package services

import (
	"context"
	"crypto/subtle"
	"database/sql"
	"errors"
	"strings"

	"go-backend/internal/auth"
	"go-backend/internal/database/sqlc"
)

type AuthService struct {
	db      *sql.DB
	queries *sqlc.Queries
}

func NewAuthService(db *sql.DB, queries *sqlc.Queries) *AuthService {
	return &AuthService{
		db:      db,
		queries: queries,
	}
}

type SessionWithToken struct {
	Session sqlc.UserSession
	Token   string
}

func (s *AuthService) CreateSession(ctx context.Context, userID string) (*SessionWithToken, error) {
	id, err := auth.GenerateSecureRandomString()
	if err != nil {
		return nil, err
	}
	secret, err := auth.GenerateSecureRandomString()
	if err != nil {
		return nil, err
	}

	secretHash := auth.HashSecret(secret)
	token := id + "." + secret

	session, err := s.queries.InsertSession(ctx, sqlc.InsertSessionParams{
		ID:         id,
		SecretHash: secretHash,
		UserID:     userID,
	})

	if err != nil {
		return nil, err
	}

	return &SessionWithToken{
		Session: session,
		Token:   token,
	}, nil

}

func (s *AuthService) ValidateSessionToken(ctx context.Context, token string) (*sqlc.UserSession, error) {
	tokenParts := strings.Split(token, ".")
	if len(tokenParts) != 2 {
		return nil, nil
	}

	sessionID := tokenParts[0]
	sessionSecret := tokenParts[1]

	session, err := s.queries.SelectSessionById(ctx, sessionID)

	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return nil, nil
		}

		return nil, err
	}

	if auth.CheckExpiration(session.CreatedAt) {
		err = s.queries.DeleteSessionById(ctx, sessionID)

		if err != nil {
			return nil, err
		}

		return nil, nil
	}

	tokenSecretHash := auth.HashSecret(sessionSecret)
	if subtle.ConstantTimeCompare(tokenSecretHash, session.SecretHash) != 1 {
		return nil, nil
	}

	return &session, nil
}

func (s *AuthService) DeleteSession(ctx context.Context, token string) error {
	tokenParts := strings.Split(token, ".")
	if len(tokenParts) != 2 {
		return nil
	}

	sessionID := tokenParts[0]

	err := s.queries.DeleteSessionById(ctx, sessionID)

	return err
}