Scheduler implementation

scheduler/scheduler.go

@@ -0,0 +1,78 @@
+package scheduler
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+	log "gitlab.com/gdulai/simpleloglvl"
+)
+
+// The main scheduler instance created by default
+var mainScheduler *Scheduler
+
+// Type that can be executed at a certain time.
+type Schedulable interface {
+	Execute(scheduler *Scheduler)
+}
+
+// Describes an item that the scheduler can execute at a given time.
+type ScheduleItem struct {
+	id          uuid.UUID
+	runAt       time.Time
+	schedulable *Schedulable
+}
+
+type Scheduler struct {
+	scheduled map[uuid.UUID]*ScheduleItem
+}
+
+func InitScheduler() {
+	mainScheduler = NewScheduler()
+}
+
+// Creates a new scheduler, returns the pointer of it
+func NewScheduler() *Scheduler {
+	schedulr := &Scheduler{scheduled: make(map[uuid.UUID]*ScheduleItem)}
+
+	example := TestSchedule{}
+	schedulr.Schedule(time.Now().Add(5*time.Second), &example)
+
+	return schedulr
+}
+
+// Schedules an instance of Schedulable.
+func (s *Scheduler) Schedule(runAt time.Time, schedulable Schedulable) (uuid.UUID, error) {
+	newUuid, err := uuid.NewRandom()
+	if err != nil {
+		return uuid.UUID{}, err
+	}
+	item := &ScheduleItem{id: newUuid, runAt: runAt, schedulable: &schedulable}
+	s.scheduled[newUuid] = item
+
+	time.AfterFunc(time.Until(runAt), func() {
+		schedulable.Execute(s)
+	})
+
+	return newUuid, nil
+}
+
+// Test schedule which is added when the scheduler is created.
+// Used for showing that the scheduler started and working correctly.
+type TestSchedule struct {
+}
+
+// Simple Schedulable implementation.
+// Logs that the scheduler is running.
+func (ex *TestSchedule) Execute(scheduler *Scheduler) {
+	log.LogInfo("Scheduler running!")
+}
+
+// Scheduled web scraping for news
+type ScheduledScraping struct {
+	Url string
+}
+
+// Returns the refernce of the main scheduler
+func MainScheduler() *Scheduler {
+	return mainScheduler
+}