// Copyright (C) 2022 Marius Schellenberger

package fs

import (
	"errors"
	"math"
	"sync/atomic"

	"github.com/go-logr/logr"
)

var InvalidMaxQuota = errors.New("invalid max quota")

type Quota struct {
	log logr.Logger
	fs  *FS
	max int64
	cur int64
}

func NewQuota(max int64, fs *FS, log logr.Logger) (q *Quota, err error) {
	if max <= 0 {
		err = InvalidMaxQuota
		return
	}
	q = &Quota{log: log, fs: fs, max: max}
	return
}

func (q *Quota) Init() {
	for _, v := range q.fs.md {
		q.cur += v.Chunks.Size()
	}
	q.log.Info("quota usage", "current", q.cur, "max", q.max)
}

func (q *Quota) cleanup() {
	if !q.fs.mu.TryLock() {
		return
	}
	q.log.Info("quota usage", "current", q.cur, "max", q.max)
	defer q.fs.mu.Unlock()
	atime := int64(math.MaxInt64)
	var m *Metadata
	for _, v := range q.fs.md {
		if v.Atime != 0 && v.f != nil && v.Atime < atime {
			atime = v.Atime
			m = v
		}
	}
	if m != nil {
		log := q.log.WithValues("file", m.name)
		log.Info("deleting oldest file")
		err := m.Delete()
		if err != nil {
			q.log.Error(err, "error deleting oldest file")
			return
		}
		atomic.AddInt64(&q.cur, -m.Size)
	}
}

func (q *Quota) Add(n int) {
	if q.max < atomic.AddInt64(&q.cur, int64(n)) {
		q.cleanup()
	}
}