system: wrap op errors

This passes more information allowing for better error handling. This eliminates generic WrapErr from system.

Signed-off-by: Ophestra <cat@gensokyo.uk>

system/output.go

@@ -1,6 +1,10 @@
 package system
 
 import (
+	"errors"
+	"net"
+	"os"
+
 	"hakurei.app/container"
 )
 
@@ -14,9 +18,59 @@ func SetOutput(v container.Msg) {
 	}
 }
 
-func wrapErrSuffix(err error, a ...any) error {
+// OpError is returned by [I.Commit] and [I.Revert].
+type OpError struct {
+	Op      string
+	Err     error
+	Message string
+	Revert  bool
+}
+
+func (e *OpError) Unwrap() error { return e.Err }
+func (e *OpError) Error() string {
+	if e.Message != "" {
+		return e.Message
+	}
+
+	switch {
+	case errors.As(e.Err, new(*os.PathError)), errors.As(e.Err, new(*net.OpError)):
+		return e.Err.Error()
+
+	default:
+		if !e.Revert {
+			return "cannot apply " + e.Op + ": " + e.Err.Error()
+		} else {
+			return "cannot revert " + e.Op + ": " + e.Err.Error()
+		}
+	}
+}
+
+// newOpError returns an [OpError] without a message string.
+func newOpError(op string, err error, revert bool) error {
 	if err == nil {
 		return nil
 	}
-	return msg.WrapErr(err, append(a, err)...)
+	return &OpError{op, err, "", revert}
+}
+
+// newOpErrorMessage returns an [OpError] with an overriding message string.
+func newOpErrorMessage(op string, err error, message string, revert bool) error {
+	if err == nil {
+		return nil
+	}
+	return &OpError{op, err, message, revert}
+}
+
+func printJoinedError(println func(v ...any), fallback string, err error) {
+	var joinErr interface {
+		Unwrap() []error
+		error
+	}
+	if !errors.As(err, &joinErr) {
+		println(fallback, err)
+	} else {
+		for _, err = range joinErr.Unwrap() {
+			println(err.Error())
+		}
+	}
 }