package config

import (
	"errors"
	"reflect"
	"strings"
)

// Clone only configuration data. json:"-" capabilities remain borrowed and
// are never traversed (log writers, clients and mutex-bearing runtime objects).
// Unexported immutable implementation details such as time.Time are copied.
func cloneConfiguration(v reflect.Value, depth int) (reflect.Value, error) {
	if depth > 64 {
		return reflect.Value{}, errors.New("config: defaults contain cycles or excessive nesting")
	}
	result := reflect.New(v.Type()).Elem()
	result.Set(v)
	switch v.Kind() {
	case reflect.Struct:
		for i := 0; i < v.NumField(); i++ {
			field := v.Type().Field(i)
			if field.PkgPath != "" || strings.Split(field.Tag.Get("json"), ",")[0] == "-" {
				continue
			}
			child, err := cloneConfiguration(v.Field(i), depth+1)
			if err != nil {
				return reflect.Value{}, err
			}
			result.Field(i).Set(child)
		}
	case reflect.Pointer:
		if !v.IsNil() {
			child, err := cloneConfiguration(v.Elem(), depth+1)
			if err != nil {
				return reflect.Value{}, err
			}
			result.Set(reflect.New(v.Type().Elem()))
			result.Elem().Set(child)
		}
	case reflect.Interface:
		if !v.IsNil() {
			child, err := cloneConfiguration(v.Elem(), depth+1)
			if err != nil {
				return reflect.Value{}, err
			}
			result.Set(child)
		}
	case reflect.Slice:
		if !v.IsNil() {
			result = reflect.MakeSlice(v.Type(), v.Len(), v.Len())
			for i := 0; i < v.Len(); i++ {
				child, err := cloneConfiguration(v.Index(i), depth+1)
				if err != nil {
					return reflect.Value{}, err
				}
				result.Index(i).Set(child)
			}
		}
	case reflect.Array:
		for i := 0; i < v.Len(); i++ {
			child, err := cloneConfiguration(v.Index(i), depth+1)
			if err != nil {
				return reflect.Value{}, err
			}
			result.Index(i).Set(child)
		}
	case reflect.Map:
		if !v.IsNil() {
			result = reflect.MakeMapWithSize(v.Type(), v.Len())
			iter := v.MapRange()
			for iter.Next() {
				child, err := cloneConfiguration(iter.Value(), depth+1)
				if err != nil {
					return reflect.Value{}, err
				}
				result.SetMapIndex(iter.Key(), child)
			}
		}
	}
	return result, nil
}