add auth module

backend/internal/auth/handler.go

@@ -0,0 +1,77 @@
+package auth
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+type Handler struct {
+	authService *Service
+}
+
+func NewHandler(authService *Service) *Handler {
+	return &Handler{
+		authService: authService,
+	}
+}
+
+type LoginRequest struct {
+	Username string `json:"username" binding:"required"`
+	Password string `json:"password" binding:"required"`
+}
+
+type RegisterRequest struct {
+	Username string `json:"username" binding:"required,min=3,max=50"`
+	Password string `json:"password" binding:"required,min=6"`
+}
+
+func (h *Handler) Login(c *gin.Context) {
+	var req LoginRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request", "details": err.Error()})
+		return
+	}
+
+	token, err := h.authService.Login(c.Request.Context(), req.Username, req.Password)
+	if err != nil {
+		switch err {
+		case ErrUserNotFound, ErrInvalidCredentials:
+			c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
+		default:
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "login failed"})
+		}
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"token": token})
+}
+
+func (h *Handler) Register(c *gin.Context) {
+	var req RegisterRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request", "details": err.Error()})
+		return
+	}
+
+	user, token, err := h.authService.Register(c.Request.Context(), req.Username, req.Password)
+	if err != nil {
+		switch err {
+		case ErrUserExists:
+			c.JSON(http.StatusConflict, gin.H{"error": "user already exists"})
+		case ErrPasswordTooShort:
+			c.JSON(http.StatusBadRequest, gin.H{"error": "password too short"})
+		default:
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "registration failed"})
+		}
+		return
+	}
+
+	c.JSON(http.StatusCreated, gin.H{
+		"user": gin.H{
+			"id":       user.ID,
+			"username": user.Username,
+		},
+		"token": token,
+	})
+}