refactor out cronning

src/cmd/asses/main.go

@@ -4,34 +4,11 @@ import (
 	"context"
 	"io"
 	"show-rss/src/asses"
-	"time"
+	"show-rss/src/cron"
 )
 
 func Main(ctx context.Context) error {
-	next, err := asses.Next(ctx)
-	if err != nil {
-		return err
-	}
-
-	c := time.NewTicker(3 * time.Hour)
-	defer c.Stop()
-	for {
-		select {
-		case <-ctx.Done():
-		case <-c.C:
-		case <-time.After(time.Until(next)):
-		}
-
-		if err := One(ctx); err != nil {
-			return err
-		}
-
-		next, err = asses.Next(ctx)
-		if err != nil {
-			return err
-		}
-	}
-	return ctx.Err()
+	return cron.Cron(ctx, asses.Next, One)
 }
 
 func One(ctx context.Context) error {

src/cmd/fetch/main.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"net/http"
 	"net/url"
+	"show-rss/src/cron"
 	"show-rss/src/feeds"
 	"show-rss/src/webhooks"
 	"strings"
@@ -16,19 +17,7 @@ import (
 )
 
 func Main(ctx context.Context) error {
-	c := time.NewTicker(time.Minute)
-	defer c.Stop()
-	for {
-		if err := One(ctx); err != nil {
-			return err
-		}
-
-		select {
-		case <-ctx.Done():
-		case <-c.C:
-		}
-	}
-	return ctx.Err()
+	return cron.Cron(ctx, feeds.Next, One)
 }
 
 func One(ctx context.Context) error {

src/cron/cron.go

@@ -0,0 +1,31 @@
+package cron
+
+import (
+	"context"
+	"time"
+)
+
+func Cron(ctx context.Context, next func(context.Context) (time.Time, error), do func(ctx context.Context) error) error {
+	n, err := next(ctx)
+	if err != nil {
+		return err
+	}
+
+	c := time.NewTicker(3 * time.Minute)
+	defer c.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+		case <-c.C:
+			n, err = next(ctx)
+			if err != nil {
+				return err
+			}
+		case <-time.After(time.Until(n)):
+			if err := do(ctx); err != nil {
+				return err
+			}
+		}
+	}
+	return ctx.Err()
+}

src/feeds/db.go

@@ -42,6 +42,24 @@ type (
 	}
 )
 
+func Next(ctx context.Context) (time.Time, error) {
+	result := time.Now().Add(3 * time.Minute)
+	err := ForEach(ctx, func(f Feed) error {
+		next, err := f.Next()
+		if err != nil {
+			return nil
+		}
+
+		if next.After(result) {
+			return nil
+		}
+
+		result = next
+		return nil
+	})
+	return result, err
+}
+
 func ForEach(ctx context.Context, cb func(Feed) error) error {
 	if err := initDB(ctx); err != nil {
 		return err

src/feeds/http.go

@@ -31,7 +31,11 @@ func (feed Feed) ShouldExecute() (bool, error) {
 	if !feed.Entry.Deleted.IsZero() {
 		return false, nil
 	}
+	next, err := feed.Next()
+	return time.Now().After(next), err
+}
 
+func (feed Feed) Next() (time.Time, error) {
 	schedule, err := cron.NewParser(
 		cron.SecondOptional |
 			cron.Minute |
@@ -42,10 +46,9 @@ func (feed Feed) ShouldExecute() (bool, error) {
 			cron.Descriptor,
 	).Parse(feed.Version.Cron)
 	if err != nil {
-		return false, fmt.Errorf("illegal cron %q", feed.Version.Cron)
+		return time.Time{}, fmt.Errorf("illegal cron %q", feed.Version.Cron)
 	}
-	next := schedule.Next(feed.Execution.Executed)
-	return time.Now().After(next), nil
+	return schedule.Next(feed.Execution.Executed), nil
 }
 
 func (feed Feed) Fetch(ctx context.Context) (Items, error) {