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jsonhal.go
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jsonhal.go
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// Package jsonhal provides structs and methods to easily wrap your own data
// in a HAL compatible struct with support for hyperlinks and embedded resources
// HAL specification: http:https://stateless.co/hal_specification.html
package jsonhal
import (
"errors"
"fmt"
"reflect"
"time"
"github.com/mitchellh/mapstructure"
)
// Link represents a link in "_links" object
type Link struct {
Href string `json:"href" mapstructure:"href"`
Title string `json:"title,omitempty" mapstructure:"title"`
}
// Embedded represents a resource in "_embedded" object
type Embedded interface{}
// EmbedSetter is the interface that wraps the basic setEmbedded method.
//
// SetEmbedded adds a slice of objects under a named key in the embedded map
type EmbedSetter interface {
SetEmbedded(name string, embedded Embedded)
}
// EmbedGetter is the interface that wraps the basic getEmbedded method.
//
// GetEmbedded returns a slice of embedded resources by name or error
type EmbedGetter interface {
GetEmbedded(name string) (Embedded, error)
}
// Embedder is the interface that wraps the basic setEmbedded and getEmbedded methods.
type Embedder interface {
EmbedSetter
EmbedGetter
}
// Hal is used for composition, include it as anonymous field in your structs
type Hal struct {
Links map[string]*Link `json:"_links,omitempty" mapstructure:"_links"`
Embedded map[string]Embedded `json:"_embedded,omitempty" mapstructure:"_embedded"`
decoder *mapstructure.Decoder
}
// SetLink sets a link (self, next, etc). Title argument is optional
func (h *Hal) SetLink(name, href, title string) {
if h.Links == nil {
h.Links = make(map[string]*Link, 0)
}
h.Links[name] = &Link{Href: href, Title: title}
}
// DeleteLink removes a link named name if it is found
func (h *Hal) DeleteLink(name string) {
if h.Links != nil {
delete(h.Links, name)
}
}
// GetLink returns a link by name or error
func (h *Hal) GetLink(name string) (*Link, error) {
if h.Links == nil {
return nil, fmt.Errorf("Link \"%s\" not found", name)
}
link, ok := h.Links[name]
if !ok {
return nil, fmt.Errorf("Link \"%s\" not found", name)
}
return link, nil
}
// SetEmbedded adds a slice of objects under a named key in the embedded map
func (h *Hal) SetEmbedded(name string, embedded Embedded) {
if h.Embedded == nil {
h.Embedded = make(map[string]Embedded, 0)
}
h.Embedded[name] = embedded
}
// GetEmbedded returns a slice of embedded resources by name or error
func (h *Hal) GetEmbedded(name string) (Embedded, error) {
if h.Embedded == nil {
return nil, fmt.Errorf("Embedded \"%s\" not found", name)
}
embedded, ok := h.Embedded[name]
if !ok {
return nil, fmt.Errorf("Embedded \"%s\" not found", name)
}
return embedded, nil
}
// CountEmbedded counts number of embedded items
func (h *Hal) CountEmbedded(name string) (int, error) {
e, err := h.GetEmbedded(name)
if err != nil {
return 0, err
}
if reflect.TypeOf(interface{}(e)).Kind() != reflect.Slice && reflect.TypeOf(interface{}(e)).Kind() != reflect.Map {
return 0, errors.New("Embedded object is not a slice or a map")
}
return reflect.ValueOf(interface{}(e)).Len(), nil
}
// decodeHook is used to support datatypes that mapstructure does not support native
func (h *Hal) decodeHook(f reflect.Type, t reflect.Type, data interface{}) (interface{}, error) {
// only if target datatype is time.Time and if source datatype is string
if t == reflect.TypeOf(time.Time{}) && f == reflect.TypeOf("") {
return time.Parse(time.RFC3339, data.(string))
}
//everything else would not be handled for now
return data, nil
}
// DecodeEmbedded decodes embedded objects into a struct
func (h *Hal) DecodeEmbedded(name string, result interface{}) (err error) {
var dec *mapstructure.Decoder
defer func() {
if r := recover(); r != nil {
err = r.(error)
}
}()
e, err := h.GetEmbedded(name)
if err != nil {
panic(err)
}
//setup a new decoder if not already present
if h.decoder == nil {
dec, err = mapstructure.NewDecoder(&mapstructure.DecoderConfig{Result: result, DecodeHook: h.decodeHook})
if err != nil {
panic(err)
}
h.decoder = dec
}
err = h.decoder.Decode(e)
if err != nil {
panic(err)
}
return nil
}
// DeleteEmbedded removes an embedded resource named name if it is found
func (h *Hal) DeleteEmbedded(name string) {
if h.Embedded != nil {
delete(h.Embedded, name)
}
}