annotation-go/registry.go

package annotation

import (
	"encoding/json"
	"fmt"
	"reflect"
	"strings"

	"git.loafle.net/loafer/annotation-go/annotations"
	luReflect "git.loafle.net/loafer/util-go/reflect"
)

func init() {
	registry = newRegistry()
}

// Definition is struct
type Definition struct {
	t  reflect.Type
	rt reflect.Type
}

// Regist is interface
type Regist interface {
	// Register is method
	Register(t reflect.Type) error
	// Parse is method
	Parse(tag reflect.StructTag) (map[reflect.Type]annotations.Annotation, error)
}

// Registry is struct
type Registry struct {
	definitions map[string]*Definition
}

var registry Regist

func newRegistry() Regist {
	r := &Registry{}
	r.definitions = make(map[string]*Definition, 0)

	return r
}

// Register is method
func Register(t reflect.Type) error {
	return registry.Register(t)
}

// Register is method
func (r *Registry) Register(t reflect.Type) error {
	rt, _, _ := luReflect.GetTypeInfo(t)
	f := r.getTypeAnnotationField(t)
	if nil == f {
		return fmt.Errorf("Annotation: This type[%s] is not Annotation. use TypeAnnotation", rt.Name())
	}

	name := r.parseAnnotationMeta(f.Tag)

	if _, ok := r.definitions[name]; ok {
		return fmt.Errorf("Annotation: name[%s] of annotation exist already", name)
	}

	def := &Definition{
		t:  t,
		rt: rt,
	}

	r.definitions[name] = def
	return nil
}

// Parse is method
func Parse(tag reflect.StructTag) (map[reflect.Type]annotations.Annotation, error) {
	return registry.Parse(tag)
}

// Parse is method
func (r *Registry) Parse(tag reflect.StructTag) (map[reflect.Type]annotations.Annotation, error) {
	s := strings.Trim(tag.Get(AnnotationTag), " ")
	if "" == s {
		return nil, nil
	}

	am, err := r.splitAnnotation(s)
	if nil != err {
		return nil, err
	}

	if nil == am || 0 == len(am) {
		return nil, nil
	}

	rKVs := make(map[reflect.Type]annotations.Annotation, 0)
	for name, attributes := range am {
		t, annotation, err := r.buildAnnotation(name, attributes)
		if nil != err {
			return nil, err
		}
		rKVs[t] = annotation
	}

	return rKVs, nil
}

func (r *Registry) getTypeAnnotationField(t reflect.Type) *reflect.StructField {
	rt, _, _ := luReflect.GetTypeInfo(t)
	if reflect.Struct != rt.Kind() {
		return nil
	}

	for i := 0; i < rt.NumField(); i++ {
		f := rt.Field(i)

		if f.Anonymous {
			if f.Type == annotations.TypeAnnotationType {
				return &f
			}
		}
	}
	return nil
}

func (r *Registry) parseAnnotationMeta(tag reflect.StructTag) string {
	return strings.Trim(tag.Get(AnnotationMetaTag), " ")
}

func (r *Registry) splitAnnotation(s string) (map[string]string, error) {
	ss := make(map[string]string, 0)
	ts := s
	for {
		as := strings.Index(ts, AnnotationChar)
		if -1 == as {
			break
		}
		aas := strings.Index(ts, AnnotationStartChar)
		aae := strings.Index(ts, AnnotationEndChar)

		aName := ts[as:aas]
		aAttributes := ts[aas+1 : aae]

		if 0 < len(aAttributes) {
			ss[aName] = aAttributes
		} else {
			ss[aName] = ""
		}

		if len(ts) <= (aae + 1) {
			break
		}
		ts = ts[aae+1:]
	}

	return ss, nil
}

func (r *Registry) buildAnnotation(name string, attributes string) (reflect.Type, annotations.Annotation, error) {
	def, ok := r.definitions[name]
	if !ok {
		return nil, nil, fmt.Errorf("There is no annotation[%s]", name)
	}

	v := reflect.New(def.rt)
	i := v.Interface().(annotations.Annotation)

	if "" != attributes {
		_json := fmt.Sprintf("{%s}", attributes)
		if err := json.Unmarshal([]byte(_json), i); nil != err {
			return nil, nil, err
		}

	}
	return def.t, i, nil
}