kos/util/reflect/reflect.go

package reflect

import (
	"fmt"
	"reflect"
	"strconv"
	"strings"
)

func findField(v reflect.Value, field string) reflect.Value {
	var (
		pos       int
		tagValue  string
		refValue  reflect.Value
		refType   reflect.Type
		fieldType reflect.StructField
		allowTags = []string{"json", "yaml", "xml"}
	)
	refValue = v.FieldByName(field)
	if !refValue.IsValid() {
		refType = v.Type()
		for i := 0; i < refType.NumField(); i++ {
			fieldType = refType.Field(i)
			for _, tagName := range allowTags {
				tagValue = fieldType.Tag.Get(tagName)
				if tagValue == "" {
					continue
				}
				if pos = strings.Index(tagValue, ","); pos != -1 {
					tagValue = tagValue[:pos]
				}
				if tagValue == field {
					return v.Field(i)
				}
			}
		}
	}
	return refValue
}

func safeAssignment(variable reflect.Value, value interface{}) (err error) {
	var (
		n    int64
		un   uint64
		fn   float64
		kind reflect.Kind
	)
	rv := reflect.ValueOf(value)
	kind = variable.Kind()
	if kind != reflect.Slice && kind != reflect.Array && kind != reflect.Map && kind == rv.Kind() {
		variable.Set(rv)
		return
	}
	switch kind {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetInt(rv.Int())
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetInt(int64(rv.Uint()))
		case reflect.Float32, reflect.Float64:
			variable.SetInt(int64(rv.Float()))
		case reflect.String:
			if n, err = strconv.ParseInt(rv.String(), 10, 64); err == nil {
				variable.SetInt(n)
			}
		default:
			err = fmt.Errorf("unsupported kind %s", rv.Kind())
		}
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetUint(uint64(rv.Int()))
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetUint(rv.Uint())
		case reflect.Float32, reflect.Float64:
			variable.SetUint(uint64(rv.Float()))
		case reflect.String:
			if un, err = strconv.ParseUint(rv.String(), 10, 64); err == nil {
				variable.SetUint(un)
			}
		default:
			err = fmt.Errorf("unsupported kind %s", rv.Kind())
		}
	case reflect.Float32, reflect.Float64:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetFloat(float64(rv.Int()))
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetFloat(float64(rv.Uint()))
		case reflect.Float32, reflect.Float64:
			variable.SetFloat(rv.Float())
		case reflect.String:
			if fn, err = strconv.ParseFloat(rv.String(), 64); err == nil {
				variable.SetFloat(fn)
			}
		default:
			err = fmt.Errorf("unsupported kind %s", rv.Kind())
		}
	case reflect.String:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetString(strconv.FormatInt(rv.Int(), 10))
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetString(strconv.FormatUint(rv.Uint(), 10))
		case reflect.Float32, reflect.Float64:
			variable.SetString(strconv.FormatFloat(rv.Float(), 'f', -1, 64))
		case reflect.String:
			variable.SetString(rv.String())
		default:
			variable.SetString(fmt.Sprint(value))
		}
	default:
		err = fmt.Errorf("unsupported kind %s", kind)
	}
	return
}

func Set(hacky interface{}, field string, value interface{}) (err error) {
	var (
		n        int
		refField reflect.Value
	)
	refVal := reflect.ValueOf(hacky)
	if refVal.Kind() == reflect.Ptr {
		refVal = reflect.Indirect(refVal)
	}
	if refVal.Kind() != reflect.Struct {
		return fmt.Errorf("%s kind is %v", refVal.Type().String(), refField.Kind())
	}
	refField = findField(refVal, field)
	if !refField.IsValid() {
		return fmt.Errorf("%s field `%s` not found", refVal.Type(), field)
	}
	rv := reflect.ValueOf(value)
	fieldKind := refField.Kind()
	if fieldKind != reflect.Slice && fieldKind != reflect.Array && fieldKind != reflect.Map && fieldKind == rv.Kind() {
		refField.Set(rv)
		return
	}
	switch fieldKind {
	case reflect.Array, reflect.Slice:
		innerType := refField.Type().Elem()
		if rv.Kind() == reflect.Array || rv.Kind() == reflect.Slice {
			sliceVar := reflect.MakeSlice(refField.Type(), rv.Len(), rv.Len())
			n = 0
			for i := 0; i < rv.Len(); i++ {
				srcVal := rv.Index(i)
				dstVal := reflect.New(innerType).Elem()
				if err = safeAssignment(dstVal, srcVal); err == nil {
					sliceVar.Index(n).Set(dstVal)
					n++
				}
			}
			refField.Set(sliceVar.Slice(0, n))
		}
	default:
		err = safeAssignment(refField, value)
	}
	return
}