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// Package generator implements the custom initialization of all the fields of an empty interface.
package generator
import (
"reflect"
"github.com/traefik/paerser/parser"
)
type initializer interface {
SetDefaults()
}
// Generate recursively initializes an empty structure, calling SetDefaults on each field, when it applies.
func Generate(element interface{}) {
if element == nil {
return
}
generate(element)
}
func generate(element interface{}) {
field := reflect.ValueOf(element)
fill(field)
}
func fill(field reflect.Value) {
switch field.Kind() {
case reflect.Pointer:
setPtr(field)
case reflect.Struct:
setStruct(field)
case reflect.Map:
setMap(field)
case reflect.Slice:
if field.Type().Elem().Kind() == reflect.Struct ||
field.Type().Elem().Kind() == reflect.Pointer && field.Type().Elem().Elem().Kind() == reflect.Struct {
slice := reflect.MakeSlice(field.Type(), 1, 1)
field.Set(slice)
// use Ptr to allow "SetDefaults"
value := reflect.New(reflect.PointerTo(field.Type().Elem()))
setPtr(value)
elem := value.Elem().Elem()
field.Index(0).Set(elem)
} else if field.Len() == 0 {
slice := reflect.MakeSlice(field.Type(), 0, 0)
field.Set(slice)
}
}
}
func setPtr(field reflect.Value) {
if field.IsNil() {
field.Set(reflect.New(field.Type().Elem()))
}
if field.Type().Implements(reflect.TypeOf((*initializer)(nil)).Elem()) {
method := field.MethodByName("SetDefaults")
if method.IsValid() {
method.Call([]reflect.Value{})
}
}
fill(field.Elem())
}
func setStruct(field reflect.Value) {
for i := 0; i < field.NumField(); i++ {
fd := field.Field(i)
structField := field.Type().Field(i)
if structField.Tag.Get(parser.TagLabel) == "-" {
continue
}
if parser.IsExported(structField) {
fill(fd)
}
}
}
func setMap(field reflect.Value) {
if field.IsNil() {
field.Set(reflect.MakeMap(field.Type()))
}
ptrValue := reflect.New(reflect.PointerTo(field.Type().Elem()))
fill(ptrValue)
value := ptrValue.Elem().Elem()
key := reflect.ValueOf(parser.MapNamePlaceholder)
field.SetMapIndex(key, value)
}
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