package web

import (
	"crypto/hmac"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

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

// ── The setup gate's answerer (v0.280.0, `09` §3 decision 46) ─────────────────────────────────────────
//
// traefik asks GET /__felhom_gate/auth (forwardAuth) for every request to an app whose gate is closed
// (internal/stacks/setup_gate.go writes that route). The answer:
//
//   - a valid GATE COOKIE for that app host → 200, the request goes to the app;
//   - /__felhom_gate/cb?t=<token> → the token (minted below, 60 s, one use, bound to the host) is swapped for a
//     host-only gate cookie, and the browser goes back where it was going;
//   - a browser GET without one → 302 to https://felhom.<domain>/__gate/start?rd=<where it was going>;
//   - anything else → 401 {"error": …}: a script or a phone app gets a plain refusal.
//
// GET /__gate/start is on the DASHBOARD host, where the household's own session cookie already is. With a
// valid session: a token and a 302 to the app's callback. Without: a page that says the app is waiting for its
// first setup, with a sign-in link that comes straight back here after the sign-in.
//
// The dashboard cookie is NEVER widened to the app hosts (it is host-only, auth.go) — the spike measured that
// widening it would send the household's session to every app's backend. The gate cookie reaches only its
// own app host and opens only that app's gate (HMAC over the host). The key is persisted, so a controller
// restart does not re-gate a browser that already passed.
// Pinned by internal/web/setup_gate_test.go.

const (
	gateCookieName  = "felhom_gate"
	gateCookieLife  = 7 * 24 * time.Hour
	gateTokenLife   = 60 * time.Second
	gateAuthPath    = "/__felhom_gate/auth"
	gateCallbackURI = "/__felhom_gate/cb"
	gateStartPath   = "/__gate/start"
	// signupClosedPath: the sign-up block's replacePath target (internal/stacks/signup_block.go, decision 47).
	signupClosedPath = "/__felhom_gate/signup-closed"
)

type gateState struct {
	once sync.Once
	key  []byte
	mu   sync.Mutex
	used map[string]time.Time // token nonces already swapped, until they expire
}

// gateKey loads the gate's HMAC key from the data dir, or makes one. No data dir → a key for this run only.
func (s *Server) gateKey() []byte {
	s.gate.once.Do(func() {
		s.gate.used = map[string]time.Time{}
		p := ""
		if s.cfg != nil && s.cfg.Paths.DataDir != "" {
			p = filepath.Join(s.cfg.Paths.DataDir, "setup-gate.key")
			if b, err := os.ReadFile(p); err == nil {
				if k, err := hex.DecodeString(strings.TrimSpace(string(b))); err == nil && len(k) == 32 {
					s.gate.key = k
					return
				}
			}
		}
		k := make([]byte, 32)
		_, _ = rand.Read(k)
		s.gate.key = k
		if p != "" {
			if err := os.WriteFile(p, []byte(hex.EncodeToString(k)), 0o600); err != nil {
				s.logger.Printf("[WARN] [web] setup gate: the key could not be saved (%v) — a restart will ask browsers to sign in again", err)
			}
		}
	})
	return s.gate.key
}

func (s *Server) gateMAC(parts ...string) string {
	m := hmac.New(sha256.New, s.gateKey())
	m.Write([]byte(strings.Join(parts, "\x00")))
	return hex.EncodeToString(m.Sum(nil))
}

func (s *Server) gateNow() time.Time {
	if s.gateClock != nil {
		return s.gateClock()
	}
	return time.Now()
}

// gateCookieValid: "<unix expiry>.<mac over host+expiry>".
func (s *Server) gateCookieValid(r *http.Request, host string) bool {
	c, err := r.Cookie(gateCookieName)
	if err != nil {
		return false
	}
	exp, mac, ok := strings.Cut(c.Value, ".")
	n, err := strconv.ParseInt(exp, 10, 64)
	if !ok || err != nil || s.gateNow().Unix() > n {
		return false
	}
	return hmac.Equal([]byte(mac), []byte(s.gateMAC("cookie", host, exp)))
}

type gateToken struct {
	Host  string `json:"h"`
	Exp   int64  `json:"e"`
	Nonce string `json:"n"`
	RD    string `json:"r"`
	MAC   string `json:"m"`
}

func (s *Server) mintGateToken(host, rd string) string {
	nb := make([]byte, 12)
	_, _ = rand.Read(nb)
	t := gateToken{Host: host, Exp: s.gateNow().Add(gateTokenLife).Unix(), Nonce: hex.EncodeToString(nb), RD: rd}
	t.MAC = s.gateMAC("token", t.Host, strconv.FormatInt(t.Exp, 10), t.Nonce, t.RD)
	b, _ := json.Marshal(t)
	return base64.RawURLEncoding.EncodeToString(b)
}

// takeGateToken checks a token for host and uses it up. Returns where the browser was going.
func (s *Server) takeGateToken(raw, host string) (string, error) {
	b, err := base64.RawURLEncoding.DecodeString(raw)
	if err != nil {
		return "", errors.New("malformed")
	}
	var t gateToken
	if json.Unmarshal(b, &t) != nil {
		return "", errors.New("malformed")
	}
	if !hmac.Equal([]byte(t.MAC), []byte(s.gateMAC("token", t.Host, strconv.FormatInt(t.Exp, 10), t.Nonce, t.RD))) {
		return "", errors.New("bad signature")
	}
	if t.Host != host {
		return "", errors.New("for another app")
	}
	now := s.gateNow()
	if now.Unix() > t.Exp {
		return "", errors.New("expired")
	}
	s.gateKey()
	s.gate.mu.Lock()
	defer s.gate.mu.Unlock()
	for n, until := range s.gate.used {
		if now.After(until) {
			delete(s.gate.used, n)
		}
	}
	if _, seen := s.gate.used[t.Nonce]; seen {
		return "", errors.New("already used")
	}
	s.gate.used[t.Nonce] = time.Unix(t.Exp, 0).Add(time.Second)
	return t.RD, nil
}

// gateRDHost: the host of a return address that may be used — https, on this household's domain, and an
// app whose gate is closed. Anything else is refused (no open redirect through the dashboard).
func (s *Server) gateRDHost(rd string) (string, bool) {
	u, err := url.Parse(rd)
	if err != nil || u.Scheme != "https" || u.User != nil || u.Host == "" || s.stackMgr == nil {
		return "", false
	}
	host := strings.ToLower(u.Hostname())
	if u.Port() != "" || !strings.HasSuffix(host, "."+strings.ToLower(s.cfg.Customer.Domain)) {
		return "", false
	}
	if _, closed, found := s.stackMgr.SetupGateHost(host); !found || !closed {
		return "", false
	}
	return host, true
}

func gateRefuse(w http.ResponseWriter, code int) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-store")
	w.WriteHeader(code)
	_, _ = w.Write([]byte(`{"error":"this app is waiting for its first setup"}`))
}

// ServeGateAuth is traefik's forwardAuth answer. It trusts X-Forwarded-Host/-Uri/-Method, which traefik sets
// from the request it is forwarding (the entrypoints trust no client's own X-Forwarded-* headers). Anyone who
// calls it directly on the docker network learns only yes or no about a cookie they already hold.
func (s *Server) ServeGateAuth(w http.ResponseWriter, r *http.Request) {
	host := strings.ToLower(r.Header.Get("X-Forwarded-Host"))
	if i := strings.LastIndex(host, ":"); i != -1 {
		host = host[:i]
	}
	uri := r.Header.Get("X-Forwarded-Uri")
	if uri == "" {
		uri = "/"
	}
	method := r.Header.Get("X-Forwarded-Method")
	if s.stackMgr == nil {
		gateRefuse(w, http.StatusForbidden)
		return
	}
	app, closed, found := s.stackMgr.SetupGateHost(host)
	if !found {
		// A host no app claims: fail closed. traefik only asks for hosts a gate file names.
		s.logger.Printf("[WARN] [web] setup gate: asked about %q, which no gated app owns — refused", host)
		gateRefuse(w, http.StatusForbidden)
		return
	}
	if !closed {
		// Opened; traefik has not dropped the file yet (it is removed right after the record is written).
		w.WriteHeader(http.StatusOK)
		return
	}
	if u, err := url.Parse(uri); err == nil && u.Path == gateCallbackURI {
		rd, err := s.takeGateToken(u.Query().Get("t"), host)
		if err != nil {
			s.logger.Printf("[WARN] [web] setup gate %s: a sign-in token was refused (%v) — visitor %s", app, err, clientIP(r))
			gateRefuse(w, http.StatusForbidden)
			return
		}
		exp := strconv.FormatInt(s.gateNow().Add(gateCookieLife).Unix(), 10)
		http.SetCookie(w, &http.Cookie{
			Name: gateCookieName, Value: exp + "." + s.gateMAC("cookie", host, exp), Path: "/",
			MaxAge: int(gateCookieLife.Seconds()), HttpOnly: true, Secure: true, SameSite: http.SameSiteLaxMode,
		})
		s.logger.Printf("[INFO] [web] setup gate %s: the household passed (a dashboard session vouched for this browser) — visitor %s", app, clientIP(r))
		w.Header().Set("Cache-Control", "no-store")
		http.Redirect(w, r, rd, http.StatusFound)
		return
	}
	if s.gateCookieValid(r, host) {
		w.WriteHeader(http.StatusOK)
		return
	}
	if (method == "" || method == http.MethodGet) && strings.Contains(r.Header.Get("Accept"), "text/html") {
		rd := "https://" + host + uri
		w.Header().Set("Cache-Control", "no-store")
		http.Redirect(w, r, "https://felhom."+s.cfg.Customer.Domain+gateStartPath+"?"+url.Values{"rd": {rd}}.Encode(), http.StatusFound)
		return
	}
	if s.isDebug() {
		s.logger.Printf("[DEBUG] [web] setup gate %s: %s %s without a pass — 401 (visitor %s)", app, method, uri, clientIP(r))
	}
	gateRefuse(w, http.StatusUnauthorized)
}

// ServeGateStart is /__gate/start on the dashboard host.
func (s *Server) ServeGateStart(w http.ResponseWriter, r *http.Request) {
	rd := r.URL.Query().Get("rd")
	host, ok := s.gateRDHost(rd)
	if !ok {
		http.Redirect(w, r, "/", http.StatusFound)
		return
	}
	w.Header().Set("Cache-Control", "no-store")
	if s.hasSession(r) {
		http.Redirect(w, r, "https://"+host+gateCallbackURI+"?"+url.Values{"t": {s.mintGateToken(host, rd)}}.Encode(), http.StatusFound)
		return
	}
	next := gateStartPath + "?" + url.Values{"rd": {rd}}.Encode()
	data := map[string]interface{}{
		"LoginURL": "/login?" + url.Values{"next": {next}}.Encode(),
		"Host":     host,
	}
	if app, _, found := s.stackMgr.SetupGateHost(host); found {
		if st, ok := s.stackMgr.GetStack(app); ok {
			data["AppName"] = st.Meta.DisplayName
		}
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := s.executeTemplateLang(w, r, "setupgate", data); err != nil {
		s.logger.Printf("[ERROR] [web] setup gate page: %v", err)
		http.Error(w, "Internal error", http.StatusInternalServerError)
	}
}

// appSetupGateOpenHandler is the household's "Done, I set it up" (POST /apps/<slug>/setup-gate/open).
func (s *Server) appSetupGateOpenHandler(w http.ResponseWriter, r *http.Request, slug string) {
	found := s.stackBySlug(slug)
	if found == nil {
		escrowJSON(w, http.StatusNotFound, nil, s.msg(r, "escrow.unknown_app"))
		return
	}
	// v0.281.0: an app that can say whether its setup is done is ASKED first — the press never opens an app that
	// still says "not done" (measured 2026-09-29: uptime-kuma pressed before its setup answered anyone). An
	// unreadable status refuses too (fail closed). Without a probe the page's confirm says what the press does.
	if has, done, got, perr := s.stackMgr.SetupGateProbe(found.Name); has && (perr != nil || !done) {
		s.logger.Printf("[INFO] [web] setup gate %s: the household's press refused — the app's own status says not done (value %q, err %v)", found.Name, got, perr)
		escrowJSON(w, http.StatusConflict, nil, s.msg(r, "err.setup_gate.probe_not_done"))
		return
	}
	if err := s.stackMgr.OpenSetupGate(found.Name, stacks.SetupGateByHousehold); err != nil {
		if errors.Is(err, stacks.ErrSetupGateNotClosed) {
			escrowJSON(w, http.StatusConflict, nil, s.msg(r, "err.setup_gate.not_closed"))
			return
		}
		s.logger.Printf("[ERROR] [web] setup gate %s: the household's open failed: %v", found.Name, err)
		escrowJSON(w, http.StatusInternalServerError, nil, s.msg(r, "err.setup_gate.open_failed"))
		return
	}
	escrowJSON(w, http.StatusOK, map[string]any{"opened": true}, "")
}

// appDefaultLoginChangedHandler is the household's "I changed it" under a known default login
// (POST /apps/<slug>/default-login/changed, R-710).
func (s *Server) appDefaultLoginChangedHandler(w http.ResponseWriter, r *http.Request, slug string) {
	found := s.stackBySlug(slug)
	if found == nil || !found.Deployed {
		escrowJSON(w, http.StatusNotFound, nil, s.msg(r, "escrow.unknown_app"))
		return
	}
	if err := s.stackMgr.MarkDefaultLoginChanged(found.Name, "household"); err != nil {
		s.logger.Printf("[ERROR] [web] default login %s: %v", found.Name, err)
		escrowJSON(w, http.StatusInternalServerError, nil, s.msg(r, "err.setup_gate.open_failed"))
		return
	}
	escrowJSON(w, http.StatusOK, map[string]any{"recorded": true}, "")
}

// stackBySlug resolves a page slug exactly as appDetailHandler does.
func (s *Server) stackBySlug(slug string) *stacks.Stack {
	if s.stackMgr == nil {
		return nil
	}
	for _, st := range s.stackMgr.GetStacks() {
		if st.Meta.Slug == slug {
			st := st
			return &st
		}
	}
	return nil
}

// appSignupWindowHandler is the household's "open sign-up for 15 minutes" (POST /apps/<slug>/signup-window, decision 47).
func (s *Server) appSignupWindowHandler(w http.ResponseWriter, r *http.Request, slug string) {
	found := s.stackBySlug(slug)
	if found == nil {
		escrowJSON(w, http.StatusNotFound, nil, s.msg(r, "escrow.unknown_app"))
		return
	}
	until, err := s.stackMgr.OpenSignupWindow(found.Name)
	if err != nil {
		if errors.Is(err, stacks.ErrNoSignupBlock) {
			escrowJSON(w, http.StatusConflict, nil, s.msg(r, "err.setup_gate.no_signup_block"))
			return
		}
		s.logger.Printf("[ERROR] [web] signup window %s: %v", found.Name, err)
		escrowJSON(w, http.StatusInternalServerError, nil, s.msg(r, "err.setup_gate.open_failed"))
		return
	}
	escrowJSON(w, http.StatusOK, map[string]any{"open_until": until}, "")
}

// ServeSignupClosed answers the app's own sign-up address while it is closed (the sign-up block's replacePath
// sends it here). A browser gets a page, anything else a 403 JSON. It holds no secret and changes nothing.
func (s *Server) ServeSignupClosed(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Cache-Control", "no-store")
	if !strings.Contains(r.Header.Get("Accept"), "text/html") || r.Method != http.MethodGet {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusForbidden)
		_, _ = w.Write([]byte(`{"error":"sign-up is closed on this app; its admin adds new accounts"}`))
		return
	}
	host := strings.ToLower(r.Host)
	if i := strings.LastIndex(host, ":"); i != -1 {
		host = host[:i]
	}
	data := map[string]interface{}{"Host": host}
	if s.stackMgr != nil {
		if app, _, found := s.stackMgr.SetupGateHost(host); found {
			if st, ok := s.stackMgr.GetStack(app); ok {
				data["AppName"] = st.Meta.DisplayName
			}
		}
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.WriteHeader(http.StatusForbidden)
	if err := s.executeTemplateLang(w, r, "signupclosed", data); err != nil {
		s.logger.Printf("[ERROR] [web] signup-closed page: %v", err)
	}
}

// appCloseSignupHandler is decision 49's "close sign-up now" (POST /apps/<slug>/close-signup) for an app installed
// before decision 47. It applies exactly what a fresh install gets after its setup; it never gates the app.
func (s *Server) appCloseSignupHandler(w http.ResponseWriter, r *http.Request, slug string) {
	found := s.stackBySlug(slug)
	if found == nil {
		escrowJSON(w, http.StatusNotFound, nil, s.msg(r, "escrow.unknown_app"))
		return
	}
	if err := s.stackMgr.CloseSignupNow(found.Name); err != nil {
		if errors.Is(err, stacks.ErrCloseSignupNotOffered) {
			escrowJSON(w, http.StatusConflict, nil, s.msg(r, "err.setup_gate.close_signup_not_offered"))
			return
		}
		s.logger.Printf("[ERROR] [web] close sign-up %s: %v", found.Name, err)
		escrowJSON(w, http.StatusInternalServerError, nil, s.msg(r, "err.setup_gate.open_failed"))
		return
	}
	escrowJSON(w, http.StatusOK, map[string]any{"closed": true}, "")
}