package cabana

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"log/slog"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"time"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"gorm.io/gorm"
)

const (
	// backendJWTBlacklistTable matches the framework migration in lagoon.
	// It is not the frontend jwt_blacklist table.
	backendJWTBlacklistTable = "backend_jwt_blacklist"

	msgInvalidCredentials = "Invalid credentials"
	msgUnauthenticated    = "Unauthenticated"
	msgForbidden          = "Forbidden"
	msgNotFound           = "Not found"
	msgServerError        = "Server error"
)

// BackendUsers loads activated backend principals. It never reads frontend users.
type BackendUsers struct {
	DB       *gorm.DB
	Registry *Registry
}

func (p BackendUsers) FindByID(ctx context.Context, id uint) (*bouncer.Principal, error) {
	if p.DB == nil || id == 0 {
		return nil, nil
	}
	var user BackendUser
	err := p.DB.WithContext(ctx).Preload("Role").First(&user, id).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	if !user.IsActivated {
		return nil, nil
	}
	principal := principalFrom(user)
	for code, allowed := range p.Registry.rolePermissions(user.Role.Code) {
		if !allowed {
			continue
		}
		if principal.PermissionGrants == nil {
			principal.PermissionGrants = map[string]bool{}
		}
		principal.PermissionGrants[code] = true
	}
	return principal, nil
}

func principalFrom(user BackendUser) *bouncer.Principal {
	principal := &bouncer.Principal{
		ID:               user.ID,
		Backend:          true,
		IsSuperuser:      user.IsSuperuser,
		PermissionGrants: parseGrants(user.Role.Permissions),
	}
	if user.TokensValidAfter != nil {
		principal.TokensValidAfter = *user.TokensValidAfter
	}
	return principal
}

func parseGrants(raw string) map[string]bool {
	raw = strings.TrimSpace(raw)
	if raw == "" || raw == "{}" || raw == "null" {
		return nil
	}
	var decoded map[string]any
	if err := json.Unmarshal([]byte(raw), &decoded); err != nil {
		return nil
	}
	out := make(map[string]bool, len(decoded))
	for code, value := range decoded {
		if truthyGrant(value) {
			out[code] = true
		}
	}
	if len(out) == 0 {
		return nil
	}
	return out
}

func truthyGrant(value any) bool {
	switch v := value.(type) {
	case bool:
		return v
	case float64:
		return v == 1
	case string:
		return v == "1" || strings.EqualFold(v, "true")
	case json.Number:
		return v.String() == "1"
	default:
		return false
	}
}

type loginBody struct {
	Login    string `json:"login"`
	Email    string `json:"email"`
	Password string `json:"password"`
}

func (s *service) login(w http.ResponseWriter, r *http.Request) {
	var body loginBody
	dec := json.NewDecoder(http.MaxBytesReader(w, r.Body, 4096))
	if err := dec.Decode(&body); err != nil {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgInvalidCredentials)
		return
	}
	identifier := strings.TrimSpace(body.Login)
	if identifier == "" {
		identifier = strings.TrimSpace(body.Email)
	}
	if identifier == "" || body.Password == "" {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgInvalidCredentials)
		return
	}
	db, err := s.db()
	if err != nil {
		WriteError(w, http.StatusInternalServerError, "error", msgServerError)
		return
	}
	user, found, err := findBackendLogin(db.WithContext(r.Context()), identifier)
	if err != nil {
		WriteError(w, http.StatusInternalServerError, "error", msgServerError)
		return
	}
	hash := s.missingUserHash()
	if found && user.Password != "" {
		hash = user.Password
	}
	ok := bouncer.CheckPassword(hash, body.Password)
	if !found || !ok || !user.IsActivated {
		id := uint(0)
		if found {
			id = user.ID
		}
		s.logAuth(r, "failed", id)
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgInvalidCredentials)
		return
	}
	now := time.Now().UTC()
	if err := db.WithContext(r.Context()).Model(&BackendUser{}).Where("id = ?", user.ID).Update("last_login", now).Error; err != nil {
		WriteError(w, http.StatusInternalServerError, "error", msgServerError)
		return
	}
	if bouncer.NeedsRehash(user.Password, s.bcryptCost) {
		if next, err := bouncer.HashPassword(s.bcryptCost, body.Password); err == nil {
			_ = db.WithContext(r.Context()).Model(&BackendUser{}).Where("id = ?", user.ID).Update("password", next).Error
		}
	}
	token, _, err := bouncer.MintAudience(s.secret, uitoa(user.ID), s.issuer, s.ttl, bouncer.AudienceBackend)
	if err != nil {
		WriteError(w, http.StatusInternalServerError, "error", msgServerError)
		return
	}
	s.logAuth(r, "success", user.ID)
	if isAjax(r) {
		// Cookie transport (D-19): the SPA never sees the token.
		s.writeSessionCookie(w, token)
		WriteData(w, http.StatusOK, cookieLoginData(s.ttl), map[string]any{})
		return
	}
	WriteData(w, http.StatusOK, map[string]string{
		"access_token": token,
		"token_type":   "bearer",
	}, map[string]any{})
}

// cookieLoginData is the login/refresh body under cookie transport: no token,
// only its type and the access lifetime in seconds.
func cookieLoginData(ttl time.Duration) AdminLoginData {
	return AdminLoginData{TokenType: "cookie", ExpiresIn: int(ttl / time.Second)}
}

// writeSessionCookie sets the admin JWT cookie scoped to the admin prefix.
// Max-Age is the refresh window, because refresh accepts an expired access
// token until iat plus refresh_ttl.
func (s *service) writeSessionCookie(w http.ResponseWriter, token string) {
	http.SetCookie(w, s.sessionCookie(token, int(s.refreshTTL/time.Second)))
}

// expireSessionCookie tells the browser to drop the admin cookie.
func (s *service) expireSessionCookie(w http.ResponseWriter) {
	http.SetCookie(w, s.sessionCookie("", -1))
}

func (s *service) sessionCookie(value string, maxAge int) *http.Cookie {
	return &http.Cookie{
		Name:     AdminCookieName,
		Value:    value,
		Path:     s.adminPrefix(),
		MaxAge:   maxAge,
		HttpOnly: true,
		Secure:   !s.insecureCookie,
		SameSite: http.SameSiteStrictMode,
	}
}

func (s *service) refresh(w http.ResponseWriter, r *http.Request) {
	raw, fromCookie := sessionToken(r)
	if raw == "" {
		s.logAuth(r, "failed", 0)
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	next, err := bouncer.RefreshAudienceFor(r.Context(), s.users, s.secret, raw, bouncer.AudienceBackend, s.refreshTTL, s.bl, s.grace, s.issuer)
	if err != nil {
		// A subject the guard would refuse (deactivated, deleted, or cut off
		// by tokens_valid_after) ends the browser session. Other failures,
		// including a provider error, leave the cookie alone.
		if fromCookie && errors.Is(err, bouncer.ErrSubjectRejected) {
			s.expireSessionCookie(w)
		}
		s.logAuth(r, "failed", 0)
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	s.logAuth(r, "success", 0)
	if fromCookie {
		// A cookie-authenticated request never receives a token in its body.
		s.writeSessionCookie(w, next)
		WriteData(w, http.StatusOK, cookieLoginData(s.ttl), map[string]any{})
		return
	}
	WriteData(w, http.StatusOK, map[string]string{
		"access_token": next,
		"token_type":   "bearer",
	}, map[string]any{})
}

// logout blacklists the presented token's jti and always expires the admin
// cookie, so a browser session ends even when only the Bearer was revoked.
//
// Logout is mounted outside the backend guard, which rejects an expired access
// token before any handler runs. The token is verified here instead, with
// exp unchecked, so a token whose access lifetime has passed but whose refresh
// window is still open (and which /auth/refresh would still accept) can be
// revoked. The cookie is expired on every outcome, including a refusal.
func (s *service) logout(w http.ResponseWriter, r *http.Request) {
	s.expireSessionCookie(w)
	raw, _ := sessionToken(r)
	sub, iat, exp, jti, err := bouncer.VerifyRefreshableClaimsAudience(raw, s.secret, bouncer.AudienceBackend, s.refreshTTL)
	if err != nil {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	if s.bl != nil {
		expiresAt := iat.Add(s.refreshTTL).Add(time.Minute)
		if until := exp.Add(time.Minute); until.After(expiresAt) {
			expiresAt = until
		}
		if err := s.bl.Add(r.Context(), jti, expiresAt, time.Now()); err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
	}
	id := uint(0)
	if n, err := strconv.ParseUint(sub, 10, 64); err == nil {
		id = uint(n)
	}
	s.logAuth(r, "success", id)
	WriteData(w, http.StatusOK, AdminLogoutData{Status: "logged_out"}, map[string]any{})
}

// sessionToken returns the admin JWT the same way the backend guard reads it:
// the Authorization Bearer header first, then the summer_admin cookie.
func sessionToken(r *http.Request) (token string, fromCookie bool) {
	if raw := bearerToken(r); raw != "" {
		return raw, false
	}
	if r == nil {
		return "", false
	}
	if c, err := r.Cookie(AdminCookieName); err == nil {
		if raw := strings.TrimSpace(c.Value); raw != "" {
			return raw, true
		}
	}
	return "", false
}

func (s *service) me(w http.ResponseWriter, r *http.Request) {
	principal, ok := bouncer.User(r.Context())
	if !ok || principal == nil {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	db, err := s.db()
	if err != nil {
		WriteError(w, http.StatusInternalServerError, "error", msgServerError)
		return
	}
	var user BackendUser
	err = db.WithContext(r.Context()).Preload("Role").First(&user, principal.ID).Error
	if errors.Is(err, gorm.ErrRecordNotFound) || (err == nil && !user.IsActivated) {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	if err != nil {
		WriteError(w, http.StatusInternalServerError, "error", msgServerError)
		return
	}
	WriteData(w, http.StatusOK, profileOf(user), map[string]any{})
}

func profileOf(user BackendUser) AdminProfile {
	profile := AdminProfile{
		ID:          user.ID,
		Login:       user.Login,
		Email:       user.Email,
		FirstName:   user.FirstName,
		LastName:    user.LastName,
		IsSuperuser: user.IsSuperuser,
	}
	if user.Role.ID != 0 {
		profile.Role = &AdminRoleSummary{ID: user.Role.ID, Code: user.Role.Code, Name: user.Role.Name}
	}
	return profile
}

func bearerToken(r *http.Request) string {
	if r == nil {
		return ""
	}
	value := strings.TrimSpace(r.Header.Get("Authorization"))
	token, ok := strings.CutPrefix(value, "Bearer ")
	if !ok {
		return ""
	}
	return strings.TrimSpace(token)
}

func (s *service) logAuth(r *http.Request, outcome string, adminID uint) {
	remote := ""
	method := ""
	path := ""
	if r != nil {
		method = r.Method
		if r.URL != nil {
			path = r.URL.Path
		}
		remote = r.RemoteAddr
		if host, _, err := net.SplitHostPort(remote); err == nil {
			remote = host
		}
	}
	args := []any{"outcome", outcome, "method", method, "path", path, "remote", remote}
	if adminID != 0 {
		args = append(args, "admin_id", adminID)
	}
	slog.Default().Info("admin.auth", args...)
}

func adminBlacklist(app *backpack.App) bouncer.BlacklistStore {
	var sqlDB *sql.DB
	if app != nil {
		if db, ok := app.Lookup[*sql.DB](); ok {
			sqlDB = db
		} else if gdb, ok := app.Lookup[*gorm.DB](); ok && gdb != nil {
			if db, err := gdb.DB(); err == nil {
				sqlDB = db
			}
		}
	}
	if sqlDB == nil {
		return nil
	}
	return bouncer.NewPostgresBlacklist(sqlDB, backendJWTBlacklistTable)
}

// findBackendLogin resolves a login identifier (a login or an email) to one
// administrator. An identifier that matches two rows, such as one admin's login
// equal to another's email, resolves to nobody: it is reported as not found, so
// the caller answers it like any wrong credential instead of letting the lowest
// id win and lock the other admin out.
func findBackendLogin(db *gorm.DB, identifier string) (BackendUser, bool, error) {
	email := strings.ToLower(identifier)
	var users []BackendUser
	err := db.Preload("Role").Where("login = ? OR lower(email) = ?", identifier, email).Order("id").Limit(2).Find(&users).Error
	if err != nil {
		return BackendUser{}, false, err
	}
	if len(users) != 1 {
		return BackendUser{}, false, nil
	}
	return users[0], true, nil
}

func (s *service) db() (*gorm.DB, error) {
	if s == nil || s.app == nil {
		return nil, errors.New("cabana: database is not configured")
	}
	db, ok := s.app.Lookup[*gorm.DB]()
	if !ok || db == nil {
		return nil, errors.New("cabana: database is not configured")
	}
	return db, nil
}

func adminSecret(app *backpack.App) (string, error) {
	secret := ""
	if app != nil && app.Config != nil {
		secret = strings.TrimSpace(app.Config.String("admin.jwt.secret"))
	}
	if secret == "" {
		return "", errors.New("cabana: admin.jwt.secret is empty (set SUMMER_ADMIN__JWT__SECRET)")
	}
	return secret, nil
}

func adminTTL(app *backpack.App) time.Duration {
	minutes := 60
	if app != nil && app.Config != nil && app.Config.Int("admin.jwt.ttl") > 0 {
		minutes = app.Config.Int("admin.jwt.ttl")
	}
	return time.Duration(minutes) * time.Minute
}

func adminRefreshTTL(app *backpack.App) time.Duration {
	minutes := 20160
	if app != nil && app.Config != nil && app.Config.Int("admin.jwt.refresh_ttl") > 0 {
		minutes = app.Config.Int("admin.jwt.refresh_ttl")
	}
	return time.Duration(minutes) * time.Minute
}

func adminGrace(app *backpack.App) time.Duration {
	seconds := 0
	if app != nil && app.Config != nil && app.Config.Has("admin.jwt.blacklist_grace") {
		seconds = app.Config.Int("admin.jwt.blacklist_grace")
	}
	if seconds < 0 {
		seconds = 0
	}
	return time.Duration(seconds) * time.Second
}

func adminBcryptCost(app *backpack.App) int {
	cost := 10
	if app != nil && app.Config != nil && app.Config.Int("admin.password.bcrypt_cost") > 0 {
		cost = app.Config.Int("admin.password.bcrypt_cost")
	}
	if cost < 4 || cost > 31 {
		return 10
	}
	return cost
}

func adminLoginWindow(app *backpack.App) (int, int) {
	maxAttempts, decayMinutes := 5, 1
	if app != nil && app.Config != nil {
		if n := app.Config.Int("admin.login.max_attempts"); n > 0 {
			maxAttempts = n
		}
		if n := app.Config.Int("admin.login.decay_minutes"); n > 0 {
			decayMinutes = n
		}
	}
	return maxAttempts, decayMinutes
}

// adminCookieSecure reads backend.cookie_secure (default true). false drops
// the Secure attribute for plain-http development and is refused in the
// production environment.
func adminCookieSecure(app *backpack.App) (bool, error) {
	if app == nil || app.Config == nil || !app.Config.Has("backend.cookie_secure") {
		return true, nil
	}
	if app.Config.Bool("backend.cookie_secure") {
		return true, nil
	}
	if strings.EqualFold(strings.TrimSpace(app.Config.Environment()), "production") {
		return false, errors.New("cabana: backend.cookie_secure: false is not allowed in the production environment")
	}
	return false, nil
}

// adminIssuer is app.url plus the admin API login path. JWT verification does
// not check iss, so tokens minted under an earlier prefix stay valid until
// they expire.
func adminIssuer(app *backpack.App, prefix string) string {
	base := ""
	if app != nil && app.Config != nil {
		base = strings.TrimRight(strings.TrimSpace(app.Config.String("app.url")), "/")
	}
	if prefix == "" {
		prefix = DefaultAdminPrefix
	}
	return base + prefix + adminAPIVersion + "/auth/login"
}

// missingHashes caches the unknown-login hash per bcrypt cost.
var missingHashes sync.Map

// missingUserHash is the hash a login for an unknown (or ambiguous) identifier
// is checked against, so it costs the same bcrypt work as a real admin's. It is
// built once per cost at the service's configured cost, the cost stored hashes
// are rehashed to on login.
func (s *service) missingUserHash() string {
	cost := s.bcryptCost
	if cached, ok := missingHashes.Load(cost); ok {
		return cached.(string)
	}
	hash, err := bouncer.HashPassword(cost, "cabana-invalid-credentials")
	if err != nil {
		// An unusable cost: fall back to the default, still on the bcrypt path.
		hash, _ = bouncer.HashPassword(10, "cabana-invalid-credentials")
	}
	actual, _ := missingHashes.LoadOrStore(cost, hash)
	return actual.(string)
}