package auth

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"log/slog"
	"time"

	"goAuth/internal/invite"
	"goAuth/internal/user"

	"github.com/mileusna/useragent"
)

const (
	TransactionTimeout = 15 * time.Second
)

type Service struct {
	r             *Repository
	u             *user.Service
	i             *invite.Service
	shortDuration time.Duration
	longDuration  time.Duration
	tokenSize     int
}

func NewService(r *Repository, u *user.Service, i *invite.Service, shortDuration, longDuration time.Duration, tokenSize int) (*Service, error) {
	if tokenSize <= 0 {
		tokenSize = 32
	}
	return &Service{r: r, u: u, i: i, shortDuration: shortDuration, longDuration: longDuration, tokenSize: tokenSize}, nil
}

func detachWithTimeout(ctx context.Context, timeout time.Duration) (context.Context, context.CancelFunc) {
	return context.WithTimeout(context.WithoutCancel(ctx), timeout)
}

func (s *Service) ClassifiedUserAgent(userAgent string) string {
	ua := useragent.Parse(userAgent)

	var class string
	if ua.Mobile {
		class = "Mobile"
	}
	if ua.Tablet {
		class = "Tablet"
	}
	if ua.Desktop {
		class = "Desktop"
	}
	if ua.Bot {
		class = "Bot"
	}

	device := class
	if ua.Name != "" {
		device += fmt.Sprintf(", %s %s", ua.Name, ua.Version)
	}

	if ua.OS != "" {
		device += fmt.Sprintf(", %s %s", ua.OS, ua.OSVersion)
	}

	if ua.Device != "" {
		device += fmt.Sprintf(", %s", ua.Device)
	}

	return device
}

func (s *Service) generateToken() (string, error) {
	b := make([]byte, s.tokenSize)

	_, err := rand.Read(b)
	if err != nil {
		slog.Error("generate session token", slog.String("op", "service.generateToken"), slog.Any("error", err))
		return "", ErrInternal
	}

	return base64.RawURLEncoding.EncodeToString(b), nil
}

func (s *Service) RegisterUser(ctx context.Context, login, password, invite string, address, device string) (*user.User, *Session, error) {
	err := ctx.Err()
	if err != nil {
		return nil, nil, ErrCanceled
	}

	newCtx, cancelFunc := detachWithTimeout(ctx, TransactionTimeout)
	defer cancelFunc()

	user, err := s.u.CreateUser(newCtx, login, password, false)
	if err != nil {
		return nil, nil, err
	}

	_, err = s.i.UseInvite(newCtx, invite)
	if err != nil {
		s.u.DeleteUser(newCtx, user)
		return nil, nil, err
	}

	_, err = s.u.ActivateUser(newCtx, user)
	if err != nil {
		s.u.DeleteUser(newCtx, user)
		return nil, nil, err
	}

	return s.LoginUser(newCtx, login, password, address, device, false)
}

func (s *Service) LoginUser(ctx context.Context, login, password, address, device string, isLong bool) (*user.User, *Session, error) {
	token, err := s.generateToken()
	if err != nil {
		return nil, nil, err
	}

	user, err := s.u.UserByLogin(ctx, login)
	if err != nil {
		return nil, nil, err
	}

	err = s.u.ValidatePassword(ctx, user, password)
	if err != nil {
		return nil, nil, err
	}

	var duration time.Duration
	if isLong {
		duration = s.longDuration
	} else {
		duration = s.shortDuration
	}

	session, err := s.r.CreateSession(ctx, token, user.Id, address, device, time.Now().UTC().Add(duration), isLong)
	if err != nil {
		return nil, nil, err
	}

	return user, session, nil
}

func (s *Service) BumpSession(ctx context.Context, session *Session) (*Session, error) {
	var duration time.Duration

	if session.IsLong {
		duration = s.longDuration
	} else {
		duration = s.shortDuration
	}

	halfExpire := time.Now().UTC().Add(duration / 2)
	if session.ExpiresAt.After(halfExpire) {
		return session, nil
	}

	value := *session
	cloned := &value
	cloned.ExpiresAt = time.Now().UTC().Add(duration)
	err := s.r.UpdateSession(ctx, cloned)
	if err != nil {
		return nil, err
	}

	return cloned, nil
}

func (s *Service) SessionByToken(ctx context.Context, token string) (*Session, error) {
	return s.r.SessionByToken(ctx, token)
}

func (s *Service) CountSessions(ctx context.Context, user *user.User) (int64, error) {
	return s.r.CountSessions(ctx, user.Id)
}

func (s *Service) Sessions(ctx context.Context, user *user.User, limit, offset int64) ([]*Session, error) {
	return s.r.Sessions(ctx, user.Id, limit, offset)
}

func (s *Service) DeleteSession(ctx context.Context, session *Session) error {
	return s.r.DeleteSession(ctx, session.Token)
}

func (s *Service) DeleteSessions(ctx context.Context, user *user.User) error {
	return s.r.DeleteSessions(ctx, user.Id)
}

func (s *Service) CleanupSessions(ctx context.Context) error {
	return s.r.CleanupSessions(ctx)
}