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nodes_metadata.go
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/
nodes_metadata.go
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package parser
import (
"errors"
"fmt"
"reflect"
"strings"
)
// MetadataOpts Options for the metadata.
type MetadataOpts struct {
TagName string
AllowSliceAsStruct bool
}
// AddMetadata adds metadata such as type, inferred from element, to a node.
func AddMetadata(element interface{}, node *Node, opts MetadataOpts) error {
return metadata{MetadataOpts: opts}.Add(element, node)
}
type metadata struct {
MetadataOpts
}
// Add adds metadata such as type, inferred from element, to a node.
func (m metadata) Add(element interface{}, node *Node) error {
if node == nil {
return nil
}
if len(node.Children) == 0 {
return fmt.Errorf("invalid node %s: no child", node.Name)
}
if element == nil {
return errors.New("nil structure")
}
rootType := reflect.TypeOf(element)
node.Kind = rootType.Kind()
return m.browseChildren(rootType, node)
}
func (m metadata) browseChildren(fType reflect.Type, node *Node) error {
for _, child := range node.Children {
if err := m.add(fType, child); err != nil {
return err
}
}
return nil
}
func (m metadata) add(rootType reflect.Type, node *Node) error {
rType := rootType
if rootType.Kind() == reflect.Ptr {
rType = rootType.Elem()
}
field, err := m.findTypedField(rType, node)
if err != nil {
return err
}
if err = isSupportedType(field); err != nil {
return err
}
fType := field.Type
node.Kind = fType.Kind()
node.Tag = field.Tag
if fType.Kind() == reflect.Struct || fType.Kind() == reflect.Ptr && fType.Elem().Kind() == reflect.Struct ||
fType.Kind() == reflect.Map {
if len(node.Children) == 0 && field.Tag.Get(m.TagName) != TagLabelAllowEmpty {
return fmt.Errorf("%s cannot be a standalone element (type %s)", node.Name, fType)
}
node.Disabled = len(node.Value) > 0 && !strings.EqualFold(node.Value, "true") && field.Tag.Get(m.TagName) == TagLabelAllowEmpty
}
if len(node.Children) == 0 {
return nil
}
if fType.Kind() == reflect.Struct || fType.Kind() == reflect.Ptr && fType.Elem().Kind() == reflect.Struct {
return m.browseChildren(fType, node)
}
if fType.Kind() == reflect.Map {
for _, child := range node.Children {
// elem is a map entry value type
elem := fType.Elem()
child.Kind = elem.Kind()
if elem.Kind() == reflect.Map || elem.Kind() == reflect.Struct ||
(elem.Kind() == reflect.Ptr && elem.Elem().Kind() == reflect.Struct) {
if err = m.browseChildren(elem, child); err != nil {
return err
}
}
}
return nil
}
if fType.Kind() == reflect.Slice {
if m.AllowSliceAsStruct && field.Tag.Get(TagLabelSliceAsStruct) != "" {
return m.browseChildren(fType.Elem(), node)
}
for _, ch := range node.Children {
ch.Kind = fType.Elem().Kind()
if err = m.browseChildren(fType.Elem(), ch); err != nil {
return err
}
}
return nil
}
return fmt.Errorf("invalid node %s: %v", node.Name, fType.Kind())
}
func (m metadata) findTypedField(rType reflect.Type, node *Node) (reflect.StructField, error) {
for i := 0; i < rType.NumField(); i++ {
cField := rType.Field(i)
fieldName := cField.Tag.Get(TagLabelSliceAsStruct)
if !m.AllowSliceAsStruct || len(fieldName) == 0 {
fieldName = cField.Name
}
if IsExported(cField) {
if cField.Anonymous {
if cField.Type.Kind() == reflect.Struct {
structField, err := m.findTypedField(cField.Type, node)
if err != nil {
continue
}
return structField, nil
}
}
if strings.EqualFold(fieldName, node.Name) {
node.FieldName = cField.Name
return cField, nil
}
}
}
return reflect.StructField{}, fmt.Errorf("field not found, node: %s", node.Name)
}
// IsExported reports whether f is exported.
// https://golang.org/pkg/reflect/#StructField
func IsExported(f reflect.StructField) bool {
return f.PkgPath == ""
}
func isSupportedType(field reflect.StructField) error {
fType := field.Type
if fType.Kind() == reflect.Slice {
switch fType.Elem().Kind() {
case reflect.String,
reflect.Bool,
reflect.Int,
reflect.Int8,
reflect.Int16,
reflect.Int32,
reflect.Int64,
reflect.Uint,
reflect.Uint8,
reflect.Uint16,
reflect.Uint32,
reflect.Uint64,
reflect.Uintptr,
reflect.Float32,
reflect.Float64,
reflect.Struct,
reflect.Ptr:
return nil
default:
return fmt.Errorf("unsupported slice type: %v", fType)
}
}
if fType.Kind() == reflect.Map && fType.Key().Kind() != reflect.String {
return fmt.Errorf("unsupported map key type: %v", fType.Key())
}
if fType.Kind() == reflect.Func {
return fmt.Errorf("unsupported type: %v", fType)
}
return nil
}