package gtq

import (
	"sort"
)

// Scheduler is an internal goroutine which examines the Queues and
// choses which tasks to run next. Returns true if tasks were scheduled,
// or false if there's nothing left to schedule.
type Scheduler func(tq *TaskQueue) bool

// SimpleScheduler is the simplest possible implementation, which just takes
// tasks off the highest priority queue.
func SimpleScheduler(tq *TaskQueue) bool {
	pc := tq.PriorityCounts()
	// sort priorities
	prios := make([]uint, 0, len(pc))
	for k := range pc {
		prios = append(prios, k)
	}
	sort.Sort(UIntSlice(prios))

	var queued uint
	for _, prio := range prios {
		q, ok := tq.queues.Load(prio)
		if !ok {
			continue
		}
		for q.(*Queue).Length() > 0 {
			task := q.(*Queue).Remove()
			tq.nextTask <- task
			queued++
		}
	}
	if queued >= (tq.numJobs * 2) {
		return true
	}
	return false
}