package web

import (
	"context"
	"strconv"
	"sync"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/agentapi"
	"gitea.dooplex.hu/admin/felhom-controller/internal/notify"
)

// Disk-health card + periodic degradation check (v0.169.0; ladder + persistence v0.215.0). The card
// and the check share ONE data path (the 60s-TTL-cached /disks call) and ONE verdict function
// (agentapi.DiskVerdictFor), so the chip a customer sees and the alert they receive can never
// disagree. That shared-function property is load-bearing: BOTH callers must pass the SAME prior, or
// the chip could read Hiba while the email says Figyelmeztetés. No new smartctl load — the agent
// (v0.94.0) serializes its already-computed SMART; this consumes it and feature-detects (nil Smart →
// "Nincs adat", never alarms). No global banner (CONTEXT ruling) — card + email only.

const diskCacheTTL = 60 * time.Second

type diskHealthState struct {
	mu        sync.Mutex
	cacheAt   time.Time
	cacheResp agentapi.DisksResponse
	cacheErr  error
	cacheSet  bool
	// records is the PERSISTED per-disk observation + alert history (v0.215.0), keyed by diskKey.
	// It replaced the in-memory-only baseline, whose loss on restart meant a box that rebooted while
	// a disk was already failing never alerted again. UNKNOWN is never recorded and never deletes an
	// existing record. See disk_health_state.go.
	records map[string]*diskRecord
	loaded  bool
	// clock is the injectable time source (nil → time.Now). The 24h re-alert cooldown is computed
	// from it, so it must be injectable or the cooldown cannot be tested without sleeping.
	clock func() time.Time
}

// now reads the injectable clock.
func (st *diskHealthState) now() time.Time {
	if st.clock != nil {
		return st.clock()
	}
	return time.Now()
}

// DiskHealthRow is one rendered card row.
type DiskHealthRow struct {
	Label     string
	ChipLabel string // "Rendben" | "Figyelmeztetés" | "Hiba" | "Nincs adat"
	ChipClass string // design-system state-text-* color
	Temp      string // e.g. "34" — empty when the device reports no temperature
}

// cachedDisks fetches /disks through a 60s in-process TTL cache so dashboard refresh-spam cannot
// smartctl-storm the host (the agent recomputes SMART per /disks call). disksFn is the test seam
// (nil → the real agent client). Never blocks the page: the caller treats an error as "Nincs adat".
func (s *Server) cachedDisks(ctx context.Context) (agentapi.DisksResponse, error) {
	s.diskHealth.mu.Lock()
	defer s.diskHealth.mu.Unlock()
	if s.diskHealth.cacheSet && time.Since(s.diskHealth.cacheAt) < diskCacheTTL {
		return s.diskHealth.cacheResp, s.diskHealth.cacheErr
	}
	resp, err := s.fetchDisks(ctx)
	s.diskHealth.cacheResp, s.diskHealth.cacheErr, s.diskHealth.cacheAt, s.diskHealth.cacheSet = resp, err, time.Now(), true
	return resp, err
}

func (s *Server) fetchDisks(ctx context.Context) (agentapi.DisksResponse, error) {
	if s.disksFn != nil {
		return s.disksFn(ctx)
	}
	client, err := s.agentClient()
	if err != nil {
		return agentapi.DisksResponse{}, err
	}
	return client.Disks(ctx)
}

// isPhysicalDisk reports whether a target is a physical disk SMART applies to. Logical/network
// storage (PBS, LVM-thin, NFS, CIFS) is excluded even though the agent may default its SMART to
// UNKNOWN — those are storage abstractions, not disks, and must not clutter the disk-health card.
func isPhysicalDisk(d agentapi.DiskInfo) bool {
	switch d.Type {
	case "pbs", "lvmthin", "nfs", "cifs":
		return false
	}
	return d.BackingDevice != "" || d.Smart != nil
}

// diskDisplayLabel is the customer-facing disk label (PVE name + a Hungarian speed hint when known).
func diskDisplayLabel(d agentapi.DiskInfo) string {
	// Prefer the device model (agent v0.95.0) over the raw storage name/UUID — a customer reads
	// "TOSHIBA MQ04ABF100", not "47a3361a-…". Falls back to Name (+ speed hint) on an older agent.
	if d.Smart != nil && d.Smart.ModelName != nil && *d.Smart.ModelName != "" {
		return *d.Smart.ModelName
	}
	switch d.Class {
	case "fast":
		return d.Name + " (gyors)"
	case "slow":
		return d.Name + " (lassú)"
	default:
		return d.Name
	}
}

func diskChipClass(v agentapi.DiskVerdict) string {
	switch v {
	case agentapi.DiskVerdictOK:
		return "state-text-run"
	case agentapi.DiskVerdictWarn:
		return "state-text-warn"
	case agentapi.DiskVerdictFail:
		return "state-text-crit"
	default:
		return "state-text-neutral"
	}
}

// diskHealthRows builds the "Lemezek állapota" card rows for the physical disks. Never errors: an
// unreachable agent yields nil and the card renders its empty state.
func (s *Server) diskHealthRows(ctx context.Context) []DiskHealthRow {
	resp, err := s.cachedDisks(ctx)
	if err != nil {
		return nil
	}
	// The card must consult the SAME persisted prior the check uses, or the chip and the email can
	// disagree — which is the exact property the shared verdict function exists to guarantee. Read
	// only: rendering a page never writes reporting history.
	s.diskHealth.mu.Lock()
	s.loadDiskStateLocked()
	priors := make(map[string]agentapi.DiskPrior, len(resp.Disks))
	for _, d := range resp.Disks {
		priors[diskKey(d)] = s.cardPriorFor(diskKey(d))
	}
	s.diskHealth.mu.Unlock()

	var rows []DiskHealthRow
	for _, d := range resp.Disks {
		if !isPhysicalDisk(d) {
			continue
		}
		v := agentapi.DiskVerdictFor(d.Smart, priors[diskKey(d)])
		row := DiskHealthRow{Label: diskDisplayLabel(d), ChipLabel: v.Label(), ChipClass: diskChipClass(v)}
		if d.Smart != nil && d.Smart.TemperatureC != nil {
			row.Temp = strconv.Itoa(*d.Smart.TemperatureC)
		}
		rows = append(rows, row)
	}
	return rows
}

// diskKey is a disk's stable identity across checks (durable id preferred; falls back to name).
func diskKey(d agentapi.DiskInfo) string {
	if d.DurableID != "" {
		return d.DurableID
	}
	if d.WipeDurableID != "" {
		return d.WipeDurableID
	}
	return "name:" + d.Name
}

// RunDiskHealthCheck is the periodic job. It emits disk_health_degraded per the v0.215.0 decision
// rules in diskAlertDecision: escalation against the last ALERTED verdict fires immediately, a disk
// already at Hiba re-alerts when it has both doubled its unreadable-sector count AND waited out the
// 24h cooldown, and everything else is silent.
//
// Behaviours preserved verbatim from v0.169.0:
//   - the first verdict ever for a disk baselines silently;
//   - UNKNOWN is excluded both directions — never recorded, never a transition endpoint, and it does
//     NOT delete an existing record (a transient unreadable SMART must not erase a real disk's
//     history and hand it a clean slate);
//   - a disk that disappears from the report is dropped, so a reappearance re-baselines silently;
//   - recovery (improvement) notifies nothing;
//   - an unreachable agent returns nil and changes nothing at all.
func (s *Server) RunDiskHealthCheck(ctx context.Context) error {
	// Fetch FRESH (not the 60s card cache): the check must see current SMART, and this keeps its
	// decision logic independent of dashboard render timing.
	resp, err := s.fetchDisks(ctx)
	if err != nil {
		// POSITIVE OBSERVABLE: say the check ran and why it produced nothing. An absent log line is
		// equally consistent with "healthy" and "never ran".
		if s.logger != nil {
			s.logger.Printf("[DEBUG] [web] disk-health check skipped: agent unreachable: %v", err)
		}
		return nil
	}

	var fired []notify.DiskAlert
	evaluated := 0

	s.diskHealth.mu.Lock()
	s.loadDiskStateLocked()
	now := s.diskHealth.now()
	seen := map[string]bool{}
	for _, d := range resp.Disks {
		if !isPhysicalDisk(d) {
			continue
		}
		key := diskKey(d)
		// ONE physical disk can appear as SEVERAL storage entries — on demo-hp the same NVMe is both
		// `c11-scratch` and `felhom-backup`, and both resolve to the same durable id. They must be
		// evaluated ONCE per run, for two reasons:
		//
		//  1. Correctness. The loop writes this run's record before the next entry reads it, so the
		//     second copy of the same disk would consume the FIRST copy's write as its prior — i.e.
		//     the disk would sustain against itself and reach Hiba on a FIRST sighting, defeating the
		//     entire sustain rule (truth-table row 6).
		//  2. One disk, one alert. Two entries would otherwise emit two identical events.
		//
		// Found on live hardware after the v0.215.0 deploy: the check logged "3 disk(s) evaluated"
		// while the persisted state held two records. Pinned by TestDiskCheck_SameDiskTwiceIsEvaluatedOnce.
		if seen[key] {
			continue
		}
		seen[key] = true
		prev := s.diskHealth.records[key]
		prior := s.priorFor(key)
		v := agentapi.DiskVerdictFor(d.Smart, prior)
		if v == agentapi.DiskVerdictUnknown {
			// Excluded both directions: don't record, don't transition, don't drop the existing record.
			continue
		}
		evaluated++
		sectors := agentapi.UncorrectableSectors(d.Smart)
		emit, worsened := diskAlertDecision(prev, v, sectors, now)

		// Build the successor record. The alert history is CARRIED FORWARD across an improvement —
		// that is what makes flap damping work: a disk that recovers and degrades again still knows
		// what it last told the customer.
		rec := &diskRecord{Verdict: int(v), SawUncorrectable: sectors > 0, Sectors: sectors, ChangedAt: now,
			PriorSawUncorrectable: prior.SawUncorrectable}
		if prev != nil {
			rec.Alerted, rec.AlertedVerdict = prev.Alerted, prev.AlertedVerdict
			rec.AlertedSectors, rec.AlertedAt = prev.AlertedSectors, prev.AlertedAt
			if prev.Verdict == int(v) && !prev.ChangedAt.IsZero() {
				rec.ChangedAt = prev.ChangedAt // unchanged verdict keeps its original change time
			}
		}
		if emit {
			rec.Alerted, rec.AlertedVerdict, rec.AlertedSectors, rec.AlertedAt = true, int(v), sectors, now
			fired = append(fired, notify.DiskAlert{
				Label:        diskDisplayLabel(d),
				Attributes:   agentapi.DegradedAttributes(d.Smart),
				Kind:         diskAlertKindFor(d.Smart, v, worsened),
				Sectors:      sectors,
				TemperatureC: temperatureOf(d.Smart),
			})
		}
		s.diskHealth.records[key] = rec
	}
	// Forget disks no longer reported so a reappearance re-baselines silently.
	for k := range s.diskHealth.records {
		if !seen[k] {
			delete(s.diskHealth.records, k)
		}
	}
	// ONE write per run, after every disk has been evaluated.
	s.saveDiskStateLocked()
	s.diskHealth.mu.Unlock()

	// POSITIVE OBSERVABLE, every cycle: "0 alert(s)" from a check that evaluated N disks is evidence
	// of health; silence is evidence of nothing.
	if s.logger != nil {
		s.logger.Printf("[INFO] [web] disk-health check complete: %d disk(s) evaluated, %d alert(s)", evaluated, len(fired))
	}
	for _, a := range fired {
		s.emitDiskDegraded(a)
	}
	return nil
}

// temperatureOf is the disk's reported temperature, or 0 when the device reports none.
func temperatureOf(sm *agentapi.SmartSummary) int {
	if sm != nil && sm.TemperatureC != nil {
		return *sm.TemperatureC
	}
	return 0
}

// emitDiskDegraded routes an alert to the notifier (or the test seam). nil notifier → no-op.
func (s *Server) emitDiskDegraded(a notify.DiskAlert) {
	if s.diskNotifyFn != nil {
		s.diskNotifyFn(a)
		return
	}
	if s.notifier != nil {
		s.notifier.NotifyDiskHealthDegraded(a)
	}
}