New bindings for JSON, XML and form parsing and validation

binding/binding.go

@@ -3,32 +3,89 @@ package binding
 import (
 	"encoding/json"
 	"encoding/xml"
-	"io"
+	"errors"
+	"net/http"
+	"reflect"
+	"strings"
 )
 
 type (
 	Binding interface {
-		Bind(io.Reader, interface{}) error
+		Bind(*http.Request, interface{}) error
 	}
 
 	// JSON binding
 	jsonBinding struct{}
 
-	// JSON binding
+	// XML binding
 	xmlBinding struct{}
+
+	// // form binding
+	formBinding struct{}
 )
 
 var (
 	JSON = jsonBinding{}
 	XML  = xmlBinding{}
+	Form = formBinding{} // todo
 )
 
-func (_ jsonBinding) Bind(r io.Reader, obj interface{}) error {
-	decoder := json.NewDecoder(r)
-	return decoder.Decode(&obj)
+func (_ jsonBinding) Bind(req *http.Request, obj interface{}) error {
+	decoder := json.NewDecoder(req.Body)
+	if err := decoder.Decode(obj); err == nil {
+		return Validate(obj)
+	} else {
+		return err
+	}
 }
 
-func (_ xmlBinding) Bind(r io.Reader, obj interface{}) error {
-	decoder := xml.NewDecoder(r)
-	return decoder.Decode(&obj)
+func (_ xmlBinding) Bind(req *http.Request, obj interface{}) error {
+	decoder := xml.NewDecoder(req.Body)
+	if err := decoder.Decode(obj); err == nil {
+		return Validate(obj)
+	} else {
+		return err
+	}
+}
+
+func (_ formBinding) Bind(req *http.Request, obj interface{}) error {
+	return nil
+}
+
+func Validate(obj interface{}) error {
+
+	typ := reflect.TypeOf(obj)
+	val := reflect.ValueOf(obj)
+
+	if typ.Kind() == reflect.Ptr {
+		typ = typ.Elem()
+		val = val.Elem()
+	}
+
+	for i := 0; i < typ.NumField(); i++ {
+		field := typ.Field(i)
+		fieldValue := val.Field(i).Interface()
+		zero := reflect.Zero(field.Type).Interface()
+
+		// Validate nested and embedded structs (if pointer, only do so if not nil)
+		if field.Type.Kind() == reflect.Struct ||
+			(field.Type.Kind() == reflect.Ptr && !reflect.DeepEqual(zero, fieldValue)) {
+			if err := Validate(fieldValue); err != nil {
+				return err
+			}
+		}
+
+		if strings.Index(field.Tag.Get("binding"), "required") > -1 {
+			if reflect.DeepEqual(zero, fieldValue) {
+				name := field.Name
+				if j := field.Tag.Get("json"); j != "" {
+					name = j
+				} else if f := field.Tag.Get("form"); f != "" {
+					name = f
+				}
+				return errors.New("Required " + name)
+			}
+		}
+	}
+	return nil
 }