refactor and organize code

internal/gperr/nested_error.go

@@ -0,0 +1,113 @@
+package gperr
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/yusing/go-proxy/internal/utils/strutils"
+)
+
+//nolint:recvcheck
+type nestedError struct {
+	Err    error   `json:"err"`
+	Extras []error `json:"extras"`
+}
+
+func (err nestedError) Subject(subject string) Error {
+	if err.Err == nil {
+		err.Err = newError(subject)
+	} else {
+		err.Err = PrependSubject(subject, err.Err)
+	}
+	return &err
+}
+
+func (err *nestedError) Subjectf(format string, args ...any) Error {
+	if len(args) > 0 {
+		return err.Subject(fmt.Sprintf(format, args...))
+	}
+	return err.Subject(format)
+}
+
+func (err nestedError) With(extra error) Error {
+	if extra != nil {
+		err.Extras = append(err.Extras, extra)
+	}
+	return &err
+}
+
+func (err nestedError) Withf(format string, args ...any) Error {
+	if len(args) > 0 {
+		err.Extras = append(err.Extras, fmt.Errorf(format, args...))
+	} else {
+		err.Extras = append(err.Extras, newError(format))
+	}
+	return &err
+}
+
+func (err *nestedError) Unwrap() []error {
+	if err.Err == nil {
+		if len(err.Extras) == 0 {
+			return nil
+		}
+		return err.Extras
+	}
+	return append([]error{err.Err}, err.Extras...)
+}
+
+func (err *nestedError) Is(other error) bool {
+	if errors.Is(err.Err, other) {
+		return true
+	}
+	for _, e := range err.Extras {
+		if errors.Is(e, other) {
+			return true
+		}
+	}
+	return false
+}
+
+func (err *nestedError) Error() string {
+	if err == nil {
+		return makeLine("<nil>", 0)
+	}
+
+	lines := make([]string, 0, 1+len(err.Extras))
+	if err.Err != nil {
+		lines = append(lines, makeLine(err.Err.Error(), 0))
+		lines = append(lines, makeLines(err.Extras, 1)...)
+	} else {
+		lines = append(lines, makeLines(err.Extras, 0)...)
+	}
+	return strutils.JoinLines(lines)
+}
+
+//go:inline
+func makeLine(err string, level int) string {
+	const bulletPrefix = "• "
+	const spaces = "                "
+
+	if level == 0 {
+		return err
+	}
+	return spaces[:2*level] + bulletPrefix + err
+}
+
+func makeLines(errs []error, level int) []string {
+	if len(errs) == 0 {
+		return nil
+	}
+	lines := make([]string, 0, len(errs))
+	for _, err := range errs {
+		switch err := wrap(err).(type) {
+		case *nestedError:
+			if err.Err != nil {
+				lines = append(lines, makeLine(err.Err.Error(), level))
+			}
+			lines = append(lines, makeLines(err.Extras, level+1)...)
+		default:
+			lines = append(lines, makeLine(err.Error(), level))
+		}
+	}
+	return lines
+}