package server

import (
	"errors"
	"net/http"
	"net/netip"
	"path/filepath"
	"slices"
	"strings"
	"time"

	"jarl/internal/auth"
	"jarl/internal/dnsname"
	"jarl/internal/model"
	"jarl/internal/stats"
)

// statsQuerier checks permission and that statistics are enabled. With
// ?views=internal,vps the figures are for those views only.
func (s *Server) statsQuerier(r *http.Request, p *auth.Principal) (*stats.Querier, error) {
	if err := require(p, auth.Action{Resource: auth.ResStats}); err != nil {
		return nil, err
	}
	if s.statsQ == nil {
		return nil, &httpError{http.StatusNotFound, "stats_disabled", "query statistics are disabled; set stats.enabled: true in /etc/jarl/jarl.yaml and restart jarl (see docs/stats.md)"}
	}
	var views []string
	for _, v := range strings.Split(r.URL.Query().Get("views"), ",") {
		if v = strings.TrimSpace(v); v != "" {
			views = append(views, v)
		}
	}
	if len(views) > 0 {
		return s.statsQ.ForViews(views), nil
	}
	return s.statsQ, nil
}

func statsSince(r *http.Request) (time.Duration, error) {
	d, err := stats.ParseSince(r.URL.Query().Get("since"))
	if err != nil {
		return 0, badRequest("%v", err)
	}
	return d, nil
}

func (s *Server) statsStatus(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.Action{Resource: auth.ResStats}); err != nil {
		return err
	}
	if s.cfg.Stats == nil {
		writeJSON(w, http.StatusOK, stats.Status{Enabled: false, Warnings: []string{}})
		return nil
	}
	writeJSON(w, http.StatusOK, s.cfg.Stats.Status())
	return nil
}

func (s *Server) statsSummary(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	q, err := s.statsQuerier(r, p)
	if err != nil {
		return err
	}
	since, err := statsSince(r)
	if err != nil {
		return err
	}
	sum, err := q.Summary(r.Context(), since, queryInt(r, "top", 10))
	if err != nil {
		return err
	}
	if err := s.nameClients(r, p, sum.Tops[stats.KindClient]); err != nil {
		return err
	}
	writeJSON(w, http.StatusOK, sum)
	return nil
}

func (s *Server) statsTop(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	q, err := s.statsQuerier(r, p)
	if err != nil {
		return err
	}
	since, err := statsSince(r)
	if err != nil {
		return err
	}
	kind := r.URL.Query().Get("kind")
	if kind == "" {
		kind = stats.KindName
	}
	limit := min(max(queryInt(r, "limit", 20), 1), 10000)
	es, err := q.Top(r.Context(), kind, since, limit)
	if err != nil {
		return badRequest("%v", err)
	}
	if kind == stats.KindClient || kind == stats.KindRefused || kind == stats.KindBlockedClient {
		if err := s.nameClients(r, p, es); err != nil {
			return err
		}
	}
	writeJSON(w, http.StatusOK, es)
	return nil
}

func (s *Server) statsTimeline(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	q, err := s.statsQuerier(r, p)
	if err != nil {
		return err
	}
	since, err := statsSince(r)
	if err != nil {
		return err
	}
	var keys []string
	for _, k := range r.URL.Query()["key"] {
		for _, part := range strings.Split(k, ",") {
			if part = strings.TrimSpace(part); part != "" {
				keys = append(keys, part)
			}
		}
	}
	if len(keys) == 0 {
		keys = []string{"queries"}
	}
	if len(keys) > 50 {
		return badRequest("at most 50 series")
	}
	tl, err := q.Timeline(r.Context(), since, r.URL.Query().Get("step"), keys)
	if err != nil {
		return badRequest("%v", err)
	}
	writeJSON(w, http.StatusOK, tl)
	return nil
}

func (s *Server) statsHeatmap(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	q, err := s.statsQuerier(r, p)
	if err != nil {
		return err
	}
	since := 28 * 24 * time.Hour
	if r.URL.Query().Get("since") != "" {
		if since, err = statsSince(r); err != nil {
			return err
		}
	}
	hm, err := q.Heatmap(r.Context(), r.URL.Query().Get("key"), since)
	if err != nil {
		return err
	}
	writeJSON(w, http.StatusOK, hm)
	return nil
}

func (s *Server) statsBreakdown(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	q, err := s.statsQuerier(r, p)
	if err != nil {
		return err
	}
	since, err := statsSince(r)
	if err != nil {
		return err
	}
	es, err := q.Breakdown(r.Context(), r.URL.Query().Get("group"), since)
	if errors.Is(err, stats.ErrNotPerView) {
		return &httpError{http.StatusBadRequest, "not_per_view", r.URL.Query().Get("group") + ": " + err.Error()}
	}
	if err != nil {
		return badRequest("%v", err)
	}
	writeJSON(w, http.StatusOK, es)
	return nil
}

// nameClients gives client entries the host name Jarl's records have for
// the address: the PTR record's target, or else the name of an A/AAAA
// record with the address. It sends no DNS queries, and uses only records
// the user may read. Anonymized clients (prefixes) get no name.
func (s *Server) nameClients(r *http.Request, p *auth.Principal, es []stats.Entry) error {
	if len(es) == 0 {
		return nil
	}
	want := map[netip.Addr]bool{}
	for _, e := range es {
		if a, err := netip.ParseAddr(e.Key); err == nil {
			want[a.Unmap()] = true
		}
	}
	if len(want) == 0 {
		return nil
	}
	st, err := s.state(r)
	if err != nil {
		return err
	}
	names := clientNames(st, want, func(rec *model.Record) bool { return canReadRecord(p, st, rec) })
	for i, e := range es {
		if a, err := netip.ParseAddr(e.Key); err == nil {
			es[i].Name = names[a.Unmap()]
		}
	}
	return nil
}

// clientNames finds names for the addresses in want (see nameClients).
// Where several records match, the first in name order wins.
func clientNames(st *model.State, want map[netip.Addr]bool, readable func(*model.Record) bool) map[netip.Addr]string {
	ptr, host := map[netip.Addr]string{}, map[netip.Addr]string{}
	var recs []*model.Record
	for _, rec := range st.Records {
		if !rec.Disabled && (rec.Type == "PTR" || rec.Type == "A" || rec.Type == "AAAA") {
			recs = append(recs, rec)
		}
	}
	slices.SortFunc(recs, func(a, b *model.Record) int {
		if a.Name != b.Name {
			if model.CanonicalLess(a.Name, b.Name) {
				return -1
			}
			return 1
		}
		return strings.Compare(a.Data, b.Data)
	})
	for _, rec := range recs {
		var a netip.Addr
		var name string
		if rec.Type == "PTR" {
			var ok bool
			if a, ok = dnsname.AddrFromReverse(rec.Name); !ok {
				continue
			}
			name = rec.Data
		} else {
			var err error
			if a, err = netip.ParseAddr(rec.Data); err != nil {
				continue
			}
			name = rec.Name
		}
		a = a.Unmap()
		m := host
		if rec.Type == "PTR" {
			m = ptr
		}
		if !want[a] || m[a] != "" || !readable(rec) {
			continue
		}
		m[a] = dnsname.Display(name)
	}
	for a, n := range host {
		if ptr[a] == "" {
			ptr[a] = n
		}
	}
	return ptr
}

// statsServer: GET /stats/server is the latest server statistics (named's
// memory, CPU, cache and sockets, the host), named's client counts and
// limits (rndc status), and the space left on the file systems Jarl and
// named write to.
func (s *Server) statsServer(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if _, err := s.statsQuerier(r, p); err != nil {
		return err
	}
	out := map[string]any{"server": s.cfg.Stats.Server()}
	if ns, err := s.eng.NamedStatus(r.Context()); err == nil {
		out["named"] = map[string]string{"recursive_clients": ns.RecursiveClients, "tcp_clients": ns.TCPClients, "zones": ns.Zones,
			"cpus": ns.CPUs, "worker_threads": ns.WorkerThreads, "last_configured": ns.LastConfigured}
	} else {
		out["named_error"] = err.Error()
	}
	paths := s.eng.Config().Paths
	dirs := map[string]string{"zone files": paths.ZoneDir, "Jarl's cache and blocklists": paths.CacheDir, "named.conf": paths.ConfigDir}
	labels := []string{"zone files", "Jarl's cache and blocklists", "named.conf"}
	if lf := s.cfg.Stats.Options().LogFile; lf != "" {
		dirs["named's logs"] = filepath.Dir(lf)
		labels = append(labels, "named's logs")
	}
	if db := s.cfg.Stats.Store().Path(); db != "" {
		dirs["statistics database"] = filepath.Dir(db)
		labels = append(labels, "statistics database")
	}
	out["disks"] = stats.DiskUsage(labels, dirs)
	writeJSON(w, http.StatusOK, out)
	return nil
}

// statsExplore: GET /stats/explore?client=&name=&domain=&view=&type=&rcode=
// &blocked=&since=24h explores the query log (docs/stats.md#exploring):
// totals, a series, the top values of each dimension left open, and the
// latest answers, with client host names.
func (s *Server) statsExplore(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	q, err := s.statsQuerier(r, p)
	if err != nil {
		return err
	}
	since, err := statsSince(r)
	if err != nil {
		return err
	}
	v := r.URL.Query()
	f := stats.ExploreFilter{Client: v.Get("client"), Name: v.Get("name"), Domain: v.Get("domain"), View: v.Get("view"),
		Type: v.Get("type"), RCode: v.Get("rcode"), Blocked: v.Get("blocked"), Since: since}
	ex, err := q.Explore(r.Context(), f, 15, 100)
	if errors.Is(err, stats.ErrNoQueryLog) {
		return &httpError{http.StatusNotFound, "query_log_off", err.Error()}
	}
	if err != nil {
		return err
	}
	if err := s.nameClients(r, p, ex.By["client"]); err != nil {
		return err
	}
	// The recent answers' clients, named once each.
	var es []stats.Entry
	seen := map[string]int{}
	for _, row := range ex.Recent {
		if _, ok := seen[row.Client]; !ok {
			seen[row.Client] = len(es)
			es = append(es, stats.Entry{Key: row.Client})
		}
	}
	if err := s.nameClients(r, p, es); err != nil {
		return err
	}
	for i := range ex.Recent {
		ex.Recent[i].ClientName = es[seen[ex.Recent[i].Client]].Name
	}
	// The filter's client, named too.
	out := struct {
		*stats.Exploration
		ClientName string `json:"client_name,omitempty"`
	}{Exploration: ex}
	if f.Client != "" {
		one := []stats.Entry{{Key: f.Client}}
		if err := s.nameClients(r, p, one); err == nil {
			out.ClientName = one[0].Name
		}
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}