From 7488e2b5e3303ad8a8fc243ac1fede5217dcce1a Mon Sep 17 00:00:00 2001
From: Tigor Hutasuhut <tigor.hutasuhut@gmail.com>
Date: Mon, 13 May 2024 21:10:48 +0700
Subject: [PATCH] api: revamped scheduler to run every minute

Schedule now triggered by a runner that loops every minute and check if cron expression passes the time check.
---
 api/api.go                 | 13 ++++---
 api/scheduler.go           | 76 ++++++++++++++++++++++++++++++++++++++
 api/scheduler/scheduler.go |  3 ++
 3 files changed, 87 insertions(+), 5 deletions(-)
 create mode 100644 api/scheduler.go
 create mode 100644 api/scheduler/scheduler.go

diff --git a/api/api.go b/api/api.go
index 1f20d6d..181fe09 100644
--- a/api/api.go
+++ b/api/api.go
@@ -24,8 +24,9 @@ type API struct {
 	db    bob.Executor
 	sqldb *sql.DB
 
-	scheduler   *cron.Cron
-	scheduleMap map[cron.EntryID]*models.Subreddit
+	scheduleStopper func()
+	scheduler       *cron.Cron
+	scheduleMap     map[cron.EntryID]*models.Subreddit
 
 	downloadBroadcast *broadcast.Relay[bmessage.ImageDownloadMessage]
 
@@ -67,9 +68,7 @@ func New(deps Dependencies) *API {
 		publisher:         deps.Publisher,
 	}
 
-	if err := api.StartScheduler(context.Background()); err != nil {
-		panic(err)
-	}
+	api.scheduleStopper = api.startScheduler()
 	go api.StartSubredditDownloadPubsub(ch)
 	return api
 }
@@ -106,3 +105,7 @@ func (api *API) scheduleSubreddit(subreddit *models.Subreddit) error {
 
 	return nil
 }
+
+func (api *API) Close() {
+	api.scheduleStopper()
+}
diff --git a/api/scheduler.go b/api/scheduler.go
new file mode 100644
index 0000000..130a8db
--- /dev/null
+++ b/api/scheduler.go
@@ -0,0 +1,76 @@
+package api
+
+import (
+	"context"
+	"time"
+
+	"github.com/robfig/cron/v3"
+	"github.com/tigorlazuardi/redmage/models"
+	"github.com/tigorlazuardi/redmage/pkg/log"
+)
+
+func (api *API) startScheduler() func() {
+	now := time.Now()
+
+	stop := make(chan struct{})
+
+	parser := cron.NewParser(cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor)
+	var ticker *time.Ticker
+
+	nextMinute := now.Truncate(time.Minute).Add(time.Minute)
+	log.New(context.Background()).Infof("starting scheduler at %s", nextMinute)
+	timer := time.AfterFunc(nextMinute.Sub(now), func() {
+		api.scheduleRun(time.Now().Truncate(time.Second).Truncate(0), parser)
+		ticker = time.NewTicker(time.Minute)
+		go func() {
+			for {
+				select {
+				case <-stop:
+					return
+				case now := <-ticker.C:
+					api.scheduleRun(now.Truncate(time.Second).Truncate(0), parser)
+				}
+			}
+		}()
+	})
+	return func() {
+		log.New(context.Background()).Info("scheduler: stop called")
+		timer.Stop()
+		if ticker != nil {
+			ticker.Stop()
+		}
+		stop <- struct{}{}
+	}
+}
+
+func (api *API) scheduleRun(now time.Time, parser cron.Parser) {
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	ctx, span := tracer.Start(ctx, "scheduler:tick")
+	defer span.End()
+
+	previous := now.Add(-time.Minute).Truncate(time.Minute)
+
+	log.New(ctx).Info("scheduler: run")
+	subreddits, err := models.Subreddits.Query(ctx, api.db, models.SelectWhere.Subreddits.EnableSchedule.EQ(1)).All()
+	if err != nil {
+		log.New(ctx).Err(err).Error("scheduler: failed to query subreddits")
+		return
+	}
+	for _, subreddit := range subreddits {
+		schedule, err := parser.Parse(subreddit.Schedule)
+		if err != nil {
+			log.New(ctx).Err(err).Error("scheduler: failed to parse schedule")
+			continue
+		}
+		next := schedule.Next(previous)
+		log.New(ctx).Info("scheduler: check time", "subreddit", subreddit.Name, "trigger_time", next, "now", now, "should_run", now.After(next))
+		if now.After(next) {
+			err := api.PubsubStartDownloadSubreddit(ctx, PubsubStartDownloadSubredditParams{Subreddit: subreddit.Name})
+			if err != nil {
+				log.New(ctx).Err(err).Error("scheduler: failed to start download", "subreddit", subreddit.Name)
+				continue
+			}
+		}
+	}
+}
diff --git a/api/scheduler/scheduler.go b/api/scheduler/scheduler.go
new file mode 100644
index 0000000..c710887
--- /dev/null
+++ b/api/scheduler/scheduler.go
@@ -0,0 +1,3 @@
+package scheduler
+
+type Scheduler struct{}