
//
//	 1. nil / "" / UNKNOWN                                      -> Nincs adat
//	 2. Health == FAILING                                       -> Hiba  (drive self-reports)
//	 3. temperature_c >= 60                                     -> Hiba
//	 4. critical_warning > 0   (NVMe's own flag: a declaration) -> Hiba
//	 5. percentage_used >= 100                                  -> Hiba
//	 6. unreadable > 0 AND prior.SawUncorrectable               -> Hiba  (SUSTAINED)
//	 7. unreadable > 0 AND reallocated > 0                      -> Hiba  (accumulating + remapping)
//	 8. unreadable >= 64                                        -> Hiba  (too large to be a blip)
//	 9. unreadable > 0                                          -> Figyelmeztetés (first sighting)
//	10. reallocated > 0                                         -> Figyelmeztetés
//	11. media_errors > 0                                        -> Figyelmeztetés
//	12. percentage_used >= 90                                   -> Figyelmeztetés
//	13. temperature_c >= 55                                     -> Figyelmeztetés
//	14. otherwise                                               -> Rendben
//
// WHY rows 2-8 exist at all: smart_status.passed CANNOT fail on unreadable sectors. Attributes 187,
// 197 and 198 all carry thresh 0, and a normalized SMART value floors at 1, so it can never drop to
// or below the threshold. The real drive stayed PASSED at 352 pending sectors with 1001 reported
// uncorrectable reads. A verdict built on the drive's own self-assessment is blind to this whole
// class of failure, which is why rows 3-8 read the raw counters instead.
//
// WHY row 6 sits ABOVE row 8: sustain is the PRIMARY rule and the count is the backstop. On the real
// drive sustain fires a full day earlier (12 Aug) than the count threshold (13 Aug). Row 8 exists for
// a box that was powered off or restarted across the sustain window and so has no prior.
//
// Pure: no clock, no I/O, no logging. Everything it needs arrives as an argument.
func DiskVerdictFor(s *SmartSummary, prior DiskPrior) DiskVerdict {
	// 1 — no data. Never alarms.
	if s == nil || s.Health == "" || s.Health == SmartUnknown {
		return DiskVerdictUnknown
	}
	// 2 — the drive admits failure.
	if s.Health == SmartFailing {
		return DiskVerdictFail
	}
	// Health == PASSED (or any non-empty non-FAILING value we treat as passing): inspect the counters,
	// because the overall verdict is structurally unable to report this class of fault.
	switch {
	case atLeast(s.TemperatureC, TemperatureFailC): // 3
		return DiskVerdictFail
	case positive(s.CriticalWarning): // 4
		return DiskVerdictFail
	case atLeast(s.PercentageUsed, percentageUsedFail): // 5
		return DiskVerdictFail
	}
	unreadable := UncorrectableSectors(s)
	switch {
	case unreadable > 0 && prior.SawUncorrectable: // 6 — sustained across two consecutive checks
		return DiskVerdictFail
	case unreadable > 0 && positive(s.ReallocatedSectors): // 7 — accumulating and remapping together
		return DiskVerdictFail
	case unreadable >= uncorrectableFailCount: // 8 — too large to be a blip
		return DiskVerdictFail
	case unreadable > 0: // 9 — first sighting, below the bar
		return DiskVerdictWarn
	case positive(s.ReallocatedSectors): // 10
		return DiskVerdictWarn
	case positive(s.MediaErrors): // 11
		return DiskVerdictWarn
	case atLeast(s.PercentageUsed, percentageUsedWarn): // 12
		return DiskVerdictWarn
	case atLeast(s.TemperatureC, temperatureWarnC): // 13
		return DiskVerdictWarn
	}
	return DiskVerdictOK // 14
}

// UncorrectableSectors is the disk's unreadable-sector count: max(pending, offline_uncorrectable).
// The two attributes track the same physical defect and on the real drive moved in lockstep, so the
// larger is the honest figure. 0 when neither is reported (an old agent or a device without them).
// Exported because the alert copy quotes this number and the persisted state remembers it.
func UncorrectableSectors(s *SmartSummary) int {
	if s == nil {
		return 0
	}
	n := 0
	if s.PendingSectors != nil && *s.PendingSectors > n {
		n = *s.PendingSectors
	}
	if s.OfflineUncorrectable != nil && *s.OfflineUncorrectable > n {
		n = *s.OfflineUncorrectable
	}
	return n
}

// Label is the exact Hungarian customer copy for the verdict (shared by the card chip and the email).
//
// There are FOUR labels and there will not be a fifth: a predicted failure is "Hiba", the same word a
// self-reported failure gets. A fourth word sharing a root with "Figyelmeztetés" would make the MORE
// severe state read as the milder one (settled operator decision, v0.215.0).
func (v DiskVerdict) Label() string {
	switch v {
	case DiskVerdictOK:
		return "Rendben"
	case DiskVerdictWarn:
		return "Figyelmeztetés"
	case DiskVerdictFail:
		return "Hiba"
	default:
		return "Nincs adat"
	}
}

// DegradedAttributes returns the human-readable Hungarian names of the attribute(s) behind a
// degraded verdict, for the alert body.
//
// v0.215.0: this now also names the attributes behind a Hiba REACHED FROM COUNTERS (truth-table rows
// 3 and 6-8), not only a Figyelmeztetés — the alert message needs to say what is wrong, and those
// rows do have a triggering counter. It returns nil ONLY for row 2 (the drive self-reports FAILING,
// a whole-disk verdict with no single triggering counter) and, naturally, for Nincs adat / Rendben.
func DegradedAttributes(s *SmartSummary) []string {
	if s == nil || s.Health == "" || s.Health == SmartUnknown || s.Health == SmartFailing {
		return nil
	}
	var out []string
	if positive(s.ReallocatedSectors) {
		out = append(out, "áthelyezett szektorok")
	}
	if positive(s.PendingSectors) {
		out = append(out, "függőben lévő szektorok")
	}
	if positive(s.OfflineUncorrectable) {
		out = append(out, "javíthatatlan szektorok")
	}
	if positive(s.CriticalWarning) {
		out = append(out, "kritikus figyelmeztetés")
	}
	if positive(s.MediaErrors) {
		out = append(out, "adathordozó-hibák")
	}
	if atLeast(s.PercentageUsed, percentageUsedWarn) {
		out = append(out, "elhasználódás")
	}
	// Newly able to trigger a verdict on its own (rows 3 and 13), so it must be nameable.
	if atLeast(s.TemperatureC, temperatureWarnC) {
		out = append(out, "hőmérséklet")
	}
	return out
}

func positive(p *int) bool       { return p != nil && *p > 0 }
func atLeast(p *int, n int) bool { return p != nil && *p >= n }