package statusproto

import (
	"context"
	"crypto/ecdsa"
	"fmt"
	"path/filepath"
	"time"

	"go.uber.org/zap"

	"github.com/pkg/errors"
	whisper "github.com/status-im/whisper/whisperv6"

	"github.com/status-im/status-protocol-go/datasync"
	datasyncpeer "github.com/status-im/status-protocol-go/datasync/peer"
	"github.com/status-im/status-protocol-go/encryption"
	"github.com/status-im/status-protocol-go/encryption/multidevice"
	"github.com/status-im/status-protocol-go/encryption/sharedsecret"
	migrations "github.com/status-im/status-protocol-go/internal/sqlite"
	"github.com/status-im/status-protocol-go/sqlite"
	transport "github.com/status-im/status-protocol-go/transport/whisper"
	"github.com/status-im/status-protocol-go/transport/whisper/filter"
	protocol "github.com/status-im/status-protocol-go/v1"
	datasyncnode "github.com/vacp2p/mvds/node"
	datasyncpeers "github.com/vacp2p/mvds/peers"
	datasyncstate "github.com/vacp2p/mvds/state"
	datasyncstore "github.com/vacp2p/mvds/store"
)

var (
	ErrChatIDEmpty    = errors.New("chat ID is empty")
	ErrNotImplemented = errors.New("not implemented")
)

// Messenger is a entity managing chats and messages.
// It acts as a bridge between the application and encryption
// layers.
// It needs to expose an interface to manage installations
// because installations are managed by the user.
// Similarly, it needs to expose an interface to manage
// mailservers because they can also be managed by the user.
type Messenger struct {
	identity    *ecdsa.PrivateKey
	persistence persistence
	adapter     *whisperAdapter
	encryptor   *encryption.Protocol
	logger      *zap.Logger

	ownMessages                map[string][]*protocol.Message
	featureFlags               featureFlags
	messagesPersistenceEnabled bool
	shutdownTasks              []func() error
}

type featureFlags struct {
	genericDiscoveryTopicEnabled bool
	// sendV1Messages indicates whether we should send
	// messages compatible only with V1 and later.
	// V1 messages adds additional wrapping
	// which contains a signature and payload.
	sendV1Messages bool

	// datasync indicates whether messages should be sent using datasync, breaking change for non-v1 clients
	datasync bool
}

type config struct {
	onNewInstallationsHandler func([]*multidevice.Installation)
	// DEPRECATED: no need to expose it
	onNewSharedSecretHandler func([]*sharedsecret.Secret)
	// DEPRECATED: no need to expose it
	onSendContactCodeHandler func(*encryption.ProtocolMessageSpec)

	encryptionLayerFilePath string
	transportLayerFilePath  string

	messagesPersistenceEnabled bool
	featureFlags               featureFlags

	logger *zap.Logger
}

type Option func(*config) error

func WithOnNewInstallationsHandler(h func([]*multidevice.Installation)) func(c *config) error {
	return func(c *config) error {
		c.onNewInstallationsHandler = h
		return nil
	}
}

func WithOnNewSharedSecret(h func([]*sharedsecret.Secret)) func(c *config) error {
	return func(c *config) error {
		c.onNewSharedSecretHandler = h
		return nil
	}
}

func WithCustomLogger(logger *zap.Logger) func(c *config) error {
	return func(c *config) error {
		c.logger = logger
		return nil
	}
}

func WithGenericDiscoveryTopicSupport() func(c *config) error {
	return func(c *config) error {
		c.featureFlags.genericDiscoveryTopicEnabled = true
		return nil
	}
}

func WithMessagesPersistenceEnabled() func(c *config) error {
	return func(c *config) error {
		c.messagesPersistenceEnabled = true
		return nil
	}
}

// TODO: use this config fileds.
func WithDatabaseFilePaths(encryptionLayerFilePath, transportLayerFilePath string) func(c *config) error {
	return func(c *config) error {
		c.encryptionLayerFilePath = encryptionLayerFilePath
		c.transportLayerFilePath = transportLayerFilePath
		return nil
	}
}

func WithSendV1Messages() func(c *config) error {
	return func(c *config) error {
		c.featureFlags.sendV1Messages = true
		return nil
	}
}

func WithDatasync() func(c *config) error {
	return func(c *config) error {
		c.featureFlags.datasync = true
		return nil
	}
}

func NewMessenger(
	identity *ecdsa.PrivateKey,
	server transport.Server,
	shh *whisper.Whisper,
	dataDir string,
	dbKey string,
	installationID string,
	opts ...Option,
) (*Messenger, error) {
	var messenger *Messenger

	c := config{}

	for _, opt := range opts {
		if err := opt(&c); err != nil {
			return nil, err
		}
	}

	logger := c.logger
	if c.logger == nil {
		var err error
		if logger, err = zap.NewDevelopment(); err != nil {
			return nil, errors.Wrap(err, "failed to create a logger")
		}
	}

	// Set default config fields.
	if c.onNewInstallationsHandler == nil {
		c.onNewInstallationsHandler = func(installations []*multidevice.Installation) {
			sugar := logger.Sugar().With("site", "onNewInstallationsHandler")
			for _, installation := range installations {
				sugar.Infow(
					"received a new installation",
					"identity", installation.Identity,
					"id", installation.ID)
			}
		}
	}
	if c.onNewSharedSecretHandler == nil {
		c.onNewSharedSecretHandler = func(secrets []*sharedsecret.Secret) {
			if err := messenger.handleSharedSecrets(secrets); err != nil {
				slogger := logger.With(zap.String("site", "onNewSharedSecretHandler"))
				slogger.Warn("failed to process secrets", zap.Error(err))
			}
		}
	}
	if c.onSendContactCodeHandler == nil {
		c.onSendContactCodeHandler = func(messageSpec *encryption.ProtocolMessageSpec) {
			slogger := logger.With(zap.String("site", "onSendContactCodeHandler"))
			slogger.Info("received a SendContactCode request")
			ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
			defer cancel()
			_, err := messenger.adapter.SendContactCode(ctx, messageSpec)
			if err != nil {
				slogger.Warn("failed to send a contact code", zap.Error(err))
			}
		}
	}

	// Set default database file paths.
	if c.encryptionLayerFilePath == "" {
		c.encryptionLayerFilePath = filepath.Join(dataDir, "sessions.sql")
	}
	if c.transportLayerFilePath == "" {
		c.transportLayerFilePath = filepath.Join(dataDir, "transport.sql")
	}

	t, err := transport.NewWhisperServiceTransport(
		server,
		shh,
		identity,
		c.transportLayerFilePath,
		dbKey,
		nil,
		logger,
	)
	if err != nil {
		return nil, errors.Wrap(err, "failed to create a WhisperServiceTransport")
	}

	encryptionProtocol, err := encryption.New(
		c.encryptionLayerFilePath,
		dbKey,
		installationID,
		c.onNewInstallationsHandler,
		c.onNewSharedSecretHandler,
		c.onSendContactCodeHandler,
		logger,
	)
	if err != nil {
		return nil, errors.Wrap(err, "failed to create the encryption layer")
	}

	messagesDatabaseFileName := fmt.Sprintf("%s.messages.sql", installationID)

	applicationLayerFilePath := filepath.Join(dataDir, messagesDatabaseFileName)
	applicationLayerPersistence, err := sqlite.Open(applicationLayerFilePath, dbKey, sqlite.MigrationConfig{
		AssetNames: migrations.AssetNames(),
		AssetGetter: func(name string) ([]byte, error) {
			return migrations.Asset(name)
		},
	})
	if err != nil {
		return nil, errors.Wrap(err, "failed to initialize messages db")
	}
	dataSyncTransport := datasync.NewDataSyncNodeTransport()
	dataSyncStore := datasyncstore.NewDummyStore()
	dataSyncNode := datasyncnode.NewNode(
		&dataSyncStore,
		dataSyncTransport,
		datasyncstate.NewSyncState(), // @todo sqlite syncstate
		datasync.CalculateSendTime,
		0,
		datasyncpeer.PublicKeyToPeerID(identity.PublicKey),
		datasyncnode.BATCH,
		datasyncpeers.NewMemoryPersistence(),
	)
	datasync := &datasync.DataSync{
		Node:                  dataSyncNode,
		DataSyncNodeTransport: dataSyncTransport,
	}

	persistence := &sqlitePersistence{db: applicationLayerPersistence}
	adapter := newWhisperAdapter(identity, t, encryptionProtocol, datasync, c.featureFlags, logger)
	messenger = &Messenger{
		identity:                   identity,
		persistence:                persistence,
		adapter:                    adapter,
		encryptor:                  encryptionProtocol,
		ownMessages:                make(map[string][]*protocol.Message),
		featureFlags:               c.featureFlags,
		messagesPersistenceEnabled: c.messagesPersistenceEnabled,
		shutdownTasks: []func() error{
			persistence.Close,
			adapter.transport.Reset,
			func() error { datasync.Node.Stop(); return nil },
			// Currently this often fails, seems like it's safe to ignore them
			// https://github.com/uber-go/zap/issues/328
			func() error { _ = logger.Sync; return nil },
		},
		logger: logger,
	}

	// Start all services immediately.
	// TODO: consider removing identity as an argument to Start().
	if err := encryptionProtocol.Start(identity); err != nil {
		return nil, err
	}
	if c.featureFlags.datasync {
		dataSyncNode.Start(300 * time.Millisecond)
	}

	logger.Debug("messages persistence", zap.Bool("enabled", c.messagesPersistenceEnabled))

	return messenger, nil
}

// Shutdown takes care of ensuring a clean shutdown of Messenger
func (m *Messenger) Shutdown() (err error) {
	for _, task := range m.shutdownTasks {
		if tErr := task(); tErr != nil {
			if err == nil {
				// First error appeared.
				err = tErr
			} else {
				// We return all errors. They will be concatenated in the order of occurrence,
				// however, they will also be returned as a single error.
				err = errors.Wrap(err, tErr.Error())
			}
		}
	}
	return
}

func (m *Messenger) handleSharedSecrets(secrets []*sharedsecret.Secret) error {
	return m.adapter.handleSharedSecrets(secrets)
}

func (m *Messenger) EnableInstallation(id string) error {
	return m.encryptor.EnableInstallation(&m.identity.PublicKey, id)
}

func (m *Messenger) DisableInstallation(id string) error {
	return m.encryptor.DisableInstallation(&m.identity.PublicKey, id)
}

func (m *Messenger) Installations() ([]*multidevice.Installation, error) {
	return m.encryptor.GetOurInstallations(&m.identity.PublicKey)
}

func (m *Messenger) SetInstallationMetadata(id string, data *multidevice.InstallationMetadata) error {
	return m.encryptor.SetInstallationMetadata(&m.identity.PublicKey, id, data)
}

// NOT IMPLEMENTED
func (m *Messenger) SelectMailserver(id string) error {
	return ErrNotImplemented
}

// NOT IMPLEMENTED
func (m *Messenger) AddMailserver(enode string) error {
	return ErrNotImplemented
}

// NOT IMPLEMENTED
func (m *Messenger) RemoveMailserver(id string) error {
	return ErrNotImplemented
}

// NOT IMPLEMENTED
func (m *Messenger) Mailservers() ([]string, error) {
	return nil, ErrNotImplemented
}

func (m *Messenger) Join(chat Chat) error {
	if chat.PublicKey() != nil {
		return m.adapter.JoinPrivate(chat.PublicKey())
	} else if chat.PublicName() != "" {
		return m.adapter.JoinPublic(chat.PublicName())
	}
	return errors.New("chat is neither public nor private")
}

func (m *Messenger) Leave(chat Chat) error {
	if chat.PublicKey() != nil {
		return m.adapter.LeavePrivate(chat.PublicKey())
	} else if chat.PublicName() != "" {
		return m.adapter.LeavePublic(chat.PublicName())
	}
	return errors.New("chat is neither public nor private")
}

func (m *Messenger) Send(ctx context.Context, chat Chat, data []byte) ([]byte, error) {
	chatID := chat.ID()
	if chatID == "" {
		return nil, ErrChatIDEmpty
	}

	clock, err := m.persistence.LastMessageClock(chat.ID())
	if err != nil {
		return nil, err
	}

	if chat.PublicKey() != nil {
		hash, message, err := m.adapter.SendPrivate(ctx, chat.PublicKey(), chat.ID(), data, clock)
		if err != nil {
			return nil, err
		}

		// Save our message because it won't be received from the transport layer.
		message.ID = hash // a Message need ID to be properly stored in the db
		message.SigPubKey = &m.identity.PublicKey

		if m.messagesPersistenceEnabled {
			_, err = m.persistence.SaveMessages(chat.ID(), []*protocol.Message{message})
			if err != nil {
				return nil, err
			}
		}

		// Cache it to be returned in Retrieve().
		m.ownMessages[chatID] = append(m.ownMessages[chatID], message)

		return hash, nil
	} else if chat.PublicName() != "" {
		return m.adapter.SendPublic(ctx, chat.PublicName(), chat.ID(), data, clock)
	}
	return nil, errors.New("chat is neither public nor private")
}

// SendRaw takes encoded data, encrypts it and sends through the wire.
// DEPRECATED
func (m *Messenger) SendRaw(ctx context.Context, chat Chat, data []byte) ([]byte, whisper.NewMessage, error) {
	if chat.PublicKey() != nil {
		return m.adapter.SendPrivateRaw(ctx, chat.PublicKey(), data)
	} else if chat.PublicName() != "" {
		return m.adapter.SendPublicRaw(ctx, chat.PublicName(), data)
	}
	return nil, whisper.NewMessage{}, errors.New("chat is neither public nor private")
}

type RetrieveConfig struct {
	From        time.Time
	To          time.Time
	latest      bool
	last24Hours bool
}

var (
	RetrieveLatest  = RetrieveConfig{latest: true}
	RetrieveLastDay = RetrieveConfig{latest: true, last24Hours: true}
)

// RetrieveAll retrieves all previously fetched messages
func (m *Messenger) RetrieveAll(ctx context.Context, c RetrieveConfig) (allMessages []*protocol.Message, err error) {
	latest, err := m.adapter.RetrieveAllMessages()
	if err != nil {
		err = errors.Wrap(err, "failed to retrieve messages")
		return
	}

	for _, messages := range latest {
		chatID := messages.ChatID

		_, err = m.persistence.SaveMessages(chatID, messages.Messages)
		if err != nil {
			return nil, errors.Wrap(err, "failed to save messages")
		}

		if !messages.Public {
			// Return any own messages for this chat as well.
			if ownMessages, ok := m.ownMessages[chatID]; ok {
				messages.Messages = append(messages.Messages, ownMessages...)
			}
		}

		retrievedMessages, err := m.retrieveSaved(ctx, chatID, c, messages.Messages)
		if err != nil {
			return nil, errors.Wrap(err, "failed to get saved messages")
		}

		allMessages = append(allMessages, retrievedMessages...)
	}

	// Delete own messages as they were added to the result.
	for _, messages := range latest {
		if !messages.Public {
			delete(m.ownMessages, messages.ChatID)
		}
	}

	return
}

func (m *Messenger) Retrieve(ctx context.Context, chat Chat, c RetrieveConfig) (messages []*protocol.Message, err error) {
	var (
		latest    []*protocol.Message
		ownLatest []*protocol.Message
	)

	if chat.PublicKey() != nil {
		latest, err = m.adapter.RetrievePrivateMessages(chat.PublicKey())
		// Return any own messages for this chat as well.
		if ownMessages, ok := m.ownMessages[chat.ID()]; ok {
			ownLatest = ownMessages
		}
	} else if chat.PublicName() != "" {
		latest, err = m.adapter.RetrievePublicMessages(chat.PublicName())
	} else {
		return nil, errors.New("chat is neither public nor private")
	}

	if err != nil {
		err = errors.Wrap(err, "failed to retrieve messages")
		return
	}

	if m.messagesPersistenceEnabled {
		_, err = m.persistence.SaveMessages(chat.ID(), latest)
		if err != nil {
			return nil, errors.Wrap(err, "failed to save latest messages")
		}
	}

	// Confirm received and decrypted messages.
	if m.messagesPersistenceEnabled && chat.PublicKey() != nil {
		for _, message := range latest {
			// Confirm received and decrypted messages.
			if err := m.encryptor.ConfirmMessageProcessed(message.ID); err != nil {
				return nil, errors.Wrap(err, "failed to confirm message being processed")
			}
		}
	}

	// We may need to add more messages from the past.
	result, err := m.retrieveSaved(ctx, chat.ID(), c, append(latest, ownLatest...))
	if err != nil {
		return nil, err
	}

	// When our messages are returned, we can delete them.
	delete(m.ownMessages, chat.ID())

	return result, nil
}

func (m *Messenger) retrieveSaved(ctx context.Context, chatID string, c RetrieveConfig, latest []*protocol.Message) (messages []*protocol.Message, err error) {
	if !m.messagesPersistenceEnabled {
		return latest, nil
	}

	if !c.latest {
		return m.persistence.Messages(chatID, c.From, c.To)
	}

	if c.last24Hours {
		to := time.Now()
		from := to.Add(-time.Hour * 24)
		return m.persistence.Messages(chatID, from, to)
	}

	return latest, nil
}

// DEPRECATED
func (m *Messenger) RetrieveRawAll() (map[filter.Chat][]*whisper.Message, error) {
	return m.adapter.RetrieveRawAll()
}

// DEPRECATED
func (m *Messenger) RetrieveRawWithFilter(filterID string) ([]*whisper.Message, error) {
	return m.adapter.RetrieveRaw(filterID)
}

// DEPRECATED
func (m *Messenger) LoadFilters(chats []*filter.Chat) ([]*filter.Chat, error) {
	return m.adapter.transport.LoadFilters(chats, m.featureFlags.genericDiscoveryTopicEnabled)
}

// DEPRECATED
func (m *Messenger) RemoveFilters(chats []*filter.Chat) error {
	return m.adapter.transport.RemoveFilters(chats)
}

// DEPRECATED
func (m *Messenger) ConfirmMessagesProcessed(messageIDs [][]byte) error {
	for _, id := range messageIDs {
		if err := m.encryptor.ConfirmMessageProcessed(id); err != nil {
			return err
		}
	}
	return nil
}