Add storage backends and safety checks

internal/storage/errors.go

@@ -0,0 +1,128 @@
+package storage
+
+import (
+	"errors"
+	"fmt"
+)
+
+type ErrorKind string
+
+const (
+	ErrNotFound     ErrorKind = "not_found"
+	ErrAlreadyExist ErrorKind = "already_exists"
+	ErrNotEmpty     ErrorKind = "not_empty"
+	ErrInvalidPath  ErrorKind = "invalid_path"
+	ErrConflict     ErrorKind = "conflict"
+	ErrPermission   ErrorKind = "permission"
+	ErrTemporary    ErrorKind = "temporary"
+	ErrUnsupported  ErrorKind = "unsupported"
+	ErrUnknown      ErrorKind = "unknown"
+)
+
+const (
+	OpValidatePath        = "validate path"
+	OpReadFile            = "read file"
+	OpOpenReader          = "open reader"
+	OpWriteFile           = "write file"
+	OpWriteFrom           = "write stream"
+	OpStat                = "stat"
+	OpWalk                = "walk"
+	OpHasAny              = "has any"
+	OpDeleteManagedBundle = "delete managed bundle"
+	OpRegisterBackend     = "register backend"
+	OpOpenBackend         = "open backend"
+)
+
+type Error struct {
+	Op      string
+	Backend string
+	Path    string
+	Kind    ErrorKind
+	Err     error
+}
+
+func NewError(op, backend, path string, kind ErrorKind, err error) *Error {
+	return &Error{
+		Op:      op,
+		Backend: backend,
+		Path:    path,
+		Kind:    kind,
+		Err:     err,
+	}
+}
+
+func (e *Error) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	message := e.Op
+	if e.Backend != "" {
+		message += " " + e.Backend
+	}
+	if e.Path != "" {
+		message += " " + e.Path
+	}
+	if e.Kind != "" {
+		message += ": " + string(e.Kind)
+	}
+	if e.Err != nil {
+		message += ": " + e.Err.Error()
+	}
+	return message
+}
+
+func (e *Error) Unwrap() error {
+	if e == nil {
+		return nil
+	}
+	return e.Err
+}
+
+func (e *Error) Is(target error) bool {
+	var targetError *Error
+	if !errors.As(target, &targetError) {
+		return false
+	}
+	return targetError.Kind == "" || e.Kind == targetError.Kind
+}
+
+func Errorf(op, backend, path string, kind ErrorKind, format string, args ...any) *Error {
+	return NewError(op, backend, path, kind, fmt.Errorf(format, args...))
+}
+
+func IsKind(err error, kind ErrorKind) bool {
+	var storageErr *Error
+	return errors.As(err, &storageErr) && storageErr.Kind == kind
+}
+
+func IsNotFound(err error) bool {
+	return IsKind(err, ErrNotFound)
+}
+
+func IsAlreadyExists(err error) bool {
+	return IsKind(err, ErrAlreadyExist)
+}
+
+func IsNotEmpty(err error) bool {
+	return IsKind(err, ErrNotEmpty)
+}
+
+func IsInvalidPath(err error) bool {
+	return IsKind(err, ErrInvalidPath)
+}
+
+func IsConflict(err error) bool {
+	return IsKind(err, ErrConflict)
+}
+
+func IsPermission(err error) bool {
+	return IsKind(err, ErrPermission)
+}
+
+func IsTemporary(err error) bool {
+	return IsKind(err, ErrTemporary)
+}
+
+func IsUnsupported(err error) bool {
+	return IsKind(err, ErrUnsupported)
+}