firehol/netdata

// SPDX-License-Identifier: GPL-3.0-or-later

package ticker

import "time"

type (
    // Ticker holds a channel that delivers ticks of a clock at intervals.
    // The ticks are aligned to interval boundaries.
    Ticker struct {
        C        <-chan int
        done     chan struct{}
        loops    int
        interval time.Duration
    }
)

// New returns a new Ticker containing a channel that will send the time with a period specified by the duration argument.
// It adjusts the intervals or drops ticks to make up for slow receivers.
// The duration must be greater than zero; if not, New will panic. Stop the Ticker to release associated resources.
func New(interval time.Duration) *Ticker {
    ticker := &Ticker{
        interval: interval,
        done:     make(chan struct{}, 1),
    }
    ticker.start()
    return ticker
}

func (t *Ticker) start() {
    ch := make(chan int)
    t.C = ch
    go func() {
    LOOP:
        for {
            now := time.Now()
            nextRun := now.Truncate(t.interval).Add(t.interval)

            time.Sleep(nextRun.Sub(now))
            select {
            case <-t.done:
                close(ch)
                break LOOP
            case ch <- t.loops:
                t.loops++
            }
        }
    }()
}

// Stop turns off a Ticker. After Stop, no more ticks will be sent.
// Stop does not close the channel, to prevent a read from the channel succeeding incorrectly.
func (t *Ticker) Stop() {
    t.done <- struct{}{}
}