add form binding and mapping functionality with tests

binding/binding.go

@@ -0,0 +1,83 @@
+package binding
+
+import (
+	"errors"
+	"net/http"
+	"reflect"
+	"strconv"
+)
+
+type FormBinding struct{}
+
+func (FormBinding) Bind(r *http.Request, obj any) error {
+	if r == nil {
+		return errors.New("request is nil")
+	}
+
+	if err := r.ParseForm(); err != nil {
+		return err
+	}
+
+	if r.Form == nil {
+		return errors.New("form is nil")
+	}
+
+	return mapForm(obj, r.Form)
+}
+
+func mapForm(obj any, form map[string][]string) error {
+	val := reflect.ValueOf(obj)
+	if val.Kind() != reflect.Ptr || val.IsNil() {
+		return errors.New("obj must be a non-nil pointer")
+	}
+	val = val.Elem()
+	if val.Kind() != reflect.Struct {
+		return errors.New("obj must be a pointer to a struct")
+	}
+
+	typ := val.Type()
+	for i := 0; i < val.NumField(); i++ {
+		field := val.Field(i)
+		fieldType := typ.Field(i)
+		formTag := fieldType.Tag.Get("form")
+
+		if formTag == "" {
+			formTag = fieldType.Name
+		}
+
+		if values, ok := form[formTag]; ok && len(values) > 0 {
+			value := values[0]
+			switch field.Kind() {
+			case reflect.String:
+				field.SetString(value)
+			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+				intValue, err := strconv.ParseInt(value, 10, 64)
+				if err != nil {
+					return err
+				}
+				field.SetInt(intValue)
+			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+				uintValue, err := strconv.ParseUint(value, 10, 64)
+				if err != nil {
+					return err
+				}
+				field.SetUint(uintValue)
+			case reflect.Float32, reflect.Float64:
+				floatValue, err := strconv.ParseFloat(value, 64)
+				if err != nil {
+					return err
+				}
+				field.SetFloat(floatValue)
+			case reflect.Bool:
+				boolValue, err := strconv.ParseBool(value)
+				if err != nil {
+					return err
+				}
+				field.SetBool(boolValue)
+			default:
+				return errors.New("unsupported field type")
+			}
+		}
+	}
+	return nil
+}