backend/auth.go

package main

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"
	"strings"
	"sync"
	"time"
)

type TokenInfo struct {
	Token     string
	CreatedAt time.Time
	UserID    int
}

var (
	tokenMap  = make(map[int]*TokenInfo)
	tokenMux  sync.RWMutex
	tokenTTL  = time.Hour
)

func GenerateToken(userID int) (string, error) {
	randomBytes := make([]byte, 32)
	_, err := rand.Read(randomBytes)
	if err != nil {
		return "", fmt.Errorf("failed to generate random bytes: %w", err)
	}

	hash := sha256.Sum256(append(randomBytes, []byte(fmt.Sprintf("%d", userID))...))
	token := base64.URLEncoding.EncodeToString(hash[:])

	tokenMux.Lock()
	defer tokenMux.Unlock()

	tokenMap[userID] = &TokenInfo{
		Token:     token,
		CreatedAt: time.Now(),
		UserID:    userID,
	}

	return token, nil
}

func ValidateToken(userID int, token string) error {
	tokenMux.RLock()
	defer tokenMux.RUnlock()

	tokenInfo, exists := tokenMap[userID]
	if !exists {
		return errors.New("token not found")
	}

	if tokenInfo.Token != token {
		return errors.New("invalid token")
	}

	if time.Since(tokenInfo.CreatedAt) > tokenTTL {
		return errors.New("token expired")
	}

	return nil
}

func RefreshToken(userID int) (string, error) {
	tokenMux.Lock()
	defer tokenMux.Unlock()

	randomBytes := make([]byte, 32)
	_, err := rand.Read(randomBytes)
	if err != nil {
		return "", fmt.Errorf("failed to generate random bytes: %w", err)
	}

	hash := sha256.Sum256(append(randomBytes, []byte(fmt.Sprintf("%d", userID))...))
	token := base64.URLEncoding.EncodeToString(hash[:])

	tokenMap[userID] = &TokenInfo{
		Token:     token,
		CreatedAt: time.Now(),
		UserID:    userID,
	}

	return token, nil
}

func RemoveToken(userID int) {
	tokenMux.Lock()
	defer tokenMux.Unlock()
	delete(tokenMap, userID)
}

func GetTokenInfo(userID int) (*TokenInfo, error) {
	tokenMux.RLock()
	defer tokenMux.RUnlock()

	tokenInfo, exists := tokenMap[userID]
	if !exists {
		return nil, errors.New("token not found")
	}

	return tokenInfo, nil
}

func extractUserIDFromToken(token string) (int, error) {
	tokenMux.RLock()
	defer tokenMux.RUnlock()
	for userID, tokenInfo := range tokenMap {
		if tokenInfo.Token == token {
			return userID, nil
		}
	}
	return 0, errors.New("invalid token")
}

func CleanupExpiredTokens() {
	tokenMux.Lock()
	defer tokenMux.Unlock()

	for userID, tokenInfo := range tokenMap {
		if time.Since(tokenInfo.CreatedAt) > tokenTTL {
			delete(tokenMap, userID)
		}
	}
}

func hashPassword(password string) (string, error) {
	hash := sha256.Sum256([]byte(password))
	return hex.EncodeToString(hash[:]), nil
}

func verifyPassword(password, hashedPassword string) bool {
	hash, err := hashPassword(password)
	if err != nil {
		return false
	}
	return hash == hashedPassword
}

func isValidPassword(password string) bool {
	if len(password) < 8 {
		return false
	}

	hasUpper := false
	hasLower := false
	hasDigit := false
	hasSpecial := false

	specialChars := "!@#$%^&*()_+-=[]{}|;:,.<>?"

	for _, char := range password {
		switch {
		case char >= 'A' && char <= 'Z':
			hasUpper = true
		case char >= 'a' && char <= 'z':
			hasLower = true
		case char >= '0' && char <= '9':
			hasDigit = true
		case strings.ContainsRune(specialChars, char):
			hasSpecial = true
		}
	}

	return hasUpper && hasLower && hasDigit && hasSpecial
}