Feat: add structure helper

common/structure/structure.go

@@ -0,0 +1,160 @@
+package structure
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// Option is the configuration that is used to create a new decoder
+type Option struct {
+	TagName          string
+	WeaklyTypedInput bool
+}
+
+// Decoder is the core of structure
+type Decoder struct {
+	option *Option
+}
+
+// NewDecoder return a Decoder by Option
+func NewDecoder(option Option) *Decoder {
+	if option.TagName == "" {
+		option.TagName = "structure"
+	}
+	return &Decoder{option: &option}
+}
+
+// Decode transform a map[string]interface{} to a struct
+func (d *Decoder) Decode(src map[string]interface{}, dst interface{}) error {
+	if reflect.TypeOf(dst).Kind() != reflect.Ptr {
+		return fmt.Errorf("Decode must recive a ptr struct")
+	}
+	t := reflect.TypeOf(dst).Elem()
+	v := reflect.ValueOf(dst).Elem()
+	for idx := 0; idx < v.NumField(); idx++ {
+		field := t.Field(idx)
+
+		tag := field.Tag.Get(d.option.TagName)
+		str := strings.SplitN(tag, ",", 2)
+		key := str[0]
+		omitempty := false
+		if len(str) > 1 {
+			omitempty = str[1] == "omitempty"
+		}
+
+		value, ok := src[key]
+		if !ok {
+			if omitempty {
+				continue
+			}
+			return fmt.Errorf("key %s missing", key)
+		}
+
+		err := d.decode(key, value, v.Field(idx))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (d *Decoder) decode(name string, data interface{}, val reflect.Value) error {
+	switch val.Kind() {
+	case reflect.Int:
+		return d.decodeInt(name, data, val)
+	case reflect.String:
+		return d.decodeString(name, data, val)
+	case reflect.Bool:
+		return d.decodeBool(name, data, val)
+	case reflect.Slice:
+		return d.decodeSlice(name, data, val)
+	default:
+		return fmt.Errorf("type %s not support", val.Kind().String())
+	}
+}
+
+func (d *Decoder) decodeInt(name string, data interface{}, val reflect.Value) (err error) {
+	dataVal := reflect.ValueOf(data)
+	kind := dataVal.Kind()
+	switch {
+	case kind == reflect.Int:
+		val.SetInt(dataVal.Int())
+	case kind == reflect.String && d.option.WeaklyTypedInput:
+		var i int64
+		i, err = strconv.ParseInt(dataVal.String(), 0, val.Type().Bits())
+		if err == nil {
+			val.SetInt(i)
+		} else {
+			err = fmt.Errorf("cannot parse '%s' as int: %s", name, err)
+		}
+	default:
+		err = fmt.Errorf(
+			"'%s' expected type '%s', got unconvertible type '%s'",
+			name, val.Type(), dataVal.Type(),
+		)
+	}
+	return err
+}
+
+func (d *Decoder) decodeString(name string, data interface{}, val reflect.Value) (err error) {
+	dataVal := reflect.ValueOf(data)
+	kind := dataVal.Kind()
+	switch {
+	case kind == reflect.String:
+		val.SetString(dataVal.String())
+	case kind == reflect.Int && d.option.WeaklyTypedInput:
+		val.SetString(strconv.FormatInt(dataVal.Int(), 10))
+	default:
+		err = fmt.Errorf(
+			"'%s' expected type'%s', got unconvertible type '%s'",
+			name, val.Type(), dataVal.Type(),
+		)
+	}
+	return err
+}
+
+func (d *Decoder) decodeBool(name string, data interface{}, val reflect.Value) (err error) {
+	dataVal := reflect.ValueOf(data)
+	kind := dataVal.Kind()
+	switch {
+	case kind == reflect.Bool:
+		val.SetBool(dataVal.Bool())
+	case kind == reflect.Int && d.option.WeaklyTypedInput:
+		val.SetBool(dataVal.Int() != 0)
+	default:
+		err = fmt.Errorf(
+			"'%s' expected type'%s', got unconvertible type '%s'",
+			name, val.Type(), dataVal.Type(),
+		)
+	}
+	return err
+}
+
+func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value) error {
+	dataVal := reflect.Indirect(reflect.ValueOf(data))
+	valType := val.Type()
+	valElemType := valType.Elem()
+
+	if dataVal.Kind() != reflect.Slice {
+		return fmt.Errorf("'%s' is not a slice", name)
+	}
+
+	valSlice := val
+	for i := 0; i < dataVal.Len(); i++ {
+		currentData := dataVal.Index(i).Interface()
+		for valSlice.Len() <= i {
+			valSlice = reflect.Append(valSlice, reflect.Zero(valElemType))
+		}
+		currentField := valSlice.Index(i)
+
+		fieldName := fmt.Sprintf("%s[%d]", name, i)
+		if err := d.decode(fieldName, currentData, currentField); err != nil {
+			return err
+		}
+	}
+
+	val.Set(valSlice)
+	return nil
+}