config minmod | error 'AddArgument' + 'MarshalJSON'

config.go

@@ -5,9 +5,9 @@ import (
 	"os"
 )
 
-// LoadConfig builds a struct representation of the
+// LoadConfig builds a structured representation of the
 // configuration file located at @path
-// The structure checks for most format errors
+// The struct definition checks for most format errors
 func LoadConfig(path string) (*controller, error) {
 
 	/* (1) Extract data

errors.go

@@ -1,6 +1,7 @@
 package gfw
 
 import (
+	"encoding/json"
 	"fmt"
 )
 
@@ -43,6 +44,42 @@ var (
 	InvalidDefaultParam = &Err{402, "invalid default param", nil}
 )
 
-func (e Err) Error() string {
-	return fmt.Sprintf("[%d] %s", e.Code, e.Reason)
+// BindArgument adds an argument to the error
+// to be displayed back to API caller
+func (e *Err) BindArgument(arg interface{}) {
+
+	/* (1) Make slice if not */
+	if e.Arguments == nil {
+		e.Arguments = make([]interface{}, 0)
+	}
+
+	/* (2) Append argument */
+	e.Arguments = append(e.Arguments, arg)
+
+}
+
+// Implements 'error'
+func (e Err) Error() string {
+
+	return fmt.Sprintf("[%d] %s", e.Code, e.Reason)
+
+}
+
+// Implements json.Marshaler
+func (e Err) MarshalJSON() ([]byte, error) {
+
+	var json_arguments string
+
+	/* (1) Marshal 'Arguments' if set */
+	if e.Arguments != nil && len(e.Arguments) > 0 {
+		arg_representation, err := json.Marshal(e.Arguments)
+		if err == nil {
+			json_arguments = fmt.Sprintf(",\"arguments\":%s", arg_representation)
+		}
+
+	}
+
+	/* (2) Render JSON manually */
+	return []byte(fmt.Sprintf("{\"error\":%d,\"reason\":\"%s\"%s}", e.Code, e.Reason, json_arguments)), nil
+
 }