package dataprovider

import (
	"crypto/x509"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"sync"
	"time"

	"github.com/drakkan/sftpgo/logger"
	"github.com/drakkan/sftpgo/utils"
	"github.com/drakkan/sftpgo/vfs"
)

var (
	errMemoryProviderClosed = errors.New("memory provider is closed")
)

type memoryProviderHandle struct {
	// configuration file to use for loading users
	configFile string
	sync.Mutex
	isClosed bool
	// slice with ordered usernames
	usernames []string
	// map for users, username is the key
	users map[string]User
	// map for virtual folders, folder name is the key
	vfolders map[string]vfs.BaseVirtualFolder
	// slice with ordered folder names
	vfoldersNames []string
	// map for admins, username is the key
	admins map[string]Admin
	// slice with ordered admins
	adminsUsernames []string
}

// MemoryProvider auth provider for a memory store
type MemoryProvider struct {
	dbHandle *memoryProviderHandle
}

func initializeMemoryProvider(basePath string) {
	configFile := ""
	if utils.IsFileInputValid(config.Name) {
		configFile = config.Name
		if !filepath.IsAbs(configFile) {
			configFile = filepath.Join(basePath, configFile)
		}
	}
	provider = &MemoryProvider{
		dbHandle: &memoryProviderHandle{
			isClosed:        false,
			usernames:       []string{},
			users:           make(map[string]User),
			vfolders:        make(map[string]vfs.BaseVirtualFolder),
			vfoldersNames:   []string{},
			admins:          make(map[string]Admin),
			adminsUsernames: []string{},
			configFile:      configFile,
		},
	}
	if err := provider.reloadConfig(); err != nil {
		logger.Error(logSender, "", "unable to load initial data: %v", err)
		logger.ErrorToConsole("unable to load initial data: %v", err)
	}
}

func (p *MemoryProvider) checkAvailability() error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	return nil
}

func (p *MemoryProvider) close() error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	p.dbHandle.isClosed = true
	return nil
}

func (p *MemoryProvider) validateUserAndTLSCert(username, protocol string, tlsCert *x509.Certificate) (User, error) {
	var user User
	if tlsCert == nil {
		return user, errors.New("TLS certificate cannot be null or empty")
	}
	user, err := p.userExists(username)
	if err != nil {
		providerLog(logger.LevelWarn, "error authenticating user %#v: %v", username, err)
		return user, err
	}
	return checkUserAndTLSCertificate(&user, protocol, tlsCert)
}

func (p *MemoryProvider) validateUserAndPass(username, password, ip, protocol string) (User, error) {
	var user User
	if password == "" {
		return user, errors.New("credentials cannot be null or empty")
	}
	user, err := p.userExists(username)
	if err != nil {
		providerLog(logger.LevelWarn, "error authenticating user %#v: %v", username, err)
		return user, err
	}
	return checkUserAndPass(&user, password, ip, protocol)
}

func (p *MemoryProvider) validateUserAndPubKey(username string, pubKey []byte) (User, string, error) {
	var user User
	if len(pubKey) == 0 {
		return user, "", errors.New("credentials cannot be null or empty")
	}
	user, err := p.userExists(username)
	if err != nil {
		providerLog(logger.LevelWarn, "error authenticating user %#v: %v", username, err)
		return user, "", err
	}
	return checkUserAndPubKey(&user, pubKey)
}

func (p *MemoryProvider) validateAdminAndPass(username, password, ip string) (Admin, error) {
	admin, err := p.adminExists(username)
	if err != nil {
		providerLog(logger.LevelWarn, "error authenticating admin %#v: %v", username, err)
		return admin, ErrInvalidCredentials
	}
	err = admin.checkUserAndPass(password, ip)
	return admin, err
}

func (p *MemoryProvider) updateLastLogin(username string) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	user, err := p.userExistsInternal(username)
	if err != nil {
		return err
	}
	user.LastLogin = utils.GetTimeAsMsSinceEpoch(time.Now())
	p.dbHandle.users[user.Username] = user
	return nil
}

func (p *MemoryProvider) updateQuota(username string, filesAdd int, sizeAdd int64, reset bool) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	user, err := p.userExistsInternal(username)
	if err != nil {
		providerLog(logger.LevelWarn, "unable to update quota for user %#v error: %v", username, err)
		return err
	}
	if reset {
		user.UsedQuotaSize = sizeAdd
		user.UsedQuotaFiles = filesAdd
	} else {
		user.UsedQuotaSize += sizeAdd
		user.UsedQuotaFiles += filesAdd
	}
	user.LastQuotaUpdate = utils.GetTimeAsMsSinceEpoch(time.Now())
	providerLog(logger.LevelDebug, "quota updated for user %#v, files increment: %v size increment: %v is reset? %v",
		username, filesAdd, sizeAdd, reset)
	p.dbHandle.users[user.Username] = user
	return nil
}

func (p *MemoryProvider) getUsedQuota(username string) (int, int64, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return 0, 0, errMemoryProviderClosed
	}
	user, err := p.userExistsInternal(username)
	if err != nil {
		providerLog(logger.LevelWarn, "unable to get quota for user %#v error: %v", username, err)
		return 0, 0, err
	}
	return user.UsedQuotaFiles, user.UsedQuotaSize, err
}

func (p *MemoryProvider) addUser(user *User) error {
	// we can query virtual folder while validating a user
	// so we have to check without holding the lock
	err := ValidateUser(user)
	if err != nil {
		return err
	}

	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}

	_, err = p.userExistsInternal(user.Username)
	if err == nil {
		return fmt.Errorf("username %#v already exists", user.Username)
	}
	user.ID = p.getNextID()
	user.LastQuotaUpdate = 0
	user.UsedQuotaSize = 0
	user.UsedQuotaFiles = 0
	user.LastLogin = 0
	user.VirtualFolders = p.joinVirtualFoldersFields(user)
	p.dbHandle.users[user.Username] = user.getACopy()
	p.dbHandle.usernames = append(p.dbHandle.usernames, user.Username)
	sort.Strings(p.dbHandle.usernames)
	return nil
}

func (p *MemoryProvider) updateUser(user *User) error {
	// we can query virtual folder while validating a user
	// so we have to check without holding the lock
	err := ValidateUser(user)
	if err != nil {
		return err
	}

	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}

	u, err := p.userExistsInternal(user.Username)
	if err != nil {
		return err
	}
	for _, oldFolder := range u.VirtualFolders {
		p.removeUserFromFolderMapping(oldFolder.Name, u.Username)
	}
	user.VirtualFolders = p.joinVirtualFoldersFields(user)
	user.LastQuotaUpdate = u.LastQuotaUpdate
	user.UsedQuotaSize = u.UsedQuotaSize
	user.UsedQuotaFiles = u.UsedQuotaFiles
	user.LastLogin = u.LastLogin
	user.ID = u.ID
	// pre-login and external auth hook will use the passed *user so save a copy
	p.dbHandle.users[user.Username] = user.getACopy()
	return nil
}

func (p *MemoryProvider) deleteUser(user *User) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	u, err := p.userExistsInternal(user.Username)
	if err != nil {
		return err
	}
	for _, oldFolder := range u.VirtualFolders {
		p.removeUserFromFolderMapping(oldFolder.Name, u.Username)
	}
	delete(p.dbHandle.users, user.Username)
	// this could be more efficient
	p.dbHandle.usernames = make([]string, 0, len(p.dbHandle.users))
	for username := range p.dbHandle.users {
		p.dbHandle.usernames = append(p.dbHandle.usernames, username)
	}
	sort.Strings(p.dbHandle.usernames)
	return nil
}

func (p *MemoryProvider) dumpUsers() ([]User, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	users := make([]User, 0, len(p.dbHandle.usernames))
	var err error
	if p.dbHandle.isClosed {
		return users, errMemoryProviderClosed
	}
	for _, username := range p.dbHandle.usernames {
		u := p.dbHandle.users[username]
		user := u.getACopy()
		err = addCredentialsToUser(&user)
		if err != nil {
			return users, err
		}
		users = append(users, user)
	}
	return users, err
}

func (p *MemoryProvider) dumpFolders() ([]vfs.BaseVirtualFolder, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	folders := make([]vfs.BaseVirtualFolder, 0, len(p.dbHandle.vfoldersNames))
	if p.dbHandle.isClosed {
		return folders, errMemoryProviderClosed
	}
	for _, f := range p.dbHandle.vfolders {
		folders = append(folders, f)
	}
	return folders, nil
}

func (p *MemoryProvider) getUsers(limit int, offset int, order string) ([]User, error) {
	users := make([]User, 0, limit)
	var err error
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return users, errMemoryProviderClosed
	}
	if limit <= 0 {
		return users, err
	}
	itNum := 0
	if order == OrderASC {
		for _, username := range p.dbHandle.usernames {
			itNum++
			if itNum <= offset {
				continue
			}
			u := p.dbHandle.users[username]
			user := u.getACopy()
			user.PrepareForRendering()
			users = append(users, user)
			if len(users) >= limit {
				break
			}
		}
	} else {
		for i := len(p.dbHandle.usernames) - 1; i >= 0; i-- {
			itNum++
			if itNum <= offset {
				continue
			}
			username := p.dbHandle.usernames[i]
			u := p.dbHandle.users[username]
			user := u.getACopy()
			user.PrepareForRendering()
			users = append(users, user)
			if len(users) >= limit {
				break
			}
		}
	}
	return users, err
}

func (p *MemoryProvider) userExists(username string) (User, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return User{}, errMemoryProviderClosed
	}
	return p.userExistsInternal(username)
}

func (p *MemoryProvider) userExistsInternal(username string) (User, error) {
	if val, ok := p.dbHandle.users[username]; ok {
		return val.getACopy(), nil
	}
	return User{}, &RecordNotFoundError{err: fmt.Sprintf("username %#v does not exist", username)}
}

func (p *MemoryProvider) addAdmin(admin *Admin) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	err := admin.validate()
	if err != nil {
		return err
	}
	_, err = p.adminExistsInternal(admin.Username)
	if err == nil {
		return fmt.Errorf("admin %#v already exists", admin.Username)
	}
	admin.ID = p.getNextAdminID()
	p.dbHandle.admins[admin.Username] = admin.getACopy()
	p.dbHandle.adminsUsernames = append(p.dbHandle.adminsUsernames, admin.Username)
	sort.Strings(p.dbHandle.adminsUsernames)
	return nil
}

func (p *MemoryProvider) updateAdmin(admin *Admin) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	err := admin.validate()
	if err != nil {
		return err
	}
	a, err := p.adminExistsInternal(admin.Username)
	if err != nil {
		return err
	}
	admin.ID = a.ID
	p.dbHandle.admins[admin.Username] = admin.getACopy()
	return nil
}

func (p *MemoryProvider) deleteAdmin(admin *Admin) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	_, err := p.adminExistsInternal(admin.Username)
	if err != nil {
		return err
	}

	delete(p.dbHandle.admins, admin.Username)
	// this could be more efficient
	p.dbHandle.adminsUsernames = make([]string, 0, len(p.dbHandle.admins))
	for username := range p.dbHandle.admins {
		p.dbHandle.adminsUsernames = append(p.dbHandle.adminsUsernames, username)
	}
	sort.Strings(p.dbHandle.adminsUsernames)
	return nil
}

func (p *MemoryProvider) adminExists(username string) (Admin, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return Admin{}, errMemoryProviderClosed
	}
	return p.adminExistsInternal(username)
}

func (p *MemoryProvider) adminExistsInternal(username string) (Admin, error) {
	if val, ok := p.dbHandle.admins[username]; ok {
		return val.getACopy(), nil
	}
	return Admin{}, &RecordNotFoundError{err: fmt.Sprintf("admin %#v does not exist", username)}
}

func (p *MemoryProvider) dumpAdmins() ([]Admin, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()

	admins := make([]Admin, 0, len(p.dbHandle.admins))
	if p.dbHandle.isClosed {
		return admins, errMemoryProviderClosed
	}
	for _, admin := range p.dbHandle.admins {
		admins = append(admins, admin)
	}
	return admins, nil
}

func (p *MemoryProvider) getAdmins(limit int, offset int, order string) ([]Admin, error) {
	admins := make([]Admin, 0, limit)

	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()

	if p.dbHandle.isClosed {
		return admins, errMemoryProviderClosed
	}
	if limit <= 0 {
		return admins, nil
	}
	itNum := 0
	if order == OrderASC {
		for _, username := range p.dbHandle.adminsUsernames {
			itNum++
			if itNum <= offset {
				continue
			}
			a := p.dbHandle.admins[username]
			admin := a.getACopy()
			admin.HideConfidentialData()
			admins = append(admins, admin)
			if len(admins) >= limit {
				break
			}
		}
	} else {
		for i := len(p.dbHandle.adminsUsernames) - 1; i >= 0; i-- {
			itNum++
			if itNum <= offset {
				continue
			}
			username := p.dbHandle.adminsUsernames[i]
			a := p.dbHandle.admins[username]
			admin := a.getACopy()
			admin.HideConfidentialData()
			admins = append(admins, admin)
			if len(admins) >= limit {
				break
			}
		}
	}

	return admins, nil
}

func (p *MemoryProvider) updateFolderQuota(name string, filesAdd int, sizeAdd int64, reset bool) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	folder, err := p.folderExistsInternal(name)
	if err != nil {
		providerLog(logger.LevelWarn, "unable to update quota for folder %#v error: %v", name, err)
		return err
	}
	if reset {
		folder.UsedQuotaSize = sizeAdd
		folder.UsedQuotaFiles = filesAdd
	} else {
		folder.UsedQuotaSize += sizeAdd
		folder.UsedQuotaFiles += filesAdd
	}
	folder.LastQuotaUpdate = utils.GetTimeAsMsSinceEpoch(time.Now())
	p.dbHandle.vfolders[name] = folder
	return nil
}

func (p *MemoryProvider) getUsedFolderQuota(name string) (int, int64, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return 0, 0, errMemoryProviderClosed
	}
	folder, err := p.folderExistsInternal(name)
	if err != nil {
		providerLog(logger.LevelWarn, "unable to get quota for folder %#v error: %v", name, err)
		return 0, 0, err
	}
	return folder.UsedQuotaFiles, folder.UsedQuotaSize, err
}

func (p *MemoryProvider) joinVirtualFoldersFields(user *User) []vfs.VirtualFolder {
	var folders []vfs.VirtualFolder
	for idx := range user.VirtualFolders {
		folder := &user.VirtualFolders[idx]
		f, err := p.addOrUpdateFolderInternal(&folder.BaseVirtualFolder, user.Username, 0, 0, 0)
		if err == nil {
			folder.BaseVirtualFolder = f
			folders = append(folders, *folder)
		}
	}
	return folders
}

func (p *MemoryProvider) removeUserFromFolderMapping(folderName, username string) {
	folder, err := p.folderExistsInternal(folderName)
	if err == nil {
		var usernames []string
		for _, user := range folder.Users {
			if user != username {
				usernames = append(usernames, user)
			}
		}
		folder.Users = usernames
		p.dbHandle.vfolders[folder.Name] = folder
	}
}

func (p *MemoryProvider) updateFoldersMappingInternal(folder vfs.BaseVirtualFolder) {
	p.dbHandle.vfolders[folder.Name] = folder
	if !utils.IsStringInSlice(folder.Name, p.dbHandle.vfoldersNames) {
		p.dbHandle.vfoldersNames = append(p.dbHandle.vfoldersNames, folder.Name)
		sort.Strings(p.dbHandle.vfoldersNames)
	}
}

func (p *MemoryProvider) addOrUpdateFolderInternal(baseFolder *vfs.BaseVirtualFolder, username string, usedQuotaSize int64,
	usedQuotaFiles int, lastQuotaUpdate int64) (vfs.BaseVirtualFolder, error) {
	folder, err := p.folderExistsInternal(baseFolder.Name)
	if err == nil {
		// exists
		folder.MappedPath = baseFolder.MappedPath
		folder.Description = baseFolder.Description
		folder.FsConfig = baseFolder.FsConfig.GetACopy()
		if !utils.IsStringInSlice(username, folder.Users) {
			folder.Users = append(folder.Users, username)
		}
		p.updateFoldersMappingInternal(folder)
		return folder, nil
	}
	if _, ok := err.(*RecordNotFoundError); ok {
		folder = baseFolder.GetACopy()
		folder.ID = p.getNextFolderID()
		folder.UsedQuotaSize = usedQuotaSize
		folder.UsedQuotaFiles = usedQuotaFiles
		folder.LastQuotaUpdate = lastQuotaUpdate
		folder.Users = []string{username}
		p.updateFoldersMappingInternal(folder)
		return folder, nil
	}
	return folder, err
}

func (p *MemoryProvider) folderExistsInternal(name string) (vfs.BaseVirtualFolder, error) {
	if val, ok := p.dbHandle.vfolders[name]; ok {
		return val, nil
	}
	return vfs.BaseVirtualFolder{}, &RecordNotFoundError{err: fmt.Sprintf("folder %#v does not exist", name)}
}

func (p *MemoryProvider) getFolders(limit, offset int, order string) ([]vfs.BaseVirtualFolder, error) {
	folders := make([]vfs.BaseVirtualFolder, 0, limit)
	var err error
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return folders, errMemoryProviderClosed
	}
	if limit <= 0 {
		return folders, err
	}
	itNum := 0
	if order == OrderASC {
		for _, name := range p.dbHandle.vfoldersNames {
			itNum++
			if itNum <= offset {
				continue
			}
			f := p.dbHandle.vfolders[name]
			folder := f.GetACopy()
			folder.PrepareForRendering()
			folders = append(folders, folder)
			if len(folders) >= limit {
				break
			}
		}
	} else {
		for i := len(p.dbHandle.vfoldersNames) - 1; i >= 0; i-- {
			itNum++
			if itNum <= offset {
				continue
			}
			name := p.dbHandle.vfoldersNames[i]
			f := p.dbHandle.vfolders[name]
			folder := f.GetACopy()
			folder.PrepareForRendering()
			folders = append(folders, folder)
			if len(folders) >= limit {
				break
			}
		}
	}
	return folders, err
}

func (p *MemoryProvider) getFolderByName(name string) (vfs.BaseVirtualFolder, error) {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return vfs.BaseVirtualFolder{}, errMemoryProviderClosed
	}
	folder, err := p.folderExistsInternal(name)
	if err != nil {
		return vfs.BaseVirtualFolder{}, err
	}
	return folder.GetACopy(), nil
}

func (p *MemoryProvider) addFolder(folder *vfs.BaseVirtualFolder) error {
	err := ValidateFolder(folder)
	if err != nil {
		return err
	}

	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}

	_, err = p.folderExistsInternal(folder.Name)
	if err == nil {
		return fmt.Errorf("folder %#v already exists", folder.Name)
	}
	folder.ID = p.getNextFolderID()
	folder.Users = nil
	p.dbHandle.vfolders[folder.Name] = folder.GetACopy()
	p.dbHandle.vfoldersNames = append(p.dbHandle.vfoldersNames, folder.Name)
	sort.Strings(p.dbHandle.vfoldersNames)
	return nil
}

func (p *MemoryProvider) updateFolder(folder *vfs.BaseVirtualFolder) error {
	err := ValidateFolder(folder)
	if err != nil {
		return err
	}

	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}
	f, err := p.folderExistsInternal(folder.Name)
	if err != nil {
		return err
	}
	folder.ID = f.ID
	folder.LastQuotaUpdate = f.LastQuotaUpdate
	folder.UsedQuotaFiles = f.UsedQuotaFiles
	folder.UsedQuotaSize = f.UsedQuotaSize
	folder.Users = f.Users
	p.dbHandle.vfolders[folder.Name] = folder.GetACopy()
	// now update the related users
	for _, username := range folder.Users {
		user, err := p.userExistsInternal(username)
		if err == nil {
			var folders []vfs.VirtualFolder
			for idx := range user.VirtualFolders {
				userFolder := &user.VirtualFolders[idx]
				if folder.Name == userFolder.Name {
					userFolder.BaseVirtualFolder = folder.GetACopy()
				}
				folders = append(folders, *userFolder)
			}
			user.VirtualFolders = folders
			p.dbHandle.users[user.Username] = user
		}
	}
	return nil
}

func (p *MemoryProvider) deleteFolder(folder *vfs.BaseVirtualFolder) error {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	if p.dbHandle.isClosed {
		return errMemoryProviderClosed
	}

	_, err := p.folderExistsInternal(folder.Name)
	if err != nil {
		return err
	}
	for _, username := range folder.Users {
		user, err := p.userExistsInternal(username)
		if err == nil {
			var folders []vfs.VirtualFolder
			for idx := range user.VirtualFolders {
				userFolder := &user.VirtualFolders[idx]
				if folder.Name != userFolder.Name {
					folders = append(folders, *userFolder)
				}
			}
			user.VirtualFolders = folders
			p.dbHandle.users[user.Username] = user
		}
	}
	delete(p.dbHandle.vfolders, folder.Name)
	p.dbHandle.vfoldersNames = []string{}
	for name := range p.dbHandle.vfolders {
		p.dbHandle.vfoldersNames = append(p.dbHandle.vfoldersNames, name)
	}
	sort.Strings(p.dbHandle.vfoldersNames)
	return nil
}

func (p *MemoryProvider) getNextID() int64 {
	nextID := int64(1)
	for _, v := range p.dbHandle.users {
		if v.ID >= nextID {
			nextID = v.ID + 1
		}
	}
	return nextID
}

func (p *MemoryProvider) getNextFolderID() int64 {
	nextID := int64(1)
	for _, v := range p.dbHandle.vfolders {
		if v.ID >= nextID {
			nextID = v.ID + 1
		}
	}
	return nextID
}

func (p *MemoryProvider) getNextAdminID() int64 {
	nextID := int64(1)
	for _, a := range p.dbHandle.admins {
		if a.ID >= nextID {
			nextID = a.ID + 1
		}
	}
	return nextID
}

func (p *MemoryProvider) clear() {
	p.dbHandle.Lock()
	defer p.dbHandle.Unlock()
	p.dbHandle.usernames = []string{}
	p.dbHandle.users = make(map[string]User)
	p.dbHandle.vfoldersNames = []string{}
	p.dbHandle.vfolders = make(map[string]vfs.BaseVirtualFolder)
	p.dbHandle.admins = make(map[string]Admin)
	p.dbHandle.adminsUsernames = []string{}
}

func (p *MemoryProvider) reloadConfig() error {
	if p.dbHandle.configFile == "" {
		providerLog(logger.LevelDebug, "no dump configuration file defined")
		return nil
	}
	providerLog(logger.LevelDebug, "loading dump from file: %#v", p.dbHandle.configFile)
	fi, err := os.Stat(p.dbHandle.configFile)
	if err != nil {
		providerLog(logger.LevelWarn, "error loading dump: %v", err)
		return err
	}
	if fi.Size() == 0 {
		err = errors.New("dump configuration file is invalid, its size must be > 0")
		providerLog(logger.LevelWarn, "error loading dump: %v", err)
		return err
	}
	if fi.Size() > 10485760 {
		err = errors.New("dump configuration file is invalid, its size must be <= 10485760 bytes")
		providerLog(logger.LevelWarn, "error loading dump: %v", err)
		return err
	}
	content, err := os.ReadFile(p.dbHandle.configFile)
	if err != nil {
		providerLog(logger.LevelWarn, "error loading dump: %v", err)
		return err
	}
	dump, err := ParseDumpData(content)
	if err != nil {
		providerLog(logger.LevelWarn, "error loading dump: %v", err)
		return err
	}
	p.clear()

	if err := p.restoreFolders(&dump); err != nil {
		return err
	}

	if err := p.restoreUsers(&dump); err != nil {
		return err
	}

	if err := p.restoreAdmins(&dump); err != nil {
		return err
	}

	providerLog(logger.LevelDebug, "config loaded from file: %#v", p.dbHandle.configFile)
	return nil
}

func (p *MemoryProvider) restoreAdmins(dump *BackupData) error {
	for _, admin := range dump.Admins {
		a, err := p.adminExists(admin.Username)
		admin := admin // pin
		if err == nil {
			admin.ID = a.ID
			err = p.updateAdmin(&admin)
			if err != nil {
				providerLog(logger.LevelWarn, "error updating admin %#v: %v", admin.Username, err)
				return err
			}
		} else {
			err = p.addAdmin(&admin)
			if err != nil {
				providerLog(logger.LevelWarn, "error adding admin %#v: %v", admin.Username, err)
				return err
			}
		}
	}
	return nil
}

func (p *MemoryProvider) restoreFolders(dump *BackupData) error {
	for _, folder := range dump.Folders {
		folder := folder // pin
		f, err := p.getFolderByName(folder.Name)
		if err == nil {
			folder.ID = f.ID
			err = p.updateFolder(&folder)
			if err != nil {
				providerLog(logger.LevelWarn, "error updating folder %#v: %v", folder.Name, err)
				return err
			}
		} else {
			folder.Users = nil
			err = p.addFolder(&folder)
			if err != nil {
				providerLog(logger.LevelWarn, "error adding folder %#v: %v", folder.Name, err)
				return err
			}
		}
	}
	return nil
}

func (p *MemoryProvider) restoreUsers(dump *BackupData) error {
	for _, user := range dump.Users {
		user := user // pin
		u, err := p.userExists(user.Username)
		if err == nil {
			user.ID = u.ID
			err = p.updateUser(&user)
			if err != nil {
				providerLog(logger.LevelWarn, "error updating user %#v: %v", user.Username, err)
				return err
			}
		} else {
			err = p.addUser(&user)
			if err != nil {
				providerLog(logger.LevelWarn, "error adding user %#v: %v", user.Username, err)
				return err
			}
		}
	}
	return nil
}

// initializeDatabase does nothing, no initilization is needed for memory provider
func (p *MemoryProvider) initializeDatabase() error {
	return ErrNoInitRequired
}

func (p *MemoryProvider) migrateDatabase() error {
	return ErrNoInitRequired
}

func (p *MemoryProvider) revertDatabase(targetVersion int) error {
	return errors.New("memory provider does not store data, revert not possible")
}