package meta

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"os"

	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
	metamode "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
	"go.etcd.io/bbolt"
)

var (
	shardInfoBucket = []byte{shardInfoPrefix}
	shardIDKey      = []byte("id")
)

// GetShardID sets metabase operation mode
// and reads shard id from db.
// If id is missing, returns nil, nil.
//
// GetShardID does not report any metrics.
func (db *DB) GetShardID(ctx context.Context, mode metamode.Mode) ([]byte, error) {
	db.modeMtx.Lock()
	defer db.modeMtx.Unlock()
	db.mode = mode

	if _, err := os.Stat(db.info.Path); errors.Is(err, os.ErrNotExist) {
		return nil, nil
	}

	if err := db.openDB(ctx, mode); err != nil {
		return nil, fmt.Errorf("failed to open metabase: %w", err)
	}

	id, err := db.readShardID()

	if cErr := db.close(); cErr != nil {
		err = errors.Join(err, fmt.Errorf("failed to close metabase: %w", cErr))
	}

	return id, metaerr.Wrap(err)
}

// ReadShardID reads shard id from db.
// If id is missing, returns nil, nil.
func (db *DB) readShardID() ([]byte, error) {
	var id []byte
	err := db.boltDB.View(func(tx *bbolt.Tx) error {
		b := tx.Bucket(shardInfoBucket)
		if b != nil {
			id = bytes.Clone(b.Get(shardIDKey))
		}
		return nil
	})
	return id, metaerr.Wrap(err)
}

// SetShardID sets metabase operation mode
// and writes shard id to db.
func (db *DB) SetShardID(ctx context.Context, id []byte, mode metamode.Mode) error {
	db.modeMtx.Lock()
	defer db.modeMtx.Unlock()
	db.mode = mode

	if mode.ReadOnly() {
		return ErrReadOnlyMode
	}

	if err := db.openDB(ctx, mode); err != nil {
		return fmt.Errorf("failed to open metabase: %w", err)
	}

	err := db.writeShardID(id)
	if err == nil {
		db.metrics.SetMode(metamode.ConvertToComponentModeDegraded(mode))
	}

	if cErr := db.close(); cErr != nil {
		err = errors.Join(err, fmt.Errorf("failed to close metabase: %w", cErr))
	}

	return metaerr.Wrap(err)
}

// writeShardID writes shard id to db.
func (db *DB) writeShardID(id []byte) error {
	return metaerr.Wrap(db.boltDB.Update(func(tx *bbolt.Tx) error {
		b, err := tx.CreateBucketIfNotExists(shardInfoBucket)
		if err != nil {
			return err
		}
		return b.Put(shardIDKey, id)
	}))
}