package writecachebbolt

import (
	"fmt"
	"sync/atomic"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"go.etcd.io/bbolt"
	"go.uber.org/zap"
	"golang.org/x/sync/errgroup"
)

func (c *cache) estimateCacheSize() uint64 {
	db := c.objCounters.DB() * c.smallObjectSize
	fstree := c.objCounters.FS() * c.maxObjectSize
	c.metrics.SetEstimateSize(db, fstree)
	return db + fstree
}

func (c *cache) incSizeDB(sz uint64) uint64 {
	return sz + c.smallObjectSize
}

func (c *cache) incSizeFS(sz uint64) uint64 {
	return sz + c.maxObjectSize
}

type counters struct {
	cDB, cFS atomic.Uint64
}

func (x *counters) DB() uint64 {
	return x.cDB.Load()
}

func (x *counters) FS() uint64 {
	return x.cFS.Load()
}

func (c *cache) setCounters() error {
	var inDB uint64
	var inFS uint64

	var eg errgroup.Group

	eg.Go(func() error {
		err := c.db.View(func(tx *bbolt.Tx) error {
			b := tx.Bucket(defaultBucket)
			if b != nil {
				inDB = uint64(b.Stats().KeyN)
			}
			return nil
		})
		if err != nil {
			return fmt.Errorf("could not read write-cache DB counter: %w", err)
		}
		c.objCounters.cDB.Store(inDB)
		return nil
	})

	eg.Go(func() error {
		var err error
		inFS, err = c.fsTree.NumberOfObjects()
		if err != nil {
			return fmt.Errorf("could not read write-cache FS counter: %w", err)
		}
		if inFS > 0 {
			inFS-- //small.bolt DB file
		}
		c.objCounters.cFS.Store(inFS)
		return nil
	})
	if err := eg.Wait(); err != nil {
		return err
	}
	c.metrics.SetActualCounters(inDB, inFS)
	return nil
}

func (c *cache) runDBCounterLoop() {
	go func() {
		t := time.NewTicker(time.Second * 30)
		defer t.Stop()
		for {
			select {
			case <-t.C:
				err := c.setCounters()
				if err != nil {
					c.log.Warn(logs.FailedToCountWritecacheItems, zap.Error(err))
				}
			case <-c.closeCh:
				return
			}
		}
	}()
}