feat: authsession service

authsession/internal/api/publichttp/json.go

@@ -0,0 +1,93 @@
+package publichttp
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	"galaxy/authsession/internal/service/shared"
+
+	"github.com/gin-gonic/gin"
+)
+
+const publicErrorCodeContextKey = "public_error_code"
+
+type malformedJSONRequestError struct {
+	message string
+}
+
+func (e *malformedJSONRequestError) Error() string {
+	if e == nil {
+		return ""
+	}
+
+	return e.message
+}
+
+func decodeJSONRequest(request *http.Request, target any) error {
+	if request == nil || request.Body == nil {
+		return &malformedJSONRequestError{message: "request body must not be empty"}
+	}
+
+	return decodeJSONReader(request.Body, target)
+}
+
+func decodeJSONReader(reader io.Reader, target any) error {
+	decoder := json.NewDecoder(reader)
+	decoder.DisallowUnknownFields()
+
+	if err := decoder.Decode(target); err != nil {
+		return describeJSONDecodeError(err)
+	}
+
+	if err := decoder.Decode(&struct{}{}); err != nil {
+		if errors.Is(err, io.EOF) {
+			return nil
+		}
+
+		return &malformedJSONRequestError{message: "request body must contain a single JSON object"}
+	}
+
+	return &malformedJSONRequestError{message: "request body must contain a single JSON object"}
+}
+
+func describeJSONDecodeError(err error) error {
+	var syntaxErr *json.SyntaxError
+	var typeErr *json.UnmarshalTypeError
+
+	switch {
+	case errors.Is(err, io.EOF):
+		return &malformedJSONRequestError{message: "request body must not be empty"}
+	case errors.As(err, &syntaxErr):
+		return &malformedJSONRequestError{message: "request body contains malformed JSON"}
+	case errors.Is(err, io.ErrUnexpectedEOF):
+		return &malformedJSONRequestError{message: "request body contains malformed JSON"}
+	case errors.As(err, &typeErr):
+		if strings.TrimSpace(typeErr.Field) != "" {
+			return &malformedJSONRequestError{
+				message: fmt.Sprintf("request body contains an invalid value for %q", typeErr.Field),
+			}
+		}
+
+		return &malformedJSONRequestError{message: "request body contains an invalid JSON value"}
+	case strings.HasPrefix(err.Error(), "json: unknown field "):
+		return &malformedJSONRequestError{
+			message: fmt.Sprintf("request body contains unknown field %s", strings.TrimPrefix(err.Error(), "json: unknown field ")),
+		}
+	default:
+		return &malformedJSONRequestError{message: "request body contains invalid JSON"}
+	}
+}
+
+func abortWithProjection(c *gin.Context, projection shared.PublicErrorProjection) {
+	c.Set(publicErrorCodeContextKey, projection.Code)
+	c.AbortWithStatusJSON(projection.StatusCode, errorResponse{
+		Error: errorBody{
+			Code:    projection.Code,
+			Message: projection.Message,
+		},
+	})
+}