init(api): add user authentication handler

also add error casting function to db.go

backend/api/handlers.go

@@ -0,0 +1,54 @@
+package api
+
+import (
+	"context"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/H1K0/SkazaNull/db"
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-gonic/gin"
+)
+
+//#region User
+
+func userAuth(c *gin.Context) {
+	var credentials struct {
+		Login    string `form:"login"    binding:"required"`
+		Password string `form:"password" binding:"required"`
+	}
+	err := c.ShouldBind(&credentials)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "И че за шнягу ты мне кинул?"})
+		return
+	}
+	user, err := db.UserAuth(context.Background(), credentials.Login, credentials.Password)
+	if err != nil {
+		pqErr := db.CastToPgError(err)
+		if pqErr == nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
+		statusStr := pqErr.Message[:3]
+		msg := pqErr.Message[4:]
+		status, _err := strconv.ParseInt(statusStr, 10, 0)
+		if _err == nil {
+			c.JSON(int(status), gin.H{"error": msg})
+		} else {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		}
+		return
+	}
+	session := sessions.Default(c)
+	session.Set("user_id", user.ID)
+	session.Set("started", time.Now().Unix())
+	session.Save()
+	c.JSON(http.StatusOK, user)
+}
+
+//#endregion User
+
+//#region Quotes
+
+//#endregion Quotes

backend/db/db.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/H1K0/SkazaNull/models"
+	"github.com/jackc/pgx/v5/pgconn"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
@@ -30,6 +31,14 @@ func InitDB(connString string) error {
 	return nil
 }
 
+func CastToPgError(err error) *pgconn.PgError {
+	pqErr, ok := err.(*pgconn.PgError)
+	if ok {
+		return pqErr
+	}
+	return nil
+}
+
 //#region User
 
 func UserAuth(ctx context.Context, login string, password string) (user models.User, err error) {