package writecache

import (
	"context"
	"fmt"
	"math"
	"os"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"go.etcd.io/bbolt"
	"go.uber.org/zap"
)

// store represents persistent storage with in-memory LRU cache
// for flushed items on top of it.
type store struct {
	db *bbolt.DB
}

const dbName = "small.bolt"

func (c *cache) openStore(readOnly bool) error {
	err := util.MkdirAllX(c.path, os.ModePerm)
	if err != nil {
		return err
	}

	c.db, err = OpenDB(c.path, readOnly, c.openFile)
	if err != nil {
		return fmt.Errorf("could not open database: %w", err)
	}

	c.db.MaxBatchSize = c.maxBatchSize
	c.db.MaxBatchDelay = c.maxBatchDelay

	if !readOnly {
		err = c.db.Update(func(tx *bbolt.Tx) error {
			_, err := tx.CreateBucketIfNotExists(defaultBucket)
			return err
		})
		if err != nil {
			return fmt.Errorf("could not create default bucket: %w", err)
		}
	}

	c.fsTree = fstree.New(
		fstree.WithPath(c.path),
		fstree.WithPerm(os.ModePerm),
		fstree.WithDepth(1),
		fstree.WithDirNameLen(1),
		fstree.WithNoSync(c.noSync),
		fstree.WithFileCounter(&c.objCounters),
	)
	if err := c.fsTree.Open(readOnly); err != nil {
		return fmt.Errorf("could not open FSTree: %w", err)
	}
	if err := c.fsTree.Init(); err != nil {
		return fmt.Errorf("could not init FSTree: %w", err)
	}

	return nil
}

func (c *cache) deleteFromDB(key string) {
	var recordDeleted bool
	err := c.db.Batch(func(tx *bbolt.Tx) error {
		b := tx.Bucket(defaultBucket)
		key := []byte(key)
		recordDeleted = b.Get(key) != nil
		return b.Delete(key)
	})

	if err == nil {
		c.metrics.Evict(StorageTypeDB)
		storagelog.Write(c.log,
			storagelog.AddressField(key),
			storagelog.StorageTypeField(wcStorageType),
			storagelog.OpField("db DELETE"),
		)
		if recordDeleted {
			c.objCounters.cDB.Add(math.MaxUint64)
			c.estimateCacheSize()
		}
	} else {
		c.log.Error(logs.WritecacheCantRemoveObjectsFromTheDatabase, zap.Error(err))
	}
}

func (c *cache) deleteFromDisk(ctx context.Context, addr oid.Address) {
	_, err := c.fsTree.Delete(ctx, common.DeletePrm{Address: addr})
	if err != nil && !client.IsErrObjectNotFound(err) {
		c.log.Error(logs.WritecacheCantRemoveObjectFromWritecache, zap.Error(err))
	} else if err == nil {
		storagelog.Write(c.log,
			storagelog.AddressField(addr.EncodeToString()),
			storagelog.StorageTypeField(wcStorageType),
			storagelog.OpField("fstree DELETE"),
		)
		c.metrics.Evict(StorageTypeFSTree)
		// counter changed by fstree
		c.estimateCacheSize()
	}
}