support for cron based subscriptions management

server/subscription/task/runner.go

@@ -0,0 +1,117 @@
+package task
+
+import (
+	"bytes"
+	"context"
+	"log/slog"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"time"
+
+	"github.com/marcopiovanello/yt-dlp-web-ui/v3/server/config"
+	"github.com/marcopiovanello/yt-dlp-web-ui/v3/server/internal"
+	"github.com/marcopiovanello/yt-dlp-web-ui/v3/server/subscription/domain"
+	"github.com/robfig/cron/v3"
+)
+
+type TaskRunner interface {
+	Submit(subcription *domain.Subscription) error
+	Spawner(ctx context.Context)
+	Recoverer()
+}
+
+type taskPair struct {
+	Schedule     cron.Schedule
+	Subscription *domain.Subscription
+}
+
+type CronTaskRunner struct {
+	mq *internal.MessageQueue
+	db *internal.MemoryDB
+
+	tasks  chan taskPair
+	errors chan error
+}
+
+func NewCronTaskRunner(mq *internal.MessageQueue, db *internal.MemoryDB) TaskRunner {
+	return &CronTaskRunner{
+		mq:     mq,
+		db:     db,
+		tasks:  make(chan taskPair),
+		errors: make(chan error),
+	}
+}
+
+const commandTemplate = "-I1 --flat-playlist --print webpage_url $1"
+
+var argsSplitterRe = regexp.MustCompile(`(?mi)[^\s"']+|"([^"]*)"|'([^']*)'`)
+
+func (t *CronTaskRunner) Submit(subcription *domain.Subscription) error {
+	schedule, err := cron.ParseStandard(subcription.CronExpr)
+	if err != nil {
+		return err
+	}
+
+	job := taskPair{
+		Schedule:     schedule,
+		Subscription: subcription,
+	}
+
+	t.tasks <- job
+
+	return nil
+}
+
+func (t *CronTaskRunner) Spawner(ctx context.Context) {
+	for task := range t.tasks {
+		go func() {
+			for {
+				slog.Info("fetching latest video for channel", slog.String("channel", task.Subscription.URL))
+
+				fetcherParams := strings.Split(strings.Replace(commandTemplate, "$1", task.Subscription.URL, 1), " ")
+
+				cmd := exec.CommandContext(
+					ctx,
+					config.Instance().DownloaderPath,
+					fetcherParams...,
+				)
+
+				stdout, err := cmd.Output()
+				if err != nil {
+					t.errors <- err
+					return
+				}
+
+				latestChannelURL := string(bytes.Trim(stdout, "\n"))
+
+				p := &internal.Process{
+					Url: latestChannelURL,
+					Params: append(argsSplitterRe.FindAllString(task.Subscription.Params, 1), []string{
+						"--download-archive",
+						filepath.Join(config.Instance().Dir(), "archive.txt"),
+					}...),
+					AutoRemove: true,
+				}
+
+				t.db.Set(p)
+				t.mq.Publish(p)
+
+				nextSchedule := time.Until(task.Schedule.Next(time.Now()))
+
+				slog.Info(
+					"cron task runner next schedule",
+					slog.String("url", task.Subscription.URL),
+					slog.Any("duration", nextSchedule),
+				)
+
+				time.Sleep(nextSchedule)
+			}
+		}()
+	}
+}
+
+func (t *CronTaskRunner) Recoverer() {
+	panic("Unimplemented")
+}