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oneoff.go
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oneoff.go
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package bus
import (
"context"
"github.com/aperturerobotics/controllerbus/directive"
"github.com/aperturerobotics/util/broadcast"
)
// ExecIdleCallback is an idle callback for ExecOneOffWithFilter.
//
// idleCb is called with the idle state and list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: continues to wait when the directive becomes idle
// errs is the list of errors from the resolvers (if any)
type ExecIdleCallback func(isIdle bool, errs []error) (bool, error)
// WaitWhenIdle returns an ExecIdleCallback that waits when the directive becomes idle.
//
// if ignoreErrors is false, returns any non-nil resolver error that occurs.
func WaitWhenIdle(ignoreErrors bool) ExecIdleCallback {
return func(isIdle bool, errs []error) (bool, error) {
if !ignoreErrors {
for _, err := range errs {
if err != nil {
return false, err
}
}
}
return true, nil
}
}
// ReturnWhenIdle returns an ExecIdleCallback that returns when the directive becomes idle.
func ReturnWhenIdle() ExecIdleCallback {
return func(isIdle bool, errs []error) (bool, error) {
if !isIdle {
return true, nil
}
for _, err := range errs {
if err != nil {
return false, err
}
}
return false, nil
}
}
// ReturnIfIdle returns an ExecIdleCallback that returns when the directive becomes idle if true.
func ReturnIfIdle(returnIfIdle bool) ExecIdleCallback {
if returnIfIdle {
return ReturnWhenIdle()
}
return WaitWhenIdle(false)
}
// ExecOneOff executes a one-off directive.
//
// idleCb is called when idle with the list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: continues to wait when the directive becomes idle
// errs is the list of errors from the resolvers (if any)
//
// If any resolvers return an error, returns that error.
// valDisposeCb is called if the value is no longer valid.
// valDisposeCb might be called multiple times.
// If err != nil, ref == nil.
func ExecOneOff(
ctx context.Context,
bus Bus,
dir directive.Directive,
idleCb ExecIdleCallback,
valDisposeCallback func(),
) (directive.AttachedValue, directive.Instance, directive.Reference, error) {
return ExecOneOffWithFilter(ctx, bus, dir, idleCb, valDisposeCallback, nil)
}
// ExecOneOffWithFilter executes a one-off directive with a filter cb.
//
// Waits until the callback returns true before returning a value.
// valDisposeCb is called if the value is no longer valid.
// valDisposeCb might be called multiple times.
//
// idleCb is called when idle with the list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: if the directive becomes idle & any resolvers failed, returns the resolver error.
// errs is the list of errors from the resolvers (if any)
//
// If err != nil, ref == nil.
func ExecOneOffWithFilter(
ctx context.Context,
bus Bus,
dir directive.Directive,
idleCb ExecIdleCallback,
valDisposeCallback func(),
filterCb func(val directive.AttachedValue) (bool, error),
) (directive.AttachedValue, directive.Instance, directive.Reference, error) {
// mtx, bcast guard these variables
var bcast broadcast.Broadcast
var val directive.AttachedValue
var resErr error
var idle, wait bool
if idleCb == nil {
// register a callback to catch any resolver errors
idleCb = WaitWhenIdle(false)
}
di, ref, err := bus.AddDirective(
dir,
NewCallbackHandler(
func(v directive.AttachedValue) {
bcast.HoldLock(func(broadcast func(), getWaitCh func() <-chan struct{}) {
if val == nil && resErr == nil {
ok := filterCb == nil
if !ok {
ok, resErr = filterCb(v)
if resErr != nil {
broadcast()
}
}
if ok && resErr == nil {
val = v
broadcast()
}
}
})
},
func(v directive.AttachedValue) {
if valDisposeCallback == nil {
return
}
var valueRemoved bool
bcast.HoldLock(func(broadcast func(), getWaitCh func() <-chan struct{}) {
valueRemoved = val != nil && val.GetValueID() == v.GetValueID()
})
if valueRemoved {
valDisposeCallback()
}
},
func() {
bcast.HoldLock(func(broadcast func(), getWaitCh func() <-chan struct{}) {
if resErr == nil {
resErr = ErrDirectiveDisposed
broadcast()
}
})
if valDisposeCallback != nil {
valDisposeCallback()
}
},
),
)
if err != nil {
if ref != nil {
ref.Release()
}
return nil, nil, nil, err
}
defer di.AddIdleCallback(func(isIdle bool, errs []error) {
bcast.HoldLock(func(broadcast func(), getWaitCh func() <-chan struct{}) {
// idle or errors list changed
idle = isIdle
wait, resErr = idleCb(idle, errs)
broadcast()
})
})()
for {
var currVal directive.AttachedValue
var currResErr error
var currIdle, currWait bool
var waitCh <-chan struct{}
bcast.HoldLock(func(broadcast func(), getWaitCh func() <-chan struct{}) {
waitCh = getWaitCh()
currVal, currResErr, currIdle, currWait = val, resErr, idle, wait
})
if currVal != nil {
return currVal, di, ref, nil
}
if currResErr != nil || (currIdle && !currWait) {
ref.Release()
return nil, nil, nil, currResErr
}
select {
case <-ctx.Done():
ref.Release()
return nil, nil, nil, context.Canceled
case <-waitCh:
}
}
}
// ExecOneOffTyped executes a one-off directive with a value type.
//
// idleCb is called when idle with the list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: continues to wait when the directive becomes idle
// errs is the list of errors from the resolvers (if any)
//
// If any resolvers return an error, returns that error.
// valDisposeCb is called if the value is no longer valid.
// valDisposeCb might be called multiple times.
// If err != nil, ref == nil.
func ExecOneOffTyped[T comparable](
ctx context.Context,
bus Bus,
dir directive.Directive,
idleCb ExecIdleCallback,
valDisposeCallback func(),
) (directive.TypedAttachedValue[T], directive.Instance, directive.Reference, error) {
return ExecOneOffWithFilterTyped[T](ctx, bus, dir, idleCb, valDisposeCallback, nil)
}
// ExecOneOffWithFilterTyped executes a one-off directive with a filter cb.
//
// Waits until the callback returns true before returning a value.
// valDisposeCb is called if the value is no longer valid.
// valDisposeCb might be called multiple times.
//
// idleCb is called when idle with the list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: continues to wait when the directive becomes idle
// errs is the list of errors from the resolvers (if any)
//
// If err != nil, ref == nil.
func ExecOneOffWithFilterTyped[T comparable](
ctx context.Context,
bus Bus,
dir directive.Directive,
idleCb ExecIdleCallback,
valDisposeCallback func(),
filterCb func(val directive.TypedAttachedValue[T]) (bool, error),
) (directive.TypedAttachedValue[T], directive.Instance, directive.Reference, error) {
av, di, ref, err := ExecOneOffWithFilter(
ctx,
bus,
dir,
idleCb,
valDisposeCallback,
func(val directive.AttachedValue) (bool, error) {
tval, ok := val.GetValue().(T)
if !ok {
return false, nil
}
if filterCb != nil {
return filterCb(directive.NewTypedAttachedValue(val.GetValueID(), tval))
}
return true, nil
},
)
if err != nil || ref == nil {
return nil, di, ref, err
}
// we type asserted in filterCb above.
avVal := av.GetValue().(T)
return directive.NewTypedAttachedValue(av.GetValueID(), avVal), di, ref, nil
}
// ExecOneOffWithXfrm executes a one-off directive with a transformation filter cb.
//
// Waits until the callback returns true and nil err before returning.
// valDisposeCb is called if the value is no longer valid.
// valDisposeCb might be called multiple times.
//
// idleCb is called when idle with the list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: continues to wait when the directive becomes idle
// errs is the list of errors from the resolvers (if any)
//
// If err != nil, ref == nil.
func ExecOneOffWithXfrm(
ctx context.Context,
bus Bus,
dir directive.Directive,
idleCb ExecIdleCallback,
valDisposeCallback func(),
xfrmCb func(val directive.AttachedValue) (directive.Value, bool, error),
) (directive.Value, directive.AttachedValue, directive.Instance, directive.Reference, error) {
var xfrm directive.Value
av, di, ref, err := ExecOneOffWithFilter(
ctx,
bus,
dir,
idleCb,
valDisposeCallback,
func(val directive.AttachedValue) (bool, error) {
var ok bool
xval, ok, err := xfrmCb(val)
if !ok || err != nil {
return false, err
}
xfrm = xval
return true, nil
},
)
return xfrm, av, di, ref, err
}
// ExecOneOffWithXfrmTyped executes a one-off directive with a transformation filter cb.
//
// Waits until the callback returns true and nil err before returning.
// valDisposeCb is called if the value is no longer valid.
// valDisposeCb might be called multiple times.
//
// idleCb is called when idle with the list of resolver errors.
// idleCb should return (wait, error): if wait=true, continues to wait.
// if idleCb is nil: continues to wait when the directive becomes idle
// errs is the list of errors from the resolvers (if any)
//
// If err != nil, ref == nil.
func ExecOneOffWithXfrmTyped[T, R directive.ComparableValue](
ctx context.Context,
bus Bus,
dir directive.Directive,
idleCb ExecIdleCallback,
valDisposeCallback func(),
xfrmCb func(val directive.TypedAttachedValue[T]) (R, bool, error),
) (R, directive.TypedAttachedValue[T], directive.Instance, directive.Reference, error) {
var xfrm R
av, di, ref, err := ExecOneOffWithFilterTyped(
ctx,
bus,
dir,
idleCb,
valDisposeCallback,
func(val directive.TypedAttachedValue[T]) (bool, error) {
var ok bool
xval, ok, err := xfrmCb(val)
if !ok || err != nil {
return false, err
}
xfrm = xval
return true, nil
},
)
if err != nil || av == nil {
// ensure xfrm is empty too
var empty R
xfrm = empty
}
return xfrm, av, di, ref, err
}