fancy-dns/internal/app/hooks.go

package app

import (
	"context"
	"fmt"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/miekg/dns"

	"git.k8s-git-k6n.net/mats/fancy-dns/internal/api"
	"git.k8s-git-k6n.net/mats/fancy-dns/internal/blocklist"
	"git.k8s-git-k6n.net/mats/fancy-dns/internal/config"
	"git.k8s-git-k6n.net/mats/fancy-dns/internal/metrics"
	"git.k8s-git-k6n.net/mats/fancy-dns/internal/qlog"
	"git.k8s-git-k6n.net/mats/fancy-dns/internal/resolver"
)

// hooks builds the api.Hooks that connect the admin API to the live
// components. Everything the UI can read or change goes through here.
func (a *App) hooks() api.Hooks {
	return api.Hooks{
		Store:             a.cfg,
		Logger:            a.log,
		Version:           a.ver,
		StartedAt:         a.startedAt,
		Dashboard:         a.dashboard,
		Status:            a.status,
		Health:            a.health,
		BlocklistState:    a.blocklistState,
		BlocklistStats:    a.blocklistStats,
		RefreshBlocklists: a.refreshBlocklists,
		ToggleBlocklist:   a.toggleBlocklist,
		DomainCheck:       a.domainCheck,
		ListDomains:       a.listDomains,
		AddDomain:         a.addDomain,
		DeleteDomain:      a.deleteDomain,
		GetACL:            a.getACL,
		PutACL:            a.putACL,
		GetUpstream:       a.getUpstreams,
		PutUpstream:       a.putUpstream,
		SearchLog:         a.searchLog,
		LogStats:          a.logStats,
		SubscribeLog:      a.subscribeLog,
		ClearLog:          a.clearLog,
		CacheStats:        a.cacheStats,
		CacheTop:          a.cacheTop,
		FlushCache:        a.flushCache,
		Flush:             a.flush,
	}
}

// health is the unauthenticated probe payload.
func (a *App) health() any {
	status := "ok"
	problems := a.Degraded()
	switch {
	case len(problems) > 0:
		status = "degraded"
	}
	if a.dns == nil || len(a.dns.Listeners()) == 0 {
		status = "down"
	}
	if a.logger != nil && a.logger.ErrorCount() > 0 && status == "ok" {
		status = "degraded"
		problems = append(problems, "query log write errors")
	}
	return map[string]any{
		"status":         status,
		"version":        a.ver,
		"uptime_s":       int64(time.Since(a.startedAt).Seconds()),
		"config_version": a.cfg.Get().Version,
		"problems":       problems,
	}
}

// status is the per-component runtime view.
func (a *App) status() any {
	out := map[string]any{
		"listeners":  a.dns.Listeners(),
		"transports": a.dns.ByTransport(),
		"degraded":   a.Degraded(),
	}
	if a.blocks != nil {
		st := a.blocks.State()
		if st != nil {
			out["blocklist"] = map[string]any{
				"rules":      st.Set.Len(),
				"sources":    len(st.Sources),
				"duration":   st.Duration,
				"built_at":   st.Set.BuiltAt(),
				"errors":     st.Errors,
				"digest":     st.Digest,
				"has_wild":   st.Set.HasWildcards(),
				"duplicates": st.Set.DuplicatesN(),
			}
		}
	}
	if a.local != nil {
		if store := a.local.Get(); store != nil {
			out["local_zones"] = map[string]any{
				"zones":   store.Zones(),
				"records": store.Count(),
				"files":   store.Files(),
			}
		}
	}
	if a.cache != nil {
		out["cache"] = a.cacheStats()
	}
	if a.logger != nil {
		out["qlog"] = a.logger.Stats()
	}
	if a.pool != nil {
		out["upstream"] = a.getUpstreams()
	}
	if a.aclH != nil {
		out["acl"] = a.getACL()
	}
	if a.cl != nil {
		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
		out["cluster"] = a.cl.Status(ctx)
		cancel()
	}
	if a.engine != nil {
		out["engine"] = map[string]any{
			"inflight":    a.engine.Inflight(),
			"dropped":     a.engine.Dropped(),
			"group_stats": a.engine.GroupStats(),
		}
	}
	return out
}

// blocklistState is the full per-source view for the UI.
func (a *App) blocklistState() any {
	if a.blocks == nil {
		return map[string]any{
			"items": []any{},
			"stats": map[string]any{"total": 0},
		}
	}
	st := a.blocks.State()
	items := make([]blocklist.Source, 0, len(st.Sources))
	for _, s := range st.Sources {
		items = append(items, s)
	}
	sort.Slice(items, func(i, j int) bool { return items[i].Name < items[j].Name })
	return map[string]any{
		"items":  items,
		"stats":  blocklistSourceStats(st),
		"errors": st.Errors,
		"digest": st.Digest,
	}
}

func blocklistSourceStats(st *blocklist.State) map[string]any {
	if st == nil || st.Set == nil {
		return map[string]any{"total": 0}
	}
	s := st.Set.Stats()
	return map[string]any{
		"total":           s.Total,
		"exact":           s.Exact,
		"subdomain_rules": s.Subdomains,
		"root_rules":      s.RootRules,
		"allow":           s.Allow,
		"block":           s.Block,
		"passthrough":     s.Passthru,
		"drop":            s.Drop,
		"duplicates":      s.Duplicates,
		"sources":         s.Sources,
		"built_at":        s.BuiltAt,
		"sources_detail":  s.PerSource,
	}
}

func (a *App) blocklistStats() any {
	if a.blocks == nil {
		return map[string]any{"total": 0}
	}
	return blocklistSourceStats(a.blocks.State())
}

// invalidateBlocklistCache drops every cached answer whose verdict the new
// rules might change. Without this, a name that has just become blocked keeps
// serving its cached good answer until the TTL expires, which is exactly the
// bug an operator hits right after clicking "add rule".
func (a *App) invalidateBlocklistCache() {
	if a.cache == nil {
		return
	}
	a.cache.Flush()
}

// refreshBlocklists recompiles the list sources.
func (a *App) refreshBlocklists(ctx context.Context, names []string) error {
	if a.blocks == nil {
		return fmt.Errorf("blocklists are disabled")
	}
	a.invalidateBlocklistCache()
	go func() {
		if len(names) == 0 {
			if _, err := a.blocks.RefreshAll(ctx); err != nil {
				a.log.Warn("blocklist refresh failed", "error", err)
			}
			return
		}
		// The manager compiles everything in one pass, which is cheaper than
		// a pass per name and keeps the compiled set internally consistent.
		if _, err := a.blocks.RefreshAll(ctx); err != nil {
			a.log.Warn("blocklist refresh failed", "error", err, "names", names)
		}
	}()
	// Tell the cluster leader so every instance ends up on the same content.
	if a.cl != nil {
		_ = a.cl.BroadcastRefresh(ctx, names)
	}
	return nil
}

// toggleBlocklist flips one source's enabled flag and persists it.
func (a *App) toggleBlocklist(name string, enabled bool) error {
	if a.blocks == nil {
		return fmt.Errorf("blocklists are disabled")
	}
	err := a.mutateConfig(func(c *config.Config) error {
		found := false
		for i := range c.Block.Lists {
			if c.Block.Lists[i].Name == name {
				c.Block.Lists[i].Enabled = enabled
				found = true
			}
		}
		if !found {
			return fmt.Errorf("no blocklist named %q", name)
		}
		return nil
	})
	if err != nil {
		return err
	}
	a.invalidateBlocklistCache()
	go func() {
		if _, rerr := a.blocks.RefreshAll(context.Background()); rerr != nil {
			a.log.Warn("refresh after toggle failed", "error", rerr)
		}
	}()
	return nil
}

// mutateConfig clones, mutates, validates and commits the config, returning
// the validation error when the change is rejected.
func (a *App) mutateConfig(fn func(*config.Config) error) error {
	cur := a.cfg.Get()
	next := *cur
	// A shallow copy is not enough: the slices and maps we touch need their own
	// backing arrays, or a rejected change would corrupt the live config.
	next.Block = cur.Block
	next.Block.Lists = append([]config.ListSource(nil), cur.Block.Lists...)
	next.Block.LocalZones = append([]string(nil), cur.Block.LocalZones...)
	next.Block.BlockEntries = append([]string(nil), cur.Block.BlockEntries...)
	next.Block.AllowEntries = append([]string(nil), cur.Block.AllowEntries...)
	next.ACL = cur.ACL
	next.ACL.Groups = append([]config.Group(nil), cur.ACL.Groups...)
	next.Upstream = cur.Upstream
	next.Upstream.Servers = append([]config.UpstreamServer(nil), cur.Upstream.Servers...)
	next.Upstream.Bootstraps = append([]config.UpstreamBootstrap(nil), cur.Upstream.Bootstraps...)

	if err := fn(&next); err != nil {
		return err
	}
	if err := next.Validate(); err != nil {
		return err
	}
	if a.api == nil {
		return a.cfg.Swap(&next)
	}
	return a.api.Commit(&next)
}

// domainCheck explains how a name would be treated.
func (a *App) domainCheck(name string) (any, error) {
	entry := (*blocklist.Entry)(nil)
	if a.blocks != nil {
		if set := a.blocks.Holder().Get(); set != nil {
			entry = set.Match(name)
		}
	}
	out := map[string]any{
		"name":  name,
		"query": strings.TrimSuffix(name, "."),
	}
	if entry == nil {
		out["matched"] = false
		out["action"] = "none"
		out["source"] = ""
		return out, nil
	}
	kind := "exact"
	pattern := entry.Name
	if set := a.blocks.Holder().Get(); set != nil {
		// Recover which of the three maps matched so the UI can say *why*.
		switch set.MatchPattern(name) {
		case blocklist.PatternSub:
			kind = "subdomain"
			pattern = "*." + entry.Name
		case blocklist.PatternRoot:
			kind = "domain"
			pattern = "**." + entry.Name
		}
	}
	out["matched"] = true
	out["action"] = entry.Action.String()
	out["source"] = entry.Source
	out["categories"] = entry.Categories
	out["hits"] = entry.Hits()
	out["rule"] = pattern
	out["matched_pattern"] = pattern
	out["match_kind"] = kind
	return out, nil
}

// listDomains pages the compiled rules. Walking a million-entry map on every
// request would be too slow, so the filter runs over a bounded sample unless
// the query is a prefix/exact lookup, which the LRU can answer directly.
func (a *App) listDomains(q api.DomainQuery) (any, error) {
	if a.blocks == nil {
		return map[string]any{"items": []any{}, "total": 0, "page": 1, "per_page": q.PerPage}, nil
	}
	set := a.blocks.Holder().Get()
	if set == nil {
		return map[string]any{"items": []any{}, "total": 0, "page": 1, "per_page": q.PerPage}, nil
	}
	if q.Text != "" && (q.Action == "" && q.List == "") {
		if e := set.Lookup(q.Text); e != nil {
			return map[string]any{
				"items":    []blocklist.Entry{*e},
				"total":    1,
				"page":     1,
				"per_page": q.PerPage,
			}, nil
		}
	}
	type row struct {
		Name       string   `json:"name"`
		Action     string   `json:"action"`
		Source     string   `json:"source"`
		Categories []string `json:"categories"`
		Hits       uint64   `json:"hits"`
		Rule       string   `json:"rule"`
	}
	text := strings.ToLower(strings.TrimSpace(q.Text))
	action := strings.ToLower(q.Action)
	// The cap keeps a request bounded on a large set; the UI pages anyway.
	const scanCap = 400000
	matches := make([]row, 0, 256)
	total := 0
	set.Each(func(pattern string, e *blocklist.Entry, kind blocklist.PatternKind) bool {
		if len(matches) >= scanCap {
			return false
		}
		if action != "" && e.Action.String() != action {
			return true
		}
		if q.List != "" && e.Source != q.List {
			return true
		}
		if text != "" && !strings.Contains(pattern, text) {
			return true
		}
		total++
		matches = append(matches, row{
			Name:       pattern,
			Action:     e.Action.String(),
			Source:     e.Source,
			Categories: e.Categories,
			Hits:       e.Hits(),
			Rule:       kind.Pattern(pattern),
		})
		return true
	})
	sort.Slice(matches, func(i, j int) bool {
		if matches[i].Hits != matches[j].Hits {
			return matches[i].Hits > matches[j].Hits
		}
		return matches[i].Name < matches[j].Name
	})
	start := (q.Page - 1) * q.PerPage
	if start > len(matches) {
		start = len(matches)
	}
	end := start + q.PerPage
	if end > len(matches) {
		end = len(matches)
	}
	return map[string]any{
		"items":     matches[start:end],
		"total":     total,
		"page":      q.Page,
		"per_page":  q.PerPage,
		"truncated": total > len(matches),
	}, nil
}

// addDomain appends an inline rule and persists it.
func (a *App) addDomain(_ context.Context, in api.DomainInput) (any, error) {
	name := strings.TrimSpace(in.Name)
	if name == "" {
		return nil, fmt.Errorf("name is required")
	}
	act, ok := blocklist.ParseAction(in.Action)
	if !ok {
		return nil, fmt.Errorf("unknown action %q", in.Action)
	}
	// A bulk paste goes in as several entries; a single name goes in as one.
	entries := []string{}
	if in.Content != "" {
		entries = strings.Split(in.Content, "\n")
	} else {
		entries = []string{name}
	}
	err := a.mutateConfig(func(c *config.Config) error {
		for _, e := range entries {
			e = strings.TrimSpace(e)
			if e == "" || strings.HasPrefix(e, "#") {
				continue
			}
			entry := e
			if act == blocklist.ActionBlock {
				c.Block.BlockEntries = append(c.Block.BlockEntries, entry)
			} else {
				c.Block.AllowEntries = append(c.Block.AllowEntries, entry)
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	if a.blocks != nil {
		if _, rerr := a.blocks.RefreshAll(context.Background()); rerr != nil {
			a.log.Warn("refresh after add failed", "error", rerr)
		}
	}
	// A new rule changes the verdict for the whole subtree it covers, and an
	// allow rule can rescue a name many other lists blocked, so the honest
	// thing is to drop the affected answers rather than guess.
	a.invalidateBlocklistCache()
	return map[string]any{"ok": true, "name": name, "count": len(entries)}, nil
}

// deleteDomain removes a rule and persists the change.
func (a *App) deleteDomain(_ context.Context, name, action, list string) error {
	target := strings.ToLower(strings.TrimSpace(name))
	removed := 0
	err := a.mutateConfig(func(c *config.Config) error {
		strip := func(entries []string) []string {
			out := entries[:0]
			for _, e := range entries {
				normal := strings.ToLower(strings.TrimSpace(e))
				normal = strings.TrimPrefix(strings.TrimPrefix(normal, "*."), "**.")
				normal = strings.TrimSuffix(normal, ".")
				if normal == target {
					removed++
					continue
				}
				out = append(out, e)
			}
			return out
		}
		c.Block.BlockEntries = strip(c.Block.BlockEntries)
		c.Block.AllowEntries = strip(c.Block.AllowEntries)
		// A file-backed list is edited by editing the file, so the API only
		// reports that rather than pretending it removed something.
		if list != "" && removed == 0 {
			return fmt.Errorf("%q comes from list %q; edit that list instead", name, list)
		}
		if removed == 0 {
			return fmt.Errorf("no inline rule matches %q", name)
		}
		return nil
	})
	if err != nil {
		return err
	}
	if a.blocks != nil {
		if _, rerr := a.blocks.RefreshAll(context.Background()); rerr != nil {
			a.log.Warn("refresh after delete failed", "error", rerr)
		}
	}
	a.invalidateBlocklistCache()
	return nil
}

// getACL returns the ACL groups.
func (a *App) getACL() any {
	groups := a.engine.GroupStats()
	return map[string]any{
		"groups":             groups,
		"default_policy":     a.cfg.Get().ACL.DefaultPolicy,
		"default_rate_limit": a.cfg.Get().ACL.DefaultRateLimit,
	}
}

// putACL validates and persists new ACL groups.
func (a *App) putACL(_ context.Context, groups []config.Group, def string) (int64, error) {
	err := a.mutateConfig(func(c *config.Config) error {
		c.ACL.Groups = groups
		if def != "" {
			c.ACL.DefaultPolicy = def
		}
		return nil
	})
	if err != nil {
		return 0, err
	}
	// An allow_domains or deny_domains change alters the verdict for names
	// already in the cache, so the cached answers are no longer trustworthy.
	if a.cache != nil {
		a.cache.Flush()
	}
	return a.cfg.Get().Version, nil
}

// getUpstreams returns the pool state.
func (a *App) getUpstreams() any {
	cfg := a.cfg.Get()
	servers := make([]resolver.Stats, 0, len(a.pool.All()))
	for _, s := range a.pool.Stats() {
		servers = append(servers, s)
	}
	return map[string]any{
		"policy":               cfg.Upstream.Policy,
		"servers":              servers,
		"bootstraps":           cfg.Upstream.Bootstraps,
		"healthcheck_interval": cfg.Upstream.HealthCheck.D().Seconds(),
		"max_attempts":         cfg.Upstream.MaxAttempts,
		"breaker_threshold":    cfg.Upstream.BreakerThreshold,
		"breaker_cooldown":     cfg.Upstream.BreakerCooldown.D().Seconds(),
	}
}

// putUpstream validates and persists a new upstream config.
func (a *App) putUpstream(_ context.Context, up config.Upstream) (int64, error) {
	err := a.mutateConfig(func(c *config.Config) error {
		c.Upstream = up
		return nil
	})
	if err != nil {
		return 0, err
	}
	// The pool rebinds itself on the config swap; do it now so the UI sees
	// the new servers immediately rather than after the next reload.
	a.pool.Rebind(up)
	return a.cfg.Get().Version, nil
}

// searchLog pages the query log.
func (a *App) searchLog(_ context.Context, q api.LogQuery) (any, error) {
	if a.logger == nil {
		return map[string]any{"items": []any{}, "total": 0, "offset": 0}, nil
	}
	page, err := a.logger.Search(qlog.Query{
		Limit: q.Limit, Offset: q.Offset, Text: q.Text, Action: q.Action,
		Client: q.Client, RCode: q.RCode, BlockedOnly: q.BlockedOnly, Since: q.Since,
	})
	if err != nil {
		return nil, err
	}
	out := make([]api.LogEntry, 0, len(page.Items))
	for _, e := range page.Items {
		out = append(out, toLogEntry(e))
	}
	return map[string]any{
		"items":    out,
		"total":    page.Total,
		"offset":   page.Offset,
		"limit":    page.Limit,
		"has_more": len(out) == page.Limit,
	}, nil
}

func toLogEntry(e qlog.Entry) api.LogEntry {
	return api.LogEntry{
		ID: e.ID, TS: e.TS, Client: e.Client, Group: e.Group, Name: e.Name,
		QType: e.QType, QTypeStr: e.QTypeStr, RCode: e.RCode,
		RCodeStr: e.RCodeName(), Action: string(e.Action), Response: e.Response,
		Duration: e.Duration, Upstream: e.Upstream, List: e.List, Protocol: e.Protocol,
		Blocked: e.Blocked,
	}
}

// logStats is the live stats frame pushed over SSE.
func (a *App) logStats() any {
	t := metrics.TotalsNow()
	var hitRate float64
	if t.Hits+t.Misses > 0 {
		hitRate = float64(t.Hits) / float64(t.Hits+t.Misses)
	}
	var blockedPct float64
	if t.Queries > 0 {
		blockedPct = float64(t.Blocked) / float64(t.Queries)
	}
	return map[string]any{
		"qps":            a.series.qps(),
		"blocked_pct":    blockedPct,
		"cache_hit_rate": hitRate,
		"queries_total":  t.Queries,
		"blocked_total":  t.Blocked,
		"errors_total":   t.Errors,
		"inflight":       t.Concurrent,
		"uptime_s":       int64(time.Since(a.startedAt).Seconds()),
	}
}

// subscribeLog streams new entries to one SSE client.
func (a *App) subscribeLog() (<-chan api.LogEntry, func()) {
	if a.logger == nil {
		ch := make(chan api.LogEntry)
		close(ch)
		return ch, func() {}
	}
	src, cancel := a.logger.Subscribe()
	out := make(chan api.LogEntry, 256)
	done := make(chan struct{})
	go func() {
		defer close(out)
		for {
			select {
			case <-done:
				return
			case e, ok := <-src:
				if !ok {
					return
				}
				select {
				case out <- toLogEntry(e):
				case <-done:
					return
				}
			}
		}
	}()
	return out, func() {
		close(done)
		cancel()
	}
}

// clearLog empties the query log.
func (a *App) clearLog() error {
	if a.logger == nil {
		return nil
	}
	return a.logger.Clear()
}

// cacheStats returns the cache snapshot.
func (a *App) cacheStats() any {
	if a.cache == nil {
		return map[string]any{"enabled": false}
	}
	st := a.cache.Stats()
	return map[string]any{
		"enabled":         st.Enabled,
		"size":            st.Size,
		"entries":         st.Entries,
		"shards":          st.Shards,
		"min_ttl_ms":      st.MinTTLMS,
		"max_ttl_ms":      st.MaxTTLMS,
		"serve_stale_ms":  st.ServeStaleM,
		"negative_ttl_ms": st.NegativeMS,
		"hit_rate":        st.HitRate,
		"hits":            st.Hits,
		"misses":          st.Misses,
		"stale_hits":      st.StaleHits,
		"evictions":       st.Evictions,
		"bytes":           st.Bytes,
		"bytes_human":     st.MemoryHuman,
		"persisted":       st.Persist,
	}
}

// cacheTop returns the hottest cached names.
func (a *App) cacheTop(limit int) any {
	if a.cache == nil {
		return []any{}
	}
	entries := a.cache.TopEntries(limit)
	out := make([]map[string]any, 0, len(entries))
	for _, e := range entries {
		out = append(out, map[string]any{
			"name":       e.Name,
			"qtype":      e.Type,
			"qtype_name": dns.Type(e.Type).String(),
			"hits":       e.Hits,
			"bytes":      e.Bytes,
		})
	}
	return out
}

// flushCache empties the cache.
func (a *App) flushCache() int64 {
	if a.cache == nil {
		return 0
	}
	st := a.cache.Stats()
	a.cache.Flush()
	return int64(st.Entries)
}

// flush persists buffered state.
func (a *App) flush() {
	if a.logger != nil {
		a.logger.Flush()
	}
	a.snapshotCache()
}

// seriesStore keeps the rolling counters the dashboard charts read.
type seriesStore struct {
	mu       sync.Mutex
	queries  *metrics.Ring
	blocked  *metrics.Ring
	errors   *metrics.Ring
	cacheHit *metrics.Ring
	// The previous totals, used to derive per-bucket deltas.
	lastQueries uint64
	lastBlocked uint64
	lastErrors  uint64
	lastHits    uint64
	lastAt      time.Time
	qpsValue    float64
}

func newSeriesStore() *seriesStore {
	return &seriesStore{
		queries:  metrics.NewRing(300, 5*time.Second),
		blocked:  metrics.NewRing(300, 5*time.Second),
		errors:   metrics.NewRing(300, 5*time.Second),
		cacheHit: metrics.NewRing(300, 5*time.Second),
		lastAt:   time.Now(),
	}
}

// sample folds the delta since the last sample into the rings. Sampling on a
// timer rather than per query keeps the query path free of any extra work and
// is accurate enough for a chart.
func (s *seriesStore) sample() {
	t := metrics.TotalsNow()
	s.mu.Lock()
	now := time.Now()
	dt := now.Sub(s.lastAt).Seconds()
	if dt > 0 {
		s.qpsValue = float64(t.Queries-s.lastQueries) / dt
	}
	// Ring buckets are 5s wide; scale the interval delta accordingly.
	scale := dt / 5
	if scale < 0 {
		scale = 0
	}
	dq := int64(float64(t.Queries-s.lastQueries) * scale)
	db := int64(float64(t.Blocked-s.lastBlocked) * scale)
	de := int64(float64(t.Errors-s.lastErrors) * scale)
	dc := int64(float64(t.Hits-s.lastHits) * scale)
	if dq > 0 {
		s.queries.Add(dq)
	}
	if db > 0 {
		s.blocked.Add(db)
	}
	if de > 0 {
		s.errors.Add(de)
	}
	if dc > 0 {
		s.cacheHit.Add(dc)
	}
	s.lastQueries, s.lastBlocked, s.lastErrors, s.lastHits = t.Queries, t.Blocked, t.Errors, t.Hits
	s.lastAt = now
	s.mu.Unlock()
}

func (s *seriesStore) qps() float64 {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.qpsValue
}

// dashboard builds the aggregated payload.
func (a *App) dashboard(_ context.Context, rangeKey string) (any, error) {
	spec, ok := ranges[rangeKey]
	if !ok {
		spec = ranges["1h"]
	}
	t := metrics.TotalsNow()
	hitRate := 0.0
	if t.Hits+t.Misses > 0 {
		hitRate = float64(t.Hits) / float64(t.Hits+t.Misses)
	}
	blockedPct := 0.0
	if t.Queries > 0 {
		blockedPct = float64(t.Blocked) / float64(t.Queries) * 100
	}

	// Build the series by walking the rings oldest-first and dropping anything
	// older than the requested range.
	var series []map[string]any
	now := time.Now()
	qts, qv := a.series.queries.Snapshot()
	_, bv := a.series.blocked.Snapshot()
	_, ev := a.series.errors.Snapshot()
	_, cv := a.series.cacheHit.Snapshot()
	series = make([]map[string]any, 0, len(qts))
	for i := range qts {
		age := now.Sub(time.Unix(qts[i], 0))
		if age > spec.duration {
			break
		}
		series = append(series, map[string]any{
			"t":          qts[i],
			"queries":    qv[i],
			"blocked":    bv[i],
			"errors":     ev[i],
			"cache_hits": cv[i],
		})
	}

	topBlocked := []any{}
	topQueried := []any{}
	if a.logger != nil {
		for _, d := range a.logger.TopBlocked(15) {
			topBlocked = append(topBlocked, map[string]any{
				"domain": d.Name, "count": d.Count, "list": "", "qtype": d.QType,
			})
		}
		for _, d := range a.logger.TopQueried(15) {
			topQueried = append(topQueried, map[string]any{
				"domain": d.Name, "count": d.Count, "qtype": d.QType, "blocked": d.Blocked > 0,
			})
		}
	}

	problems := a.Degraded()
	status := "ok"
	if len(problems) > 0 {
		status = "degraded"
	}
	out := map[string]any{
		"health":          status,
		"degraded_reason": strings.Join(problems, "; "),
		"version":         a.ver,
		"node_id":         a.clusterNodeID(),
		"uptime_seconds":  int64(time.Since(a.startedAt).Seconds()),
		"queries_total":   t.Queries,
		"queries_per_sec": a.series.qps(),
		"cache_hit_rate":  hitRate,
		"blocked_total":   t.Blocked,
		"blocked_pct":     blockedPct,
		"errors_total":    t.Errors,
		"inflight":        t.Concurrent,
		"series":          series,
		"top_blocked":     topBlocked,
		"top_queried":     topQueried,
		"upstreams":       a.pool.Stats(),
		"listeners":       a.dns.Listeners(),
		"transports":      a.dns.ByTransport(),
		"blocklist_rules": a.blocklistRuleCount(),
		"cache_entries":   a.cacheEntries(),
		"config_version":  a.cfg.Get().Version,
		"generation":      a.cfg.Generation(),
	}
	if a.logger != nil {
		recent := a.logger.Recent(20)
		items := make([]api.LogEntry, 0, len(recent))
		for _, e := range recent {
			items = append(items, toLogEntry(e))
		}
		out["recent"] = items
	}
	return out, nil
}

func (a *App) clusterNodeID() string {
	if a.cl != nil {
		return a.cl.NodeID()
	}
	return ""
}

func (a *App) blocklistRuleCount() int {
	if a.blocks == nil {
		return 0
	}
	if st := a.blocks.State(); st != nil && st.Set != nil {
		return st.Set.Len()
	}
	return 0
}

func (a *App) cacheEntries() int {
	if a.cache == nil {
		return 0
	}
	return a.cache.Stats().Entries
}

// rangeSpec is one dashboard time range.
type rangeSpec struct {
	duration time.Duration
	buckets  int
}

var ranges = map[string]rangeSpec{
	"15m": {duration: 15 * time.Minute, buckets: 45},
	"1h":  {duration: time.Hour, buckets: 60},
	"6h":  {duration: 6 * time.Hour, buckets: 72},
	"24h": {duration: 24 * time.Hour, buckets: 96},
}