From c0dc44e28e84ad989ed6d52b8febc89b3a7adc7e Mon Sep 17 00:00:00 2001
From: Dan Jones <danjones@goodevilgenius.org>
Date: Wed, 17 Jan 2024 15:51:28 -0600
Subject: [PATCH] =?UTF-8?q?=E2=9C=A8=20Add=20SettableError?=
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---
 errorf.go      | 48 +++++++++++++++++++++++++++++++++++++++++++-----
 errorf_test.go | 33 +++++++++++++++++++++++++++++++++
 interface.go   | 12 ++++++++++++
 3 files changed, 88 insertions(+), 5 deletions(-)

diff --git a/errorf.go b/errorf.go
index 40e2e1d..03bde47 100644
--- a/errorf.go
+++ b/errorf.go
@@ -1,15 +1,28 @@
 package errors
 
-import "fmt"
+import (
+	"fmt"
+	"net/http"
+)
 
-// Returns a ResponsableError formatted from the message, with the specified status.
+// Returns a SettableError formatted from the message, with the specified status.
 // Errorf passes the heavy lifting off to fmt.Errorf, and returns a similar error.
 // If one error is passed in the format, this will return an UnwrappableError.
 // If more than one error is passed in the format, this will return an UnwrappableErrors.
-func Errorf(status int, format string, parts ...any) ResponsableError {
+//
+// The Msg method may also be formatted.
+//
+// If you want a different user message, use Msg, such as:
+//
+//	err := errors.Errorf(http.StatusNotFound, "%w", sqlError).Msg("user not found %d", userId)
+func Errorf(status int, format string, parts ...any) SettableError {
+	if len(parts) == 0 {
+		return &erf{status, format, ""}
+	}
+
 	err := fmt.Errorf(format, parts...)
 	msg := err.Error()
-	er := &erf{status, msg}
+	er := &erf{status, msg, ""}
 	if we, ok := err.(wrappedError); ok {
 		return &wrapErr{er, we.Unwrap()}
 	}
@@ -20,24 +33,49 @@ func Errorf(status int, format string, parts ...any) ResponsableError {
 }
 
 var _ ResponsableError = new(erf)
+var _ SettableError = new(erf)
 
 type erf struct {
 	stat int
+	err  string
 	msg  string
 }
 
 func (e *erf) GetStatus() int {
+	if e.stat < http.StatusContinue || e.stat >= 600 {
+		e.stat = http.StatusInternalServerError
+	}
 	return e.stat
 }
 
 func (e *erf) Error() string {
-	return e.msg
+	return e.err
 }
 
 func (e *erf) GetMsg() string {
+	if e.msg == "" {
+		return e.err
+	}
 	return e.msg
 }
 
+func (e *erf) Status(status int) SettableError {
+	// GetStatus already handles invalid values, so we'll just ignore this.
+	if status < http.StatusContinue || status >= 600 {
+		return e
+	}
+	e.stat = status
+	return e
+}
+
+func (e *erf) Msg(msg string, parts ...any) SettableError {
+	e.msg = msg
+	if len(parts) > 0 {
+		e.msg = fmt.Sprintf(msg, parts...)
+	}
+	return e
+}
+
 var _ UnwrappableError = new(wrapErr)
 
 type wrapErr struct {
diff --git a/errorf_test.go b/errorf_test.go
index f48b0a5..1a83ca0 100644
--- a/errorf_test.go
+++ b/errorf_test.go
@@ -69,3 +69,36 @@ func (s *ErrorfTestSuite) TestWrapTwo() {
 	s.Assert().Same(wrappedOne, unwrapped[0])
 	s.Assert().Same(wrappedTwo, unwrapped[1])
 }
+
+func (s *ErrorfTestSuite) TestSet() {
+	var err SettableError = Errorf(http.StatusTeapot, "Unable to BREW")
+	s.Assert().NotNil(err)
+
+	err.Status(http.StatusTooEarly).Msg("It's only %dAM", 2)
+	s.Assert().Equal(http.StatusTooEarly, err.GetStatus())
+	s.Assert().Equal("It's only 2AM", err.GetMsg())
+	s.Assert().Equal("Unable to BREW", err.Error())
+
+	err.Msg("I am so great")
+	s.Assert().Equal("I am so great", err.GetMsg())
+}
+
+func (s *ErrorfTestSuite) TestGetStatusOutsideRange() {
+	var err ResponsableError = Errorf(5, "Hello")
+	s.Assert().NotNil(err)
+	s.Assert().Equal(http.StatusInternalServerError, err.GetStatus())
+
+	err = Errorf(5, "Hello")
+	s.Assert().NotNil(err)
+	s.Assert().Equal(http.StatusInternalServerError, err.GetStatus())
+}
+
+func (s *ErrorfTestSuite) TestSetStatusOutsideRange() {
+	var err SettableError = Errorf(http.StatusPaymentRequired, "Hello")
+	s.Assert().NotNil(err)
+
+	err.Status(10)
+	s.Assert().Equal(http.StatusPaymentRequired, err.GetStatus())
+	err.Status(600)
+	s.Assert().Equal(http.StatusPaymentRequired, err.GetStatus())
+}
diff --git a/interface.go b/interface.go
index 4a687d6..da03a48 100644
--- a/interface.go
+++ b/interface.go
@@ -6,12 +6,24 @@ package errors
 // GetStatus should return an appropriate HTTP status.
 // GetMsg should return a message suitable to display to the end user. If the message
 // returned by Error is safe for the end user, it may simply call that.
+// GetStatus should not return a value outside of the 100 - 599 range.
 type ResponsableError interface {
 	Error() string
 	GetStatus() int
 	GetMsg() string
 }
 
+// SettableError is a ResponsableError which can be modified after initial creation.
+// The Status method can set the status, while the Msg method can set user message.
+// If any values are passed after the message, it should be passed to fmt.Sprintf for formatting.
+// Methods are chainable.
+// SetStatus should not use a value outside of 100-599. It may either ignore such values, or panic.
+type SettableError interface {
+	ResponsableError
+	Status(int) SettableError
+	Msg(string, ...any) SettableError
+}
+
 // UnwrappableError allows a ResponsableError to wrap another error.
 // It may be appropriate for Error() to delegate to the wrapped error.
 type UnwrappableError interface {