package server

import (
	"context"
	"fmt"
	"net/http"
	"os"
	"sort"
	"strings"
	"sync"
	"time"

	"housecarl/internal/api"
	"housecarl/internal/auth"
	"housecarl/internal/model"
	"housecarl/internal/render"
	"housecarl/internal/store"
	"housecarl/internal/validate"
	"housecarl/internal/version"
)

// ---- status

func (s *Server) status(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if !p.Can(auth.ResConfig, false) && !p.Can(auth.ResLog, false) {
		return forbidden("permission denied: this needs config:read or log:read")
	}
	st := s.eng.State()
	out := api.Status{Build: version.Info(), Started: s.started, Problems: s.eng.Problems(), Probation: s.probationStatus(),
		Interfaces: s.hostInterfaces(st), Counts: map[string]int{}, OtherTables: []string{}}
	if out.Problems == nil {
		out.Problems = []validate.Problem{}
	}
	if p.IsAdmin() {
		out.Database = s.store.Path()
	}
	for _, k := range model.Kinds {
		out.Counts[k] = len(st.Objects(k))
	}
	if t, err := s.fw.Table(r.Context()); err != nil && st.Empty() {
		out.Unconfigured = true
	} else if err != nil {
		out.ApplyError = err.Error()
	} else if t.Fallback {
		out.ApplyError = fallbackInForce
	} else {
		out.Applied = true
	}
	if data, err := s.fw.ListRuleset(r.Context()); err == nil {
		out.OtherTables = otherTables(data)
	}
	out.Problems = append(out.Problems, s.hostProblems(r.Context(), out.OtherTables)...)
	out.Problems = append(out.Problems, s.statsProblems()...)
	writeJSON(w, http.StatusOK, out)
	return nil
}

const importedTableKey = "imported_table"

// nftablesUnitLinks are where an enabled nftables.service shows (Debian
// enables it for sysinit.target).
var nftablesUnitLinks = []string{
	"/etc/systemd/system/sysinit.target.wants/nftables.service",
	"/etc/systemd/system/multi-user.target.wants/nftables.service",
}

// hostProblems are warnings about the machine rather than the
// configuration: another ruleset that still loads at boot, or the table
// an import came from, still in force beside Housecarl's.
func (s *Server) hostProblems(ctx context.Context, others []string) []validate.Problem {
	var out []validate.Problem
	for _, link := range s.unitLinks {
		if _, err := os.Lstat(link); err == nil {
			out = append(out, validate.Problem{Severity: validate.Warning, Code: "nftables_service", Object: "nftables.service",
				Message: "nftables.service is enabled: at boot it loads /etc/nftables.conf, and stopping or restarting it flushes every table, Housecarl's included; disable it (systemctl disable nftables, without --now)"})
			break
		}
	}
	if t, err := s.store.GetMeta(ctx, importedTableKey); err == nil && t != "" {
		for _, o := range others {
			if o == t {
				out = append(out, validate.Problem{Severity: validate.Warning, Code: "takeover_pending", Object: "table " + t,
					Message: fmt.Sprintf("%s, the table you imported, still applies beside Housecarl's: a packet must get past both; once Housecarl's rules are right, delete it with 'hc takeover %q'", t, t)})
			}
		}
	}
	return out
}

// hostInterfaces lists the machine's interfaces with their zones.
func (s *Server) hostInterfaces(st *model.State) []api.HostInterface {
	out := []api.HostInterface{}
	if s.ifaces == nil {
		return out
	}
	all, err := s.ifaces.All()
	if err != nil {
		return out
	}
	for name, ps := range all {
		hi := api.HostInterface{Name: name, Addresses: []string{}, Up: s.ifaces.Up(name), Zone: zoneOf(st, name)}
		for _, a := range ps {
			hi.Addresses = append(hi.Addresses, a.String())
		}
		out = append(out, hi)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}

// zoneOf names the zone an interface is in: an exact name, else the
// longest matching wildcard.
func zoneOf(st *model.State, name string) string {
	best, bestLen := "", -1
	for _, z := range st.Zones {
		for _, i := range z.Interfaces {
			if i == name {
				return z.Name
			}
			if p, ok := strings.CutSuffix(i, "*"); ok && strings.HasPrefix(name, p) && len(p) > bestLen {
				best, bestLen = z.Name, len(p)
			}
		}
	}
	return best
}

func (s *Server) interfaces(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.ResConfig, false); err != nil {
		return err
	}
	writeJSON(w, http.StatusOK, s.hostInterfaces(s.eng.State()))
	return nil
}

func (s *Server) counters(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.ResLog, false); err != nil {
		return err
	}
	t, err := s.fw.Table(r.Context())
	if err != nil && s.eng.State().Empty() {
		// Nothing applied yet: nothing counted.
		writeJSON(w, http.StatusOK, api.Counters{Since: s.started, Counters: map[string]api.Counter{}})
		return nil
	}
	if err != nil {
		return err
	}
	out := api.Counters{Since: t.Since, Counters: map[string]api.Counter{}}
	for k, c := range t.Counters {
		out.Counters[k] = api.Counter{Packets: c.Packets, Bytes: c.Bytes}
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

func (s *Server) listAudit(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.ResAudit, false); err != nil {
		return err
	}
	q := r.URL.Query()
	evs, err := s.store.ListAudit(r.Context(), store.AuditFilter{Username: q.Get("user"), Action: q.Get("action"), Result: q.Get("result"),
		Search: q.Get("q"), Before: int64(queryInt(r, "before", 0)), Limit: queryInt(r, "limit", 200)})
	if err != nil {
		return err
	}
	writeJSON(w, http.StatusOK, evs)
	return nil
}

func (s *Server) catalog(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	roles := map[string][]string{}
	for n, gs := range auth.Roles {
		roles[n] = grantStrings(gs)
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"services": model.BuiltinServices(), "chains": model.Chains, "actions": model.Actions,
		"roles": roles, "log_group": render.LogGroup,
	})
	return nil
}

// ---- dynamic sets' entries

func (s *Server) dynamicSet(r *http.Request, p *auth.Principal, write bool) (*model.AddressSet, error) {
	name := r.PathValue("ref")
	if !p.CanSet(name, write) {
		access := "read"
		if write {
			access = "write"
		}
		return nil, forbidden("permission denied: this needs sets:%s for %s", access, name)
	}
	set := s.eng.State().Set(name)
	if set == nil {
		return nil, notFound("no set %s", name)
	}
	if !set.Dynamic {
		return nil, badRequest("set %s isn't dynamic: change its entries with PATCH /sets/%s", set.Name, set.Name)
	}
	return set, nil
}

func (s *Server) listElements(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	set, err := s.dynamicSet(r, p, false)
	if err != nil {
		return err
	}
	t, err := s.fw.Table(r.Context())
	if err != nil {
		return err
	}
	out := []api.Element{}
	for _, e := range t.Elements[set.Name] {
		out = append(out, api.Element{Address: e.Addr, Timeout: e.Timeout})
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

func (s *Server) addElement(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	set, err := s.dynamicSet(r, p, true)
	if err != nil {
		return err
	}
	var in api.Element
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	a, err := model.ParseAddress(in.Address)
	if err != nil || !a.Prefix.IsSingleIP() {
		return badRequest("a dynamic set takes single addresses (%q)", in.Address)
	}
	if in.Timeout < 0 || in.Timeout > 366*24*3600 {
		return badRequest("the timeout is in seconds, up to a year")
	}
	if err := s.fw.AddElement(r.Context(), set.Name, a.String(), in.Timeout); err != nil {
		return err
	}
	s.eng.Audit(r.Context(), p, "set.add", set.Name+" "+a.String(), "success", "")
	writeJSON(w, http.StatusCreated, api.Element{Address: a.String(), Timeout: in.Timeout})
	return nil
}

func (s *Server) deleteElement(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	set, err := s.dynamicSet(r, p, true)
	if err != nil {
		return err
	}
	a, err := model.ParseAddress(r.PathValue("addr"))
	if err != nil {
		return badRequest("%v", err)
	}
	if err := s.fw.DeleteElement(r.Context(), set.Name, a.String()); err != nil {
		return notFound("%s isn't in set %s", a, set.Name)
	}
	s.eng.Audit(r.Context(), p, "set.delete", set.Name+" "+a.String(), "success", "")
	w.WriteHeader(http.StatusNoContent)
	return nil
}

// ---- the log

// logRing keeps the latest logged packets.
type logRing struct {
	mu   sync.Mutex
	max  int
	list []api.LogEntry
}

func newLogRing(max int) *logRing { return &logRing{max: max} }

// Add records a logged packet.
func (l *logRing) Add(e api.LogEntry) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.list = append(l.list, e)
	if len(l.list) > l.max {
		l.list = append([]api.LogEntry(nil), l.list[len(l.list)-l.max:]...)
	}
}

// Latest returns up to n entries, newest first, after a time.
func (l *logRing) Latest(n int, after time.Time, keep func(api.LogEntry) bool) []api.LogEntry {
	l.mu.Lock()
	defer l.mu.Unlock()
	out := []api.LogEntry{}
	for i := len(l.list) - 1; i >= 0 && (n <= 0 || len(out) < n); i-- {
		e := l.list[i]
		if !e.Time.After(after) {
			break
		}
		if keep == nil || keep(e) {
			out = append(out, e)
		}
	}
	return out
}

// LogPacket records a packet the firewall logged (internal/nflog calls
// it).
func (s *Server) LogPacket(e api.LogEntry) {
	s.logs.Add(e)
	if s.stats != nil {
		s.stats.Packet(e)
	}
}

func (s *Server) listLog(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.ResLog, false); err != nil {
		return err
	}
	q := r.URL.Query()
	var after time.Time
	if v := q.Get("after"); v != "" {
		after, _ = time.Parse(time.RFC3339Nano, v)
	}
	search := strings.ToLower(q.Get("q"))
	writeJSON(w, http.StatusOK, s.logs.Latest(queryInt(r, "limit", 200), after, func(e api.LogEntry) bool {
		if search == "" {
			return true
		}
		return strings.Contains(strings.ToLower(e.Prefix+" "+e.Source+" "+e.Dest+" "+e.In+" "+e.Out+" "+e.Protocol), search)
	}))
	return nil
}