package acp

import (
	"fmt"
	"sync"

	"github.com/samuelncui/godf"
)

const (
	defaultDiskUsageFreshInterval = 1024 * 1024 * 1024 * 2
)

type diskUsageCache struct {
	mountPoint    string
	freshInterval int64

	lock      sync.Mutex
	freeSpace int64
	used      int64
}

func newDiskUsageCache(mountPoint string, freshInterval int64) *diskUsageCache {
	return &diskUsageCache{
		mountPoint:    mountPoint,
		freshInterval: freshInterval,
	}
}

func (m *diskUsageCache) check(need int64) error {
	m.lock.Lock()
	defer m.lock.Unlock()

	m.used += need
	if m.used <= m.freeSpace && m.used < m.freshInterval {
		return nil
	}

	usage, err := godf.NewDiskUsage(m.mountPoint)
	if err != nil {
		return fmt.Errorf("get disk usage fail, mount_point= %s, %w", m.mountPoint, err)
	}

	m.freeSpace = int64(usage.Available())
	m.used = need
	if m.used > m.freeSpace {
		return fmt.Errorf("%w, want= %d have= %d", ErrTargetNoSpace, m.used, m.freeSpace)
	}

	return nil
}