package blobovnicza

import (
	"context"
	"errors"
	"fmt"
	"path/filepath"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
	"go.etcd.io/bbolt"
	"go.uber.org/zap"
)

// Open opens an internal database at the configured path with the configured permissions.
//
// If the database file does not exist, it will be created automatically.
// If blobovnicza is already open, does nothing.
func (b *Blobovnicza) Open(ctx context.Context) error {
	b.controlMtx.Lock()
	defer b.controlMtx.Unlock()

	if b.opened {
		return nil
	}

	b.log.Debug(ctx, logs.BlobovniczaCreatingDirectoryForBoltDB,
		zap.String("path", b.path),
		zap.Bool("ro", b.boltOptions.ReadOnly),
	)

	var err error

	if !b.boltOptions.ReadOnly {
		err = util.MkdirAllX(filepath.Dir(b.path), b.perm)
		if err != nil {
			return err
		}
	}

	b.log.Debug(ctx, logs.BlobovniczaOpeningBoltDB,
		zap.String("path", b.path),
		zap.Stringer("permissions", b.perm),
	)

	b.boltDB, err = bbolt.Open(b.path, b.perm, b.boltOptions)
	if err == nil {
		b.opened = true
		b.metrics.IncOpenBlobovniczaCount()
	}

	return err
}

// Init initializes internal database structure.
//
// If Blobovnicza is already initialized, no action is taken.
// Blobovnicza must be open, otherwise an error will return.
func (b *Blobovnicza) Init(ctx context.Context) error {
	b.controlMtx.Lock()
	defer b.controlMtx.Unlock()

	if !b.opened {
		return errors.New("blobovnicza is not open")
	}

	b.log.Debug(ctx, logs.BlobovniczaInitializing,
		zap.Uint64("object size limit", b.objSizeLimit),
		zap.Uint64("storage size limit", b.fullSizeLimit),
	)

	size := b.dataSize.Load()
	items := b.itemsCount.Load()
	if size != 0 || items != 0 {
		b.log.Debug(ctx, logs.BlobovniczaAlreadyInitialized, zap.Uint64("size", size), zap.Uint64("items", items))
		return nil
	}

	if !b.boltOptions.ReadOnly {
		err := b.boltDB.Update(func(tx *bbolt.Tx) error {
			return b.iterateBucketKeys(true, func(lower, upper uint64, key []byte) (bool, error) {
				// create size range bucket

				rangeStr := stringifyBounds(lower, upper)
				b.log.Debug(ctx, logs.BlobovniczaCreatingBucketForSizeRange,
					zap.String("range", rangeStr))

				_, err := tx.CreateBucketIfNotExists(key)
				if err != nil {
					return false, fmt.Errorf("(%T) could not create bucket for bounds %s: %w",
						b, rangeStr, err)
				}

				return false, nil
			})
		})
		if err != nil {
			return err
		}
	}

	return b.initializeCounters(ctx)
}

func (b *Blobovnicza) ObjectsCount() uint64 {
	return b.itemsCount.Load()
}

func (b *Blobovnicza) initializeCounters(ctx context.Context) error {
	var size uint64
	var items uint64
	var sizeExists bool
	var itemsCountExists bool

	err := b.boltDB.View(func(tx *bbolt.Tx) error {
		size, sizeExists = hasDataSize(tx)
		items, itemsCountExists = hasItemsCount(tx)

		if sizeExists && itemsCountExists {
			return nil
		}

		return b.iterateAllDataBuckets(tx, func(_, _ uint64, b *bbolt.Bucket) (bool, error) {
			return false, b.ForEach(func(k, v []byte) error {
				size += uint64(len(k) + len(v))
				items++
				return nil
			})
		})
	})
	if err != nil {
		return fmt.Errorf("can't determine DB size: %w", err)
	}
	if (!sizeExists || !itemsCountExists) && !b.boltOptions.ReadOnly {
		b.log.Debug(ctx, logs.BlobovniczaSavingCountersToMeta, zap.Uint64("size", size), zap.Uint64("items", items))
		if err := b.boltDB.Update(func(tx *bbolt.Tx) error {
			if err := saveDataSize(tx, size); err != nil {
				return err
			}
			return saveItemsCount(tx, items)
		}); err != nil {
			b.log.Debug(ctx, logs.BlobovniczaSavingCountersToMetaFailed, zap.Uint64("size", size), zap.Uint64("items", items))
			return fmt.Errorf("can't save blobovnicza's size and items count: %w", err)
		}
		b.log.Debug(ctx, logs.BlobovniczaSavingCountersToMetaSuccess, zap.Uint64("size", size), zap.Uint64("items", items))
	}

	b.dataSize.Store(size)
	b.itemsCount.Store(items)
	b.metrics.AddOpenBlobovniczaSize(size)
	b.metrics.AddOpenBlobovniczaItems(items)
	return nil
}

// Close releases all internal database resources.
//
// If blobovnicza is already closed, does nothing.
func (b *Blobovnicza) Close(ctx context.Context) error {
	b.controlMtx.Lock()
	defer b.controlMtx.Unlock()

	if !b.opened {
		return nil
	}

	b.log.Debug(ctx, logs.BlobovniczaClosingBoltDB,
		zap.String("path", b.path),
	)

	if err := b.boltDB.Close(); err != nil {
		return err
	}

	b.metrics.DecOpenBlobovniczaCount()
	b.metrics.SubOpenBlobovniczaSize(b.dataSize.Load())
	b.metrics.SubOpenBlobovniczaItems(b.itemsCount.Load())
	b.dataSize.Store(0)
	b.itemsCount.Store(0)

	b.opened = false

	return nil
}