gcal refreshes next event list every 13m

gcal.go

@@ -36,6 +36,7 @@ func (gcal *GCal) EventsToday(ctx context.Context) ([]Event, error) {
 
 	today := time.Now().Add(-1 * time.Hour * time.Duration(time.Now().Hour()))
 	tomorrow := today.Add(24 * time.Hour)
+
 	events, err := srv.Events.
 		List("primary").
 		ShowDeleted(false).

main.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"os"
 	"os/signal"
+	"slices"
 	"strings"
 	"syscall"
 	"time"
@@ -27,53 +28,93 @@ func main() {
 		panic(err)
 	}
 
-	if *gcal {
-		if err := alertGCal(ctx, *ntfy); err != nil {
-			panic(err)
-		}
-	} else {
-		if err := alertAfter(ctx, *ntfy, fs.Args()[0]); err != nil {
+	alerts, err := alerts(ctx, *gcal, fs.Args())
+	if err != nil {
+		panic(err)
+	}
+
+	for alert := range alerts {
+		if err := alertAt(ctx, *ntfy, time.Now(), alert, time.Now().Format("15:04")); err != nil {
 			panic(err)
 		}
 	}
 }
 
-func alertGCal(ctx context.Context, ntfy string) error {
+func alerts(ctx context.Context, gcal bool, args []string) (chan string, error) {
+	if gcal {
+		return alertsGCal(ctx)
+	}
+	duration, err := time.ParseDuration(args[0])
+	if err != nil {
+		return nil, err
+	}
+	return alertsAfter(ctx, duration)
+}
+
+func alertsAfter(ctx context.Context, dur time.Duration) (chan string, error) {
+	ch := make(chan string)
+	go func() {
+		defer close(ch)
+		select {
+		case <-ctx.Done():
+		case <-time.After(dur):
+		}
+		ch <- "alerting after " + dur.String()
+	}()
+	return ch, nil
+}
+
+func alertsGCal(ctx context.Context) (chan string, error) {
 	gcal := NewGCal()
 	if err := gcal.Login(ctx); err != nil {
-		return err
+		return nil, err
 	}
 
-	events, err := gcal.EventsToday(ctx)
-	if err != nil {
-		return err
-	}
-
-	for _, event := range events {
-		until := event.Time.Add(-1 * time.Minute)
-		if until.Sub(time.Now()) < 1 {
-			continue
+	var events []Event
+	refresh := func() error {
+		es, err := gcal.EventsToday(ctx)
+		es = slices.DeleteFunc(es, func(s Event) bool {
+			return time.Now().After(s.Time)
+		})
+		if !slices.Equal(es, events) {
+			events = es
+			if len(events) > 0 {
+				log.Println("alerting about", events[0].Name, "at", events[0].Time.Format("15:04"), "(", time.Until(events[0].Time), ")")
+			}
 		}
-
-		log.Println("alerting about", event.Name, "at", until.Format("15:04"), "(", time.Until(until), ")")
-		if err := alertAt(ctx, ntfy, until, event.Name, until.Format("15:04")); err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
-func alertAfter(ctx context.Context, ntfy string, duration string) error {
-	d, err := time.ParseDuration(duration)
-	if err != nil {
 		return err
 	}
-	return alertAt(ctx, ntfy, time.Now().Add(d), os.Args[0], "alerting after "+d.String())
+	if err := refresh(); err != nil {
+		return nil, err
+	}
+
+	ch := make(chan string)
+	go func() {
+		defer close(ch)
+
+		c := time.NewTicker(time.Minute * 13)
+		defer c.Stop()
+		for ctx.Err() == nil && len(events) > 0 {
+			select {
+			case <-c.C:
+				if err := refresh(); err != nil {
+					panic(err)
+				}
+			case <-time.After(time.Until(events[0].Time.Add(-2 * time.Minute))):
+				select {
+				case <-ctx.Done():
+				case ch <- events[0].Name:
+				}
+				events = events[1:]
+			case <-ctx.Done():
+			}
+		}
+	}()
+
+	return ch, nil
 }
 
 func alertAt(ctx context.Context, ntfy string, deadline time.Time, title, msg string) error {
-	// n := int64(time.Until(deadline) / time.Second)
 	c := time.NewTicker(time.Second)
 	defer c.Stop()
 	func() {