package cabana

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

	"git.golem15.com/golem15/summercms/backpack"
	"git.golem15.com/golem15/summercms/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
}

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
	}
	return principalFrom(user), nil
}

func principalFrom(user BackendUser) *bouncer.Principal {
	principal := &bouncer.Principal{
		ID:               user.ID,
		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 := dummyPasswordHash
	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)
	WriteData(w, http.StatusOK, map[string]string{
		"access_token": token,
		"token_type":   "bearer",
	}, map[string]any{})
}

func (s *service) refresh(w http.ResponseWriter, r *http.Request) {
	raw := bearerToken(r)
	if raw == "" {
		s.logAuth(r, "failed", 0)
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	next, err := bouncer.RefreshAudience(s.secret, raw, bouncer.AudienceBackend, s.refreshTTL, s.bl, s.grace, s.issuer)
	if err != nil {
		s.logAuth(r, "failed", 0)
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	s.logAuth(r, "success", 0)
	WriteData(w, http.StatusOK, map[string]string{
		"access_token": next,
		"token_type":   "bearer",
	}, map[string]any{})
}

func (s *service) logout(w http.ResponseWriter, r *http.Request) {
	raw := bearerToken(r)
	_, iat, exp, jti, err := bouncer.VerifyClaimsAudience(raw, s.secret, bouncer.AudienceBackend)
	if err != nil || jti == "" {
		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 principal, ok := bouncer.User(r.Context()); ok {
		id = principal.ID
	}
	s.logAuth(r, "success", id)
	WriteData(w, http.StatusOK, map[string]any{"status": "logged_out"}, map[string]any{})
}

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) map[string]any {
	data := map[string]any{
		"id":           user.ID,
		"login":        user.Login,
		"email":        user.Email,
		"first_name":   user.FirstName,
		"last_name":    user.LastName,
		"is_superuser": user.IsSuperuser,
	}
	if user.Role.ID != 0 {
		data["role"] = map[string]any{
			"id":   user.Role.ID,
			"code": user.Role.Code,
			"name": user.Role.Name,
		}
	}
	return data
}

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)
}

func findBackendLogin(db *gorm.DB, identifier string) (BackendUser, bool, error) {
	email := strings.ToLower(identifier)
	var user BackendUser
	err := db.Preload("Role").Where("login = ? OR lower(email) = ?", identifier, email).First(&user).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return BackendUser{}, false, nil
	}
	if err != nil {
		return BackendUser{}, false, err
	}
	return user, 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
}

func adminIssuer(app *backpack.App) string {
	base := ""
	if app != nil && app.Config != nil {
		base = strings.TrimRight(strings.TrimSpace(app.Config.String("app.url")), "/")
	}
	if base == "" {
		return "/_admin/api/v1/auth/login"
	}
	return base + "/_admin/api/v1/auth/login"
}

// dummyPasswordHash keeps a missing-user login on the bcrypt path.
var dummyPasswordHash = func() string {
	hash, err := bouncer.HashPassword(10, "cabana-invalid-credentials")
	if err != nil {
		return ""
	}
	return hash
}()