// Command subscription-admin is the standalone read-only subscription business plugin.
// It deliberately uses net/http and the Core public HTTP contract; it does not import
// Core internal packages or the .s2plugin transport ABI.
package main

import (
	"context"
	"crypto/rand"
	"embed"
	"encoding/hex"
	"encoding/json"
	"errors"
	"html"
	"io"
	"log/slog"
	"net"
	"net/http"
	"net/url"
	"os"
	"path"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"
)

const (
	sessionCookieName = "subscription_admin_session"
	maxBodyBytes      = 1 << 20
	coreRequestLimit  = 4 << 20
	sessionTTL        = 30 * time.Minute
	sessionMaxTTL     = 8 * time.Hour
	pendingTTL        = 5 * time.Minute
	pluginID          = "qiu.subscription-admin"
	pluginVersion     = "0.1.1"
	requestIDHeader   = "X-Request-ID"
	maxRequestIDBytes = 64
)

var requestIDPattern = regexp.MustCompile(`^[A-Za-z0-9._:-]+$`)

//go:embed ui/*
var uiFS embed.FS

type coreClient struct {
	base string
	http *http.Client
}

func newCoreClient(base string) (*coreClient, error) {
	base = strings.TrimRight(strings.TrimSpace(base), "/")
	u, err := url.Parse(base)
	if err != nil || u.Host == "" || (u.Scheme != "http" && u.Scheme != "https") || u.User != nil || u.RawQuery != "" || u.Fragment != "" || (u.Path != "" && u.Path != "/") {
		return nil, errors.New("CORE_BASE_URL must be an absolute origin URL without credentials, path, query, or fragment")
	}
	if u.Scheme == "http" && !isLoopbackHost(u.Hostname()) {
		return nil, errors.New("CORE_BASE_URL must use HTTPS unless Core is on loopback")
	}
	transport := http.DefaultTransport.(*http.Transport).Clone()
	transport.Proxy = nil
	return &coreClient{
		base: base,
		http: &http.Client{
			Timeout:   10 * time.Second,
			Transport: transport,
			// Core API calls must never follow a redirect to an untrusted host.
			CheckRedirect: func(_ *http.Request, _ []*http.Request) error { return http.ErrUseLastResponse },
		},
	}, nil
}

func isLoopbackHost(host string) bool {
	if strings.EqualFold(strings.TrimSuffix(host, "."), "localhost") {
		return true
	}
	ip := net.ParseIP(host)
	return ip != nil && ip.IsLoopback()
}

type coreEnvelope struct {
	Code    int             `json:"code"`
	Message string          `json:"message"`
	Data    json.RawMessage `json:"data"`
	status  int
}

type coreError struct {
	status int
}

func (e *coreError) Error() string {
	return "core request failed"
}

// call is the only Core HTTP boundary. Paths are selected by typed methods below,
// never from a browser-supplied URL.
func (c *coreClient) call(ctx context.Context, method, requestPath string, body any, accessToken, correlationID, clientIP string) (coreEnvelope, error) {
	var reader io.Reader
	if body != nil {
		payload, err := json.Marshal(body)
		if err != nil {
			return coreEnvelope{}, err
		}
		reader = strings.NewReader(string(payload))
	}
	req, err := http.NewRequestWithContext(ctx, method, c.base+requestPath, reader)
	if err != nil {
		return coreEnvelope{}, err
	}
	req.Header.Set("Accept", "application/json")
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	if accessToken != "" {
		req.Header.Set("Authorization", "Bearer "+accessToken)
	}
	req.Header.Set(requestIDHeader, normalizeRequestID(correlationID))
	if clientIP != "" {
		req.Header.Set("X-Forwarded-For", clientIP)
		req.Header.Set("X-Real-IP", clientIP)
	}
	res, err := c.http.Do(req)
	if err != nil {
		return coreEnvelope{}, err
	}
	defer res.Body.Close()
	var envelope coreEnvelope
	if err := json.NewDecoder(io.LimitReader(res.Body, coreRequestLimit)).Decode(&envelope); err != nil {
		return coreEnvelope{}, err
	}
	envelope.status = res.StatusCode
	if res.StatusCode >= http.StatusMultipleChoices {
		return envelope, &coreError{status: res.StatusCode}
	}
	if envelope.Code != 0 {
		status := envelope.Code
		if status < http.StatusBadRequest || status >= 600 {
			status = http.StatusBadGateway
		}
		return envelope, &coreError{status: status}
	}
	return envelope, nil
}

type loginRequest struct {
	Email                 string `json:"email"`
	Password              string `json:"password"`
	TurnstileToken        string `json:"turnstile_token,omitempty"`
	TencentCaptchaTicket  string `json:"tencent_captcha_ticket,omitempty"`
	TencentCaptchaRandstr string `json:"tencent_captcha_randstr,omitempty"`
}

func (c *coreClient) login(ctx context.Context, in loginRequest, correlationID, clientIP string) (coreEnvelope, error) {
	return c.call(ctx, http.MethodPost, "/api/v1/auth/login", in, "", correlationID, clientIP)
}

func (c *coreClient) login2FA(ctx context.Context, tempToken, code, correlationID, clientIP string) (coreEnvelope, error) {
	return c.call(ctx, http.MethodPost, "/api/v1/auth/login/2fa", map[string]string{"temp_token": tempToken, "totp_code": code}, "", correlationID, clientIP)
}

func (c *coreClient) refresh(ctx context.Context, refreshToken, correlationID string) (coreEnvelope, error) {
	return c.call(ctx, http.MethodPost, "/api/v1/auth/refresh", map[string]string{"refresh_token": refreshToken}, "", correlationID, "")
}

func (c *coreClient) logout(ctx context.Context, refreshToken, correlationID string) {
	if c == nil || refreshToken == "" {
		return
	}
	_, _ = c.call(ctx, http.MethodPost, "/api/v1/auth/logout", map[string]string{"refresh_token": refreshToken}, "", correlationID, "")
}

func (c *coreClient) me(ctx context.Context, accessToken, correlationID string) (coreEnvelope, error) {
	return c.call(ctx, http.MethodGet, "/api/v1/auth/me", nil, accessToken, correlationID, "")
}

func (c *coreClient) publicSettings(ctx context.Context, correlationID string) (coreEnvelope, error) {
	return c.call(ctx, http.MethodGet, "/api/v1/settings/public", nil, "", correlationID, "")
}

func (c *coreClient) read(ctx context.Context, requestPath, accessToken string, correlationIDs ...string) (coreEnvelope, error) {
	correlationID := ""
	if len(correlationIDs) > 0 {
		correlationID = correlationIDs[0]
	}
	u, err := url.Parse(requestPath)
	if err != nil || u.Host != "" || u.Scheme != "" || !allowedReadPath(u.Path) {
		return coreEnvelope{}, errors.New("core path is not in the allowlist")
	}
	return c.call(ctx, http.MethodGet, u.EscapedPath()+queryString(sanitizeQuery(u.Query())), nil, accessToken, correlationID, "")
}

func queryString(values url.Values) string {
	if encoded := values.Encode(); encoded != "" {
		return "?" + encoded
	}
	return ""
}

func allowedReadPath(path string) bool {
	parsed, err := url.Parse(path)
	if err != nil || parsed.Host != "" || parsed.Scheme != "" || parsed.Fragment != "" {
		return false
	}
	path = parsed.Path
	if path == "/api/v1/admin/payment/plans" || path == "/api/v1/admin/subscriptions" {
		return true
	}
	if strings.HasPrefix(path, "/api/v1/admin/subscriptions/") {
		return positiveID(strings.TrimPrefix(path, "/api/v1/admin/subscriptions/"))
	}
	if strings.HasPrefix(path, "/api/v1/admin/users/") {
		rest := strings.TrimPrefix(path, "/api/v1/admin/users/")
		if positiveID(rest) {
			return true
		}
		parts := strings.Split(rest, "/")
		return len(parts) == 2 && positiveID(parts[0]) && parts[1] == "subscriptions"
	}
	return false
}

func allowedQuery(r *http.Request) string {
	if r == nil {
		return ""
	}
	return queryString(sanitizeQuery(r.URL.Query()))
}

func validQuery(query url.Values) bool {
	for _, key := range []string{"page", "page_size", "limit", "user_id", "group_id"} {
		for _, raw := range query[key] {
			value := strings.TrimSpace(raw)
			if value == "" {
				continue
			}
			n, err := strconv.ParseUint(value, 10, 63)
			if err != nil || n == 0 || ((key == "page_size" || key == "limit") && n > 100) {
				return false
			}
		}
	}
	return true
}

func sanitizeQuery(query url.Values) url.Values {
	allowed := []string{"page", "page_size", "limit", "user_id", "group_id", "status", "platform", "sort_by", "sort_order"}
	values := url.Values{}
	for _, key := range allowed {
		for _, value := range query[key] {
			value = strings.TrimSpace(value)
			if value == "" || len(value) > 100 {
				continue
			}
			if key == "page" || key == "page_size" || key == "limit" || key == "user_id" || key == "group_id" {
				if _, err := strconv.ParseUint(value, 10, 63); err != nil {
					continue
				}
			}
			values.Add(key, value)
		}
	}
	return values
}

func positiveID(value string) bool {
	n, err := strconv.ParseInt(value, 10, 64)
	return err == nil && n > 0
}

type session struct {
	accessToken  string
	refreshToken string
	csrfToken    string
	user         map[string]any
	createdAt    time.Time
	lastSeen     time.Time
}

type pendingLogin struct {
	tempToken string
	expires   time.Time
	clientIP  string
}

type auditEvent struct {
	Time       time.Time `json:"time"`
	PluginID   string    `json:"plugin_id"`
	Action     string    `json:"action"`
	Result     string    `json:"result"`
	UserID     any       `json:"user_id,omitempty"`
	ResourceID string    `json:"resource_id,omitempty"`
	Request    string    `json:"request_id"`
}

type app struct {
	core           *coreClient
	sessions       map[string]session
	sessionLocks   map[string]*sync.Mutex
	pending        map[string]pendingLogin
	audit          []auditEvent
	mu             sync.Mutex
	cookieSecure   bool
	cookieSameSite http.SameSite
	cookiePath     string
	publicBasePath string
	frameAncestors []string
	trustProxy     bool
	loginWindow    time.Duration
	loginLimit     int
	loginAttempts  map[string]loginAttempt
	clock          func() time.Time
}

type loginAttempt struct {
	started time.Time
	count   int
}

func newApp(core *coreClient, secure bool) *app {
	return newAppWithConfig(core, appConfig{CookieSecure: secure, CookieSameSite: http.SameSiteLaxMode, CookiePath: "/", PublicBasePath: "", FrameAncestors: []string{"'self'"}})
}

type appConfig struct {
	CookieSecure   bool
	CookieSameSite http.SameSite
	CookiePath     string
	PublicBasePath string
	FrameAncestors []string
	TrustProxy     bool
	LoginWindow    time.Duration
	LoginLimit     int
}

func newAppWithConfig(core *coreClient, cfg appConfig) *app {
	if cfg.CookieSameSite == 0 {
		cfg.CookieSameSite = http.SameSiteLaxMode
	}
	cfg.CookiePath = normalizeCookiePath(cfg.CookiePath)
	cfg.PublicBasePath = normalizeBasePath(cfg.PublicBasePath)
	if len(cfg.FrameAncestors) == 0 {
		cfg.FrameAncestors = []string{"'self'"}
	}
	if cfg.LoginWindow <= 0 {
		cfg.LoginWindow = time.Minute
	}
	if cfg.LoginLimit <= 0 {
		cfg.LoginLimit = 10
	}
	return &app{
		core:           core,
		sessions:       make(map[string]session),
		sessionLocks:   make(map[string]*sync.Mutex),
		pending:        make(map[string]pendingLogin),
		audit:          make([]auditEvent, 0, 200),
		cookieSecure:   cfg.CookieSecure,
		cookieSameSite: cfg.CookieSameSite,
		cookiePath:     cfg.CookiePath,
		publicBasePath: cfg.PublicBasePath,
		frameAncestors: append([]string(nil), cfg.FrameAncestors...),
		trustProxy:     cfg.TrustProxy,
		loginWindow:    cfg.LoginWindow,
		loginLimit:     cfg.LoginLimit,
		loginAttempts:  make(map[string]loginAttempt),
		clock:          time.Now,
	}
}

func normalizeCookiePath(value string) string {
	value = strings.TrimSpace(value)
	if value == "" || value == "/" {
		return "/"
	}
	clean := path.Clean("/" + strings.Trim(value, "/"))
	return clean + "/"
}

func normalizeBasePath(value string) string {
	value = strings.TrimSpace(value)
	if value == "" || value == "/" {
		return ""
	}
	clean := path.Clean("/" + strings.Trim(value, "/"))
	return clean
}

func (a *app) basePath() string {
	return a.publicBasePath
}

func (a *app) addAudit(ctx context.Context, action, result string, userID any, resourceID string) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.audit = append(a.audit, auditEvent{Time: a.clock(), PluginID: pluginID, Action: action, Result: result, UserID: userID, ResourceID: resourceID, Request: requestIDFromContext(ctx)})
	if len(a.audit) > 200 {
		a.audit = a.audit[len(a.audit)-200:]
	}
}

func requestID() string { return token(16) }

type requestIDContextKey struct{}

func normalizeRequestID(value string) string {
	value = strings.TrimSpace(value)
	if value == "" || len(value) > maxRequestIDBytes || !requestIDPattern.MatchString(value) {
		return requestID()
	}
	return value
}

func requestIDFromContext(ctx context.Context) string {
	if ctx != nil {
		if value, ok := ctx.Value(requestIDContextKey{}).(string); ok && value != "" {
			return value
		}
	}
	return requestID()
}

func requestIDMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		correlationID := normalizeRequestID(r.Header.Get(requestIDHeader))
		w.Header().Set(requestIDHeader, correlationID)
		ctx := context.WithValue(r.Context(), requestIDContextKey{}, correlationID)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func token(n int) string {
	b := make([]byte, n)
	if _, err := rand.Read(b); err != nil {
		panic(err)
	}
	return hex.EncodeToString(b)
}

func decodeJSON(r *http.Request, out any) error {
	defer r.Body.Close()
	dec := json.NewDecoder(io.LimitReader(r.Body, maxBodyBytes))
	dec.DisallowUnknownFields()
	return dec.Decode(out)
}

func (a *app) writeJSON(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func (a *app) sessionFromRequest(r *http.Request) (string, session, bool) {
	cookie, err := r.Cookie(sessionCookieName)
	if err != nil || cookie.Value == "" {
		return "", session{}, false
	}
	a.mu.Lock()
	defer a.mu.Unlock()
	s, ok := a.sessions[cookie.Value]
	if !ok {
		return "", session{}, false
	}
	now := a.clock()
	if now.Sub(s.createdAt) > sessionMaxTTL || now.Sub(s.lastSeen) > sessionTTL {
		delete(a.sessions, cookie.Value)
		delete(a.sessionLocks, cookie.Value)
		return "", session{}, false
	}
	s.lastSeen = now
	a.sessions[cookie.Value] = s
	return cookie.Value, s, true
}

func (a *app) setSessionCookie(w http.ResponseWriter, id string, maxAge int) {
	http.SetCookie(w, &http.Cookie{Name: sessionCookieName, Value: id, Path: a.cookiePath, HttpOnly: true, Secure: a.cookieSecure, SameSite: a.cookieSameSite, MaxAge: maxAge})
}

func (a *app) allowLoginAttempt(r *http.Request, identity string) bool {
	key := trustedClientIPWithConfig(r, a.trustProxy) + "|" + strings.ToLower(strings.TrimSpace(identity))
	now := a.clock()
	a.mu.Lock()
	defer a.mu.Unlock()
	attempt := a.loginAttempts[key]
	if attempt.started.IsZero() || now.Sub(attempt.started) >= a.loginWindow {
		attempt = loginAttempt{started: now}
	}
	if attempt.count >= a.loginLimit {
		a.loginAttempts[key] = attempt
		return false
	}
	attempt.count++
	a.loginAttempts[key] = attempt
	return true
}

func (a *app) clientIP(r *http.Request) string {
	return trustedClientIPWithConfig(r, a.trustProxy)
}

func (a *app) login(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	var in loginRequest
	if err := decodeJSON(r, &in); err != nil || strings.TrimSpace(in.Email) == "" || in.Password == "" {
		a.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid credentials"})
		return
	}
	in.Email = strings.TrimSpace(in.Email)
	if !a.allowLoginAttempt(r, in.Email) {
		w.Header().Set("Retry-After", "60")
		a.writeJSON(w, http.StatusTooManyRequests, map[string]string{"error": "too many login attempts"})
		return
	}
	out, err := a.core.login(r.Context(), in, requestIDFromContext(r.Context()), a.clientIP(r))
	if err != nil {
		a.addAudit(r.Context(), "login", "core_unavailable", nil, "")
		a.coreError(w, err, "core login failed")
		return
	}
	data := envelopeData(out)
	if requires, _ := data["requires_2fa"].(bool); requires {
		temp, _ := data["temp_token"].(string)
		if temp == "" {
			a.writeJSON(w, http.StatusBadGateway, map[string]string{"error": "core 2fa challenge missing"})
			return
		}
		pendingID := token(24)
		a.mu.Lock()
		a.pending[pendingID] = pendingLogin{tempToken: temp, expires: a.clock().Add(pendingTTL), clientIP: a.clientIP(r)}
		a.mu.Unlock()
		a.writeJSON(w, http.StatusOK, map[string]any{"requires_2fa": true, "pending_token": pendingID})
		return
	}
	a.finishLogin(w, r, data)
}

func (a *app) login2FA(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	var in struct {
		PendingToken string `json:"pending_token"`
		TotpCode     string `json:"totp_code"`
	}
	if err := decodeJSON(r, &in); err != nil || in.PendingToken == "" || len(in.TotpCode) != 6 {
		a.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid 2fa request"})
		return
	}
	if !a.allowLoginAttempt(r, in.PendingToken) {
		w.Header().Set("Retry-After", "60")
		a.writeJSON(w, http.StatusTooManyRequests, map[string]string{"error": "too many login attempts"})
		return
	}
	a.mu.Lock()
	pending, ok := a.pending[in.PendingToken]
	delete(a.pending, in.PendingToken)
	a.mu.Unlock()
	if !ok || a.clock().After(pending.expires) || (pending.clientIP != "" && pending.clientIP != a.clientIP(r)) {
		a.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "2fa session expired"})
		return
	}
	out, err := a.core.login2FA(r.Context(), pending.tempToken, in.TotpCode, requestIDFromContext(r.Context()), a.clientIP(r))
	if err != nil {
		a.coreError(w, err, "2fa verification failed")
		return
	}
	a.finishLogin(w, r, envelopeData(out))
}

func (a *app) finishLogin(w http.ResponseWriter, r *http.Request, data map[string]any) {
	access, _ := data["access_token"].(string)
	refresh, _ := data["refresh_token"].(string)
	if access == "" {
		a.writeJSON(w, http.StatusBadGateway, map[string]string{"error": "core token missing"})
		return
	}
	correlationID := requestIDFromContext(r.Context())
	me, err := a.core.me(r.Context(), access, correlationID)
	if err != nil {
		a.core.logout(r.Context(), refresh, correlationID)
		a.addAudit(r.Context(), "login", "admin_verification_failed", nil, "")
		a.writeJSON(w, http.StatusForbidden, map[string]string{"error": "admin verification failed"})
		return
	}
	user := envelopeData(me)
	if !isAdmin(user) {
		a.core.logout(r.Context(), refresh, correlationID)
		a.addAudit(r.Context(), "login", "forbidden", user["id"], "")
		a.writeJSON(w, http.StatusForbidden, map[string]string{"error": "admin role required"})
		return
	}
	now := a.clock()
	s := session{accessToken: access, refreshToken: refresh, csrfToken: token(24), user: publicUser(user), createdAt: now, lastSeen: now}
	id := token(32)
	a.mu.Lock()
	a.sessions[id] = s
	a.sessionLocks[id] = &sync.Mutex{}
	a.mu.Unlock()
	a.addAudit(r.Context(), "login", "success", user["id"], "")
	a.setSessionCookie(w, id, int(sessionMaxTTL/time.Second))
	// The response intentionally contains only the plugin CSRF token and sanitized user.
	a.writeJSON(w, http.StatusOK, map[string]any{"ok": true, "csrf_token": s.csrfToken, "user": s.user})
}

func (a *app) logout(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	if id, s, ok := a.sessionFromRequest(r); ok {
		if r.Header.Get("X-CSRF-Token") != s.csrfToken {
			a.addAudit(r.Context(), "logout", "csrf_failed", s.user["id"], "")
			a.writeJSON(w, http.StatusForbidden, map[string]string{"error": "csrf validation failed"})
			return
		}
		a.removeSessionByID(id)
		a.core.logout(r.Context(), s.refreshToken, requestIDFromContext(r.Context()))
		a.addAudit(r.Context(), "logout", "success", s.user["id"], "")
	}
	a.setSessionCookie(w, "", -1)
	a.writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
}

func (a *app) authenticate(w http.ResponseWriter, r *http.Request) (string, session, bool, bool) {
	id, s, ok := a.sessionFromRequest(r)
	if !ok {
		a.setSessionCookie(w, "", -1)
		a.writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "authentication required"})
		return "", session{}, false, false
	}
	if a.core == nil {
		a.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "core unavailable"})
		return "", session{}, false, false
	}
	if r.Method != http.MethodGet && r.Header.Get("X-CSRF-Token") != s.csrfToken {
		a.writeJSON(w, http.StatusForbidden, map[string]string{"error": "csrf validation failed"})
		return "", session{}, false, false
	}
	correlationID := requestIDFromContext(r.Context())
	me, err := a.core.me(r.Context(), s.accessToken, correlationID)
	if err != nil {
		if ce, ok := err.(*coreError); ok && ce.status == http.StatusUnauthorized && s.refreshToken != "" {
			if refreshedSession, refreshOK := a.refreshSession(r.Context(), id, s); refreshOK {
				return id, refreshedSession, true, true
			}
		}
		a.removeSessionIfCurrent(id, s.accessToken)
		a.core.logout(r.Context(), s.refreshToken, correlationID)
		a.setSessionCookie(w, "", -1)
		if ce, ok := err.(*coreError); ok && ce.status == http.StatusUnauthorized {
			a.writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "core session expired"})
		} else {
			a.coreError(w, err, "core session unavailable")
		}
		return "", session{}, false, false
	}
	if !isAdmin(envelopeData(me)) {
		a.removeSessionByID(id)
		a.core.logout(r.Context(), s.refreshToken, correlationID)
		a.setSessionCookie(w, "", -1)
		a.writeJSON(w, http.StatusForbidden, map[string]string{"error": "admin role required"})
		return "", session{}, false, false
	}
	return id, s, false, true
}

func (a *app) me(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	_, s, _, ok := a.authenticate(w, r)
	if ok {
		a.writeJSON(w, http.StatusOK, map[string]any{"user": s.user, "csrf_token": s.csrfToken, "plugin_id": pluginID, "plugin_version": pluginVersion})
	}
}

func (a *app) status(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	_, s, _, ok := a.authenticate(w, r)
	if !ok {
		return
	}
	a.writeJSON(w, http.StatusOK, map[string]any{
		"plugin_id":            pluginID,
		"plugin_version":       pluginVersion,
		"mode":                 "read_only",
		"core_base_configured": a.core != nil,
		"session_mode":         "memory",
		"credential_state":     "server_managed",
		"operator":             s.user,
	})
}

func (a *app) captchaConfig(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	if a.core == nil {
		a.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "core unavailable"})
		return
	}
	out, err := a.core.publicSettings(r.Context(), requestIDFromContext(r.Context()))
	if err != nil {
		a.coreError(w, err, "core settings unavailable")
		return
	}
	data := envelopeData(out)
	provider := ""
	if enabled, _ := data["geetest_captcha_enabled"].(bool); enabled {
		provider = "geetest"
	} else if enabled, _ := data["turnstile_enabled"].(bool); enabled {
		provider = "turnstile"
	} else if enabled, _ := data["tencent_captcha_enabled"].(bool); enabled {
		provider = "tencent"
	} else if enabled, _ := data["aliyun_captcha_enabled"].(bool); enabled {
		provider = "aliyun"
	}
	a.writeJSON(w, http.StatusOK, map[string]any{
		"enabled":                 provider != "",
		"provider":                provider,
		"geetest_captcha_id":      data["geetest_captcha_id"],
		"turnstile_site_key":      data["turnstile_site_key"],
		"tencent_captcha_app_id":  data["tencent_captcha_app_id"],
		"tencent_captcha_region":  data["tencent_captcha_region"],
		"aliyun_captcha_scene_id": data["aliyun_captcha_scene_id"],
		"aliyun_captcha_prefix":   data["aliyun_captcha_prefix"],
	})
}

func (a *app) userProxy(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	id := strings.TrimPrefix(r.URL.Path, "/api/users/")
	if !positiveID(id) || strings.Contains(id, "/") {
		http.NotFound(w, r)
		return
	}
	sessionID, s, refreshed, ok := a.authenticate(w, r)
	if !ok {
		return
	}
	correlationID := requestIDFromContext(r.Context())
	corePath := "/api/v1/admin/users/" + id
	out, err := a.core.read(r.Context(), corePath, s.accessToken, correlationID)
	if err != nil {
		if ce, unauthorized := err.(*coreError); unauthorized && ce.status == http.StatusUnauthorized && !refreshed && s.refreshToken != "" {
			if next, refreshOK := a.refreshSession(r.Context(), sessionID, s); refreshOK {
				s = next
				out, err = a.core.read(r.Context(), corePath, next.accessToken, correlationID)
			}
		}
		if err != nil {
			a.coreError(w, err, "user lookup failed")
			return
		}
	}
	a.addAudit(r.Context(), "read:/api/v1/admin/users/{id}", "success", s.user["id"], id)
	a.writeCoreEnvelope(w, out)
}

func (a *app) readProxy(path string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
			return
		}
		if !validQuery(r.URL.Query()) {
			a.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid query parameters"})
			return
		}
		id, s, refreshed, ok := a.authenticate(w, r)
		if !ok {
			return
		}
		corePath := path + allowedQuery(r)
		correlationID := requestIDFromContext(r.Context())
		out, err := a.core.read(r.Context(), corePath, s.accessToken, correlationID)
		if err != nil {
			if ce, unauthorized := err.(*coreError); unauthorized && ce.status == http.StatusUnauthorized && !refreshed && s.refreshToken != "" {
				if refreshedSession, refreshOK := a.refreshSession(r.Context(), id, s); refreshOK {
					s = refreshedSession
					out, err = a.core.read(r.Context(), corePath, s.accessToken, correlationID)
				}
			}
			if err != nil {
				if ce, ok := err.(*coreError); ok && ce.status == http.StatusUnauthorized {
					a.removeSessionIfCurrent(id, s.accessToken)
					a.setSessionCookie(w, "", -1)
					a.writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "core session expired"})
					return
				}
				a.coreError(w, err, "core request failed")
				return
			}
		}
		a.addAudit(r.Context(), "read:"+path, "success", s.user["id"], resourceIDFromPath(path))
		a.writeCoreEnvelope(w, out)
	}
}

func (a *app) updateSession(r *http.Request, updated session) {
	cookie, err := r.Cookie(sessionCookieName)
	if err != nil {
		return
	}
	a.mu.Lock()
	if current, ok := a.sessions[cookie.Value]; ok && current.accessToken != updated.accessToken {
		// A concurrent request may have refreshed the session already. Preserve
		// the newer token pair while still extending its activity timestamp.
		current.lastSeen = updated.lastSeen
		a.sessions[cookie.Value] = current
	} else {
		a.sessions[cookie.Value] = updated
	}
	a.mu.Unlock()
}

func (a *app) refreshSession(ctx context.Context, id string, stale session) (session, bool) {
	a.mu.Lock()
	lock := a.sessionLocks[id]
	a.mu.Unlock()
	if lock == nil {
		return session{}, false
	}
	lock.Lock()
	defer lock.Unlock()

	a.mu.Lock()
	current, ok := a.sessions[id]
	a.mu.Unlock()
	if !ok {
		return session{}, false
	}
	if current.accessToken != stale.accessToken {
		return current, true
	}
	if current.refreshToken == "" {
		return session{}, false
	}
	correlationID := requestIDFromContext(ctx)
	refreshed, err := a.core.refresh(ctx, current.refreshToken, correlationID)
	if err != nil {
		return session{}, false
	}
	data := envelopeData(refreshed)
	access, _ := data["access_token"].(string)
	if access == "" {
		return session{}, false
	}
	nextMe, err := a.core.me(ctx, access, correlationID)
	if err != nil || !isAdmin(envelopeData(nextMe)) {
		return session{}, false
	}
	current.accessToken = access
	if nextRefresh, ok := data["refresh_token"].(string); ok && nextRefresh != "" {
		current.refreshToken = nextRefresh
	}
	current.user = publicUser(envelopeData(nextMe))
	current.lastSeen = a.clock()
	a.mu.Lock()
	latest, exists := a.sessions[id]
	if exists && latest.accessToken == stale.accessToken {
		a.sessions[id] = current
	} else if exists {
		current = latest
	}
	a.mu.Unlock()
	return current, exists
}

func (a *app) removeSessionByID(id string) {
	a.mu.Lock()
	delete(a.sessions, id)
	delete(a.sessionLocks, id)
	a.mu.Unlock()
}

func (a *app) removeSessionIfCurrent(id, accessToken string) {
	a.mu.Lock()
	if current, ok := a.sessions[id]; ok && current.accessToken == accessToken {
		delete(a.sessions, id)
		delete(a.sessionLocks, id)
	}
	a.mu.Unlock()
}

func trustedClientIPWithConfig(r *http.Request, trustProxy bool) string {
	if r == nil {
		return ""
	}
	host, _, err := net.SplitHostPort(strings.TrimSpace(r.RemoteAddr))
	if err != nil {
		host = strings.TrimSpace(r.RemoteAddr)
	}
	peer := net.ParseIP(host)
	if trustProxy && peer != nil && peer.IsLoopback() {
		for _, candidate := range strings.Split(r.Header.Get("X-Forwarded-For"), ",") {
			candidate = strings.TrimSpace(candidate)
			if ip := net.ParseIP(candidate); ip != nil {
				return ip.String()
			}
		}
	}
	if peer != nil {
		return peer.String()
	}
	return ""
}

func resourceIDFromPath(value string) string {
	parts := strings.Split(strings.Trim(value, "/"), "/")
	for i := len(parts) - 1; i >= 0; i-- {
		if positiveID(parts[i]) {
			return parts[i]
		}
	}
	return ""
}

func (a *app) health(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	a.writeJSON(w, http.StatusOK, map[string]any{"status": "ok", "plugin_id": pluginID, "version": pluginVersion})
}

func (a *app) ready(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	a.writeJSON(w, http.StatusOK, map[string]any{"status": "ready", "plugin_id": pluginID, "version": pluginVersion})
}

func (a *app) auditLog(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		a.writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}
	_, s, _, ok := a.authenticate(w, r)
	if !ok {
		return
	}
	a.mu.Lock()
	items := append([]auditEvent(nil), a.audit...)
	a.mu.Unlock()
	a.writeJSON(w, http.StatusOK, map[string]any{"items": items, "operator": s.user})
}

func (a *app) static(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path == "/admin" {
		http.Redirect(w, r, a.basePath()+"/admin/", http.StatusPermanentRedirect)
		return
	}
	if r.URL.Path == "/" || r.URL.Path == "/admin/" {
		data, err := uiFS.ReadFile("ui/index.html")
		if err != nil {
			http.Error(w, "ui unavailable", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Cache-Control", "no-store")
		base := html.EscapeString(a.basePath())
		data = []byte(strings.ReplaceAll(string(data), "__PLUGIN_BASE_PATH__", base))
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_, _ = w.Write(data)
		return
	}
	for _, name := range []string{"ui/app.js", "ui/styles.css"} {
		if r.URL.Path == "/"+strings.TrimPrefix(name, "ui/") {
			data, err := uiFS.ReadFile(name)
			if err != nil {
				http.NotFound(w, r)
				return
			}
			if strings.HasSuffix(name, ".js") {
				w.Header().Set("Content-Type", "text/javascript; charset=utf-8")
			} else {
				w.Header().Set("Content-Type", "text/css; charset=utf-8")
			}
			_, _ = w.Write(data)
			return
		}
	}
	http.NotFound(w, r)
}

func (a *app) routes() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/healthz", a.health)
	mux.HandleFunc("/readyz", a.ready)
	mux.HandleFunc("/login", a.login)
	mux.HandleFunc("/login/2fa", a.login2FA)
	mux.HandleFunc("/logout", a.logout)
	mux.HandleFunc("/api/me", a.me)
	mux.HandleFunc("/api/status", a.status)
	mux.HandleFunc("/api/captcha-config", a.captchaConfig)
	mux.HandleFunc("/api/audit", a.auditLog)
	mux.Handle("/api/plans", a.readProxy("/api/v1/admin/payment/plans"))
	mux.Handle("/api/subscriptions", a.readProxy("/api/v1/admin/subscriptions"))
	mux.HandleFunc("/api/subscriptions/", func(w http.ResponseWriter, r *http.Request) {
		id := strings.TrimPrefix(r.URL.Path, "/api/subscriptions/")
		if !positiveID(id) || strings.Contains(id, "/") {
			http.NotFound(w, r)
			return
		}
		a.readProxy("/api/v1/admin/subscriptions/"+id)(w, r)
	})
	mux.HandleFunc("/api/users/", func(w http.ResponseWriter, r *http.Request) {
		rest := strings.TrimPrefix(r.URL.Path, "/api/users/")
		parts := strings.Split(rest, "/")
		if len(parts) == 1 {
			a.userProxy(w, r)
			return
		}
		if len(parts) != 2 || !positiveID(parts[0]) || parts[1] != "subscriptions" {
			http.NotFound(w, r)
			return
		}
		a.readProxy("/api/v1/admin/users/"+parts[0]+"/subscriptions")(w, r)
	})
	mux.HandleFunc("/", a.static)
	return requestIDMiddleware(a.securityHeaders(mux))
}

func (a *app) securityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		ancestors := strings.Join(a.frameAncestors, " ")
		if ancestors == "'self'" {
			w.Header().Set("X-Frame-Options", "SAMEORIGIN")
		}
		w.Header().Set("Referrer-Policy", "no-referrer")
		w.Header().Set("Content-Security-Policy", "default-src 'self'; script-src 'self'; style-src 'self'; connect-src 'self'; frame-ancestors "+ancestors+"; base-uri 'self'; form-action 'self'")
		next.ServeHTTP(w, r)
	})
}

func envelopeData(envelope coreEnvelope) map[string]any {
	var value map[string]any
	if len(envelope.Data) > 0 && json.Unmarshal(envelope.Data, &value) == nil && value != nil {
		return value
	}
	return map[string]any{}
}

func isAdmin(user map[string]any) bool {
	role, _ := user["role"].(string)
	return strings.EqualFold(role, "admin") || strings.EqualFold(role, "administrator")
}

func publicUser(user map[string]any) map[string]any {
	allowed := []string{"id", "email", "username", "role", "status"}
	out := make(map[string]any, len(allowed))
	for _, key := range allowed {
		if value, ok := user[key]; ok {
			out[key] = value
		}
	}
	return out
}

func (a *app) writeCoreEnvelope(w http.ResponseWriter, envelope coreEnvelope) {
	var data any
	if len(envelope.Data) > 0 {
		if json.Unmarshal(envelope.Data, &data) != nil {
			a.writeJSON(w, http.StatusBadGateway, map[string]string{"error": "invalid core response"})
			return
		}
	}
	data = sanitizeValue(data)
	status := envelope.status
	if status == 0 {
		status = http.StatusOK
	}
	a.writeJSON(w, status, map[string]any{"code": envelope.Code, "message": envelope.Message, "data": data})
}

func sanitizeValue(value any) any {
	switch typed := value.(type) {
	case []any:
		out := make([]any, 0, len(typed))
		for _, item := range typed {
			out = append(out, sanitizeValue(item))
		}
		return out
	case map[string]any:
		out := make(map[string]any, len(typed))
		for key, item := range typed {
			if sensitiveResponseKey(key) {
				continue
			}
			out[key] = sanitizeValue(item)
		}
		return out
	default:
		return value
	}
}

func sensitiveResponseKey(key string) bool {
	key = strings.ToLower(key)
	key = strings.NewReplacer("_", "", "-", "", " ", "").Replace(key)
	switch key {
	case "accesstoken", "refreshtoken", "idtoken", "token", "authorization", "apikey", "xapikey", "password", "passwordhash", "secret", "clientsecret", "privatekey", "signingkey", "cookie", "session":
		return true
	default:
		return false
	}
}

func (a *app) coreError(w http.ResponseWriter, err error, fallback string) {
	status := http.StatusBadGateway
	if ce, ok := err.(*coreError); ok && ce.status >= 400 && ce.status < 500 {
		status = ce.status
	}
	// Deliberately do not relay Core response bodies or token-bearing messages.
	a.writeJSON(w, status, map[string]string{"error": fallback})
}

func main() {
	host := os.Getenv("PLUGIN_HOST")
	if host == "" {
		host = "127.0.0.1"
	}
	port := os.Getenv("PLUGIN_PORT")
	if port == "" {
		port = "8091"
	}
	coreURL := os.Getenv("CORE_BASE_URL")
	if coreURL == "" {
		coreURL = "http://127.0.0.1:8080"
	}
	core, err := newCoreClient(coreURL)
	if err != nil {
		slog.Error("invalid Core URL", "error", err)
		os.Exit(2)
	}
	secure := strings.EqualFold(strings.TrimSpace(os.Getenv("PLUGIN_COOKIE_SECURE")), "true")
	if !isLoopbackHost(host) && !secure {
		slog.Error("PLUGIN_COOKIE_SECURE must be true when PLUGIN_HOST is not loopback")
		os.Exit(2)
	}
	sameSite, err := parseSameSite(os.Getenv("PLUGIN_COOKIE_SAMESITE"))
	if err != nil {
		slog.Error("invalid PLUGIN_COOKIE_SAMESITE", "error", err)
		os.Exit(2)
	}
	basePath := normalizeBasePath(os.Getenv("PLUGIN_PUBLIC_BASE_PATH"))
	cookiePath := strings.TrimSpace(os.Getenv("PLUGIN_COOKIE_PATH"))
	if cookiePath == "" {
		cookiePath = basePath
	}
	if sameSite == http.SameSiteNoneMode && !secure {
		slog.Error("PLUGIN_COOKIE_SAMESITE=none requires PLUGIN_COOKIE_SECURE=true")
		os.Exit(2)
	}
	ancestors := parseFrameAncestors(os.Getenv("PLUGIN_FRAME_ANCESTORS"))
	a := newAppWithConfig(core, appConfig{
		CookieSecure:   secure,
		CookieSameSite: sameSite,
		CookiePath:     cookiePath,
		PublicBasePath: basePath,
		FrameAncestors: ancestors,
		TrustProxy:     strings.EqualFold(strings.TrimSpace(os.Getenv("PLUGIN_TRUST_PROXY")), "true"),
	})
	srv := &http.Server{Addr: host + ":" + port, Handler: a.routes(), ReadHeaderTimeout: 10 * time.Second, ReadTimeout: 15 * time.Second, WriteTimeout: 20 * time.Second, IdleTimeout: 60 * time.Second}
	slog.Info("subscription-admin listening", "addr", srv.Addr)
	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		slog.Error("subscription-admin stopped", "error", err)
		os.Exit(1)
	}
}

func parseSameSite(value string) (http.SameSite, error) {
	switch strings.ToLower(strings.TrimSpace(value)) {
	case "", "lax":
		return http.SameSiteLaxMode, nil
	case "strict":
		return http.SameSiteStrictMode, nil
	case "none":
		return http.SameSiteNoneMode, nil
	default:
		return 0, errors.New("must be lax, strict, or none")
	}
}

func parseFrameAncestors(value string) []string {
	fields := strings.Fields(value)
	if len(fields) == 0 {
		return []string{"'self'"}
	}
	valid := make([]string, 0, len(fields))
	for _, field := range fields {
		if field == "'self'" || field == "'none'" {
			valid = append(valid, field)
			continue
		}
		u, err := url.Parse(field)
		if err == nil && (u.Scheme == "https" || u.Scheme == "http") && u.Host != "" && u.Path == "" && u.RawQuery == "" && u.Fragment == "" && u.User == nil {
			valid = append(valid, field)
		}
	}
	if len(valid) == 0 {
		return []string{"'self'"}
	}
	return valid
}