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|
package pipe
import (
"context"
"sync"
"sync/atomic"
"github.com/pkg/errors"
)
type channel[V any] struct {
OnSendCompletion func()
value atomic.Pointer[V]
lastValue *V
}
func (c *channel[V]) Send(v V) {
c.value.Store(&v)
if c.OnSendCompletion != nil {
c.OnSendCompletion()
}
}
func (c *channel[V]) Receive() (V, bool) {
v := c.value.Load()
if v == nil || v == c.lastValue {
return *new(V), false
}
c.lastValue = v
return *v, true
}
type Pipe[Payload, Value any] struct {
Sender Sender[Payload, Value]
Receiver Receiver[Payload, Value]
OnReceiveCompletion func()
OnSendCompletion func()
}
type Request[Payload any] struct {
Payload Payload
Canceled bool
}
type Sender[Payload, Value any] interface {
Request() Request[Payload]
Update(v Value)
Finalize(v Value, err error)
Status() Status[Value]
}
type Receiver[Payload, Value any] interface {
Receive() bool
Cancel()
Status() Status[Value]
Request() Payload
}
type Status[Value any] struct {
Canceled bool
Completed bool
Err error
Value Value
}
func NewWithFunction[Payload, Value any](f func(context.Context) (Value, error)) (*Pipe[Payload, Value], func()) {
p := New[Payload, Value](Request[Payload]{})
ctx, cancel := context.WithCancelCause(context.TODO())
p.OnReceiveCompletion = func() {
if req := p.Sender.Request(); req.Canceled {
cancel(errors.WithStack(context.Canceled))
}
}
return p, func() {
res, err := f(ctx)
if err != nil {
p.Sender.Finalize(*new(Value), err)
return
}
p.Sender.Finalize(res, nil)
}
}
func New[Payload, Value any](req Request[Payload]) *Pipe[Payload, Value] {
cancelCh := &channel[Request[Payload]]{}
roundTripCh := &channel[Status[Value]]{}
pw := &sender[Payload, Value]{
req: req,
sendChannel: roundTripCh,
}
pr := &receiver[Payload, Value]{
req: req,
recvChannel: roundTripCh,
sendChannel: cancelCh,
}
p := &Pipe[Payload, Value]{
Sender: pw,
Receiver: pr,
}
cancelCh.OnSendCompletion = func() {
v, ok := cancelCh.Receive()
if ok {
pw.setRequest(v)
}
if p.OnReceiveCompletion != nil {
p.OnReceiveCompletion()
}
}
roundTripCh.OnSendCompletion = func() {
if p.OnSendCompletion != nil {
p.OnSendCompletion()
}
}
return p
}
type sender[Payload, Value any] struct {
status Status[Value]
req Request[Payload]
sendChannel *channel[Status[Value]]
mu sync.Mutex
}
func (pw *sender[Payload, Value]) Status() Status[Value] {
return pw.status
}
func (pw *sender[Payload, Value]) Request() Request[Payload] {
pw.mu.Lock()
defer pw.mu.Unlock()
return pw.req
}
func (pw *sender[Payload, Value]) setRequest(req Request[Payload]) {
pw.mu.Lock()
defer pw.mu.Unlock()
pw.req = req
}
func (pw *sender[Payload, Value]) Update(v Value) {
pw.status.Value = v
pw.sendChannel.Send(pw.status)
}
func (pw *sender[Payload, Value]) Finalize(v Value, err error) {
pw.status.Value = v
pw.status.Err = err
pw.status.Completed = true
if errors.Is(err, context.Canceled) && pw.req.Canceled {
pw.status.Canceled = true
}
pw.sendChannel.Send(pw.status)
}
type receiver[Payload, Value any] struct {
status Status[Value]
req Request[Payload]
recvChannel *channel[Status[Value]]
sendChannel *channel[Request[Payload]]
}
func (pr *receiver[Payload, Value]) Request() Payload {
return pr.req.Payload
}
func (pr *receiver[Payload, Value]) Receive() bool {
v, ok := pr.recvChannel.Receive()
if !ok {
return false
}
pr.status = v
return true
}
func (pr *receiver[Payload, Value]) Cancel() {
req := pr.req
if req.Canceled {
return
}
req.Canceled = true
pr.sendChannel.Send(req)
}
func (pr *receiver[Payload, Value]) Status() Status[Value] {
return pr.status
}
|
