/
promise.go
87 lines (67 loc) · 1.35 KB
/
promise.go
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package volume
import (
"errors"
"sync"
)
var ErrPromiseCanceled = errors.New("promise was canceled")
var ErrPromiseNotPending = errors.New("promise is not pending")
var ErrPromiseStillPending = errors.New("promise is still pending")
type Promise interface {
IsPending() bool
GetValue() (Volume, error, error)
Fulfill(Volume) error
Reject(error) error
}
type promise struct {
volume *Volume
err error
cancel chan struct{}
sync.RWMutex
}
func NewPromise() Promise {
return &promise{
volume: nil,
err: nil,
cancel: make(chan struct{}),
}
}
func (p *promise) IsPending() bool {
p.RLock()
defer p.RUnlock()
return p.isPending()
}
func (p *promise) isPending() bool {
return p.volume == nil && p.err == nil
}
func (p *promise) GetValue() (Volume, error, error) {
p.RLock()
defer p.RUnlock()
if p.IsPending() {
return Volume{}, nil, ErrPromiseStillPending
}
if p.volume == nil {
return Volume{}, p.err, nil
}
return *p.volume, p.err, nil
}
func (p *promise) Fulfill(volume Volume) error {
p.Lock()
defer p.Unlock()
if !p.isPending() {
if p.err == ErrPromiseCanceled {
return ErrPromiseCanceled
}
return ErrPromiseNotPending
}
p.volume = &volume
return nil
}
func (p *promise) Reject(err error) error {
p.Lock()
defer p.Unlock()
if !p.isPending() {
return ErrPromiseNotPending
}
p.err = err
return nil
}