package blobovniczatree

import (
	"context"
	"errors"
	"os"
	"path/filepath"
	"strings"

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

var errFailedToChangeExtensionReadOnly = errors.New("failed to change blobovnicza extension: read only mode")

// Open opens blobovnicza tree.
func (b *Blobovniczas) Open(readOnly bool) error {
	b.readOnly = readOnly
	b.metrics.SetMode(readOnly)
	b.openManagers()
	return nil
}

// Init initializes blobovnicza tree.
//
// Should be called exactly once.
func (b *Blobovniczas) Init() error {
	b.log.Debug(logs.BlobovniczatreeInitializingBlobovniczas)

	b.log.Debug(logs.BlobovniczaTreeFixingFileExtensions)
	if err := b.addDBExtensionToDBs(b.rootPath, 0); err != nil {
		b.log.Error(logs.BlobovniczaTreeFixingFileExtensionsFailed, zap.Error(err))
		return err
	}
	b.log.Debug(logs.BlobovniczaTreeFixingFileExtensionsCompletedSuccessfully)

	if b.readOnly {
		b.log.Debug(logs.BlobovniczatreeReadonlyModeSkipBlobovniczasInitialization)
		return nil
	}

	return b.initializeDBs(context.TODO())
}

func (b *Blobovniczas) initializeDBs(ctx context.Context) error {
	err := util.MkdirAllX(b.rootPath, b.perm)
	if err != nil {
		return err
	}

	eg, egCtx := errgroup.WithContext(ctx)
	eg.SetLimit(b.blzInitWorkerCount)
	visited := make(map[string]struct{})
	err = b.iterateExistingDBPaths(egCtx, func(p string) (bool, error) {
		visited[p] = struct{}{}
		eg.Go(func() error {
			shBlz := b.getBlobovniczaWithoutCaching(p)
			_, err := shBlz.Open()
			if err != nil {
				return err
			}
			defer shBlz.Close()

			b.log.Debug(logs.BlobovniczatreeBlobovniczaSuccessfullyInitializedClosing, zap.String("id", p))
			return nil
		})
		return false, nil
	})
	if err != nil {
		_ = eg.Wait()
		return err
	}

	err = b.iterateSortedLeaves(egCtx, nil, func(p string) (bool, error) {
		if _, found := visited[p]; found {
			return false, nil
		}
		eg.Go(func() error {
			shBlz := b.getBlobovniczaWithoutCaching(p)
			_, err := shBlz.Open()
			if err != nil {
				return err
			}
			defer shBlz.Close()

			b.log.Debug(logs.BlobovniczatreeBlobovniczaSuccessfullyInitializedClosing, zap.String("id", p))
			return nil
		})
		return false, nil
	})

	if err != nil {
		_ = eg.Wait()
		return err
	}

	return eg.Wait()
}

func (b *Blobovniczas) openManagers() {
	b.commondbManager.Open() // order important
	b.activeDBManager.Open()
	b.dbCache.Open()
}

// Close implements common.Storage.
func (b *Blobovniczas) Close() error {
	b.dbCache.Close() // order important
	b.activeDBManager.Close()
	b.commondbManager.Close()

	return nil
}

// returns blobovnicza with path p
//
// If blobovnicza is already cached, instance from cache is returned w/o changes.
func (b *Blobovniczas) getBlobovnicza(p string) *sharedDB {
	return b.dbCache.GetOrCreate(p)
}

func (b *Blobovniczas) getBlobovniczaWithoutCaching(p string) *sharedDB {
	return b.commondbManager.GetByPath(p)
}

func (b *Blobovniczas) addDBExtensionToDBs(path string, depth uint64) error {
	entries, err := os.ReadDir(path)
	if os.IsNotExist(err) && depth == 0 {
		return nil
	}

	for _, entry := range entries {
		if entry.IsDir() {
			if err := b.addDBExtensionToDBs(filepath.Join(path, entry.Name()), depth+1); err != nil {
				return err
			}
			continue
		}

		if strings.HasSuffix(entry.Name(), dbExtension) {
			continue
		}
		if b.readOnly {
			return errFailedToChangeExtensionReadOnly
		}

		sourcePath := filepath.Join(path, entry.Name())
		targetPath := filepath.Join(path, entry.Name()+dbExtension)
		b.log.Debug(logs.BlobovniczaTreeFixingFileExtensionForFile, zap.String("source", sourcePath), zap.String("target", targetPath))
		if err := os.Rename(sourcePath, targetPath); err != nil {
			b.log.Error(logs.BlobovniczaTreeFixingFileExtensionFailed, zap.String("source", sourcePath), zap.String("target", targetPath), zap.Error(err))
			return err
		}
		b.log.Debug(logs.BlobovniczaTreeFixingFileExtensionCompletedSuccessfully, zap.String("source", sourcePath), zap.String("target", targetPath))
	}

	return nil
}