package utils

import (
	"errors"
	"reflect"
)

func DeepFields(ifaceType reflect.Type) []reflect.StructField {
	var fields []reflect.StructField

	for i := 0; i < ifaceType.NumField(); i++ {
		v := ifaceType.Field(i)
		if v.Anonymous && v.Type.Kind() == reflect.Struct {
			fields = append(fields, DeepFields(v.Type)...)
		} else {
			fields = append(fields, v)
		}
	}

	return fields
}

func StructCopy(DstStructPtr interface{}, SrcStructPtr interface{}) error {
	srcv := reflect.ValueOf(SrcStructPtr)
	dstv := reflect.ValueOf(DstStructPtr)
	srct := reflect.TypeOf(SrcStructPtr)
	dstt := reflect.TypeOf(DstStructPtr)
	if srct.Kind() != reflect.Ptr || dstt.Kind() != reflect.Ptr ||
		srct.Elem().Kind() == reflect.Ptr || dstt.Elem().Kind() == reflect.Ptr {
		return errors.New("Fatal error:type of parameters must be Ptr of value")
	}
	if srcv.IsNil() || dstv.IsNil() {
		return errors.New("Fatal error:value of parameters should not be nil")
	}
	srcV := srcv.Elem()
	dstV := dstv.Elem()
	srcfields := DeepFields(reflect.ValueOf(SrcStructPtr).Elem().Type())
	for _, v := range srcfields {
		if v.Anonymous {
			continue
		}
		dst := dstV.FieldByName(v.Name)
		src := srcV.FieldByName(v.Name)
		if !dst.IsValid() {
			continue
		}
		if src.Type() == dst.Type() && dst.CanSet() {
			dst.Set(src)
			continue
		}
		if src.Kind() == reflect.Ptr && !src.IsNil() && src.Type().Elem() == dst.Type() {
			dst.Set(src.Elem())
			continue
		}
		if dst.Kind() == reflect.Ptr && dst.Type().Elem() == src.Type() {
			dst.Set(reflect.New(src.Type()))
			dst.Elem().Set(src)
			continue
		}
	}
	return nil
}

func FieldByTag(value reflect.Value, tag string, tagName string) reflect.Value {
	itype := value.Type()
	for i := 0; i < itype.NumField(); i++ {
		v := itype.Field(i)
		if v.Tag.Get(tagName) == tag && tag != "" {
			return value.FieldByIndex(v.Index)
		}
	}
	return reflect.Value{}
}

func StructCopyByTag(DstStructPtr interface{}, SrcStructPtr interface{}, tagName string) error {
	srcv := reflect.ValueOf(SrcStructPtr)
	dstv := reflect.ValueOf(DstStructPtr)
	srct := reflect.TypeOf(SrcStructPtr)
	dstt := reflect.TypeOf(DstStructPtr)
	if srct.Kind() != reflect.Ptr || dstt.Kind() != reflect.Ptr ||
		srct.Elem().Kind() == reflect.Ptr || dstt.Elem().Kind() == reflect.Ptr {
		return errors.New("Fatal error:type of parameters must be Ptr of value")
	}
	if srcv.IsNil() || dstv.IsNil() {
		return errors.New("Fatal error:value of parameters should not be nil")
	}
	srcV := srcv.Elem()
	dstV := dstv.Elem()
	srcfields := DeepFields(reflect.ValueOf(SrcStructPtr).Elem().Type())
	for _, v := range srcfields {
		if v.Anonymous {
			continue
		}
		dst := FieldByTag(dstV, v.Tag.Get(tagName), tagName)
		src := FieldByTag(srcV, v.Tag.Get(tagName), tagName)
		if !dst.IsValid() {
			continue
		}
		if src.Type() == dst.Type() && dst.CanSet() {
			dst.Set(src)
			continue
		}
		if src.Kind() == reflect.Ptr && !src.IsNil() && src.Type().Elem() == dst.Type() {
			dst.Set(src.Elem())
			continue
		}
		if dst.Kind() == reflect.Ptr && dst.Type().Elem() == src.Type() {
			dst.Set(reflect.New(src.Type()))
			dst.Elem().Set(src)
			continue
		}
	}
	return nil
}