refactor: restructure in entirety
This commit is contained in:
Arkaprabha Chakraborty
166
internal/logic/auth.go
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166
internal/logic/auth.go
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@@ -0,0 +1,166 @@
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package logic
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import (
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"billit/internal/models"
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"crypto/rand"
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"encoding/hex"
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"errors"
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"os"
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"time"
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"github.com/golang-jwt/jwt/v5"
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"golang.org/x/crypto/bcrypt"
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)
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var (
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ErrInvalidCredentials = errors.New("invalid email or password")
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ErrInvalidToken = errors.New("invalid or expired token")
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ErrUserNotFound = errors.New("user not found")
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ErrUserExists = errors.New("user already exists")
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)
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// AuthConfig holds auth configuration
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type AuthConfig struct {
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JWTSecret []byte
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TokenDuration time.Duration
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}
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// Claims represents JWT claims
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type Claims struct {
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UserID string `json:"user_id"`
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Email string `json:"email"`
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jwt.RegisteredClaims
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}
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// AuthService handles authentication logic
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type AuthService struct {
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config AuthConfig
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users UserStore
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}
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// UserStore interface for user persistence (subset of database.Service)
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type UserStore interface {
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CreateUser(email, passwordHash string) (*models.User, error)
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GetUserByEmail(email string) (*models.User, error)
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GetUserByID(id string) (*models.User, error)
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}
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// NewAuthService creates a new auth service
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func NewAuthService(users UserStore) *AuthService {
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secret := os.Getenv("JWT_SECRET")
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if secret == "" {
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// Generate a random secret if not provided (not recommended for production)
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b := make([]byte, 32)
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rand.Read(b)
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secret = hex.EncodeToString(b)
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}
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return &AuthService{
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config: AuthConfig{
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JWTSecret: []byte(secret),
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TokenDuration: 24 * time.Hour,
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},
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users: users,
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}
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}
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// HashPassword hashes a password using bcrypt with high cost
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func HashPassword(password string) (string, error) {
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// Use cost of 12 for good security/performance balance
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hash, err := bcrypt.GenerateFromPassword([]byte(password), 12)
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if err != nil {
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return "", err
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}
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return string(hash), nil
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}
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// CheckPassword verifies a password against a hash
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func CheckPassword(password, hash string) bool {
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err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
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return err == nil
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}
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// Register creates a new user account
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func (s *AuthService) Register(email, password string) (*models.User, error) {
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// Check if user exists
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existing, _ := s.users.GetUserByEmail(email)
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if existing != nil {
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return nil, ErrUserExists
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}
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// Validate password strength
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if len(password) < 8 {
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return nil, errors.New("password must be at least 8 characters")
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}
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// Hash password
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hash, err := HashPassword(password)
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if err != nil {
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return nil, err
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}
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return s.users.CreateUser(email, hash)
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}
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// Login authenticates a user and returns a JWT token
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func (s *AuthService) Login(email, password string) (string, error) {
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user, err := s.users.GetUserByEmail(email)
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if err != nil || user == nil {
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return "", ErrInvalidCredentials
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}
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if !CheckPassword(password, user.Password) {
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return "", ErrInvalidCredentials
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}
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return s.generateToken(user)
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}
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// generateToken creates a new JWT token for a user
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func (s *AuthService) generateToken(user *models.User) (string, error) {
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now := time.Now()
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claims := &Claims{
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UserID: user.ID,
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Email: user.Email,
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RegisteredClaims: jwt.RegisteredClaims{
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ExpiresAt: jwt.NewNumericDate(now.Add(s.config.TokenDuration)),
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IssuedAt: jwt.NewNumericDate(now),
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NotBefore: jwt.NewNumericDate(now),
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Issuer: "billit",
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Subject: user.ID,
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},
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}
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token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
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return token.SignedString(s.config.JWTSecret)
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}
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// ValidateToken validates a JWT token and returns the claims
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func (s *AuthService) ValidateToken(tokenString string) (*Claims, error) {
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token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
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if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
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return nil, ErrInvalidToken
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}
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return s.config.JWTSecret, nil
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})
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if err != nil {
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return nil, ErrInvalidToken
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}
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if claims, ok := token.Claims.(*Claims); ok && token.Valid {
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return claims, nil
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}
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return nil, ErrInvalidToken
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}
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// GetUserFromToken retrieves the user from a valid token
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func (s *AuthService) GetUserFromToken(tokenString string) (*models.User, error) {
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claims, err := s.ValidateToken(tokenString)
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if err != nil {
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return nil, err
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}
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return s.users.GetUserByID(claims.UserID)
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}
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158
internal/logic/calculator.go
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158
internal/logic/calculator.go
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@@ -0,0 +1,158 @@
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package logic
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import (
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"math"
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)
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// Rate represents standard GST rates
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type Rate float64
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const (
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Rate0 Rate = 0.0
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Rate5 Rate = 0.05
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Rate12 Rate = 0.12
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Rate18 Rate = 0.18
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Rate28 Rate = 0.28
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)
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// CustomerType distinguishes between B2B (Wholesale) and B2C (Retail)
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type CustomerType string
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const (
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CustomerWholesale CustomerType = "wholesale"
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CustomerRetail CustomerType = "retail"
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)
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// Product represents a catalog item
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type Product struct {
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SKU string
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Name string
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HSNCode string
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BasePrice float64 // Price before tax
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WholesalePrice float64 // Discounted price for B2B
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GSTRate Rate
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SmallOrderQty int // Minimum quantity threshold
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SmallOrderFee float64 // Convenience fee when quantity is below threshold
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Unit string // Unit of measurement (e.g., "pcs", "kg", "box")
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}
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// LineItem represents a single row in the invoice
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type LineItem struct {
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Product Product
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Quantity int
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UnitPrice float64 // Actual price applied (wholesale vs retail)
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TaxableVal float64 // Quantity * UnitPrice
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CGSTAmount float64
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SGSTAmount float64
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IGSTAmount float64
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TotalAmount float64
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}
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// Invoice represents the full bill
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type Invoice struct {
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LineItems []LineItem
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SubTotal float64
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TotalCGST float64
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TotalSGST float64
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TotalIGST float64
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ConvenienceFee float64 // Flat fee for small orders (before tax)
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ConvenienceFeeTax float64 // GST on convenience fee (18% fixed)
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GrandTotal float64
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CustomerType CustomerType
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IsInterState bool // True if selling to a different state (IGST applies)
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CompanyDetails string // Multiline company details (displayed above invoice table)
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BuyerDetails string // Multiline buyer details (displayed above bank details)
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BuyerName string // Buyer's name
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BankDetails string // Multiline bank details (displayed at bottom of invoice)
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}
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// Calculator handles the GST logic
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type Calculator struct{}
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// NewCalculator creates a new calculator instance
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func NewCalculator() *Calculator {
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return &Calculator{}
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}
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// CalculateLineItem computes taxes for a single line
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func (c *Calculator) CalculateLineItem(p Product, qty int, custType CustomerType, isInterState bool) LineItem {
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// Determine price based on customer type
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price := p.BasePrice
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if custType == CustomerWholesale {
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price = p.WholesalePrice
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}
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taxableVal := price * float64(qty)
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rate := float64(p.GSTRate)
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var cgst, sgst, igst float64
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if isInterState {
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igst = taxableVal * rate
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} else {
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// Intra-state: Split tax between Center and State
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halfRate := rate / 2
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cgst = taxableVal * halfRate
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sgst = taxableVal * halfRate
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}
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total := taxableVal + cgst + sgst + igst
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return LineItem{
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Product: p,
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Quantity: qty,
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UnitPrice: price,
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TaxableVal: round(taxableVal),
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CGSTAmount: round(cgst),
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SGSTAmount: round(sgst),
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IGSTAmount: round(igst),
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TotalAmount: round(total),
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}
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}
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// CalculateInvoice computes totals for the entire invoice
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func (c *Calculator) CalculateInvoice(items []LineItem, fee float64, isInterState bool) Invoice {
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inv := Invoice{
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LineItems: items,
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ConvenienceFee: fee,
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IsInterState: isInterState,
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}
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for _, item := range items {
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inv.SubTotal += item.TaxableVal
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inv.TotalCGST += item.CGSTAmount
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inv.TotalSGST += item.SGSTAmount
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inv.TotalIGST += item.IGSTAmount
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}
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// Convenience fee is taxable at 18% fixed rate
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if fee > 0 {
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feeTax := fee * 0.18 // 18% GST on convenience fee
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inv.ConvenienceFeeTax = round(feeTax)
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// Add convenience fee to taxable subtotal
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inv.SubTotal += fee
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// Add convenience fee tax to appropriate tax fields
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if isInterState {
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inv.TotalIGST += inv.ConvenienceFeeTax
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} else {
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// Split between CGST and SGST (9% each)
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inv.TotalCGST += round(feeTax / 2)
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inv.TotalSGST += round(feeTax / 2)
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}
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}
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inv.GrandTotal = inv.SubTotal + inv.TotalCGST + inv.TotalSGST + inv.TotalIGST
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// Rounding final totals
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inv.SubTotal = round(inv.SubTotal)
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inv.TotalCGST = round(inv.TotalCGST)
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inv.TotalSGST = round(inv.TotalSGST)
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inv.TotalIGST = round(inv.TotalIGST)
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inv.GrandTotal = round(inv.GrandTotal)
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return inv
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}
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func round(num float64) float64 {
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return math.Round(num*100) / 100
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}
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