package hostfiles

import (
	"sort"
	"time"
)

// queue holds, per path, the time by which its first unpublished
// modification must be published. A later modification of a path already
// waiting does not move its deadline, so a file written without pause is
// still published every period.
type queue struct {
	d   time.Duration
	due map[string]time.Time
}

func newQueue(d time.Duration) *queue { return &queue{d: d, due: map[string]time.Time{}} }

func (q *queue) Touch(rel string, now time.Time) {
	if _, waiting := q.due[rel]; !waiting {
		q.due[rel] = now.Add(q.d)
	}
}

// Due removes and returns every path whose deadline has arrived.
func (q *queue) Due(now time.Time) []string {
	var out []string
	for rel, at := range q.due {
		if !at.After(now) {
			out = append(out, rel)
			delete(q.due, rel)
		}
	}
	sort.Strings(out)
	return out
}