go-gun/gun/scoped.go

214 lines
5.5 KiB
Go
Raw Normal View History

2019-02-20 20:54:46 +00:00
package gun
2019-02-22 06:46:19 +00:00
import (
"context"
2019-02-22 09:23:14 +00:00
"errors"
2019-02-22 06:46:19 +00:00
"sync"
)
2019-02-20 20:54:46 +00:00
type Scoped struct {
2019-02-22 09:23:14 +00:00
gun *Gun
parent *Scoped
field string
cachedParentSoul string
cachedParentSoulLock sync.RWMutex
2019-02-22 06:46:19 +00:00
valueChansToListeners map[<-chan *ValueFetch]*messageIDListener
valueChansToListenersLock sync.Mutex
2019-02-20 20:54:46 +00:00
}
2019-02-22 06:46:19 +00:00
type messageIDListener struct {
id string
values chan *ValueFetch
2019-02-22 09:23:14 +00:00
receivedMessages chan *MessageReceived
2019-02-20 20:54:46 +00:00
}
2019-02-22 09:23:14 +00:00
func newScoped(gun *Gun, parent *Scoped, field string) *Scoped {
2019-02-22 06:46:19 +00:00
return &Scoped{
2019-02-22 09:23:14 +00:00
gun: gun,
parent: parent,
field: field,
2019-02-22 06:46:19 +00:00
}
}
type ValueFetch struct {
// This can be a context error on cancelation
Err error
Field string
2019-02-22 09:23:14 +00:00
// Nil if the value doesn't exist or there's an error
Value *ValueWithState
2019-02-22 06:46:19 +00:00
// Nil when local and sometimes on error
2019-02-22 18:40:02 +00:00
peer *gunPeer
2019-02-20 20:54:46 +00:00
}
2019-02-22 09:23:14 +00:00
var ErrNotObject = errors.New("Scoped value not an object")
var ErrLookupOnTopLevel = errors.New("Cannot do lookup on top level")
// Empty string if doesn't exist, ErrNotObject if self or parent not an object
func (s *Scoped) Soul(ctx context.Context) (string, error) {
s.cachedParentSoulLock.RLock()
cachedParentSoul := s.cachedParentSoul
s.cachedParentSoulLock.RUnlock()
if cachedParentSoul != "" {
return cachedParentSoul, nil
} else if v := s.Val(ctx); v.Err != nil {
return "", v.Err
} else if v.Value == nil {
return "", nil
} else if rel, ok := v.Value.Value.(ValueRelation); !ok {
return "", ErrNotObject
} else {
s.cachedParentSoulLock.Lock()
s.cachedParentSoul = string(rel)
s.cachedParentSoulLock.Unlock()
return string(rel), nil
}
2019-02-20 20:54:46 +00:00
}
2019-02-22 06:46:19 +00:00
func (s *Scoped) Val(ctx context.Context) *ValueFetch {
// Try local before remote
if v := s.ValLocal(ctx); v != nil {
return v
}
return s.ValRemote(ctx)
}
func (s *Scoped) ValLocal(ctx context.Context) *ValueFetch {
2019-02-22 09:23:14 +00:00
// If there is no parent, this is just the relation
if s.parent == nil {
return &ValueFetch{Field: s.field, Value: &ValueWithState{Value: ValueRelation(s.field)}}
2019-02-22 06:46:19 +00:00
}
2019-02-22 09:23:14 +00:00
v := &ValueFetch{Field: s.field}
// Need parent soul for lookup
var parentSoul string
if parentSoul, v.Err = s.parent.Soul(ctx); v.Err == nil {
if v.Value, v.Err = s.gun.storage.Get(ctx, parentSoul, s.field); v.Err == ErrStorageNotFound {
return nil
}
}
return v
2019-02-22 06:46:19 +00:00
}
func (s *Scoped) ValRemote(ctx context.Context) *ValueFetch {
2019-02-22 09:23:14 +00:00
if s.parent == nil {
return &ValueFetch{Err: ErrLookupOnTopLevel, Field: s.field}
}
2019-02-22 06:46:19 +00:00
ch := s.OnRemote(ctx)
defer s.Off(ch)
return <-ch
}
func (s *Scoped) On(ctx context.Context) <-chan *ValueFetch {
ch := make(chan *ValueFetch, 1)
2019-02-22 09:23:14 +00:00
if s.parent == nil {
ch <- &ValueFetch{Err: ErrLookupOnTopLevel, Field: s.field}
} else {
if v := s.ValLocal(ctx); v != nil {
ch <- v
}
go s.onRemote(ctx, ch)
2019-02-22 06:46:19 +00:00
}
return ch
}
func (s *Scoped) OnRemote(ctx context.Context) <-chan *ValueFetch {
ch := make(chan *ValueFetch, 1)
2019-02-22 09:23:14 +00:00
if s.parent == nil {
ch <- &ValueFetch{Err: ErrLookupOnTopLevel, Field: s.field}
} else {
go s.onRemote(ctx, ch)
}
2019-02-22 06:46:19 +00:00
return ch
}
func (s *Scoped) onRemote(ctx context.Context, ch chan *ValueFetch) {
2019-02-22 09:23:14 +00:00
if s.parent == nil {
panic("No parent")
}
// We have to get the parent soul first
parentSoul, err := s.parent.Soul(ctx)
if err != nil {
ch <- &ValueFetch{Err: ErrLookupOnTopLevel, Field: s.field}
return
}
2019-02-22 06:46:19 +00:00
// Create get request
req := &Message{
ID: randString(9),
2019-02-22 09:23:14 +00:00
Get: &MessageGetRequest{Soul: parentSoul, Field: s.field},
2019-02-22 06:46:19 +00:00
}
// Make a chan to listen for received messages and link it to
// the given one so we can turn it "off". Off will close this
// chan.
2019-02-22 09:23:14 +00:00
msgCh := make(chan *MessageReceived)
2019-02-22 06:46:19 +00:00
s.valueChansToListenersLock.Lock()
s.valueChansToListeners[ch] = &messageIDListener{req.ID, ch, msgCh}
s.valueChansToListenersLock.Unlock()
// Listen for responses to this get
s.gun.RegisterMessageIDPutListener(req.ID, msgCh)
// TODO: only for children: s.gun.RegisterValueIDPutListener(s.id, msgCh)
// Handle received messages turning them to value fetches
go func() {
for {
select {
case <-ctx.Done():
ch <- &ValueFetch{Err: ctx.Err(), Field: s.field}
s.Off(ch)
return
case msg, ok := <-msgCh:
if !ok {
return
}
2019-02-22 18:40:02 +00:00
f := &ValueFetch{Field: s.field, peer: msg.peer}
2019-02-22 09:23:14 +00:00
// We asked for a single field, should only get that field or it doesn't exist
if n := msg.Put[parentSoul]; n != nil && n.Values[s.field] != nil {
f.Value = &ValueWithState{n.Values[s.field], n.State[s.field]}
2019-02-22 06:46:19 +00:00
}
2019-02-22 09:23:14 +00:00
// TODO: conflict resolution and defer
// TODO: dedupe
// TODO: store and cache
safeValueFetchSend(ch, f)
2019-02-22 06:46:19 +00:00
}
}
}()
// Send async, sending back errors
go func() {
for peerErr := range s.gun.Send(ctx, req) {
safeValueFetchSend(ch, &ValueFetch{
Err: peerErr.Err,
Field: s.field,
2019-02-22 18:40:02 +00:00
peer: peerErr.peer,
2019-02-22 06:46:19 +00:00
})
}
}()
}
func (s *Scoped) Off(ch <-chan *ValueFetch) bool {
s.valueChansToListenersLock.Lock()
l := s.valueChansToListeners[ch]
delete(s.valueChansToListeners, ch)
s.valueChansToListenersLock.Unlock()
if l != nil {
// Unregister the chan
s.gun.UnregisterMessageIDPutListener(l.id)
// Close the message chan and the value chan
close(l.receivedMessages)
close(l.values)
}
return l != nil
}
func (s *Scoped) Scoped(ctx context.Context, key string, children ...string) *Scoped {
2019-02-22 09:23:14 +00:00
ret := newScoped(s.gun, s, key)
for _, child := range children {
ret = newScoped(s.gun, ret, child)
}
return ret
2019-02-22 06:46:19 +00:00
}
func safeValueFetchSend(ch chan<- *ValueFetch, f *ValueFetch) {
// Due to the fact that we may send on a closed channel here, we ignore the panic
defer func() { recover() }()
ch <- f
}