e621-sdk-go/utils/queue.go

package utils

import (
	"errors"
	log "github.com/sirupsen/logrus"
)

type Queue struct {
	tasks         []SchedulerTask
	notifyChannel chan bool
}

func NewQueue() Queue {
	return Queue{
		notifyChannel: make(chan bool),
	}
}

// WaitForElement need to be called everytime before Popping an Element!
// Also, it is required to have this function called in a separate go-routine because Push use the NotifyChannel in the
// routine. So the thread waits, till WaitForElement pulls the Item from the channel
// FIXME this should be fixed in future. require more discussion what is the best way.
func (queue *Queue) WaitForElement() {
	log.Debug("waiting for element")
	_ = <-queue.notifyChannel
}

func (queue *Queue) Pop() (SchedulerTask, error) {
	if len(queue.tasks) == 0 {
		return nil, errors.New("try to remove an element of a empty queue")
	}
	task := queue.tasks[0]
	queue.tasks = queue.tasks[1:]
	return task, nil
}

func (queue *Queue) Push(task SchedulerTask) error {
	if task == nil {
		return errors.New("try to add task but task is empty")
	}
	queue.tasks = append(queue.tasks, task)
	queue.notifyChannel <- true
	return nil
}