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data.go
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data.go
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package aedstorm
import (
"errors"
"fmt"
"log"
"os"
"reflect"
"sync"
gocache "github.com/rubanbydesign/gocache/cache"
"github.com/rubanbydesign/rest/cache"
"cloud.google.com/go/datastore"
"golang.org/x/net/context"
"golang.org/x/sync/errgroup"
)
// Standardized error messages
var (
ErrNoModel = errors.New("Model is not loaded")
ErrNoID = errors.New("Model has no ID")
ErrNoContext = errors.New("No net/context was loaded")
ErrNilModel = errors.New("Model is nil")
ErrModelInvalid = errors.New("Model must be a struct pointer")
)
const (
// TagName is the tag name where we look for custom tag values, like "id"
TagName = "datastore"
)
// DataModel is a ORM styled structure for saving and loading entities
type DataModel struct {
model Model
ctx context.Context
verified bool
entity string
idFieldName string
uid string
sync.Mutex
}
// NewModel returns an initialized data model
func NewModel(m Model) *DataModel {
t := reflect.ValueOf(m).Type()
if t.Kind() != reflect.Ptr {
panic(ErrModelInvalid)
}
if t.Elem().Kind() != reflect.Struct {
panic(ErrModelInvalid)
}
return &DataModel{model: m}
}
// verify checks that the DataModel has an ID field, context, and non-nil model.
// It should be called before any function that needs one of those things. The
// results are stored in memory for a bit better performance.
func (dm *DataModel) verify() (err error) {
if dm.verified {
return
}
if dm.ctx == nil {
return ErrNoContext
}
if dm.model == nil {
return ErrNoModel
}
dm.Lock()
defer dm.Unlock()
// See if implements the EntityID interface, if not then try to guess the field
_, ok := dm.model.(EntityID)
// Try to get the ID field, but only fail if the model doesn't implement EntityID
if dm.idFieldName, err = dm.getIDField(); !ok && err != nil {
return err
}
dm.verified = true
return nil
}
// getIDField gets the name of the struct field which serves as an ID for the given model.
func (dm *DataModel) getIDField() (string, error) {
t := reflect.ValueOf(dm.model).Type().Elem()
// Iterate over all available fields and read the tag value or return if the field name is ID
for i := 0; i < t.NumField(); i++ {
field := t.Field(i)
tag := field.Tag.Get(TagName)
if field.Name == "ID" || tag == "id" {
return field.Name, nil
}
}
return "", fmt.Errorf("Type %s has no ID field", t.Name())
}
func (dm *DataModel) getEntityName() string {
if dm.entity != "" {
return dm.entity
}
// Try to get the entity name from a Entity() method. If not, fall back to the name of the type itself
if obj, ok := dm.model.(EntityName); ok {
if dm.entity = obj.Entity(); dm.entity != "" {
return dm.entity
}
}
dm.entity = reflect.ValueOf(dm.model).Type().Elem().Name()
return dm.entity
}
func (dm *DataModel) fromCache() error {
if err := dm.verify(); err != nil {
return err
}
return cache.New(dm.Context()).Get(dm.cacheKey(), dm.model)
}
// Load loads the entity from the datastore. Must have an ID for this to work.
func (dm *DataModel) Load() error {
if err := dm.verify(); err != nil {
return err
}
/*
if err := dm.fromCache(); err == nil {
return nil
}
*/
gcpProjectID := os.Getenv("RBD_GCP_PROJECT_ID")
dsClient, err := datastore.NewClient(dm.Context(), gcpProjectID)
if err != nil {
log.Fatalf("Failed to create DataStore client: %v", err)
return err
}
if err := dsClient.Get(dm.Context(), dm.Key(), dm.model); err != nil {
return err
}
// If successful, then cache so we'll have it next time
/*
if err := dm.Cache(); err != nil {
return err
}
*/
return nil
}
// Key returns the datastore key
func (dm *DataModel) Key() *datastore.Key {
return &datastore.Key{Kind: dm.getEntityName(), ID: 0, Name: dm.ID(), Parent: nil}
}
// ID returns the underlying data struct's unique ID. If the supplied struct
// implements this interface, then it's result will be that of the model's EntityID()
// function. Otherwise, a new random uuid v4 will be used.
func (dm *DataModel) ID() string {
if dm.uid != "" {
return dm.uid
}
// Try to get the entity name from a Entity() method. If not, fall back to a new UUID v4
if obj, ok := dm.model.(EntityID); ok {
if id := obj.GetID(); id != "" {
dm.uid = id
return dm.uid
}
}
uuid, err := NewUUID()
if err != nil {
panic(err)
}
dm.uid = uuid.String()
// If can set the id field, do it now.
setter, ok := dm.model.(SetID)
if ok {
setter.SetID(dm.uid)
}
if fieldName, err := dm.getIDField(); err == nil {
reflect.ValueOf(dm.model).Elem().FieldByName(fieldName).SetString(dm.uid)
}
return dm.uid
}
// Save writes the entity to the datastore
func (dm *DataModel) Save() error {
if err := dm.verify(); err != nil {
return err
}
// Check if the struct has en Error() method, and use it if it does.
if obj, ok := dm.model.(EntityError); ok {
if err := obj.Error(); err != nil {
return err
}
}
gcpProjectID := os.Getenv("RBD_GCP_PROJECT_ID")
dsClient, err := datastore.NewClient(dm.Context(), gcpProjectID)
if err != nil {
log.Fatalf("Failed to create DataStore client: %v", err)
return err
}
if _, err := dsClient.Put(dm.Context(), dm.Key(), dm.model); err != nil {
return err
}
// var eg errgroup.Group
// eg.Go(dm.Cache)
// eg.Wait()
var eg2 errgroup.Group
if obj, ok := dm.model.(OnSave); ok {
eg2.Go(obj.Save)
}
waitRoutine := eg2.Wait()
return waitRoutine
}
// Context returns the internal net/context
func (dm *DataModel) Context() context.Context {
return dm.ctx
}
func (dm *DataModel) cacheKey() string {
return fmt.Sprintf("model.%s.%s", dm.getEntityName(), dm.ID())
}
// Cache caches the entity in memcache
func (dm *DataModel) Cache() error {
if err := dm.verify(); err != nil {
return err
}
if err := cache.New(dm.Context()).Set(dm.cacheKey(), dm.model, 0); err != nil {
return err
}
if obj, ok := dm.model.(OnCache); ok {
if err := obj.Cache(); err != nil {
return err
}
}
return nil
}
// WithContext sets the internal context for use in future operations
func (dm *DataModel) WithContext(ctx context.Context) *DataModel {
dm.ctx = ctx
return dm
}
// Uncache removes the cached model from cache
func (dm *DataModel) Uncache() error {
if err := cache.New(dm.Context()).Del(dm.cacheKey()); err != nil {
return err
}
if obj, ok := dm.model.(OnUncache); ok {
if err := obj.Uncache(); err != nil {
return err
}
}
return nil
}
// Delete deletes the entity from the datastore and cache
func (dm *DataModel) Delete() error {
gcpProjectID := os.Getenv("RBD_GCP_PROJECT_ID")
dsClient, err := datastore.NewClient(dm.Context(), gcpProjectID)
if err != nil {
log.Fatalf("Failed to create DataStore client: %v", err)
return err
}
if err := dsClient.Delete(dm.Context(), dm.Key()); err != nil && err != gocache.ErrCacheMiss {
return err
}
var eg errgroup.Group
eg.Go(dm.Uncache)
if obj, ok := dm.model.(OnDelete); ok {
eg.Go(obj.Delete)
}
return eg.Wait()
}