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package clock
import (
"context"
"sync"
"time"
)
// LoopFn is a simple ticker-loop with io.Closer support.
// Note that ticks adapt; slow function calls may result in lost ticks.
type LoopFn struct {
ctx context.Context
cancel context.CancelFunc
ticker Ticker
fn func(ctx context.Context)
onClose func() error
wg sync.WaitGroup
}
// Close cancels the context of the ongoing function call, waits for the call to complete, and cancels further calls.
// Close is safe to call again or concurrently. The onClose callback will be called for each Close call.
func (lf *LoopFn) Close() error {
lf.cancel() // stop any ongoing function call, and close the main loop
lf.wg.Wait() // wait for completion
if lf.onClose != nil {
return lf.onClose() // optional: user can specify function to close resources with
}
return nil
}
func (lf *LoopFn) work() {
defer lf.wg.Done()
defer lf.ticker.Stop() // clean up the timer
for {
select {
case <-lf.ctx.Done():
return
case <-lf.ticker.Ch():
ctx, cancel := context.WithCancel(lf.ctx)
func() {
defer cancel()
lf.fn(ctx)
}()
}
}
}
// NewLoopFn creates a periodic function call, which can be closed,
// with an optional onClose callback to clean up resources.
func NewLoopFn(clock Clock, fn func(ctx context.Context), onClose func() error, interval time.Duration) *LoopFn {
ctx, cancel := context.WithCancel(context.Background())
lf := &LoopFn{
ctx: ctx,
cancel: cancel,
fn: fn,
ticker: clock.NewTicker(interval),
onClose: onClose,
}
lf.wg.Add(1)
go lf.work()
return lf
}