package markdown

import "time"

const (
	DefaultInterval = time.Second * 60
	DevInterval     = time.Second * 1
)

// Watch monitors the configured markdown directory for changes. It calls GenerateLinks
// when there are changes.
func Watch(md Markdown, c *Config, interval time.Duration) (stopChan chan struct{}) {
	return TickerFunc(interval, func() {
		GenerateLinks(md, c)
	})
}

// TickerFunc runs f at interval. If interval is <= 0, it loops f. A message to the
// returned channel will stop the executing goroutine.
func TickerFunc(interval time.Duration, f func()) chan struct{} {
	stopChan := make(chan struct{})

	if interval > 0 {
		ticker := time.NewTicker(interval)
		go func() {
		loop:
			for {
				select {
				case <-ticker.C:
					f()
				case <-stopChan:
					ticker.Stop()
					break loop
				}
			}
		}()
	} else {
		go func() {
		loop:
			for {
				m := make(chan struct{})
				go func() {
					f()
					m <- struct{}{}
				}()
				select {
				case <-m:
					continue loop
				case <-stopChan:
					break loop
				}
				time.Sleep(DevInterval)

			}
		}()
	}
	return stopChan
}