Improve error creation & handling by API

pkg/errors/kind.go

@@ -0,0 +1,170 @@
+package errors
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type (
+	kind uint8
+)
+
+const (
+	// internal (unspecified) error
+	// these errors yield HTTP status 500 and hide
+	// details unless in development environment
+	KindInternal kind = iota
+
+	// store error
+	KindStore
+
+	// object store (file upload/download)
+	KindObjStore
+
+	// Data validation error
+	KindInvalidData
+
+	// Requested data not found
+	KindNotFound
+
+	// Stale data submitted
+	// Internally data was already updated or is locked in another session
+	KindStaleData
+
+	// Data already exists
+	KindDuplicateData
+
+	// Access control
+	KindUnauthorized
+
+	// Expecting authenticated user
+	KindUnauthenticated
+
+	// External system failure
+	KindExternal
+)
+
+// translates error kind into http status
+func (k kind) httpStatus() int {
+	switch k {
+	case KindInvalidData:
+		return http.StatusBadRequest
+
+	case KindNotFound:
+		return http.StatusBadRequest
+
+	case KindStaleData:
+		return http.StatusConflict
+
+	case KindDuplicateData:
+		return http.StatusConflict
+
+	case KindUnauthorized:
+		return http.StatusUnauthorized
+
+	case KindUnauthenticated:
+		return http.StatusForbidden
+
+	default:
+		return http.StatusInternalServerError
+	}
+}
+
+func Internal(m string, aa ...interface{}) *Error {
+	return err(KindInternal, fmt.Sprintf(m, aa...))
+}
+
+func Store(m string, aa ...interface{}) *Error {
+	return err(KindStore, fmt.Sprintf(m, aa...))
+}
+
+func ObjStore(m string, aa ...interface{}) *Error {
+	return err(KindObjStore, fmt.Sprintf(m, aa...))
+}
+
+func InvalidData(m string, aa ...interface{}) *Error {
+	return err(KindInvalidData, fmt.Sprintf(m, aa...))
+}
+
+func NotFound(m string, aa ...interface{}) *Error {
+	return err(KindNotFound, fmt.Sprintf(m, aa...))
+}
+
+func StaleData(m string, aa ...interface{}) *Error {
+	return err(KindStaleData, fmt.Sprintf(m, aa...))
+}
+
+func DuplicateData(m string, aa ...interface{}) *Error {
+	return err(KindDuplicateData, fmt.Sprintf(m, aa...))
+}
+
+func Unauthorized(m string, aa ...interface{}) *Error {
+	return err(KindUnauthorized, fmt.Sprintf(m, aa...))
+}
+
+func Unauthenticated(m string, aa ...interface{}) *Error {
+	return err(KindUnauthenticated, fmt.Sprintf(m, aa...))
+}
+
+func External(m string, aa ...interface{}) *Error {
+	return err(KindExternal, fmt.Sprintf(m, aa...))
+}
+
+func IsKind(err error, k kind) bool {
+	t, ok := err.(*Error)
+	if !ok {
+		return false
+	}
+
+	return t.kind == k
+}
+
+// IsAny returns true if error is of type *Error
+func IsAny(err error) bool {
+	var is bool
+	if err != nil {
+		_, is = err.(*Error)
+	}
+
+	return is
+}
+
+func IsInternal(err error) bool {
+	return IsKind(err, KindInternal)
+}
+
+func IsStore(err error) bool {
+	return IsKind(err, KindStore)
+}
+
+func IsObjStore(err error) bool {
+	return IsKind(err, KindObjStore)
+}
+
+func IsInvalidData(err error) bool {
+	return IsKind(err, KindInvalidData)
+}
+
+func IsNotFound(err error) bool {
+	return IsKind(err, KindNotFound)
+}
+
+func IsStaleData(err error) bool {
+	return IsKind(err, KindStaleData)
+}
+
+func IsDuplicateData(err error) bool {
+	return IsKind(err, KindDuplicateData)
+}
+
+func IsUnauthorized(err error) bool {
+	return IsKind(err, KindUnauthorized)
+}
+
+func IsUnauthenticated(err error) bool {
+	return IsKind(err, KindUnauthenticated)
+}
+
+func IsExternal(err error) bool {
+	return IsKind(err, KindExternal)
+}