// Copyright 2019 The Waku Library Authors.
//
// The Waku library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The Waku library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty off
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the Waku library. If not, see <http://www.gnu.org/licenses/>.
//
// This software uses the go-ethereum library, which is licensed
// under the GNU Lesser General Public Library, version 3 or any later.

package wakuv2

import (
	"context"
	"crypto/ecdsa"
	"crypto/sha256"
	"errors"
	"fmt"
	"net"
	"runtime"
	"sync"
	"time"

	"github.com/ethereum/go-ethereum/common/hexutil"

	"go.uber.org/zap"

	mapset "github.com/deckarep/golang-set"
	"golang.org/x/crypto/pbkdf2"

	gethcommon "github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/event"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/p2p"
	"github.com/ethereum/go-ethereum/rpc"

	"github.com/libp2p/go-libp2p"
	"github.com/libp2p/go-libp2p-core/metrics"

	wakuprotocol "github.com/status-im/go-waku/waku/v2/protocol"
	"github.com/status-im/go-waku/waku/v2/protocol/relay"

	"github.com/status-im/status-go/eth-node/types"
	"github.com/status-im/status-go/wakuv2/common"

	node "github.com/status-im/go-waku/waku/v2/node"
	"github.com/status-im/go-waku/waku/v2/protocol/pb"
	"github.com/status-im/go-waku/waku/v2/protocol/store"
	wakurelay "github.com/status-im/go-wakurelay-pubsub"
)

const messageQueueLimit = 1024

type settings struct {
	MaxMsgSize             uint32          // Maximal message length allowed by the waku node
	EnableConfirmations    bool            // Enable sending message confirmations
	SoftBlacklistedPeerIDs map[string]bool // SoftBlacklistedPeerIDs is a list of peer ids that we want to keep connected but silently drop any envelope from
}

// Waku represents a dark communication interface through the Ethereum
// network, using its very own P2P communication layer.
type Waku struct {
	node *node.WakuNode // reference to a libp2p waku node

	filters *common.Filters // Message filters installed with Subscribe function

	privateKeys map[string]*ecdsa.PrivateKey // Private key storage
	symKeys     map[string][]byte            // Symmetric key storage
	keyMu       sync.RWMutex                 // Mutex associated with key stores

	envelopes   map[gethcommon.Hash]*common.ReceivedMessage // Pool of envelopes currently tracked by this node
	expirations map[uint32]mapset.Set                       // Message expiration pool
	poolMu      sync.RWMutex                                // Mutex to sync the message and expiration pools

	bandwidthCounter *metrics.BandwidthCounter

	msgQueue chan *common.ReceivedMessage // Message queue for waku messages that havent been decoded
	quit     chan struct{}                // Channel used for graceful exit

	settings   settings     // Holds configuration settings that can be dynamically changed
	settingsMu sync.RWMutex // Mutex to sync the settings access

	envelopeFeed event.Feed

	timeSource func() time.Time // source of time for waku

	logger *zap.Logger
}

// New creates a WakuV2 client ready to communicate through the LibP2P network.
func New(nodeKey string, cfg *Config, logger *zap.Logger) (*Waku, error) {
	if logger == nil {
		logger = zap.NewNop()
	}

	logger.Debug("starting wakuv2 with config", zap.Any("config", cfg))
	if cfg == nil {
		c := DefaultConfig
		cfg = &c
	}

	waku := &Waku{
		privateKeys: make(map[string]*ecdsa.PrivateKey),
		symKeys:     make(map[string][]byte),
		envelopes:   make(map[gethcommon.Hash]*common.ReceivedMessage),
		expirations: make(map[uint32]mapset.Set),
		msgQueue:    make(chan *common.ReceivedMessage, messageQueueLimit),
		quit:        make(chan struct{}),
		timeSource:  time.Now,
		logger:      logger,
	}

	waku.settings = settings{
		MaxMsgSize:             cfg.MaxMessageSize,
		SoftBlacklistedPeerIDs: make(map[string]bool),
	}

	waku.filters = common.NewFilters()
	waku.bandwidthCounter = metrics.NewBandwidthCounter()

	var privateKey *ecdsa.PrivateKey
	var err error
	if nodeKey != "" {
		privateKey, err = crypto.HexToECDSA(nodeKey)
	} else {
		// If no nodekey is provided, create an ephemeral key
		privateKey, err = crypto.GenerateKey()
	}

	if err != nil {
		return nil, fmt.Errorf("failed to setup the go-waku private key: %v", err)
	}

	hostAddr, err := net.ResolveTCPAddr("tcp", fmt.Sprint(cfg.Host, ":", cfg.Port))
	if err != nil {
		return nil, fmt.Errorf("failed to setup the network interface: %v", err)
	}

	waku.node, err = node.New(context.Background(),
		node.WithLibP2POptions(
			libp2p.BandwidthReporter(waku.bandwidthCounter),
		),
		node.WithPrivateKey(privateKey),
		node.WithHostAddress([]net.Addr{hostAddr}),
		node.WithWakuRelay(wakurelay.WithMaxMessageSize(int(waku.settings.MaxMsgSize))),
		node.WithWakuStore(false), // Mounts the store protocol (without storing the messages)
	)

	if err != nil {
		fmt.Println(err)
		return nil, fmt.Errorf("failed to start the go-waku node: %v", err)
	}

	for _, bootnode := range cfg.BootNodes {
		err := waku.node.DialPeer(bootnode)
		if err != nil {
			log.Warn("Could not dial peer", err)
		} else {
			log.Info("Bootnode dialed successfully", bootnode)
		}
	}

	for _, storenode := range cfg.StoreNodes {
		peerID, err := waku.node.AddStorePeer(storenode)
		if err != nil {
			log.Warn("Could not add store peer", err)
		} else {
			log.Info("Storepeeer dialed successfully", "peerId", peerID.Pretty())
		}
	}

	go waku.runMsgLoop()

	log.Info("setup the go-waku node successfully")

	return waku, nil
}

func (w *Waku) GetStats() types.StatsSummary {
	stats := w.bandwidthCounter.GetBandwidthTotals()
	return types.StatsSummary{
		UploadRate:   uint64(stats.RateOut),
		DownloadRate: uint64(stats.RateIn),
	}
}

func (w *Waku) runMsgLoop() {
	sub, err := w.node.Subscribe(nil)
	if err != nil {
		fmt.Println("Could not subscribe:", err)
		return
	}

	for env := range sub.C {
		envelopeErrors, err := w.OnNewEnvelopes(env)

		// TODO: should these be handled?
		_ = envelopeErrors
		_ = err
	}
}

// MaxMessageSize returns the maximum accepted message size.
func (w *Waku) MaxMessageSize() uint32 {
	w.settingsMu.RLock()
	defer w.settingsMu.RUnlock()
	return w.settings.MaxMsgSize
}

// ConfirmationsEnabled returns true if message confirmations are enabled.
func (w *Waku) ConfirmationsEnabled() bool {
	w.settingsMu.RLock()
	defer w.settingsMu.RUnlock()
	return w.settings.EnableConfirmations
}

// CurrentTime returns current time.
func (w *Waku) CurrentTime() time.Time {
	return w.timeSource()
}

// SetTimeSource assigns a particular source of time to a waku object.
func (w *Waku) SetTimeSource(timesource func() time.Time) {
	w.timeSource = timesource
}

// APIs returns the RPC descriptors the Waku implementation offers
func (w *Waku) APIs() []rpc.API {
	return []rpc.API{
		{
			Namespace: Name,
			Version:   VersionStr,
			Service:   NewPublicWakuAPI(w),
			Public:    false,
		},
	}
}

// Protocols returns the waku sub-protocols ran by this particular client.
func (w *Waku) Protocols() []p2p.Protocol {
	return []p2p.Protocol{}
}

func (w *Waku) SendEnvelopeEvent(event common.EnvelopeEvent) int {
	return w.envelopeFeed.Send(event)
}

// SubscribeEnvelopeEvents subscribes to envelopes feed.
// In order to prevent blocking waku producers events must be amply buffered.
func (w *Waku) SubscribeEnvelopeEvents(events chan<- common.EnvelopeEvent) event.Subscription {
	return w.envelopeFeed.Subscribe(events)
}

// NewKeyPair generates a new cryptographic identity for the client, and injects
// it into the known identities for message decryption. Returns ID of the new key pair.
func (w *Waku) NewKeyPair() (string, error) {
	key, err := crypto.GenerateKey()
	if err != nil || !validatePrivateKey(key) {
		key, err = crypto.GenerateKey() // retry once
	}
	if err != nil {
		return "", err
	}
	if !validatePrivateKey(key) {
		return "", fmt.Errorf("failed to generate valid key")
	}

	id, err := toDeterministicID(hexutil.Encode(crypto.FromECDSAPub(&key.PublicKey)), common.KeyIDSize)
	if err != nil {
		return "", err
	}

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	if w.privateKeys[id] != nil {
		return "", fmt.Errorf("failed to generate unique ID")
	}
	w.privateKeys[id] = key
	return id, nil
}

// DeleteKeyPair deletes the specified key if it exists.
func (w *Waku) DeleteKeyPair(key string) bool {
	deterministicID, err := toDeterministicID(key, common.KeyIDSize)
	if err != nil {
		return false
	}

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	if w.privateKeys[deterministicID] != nil {
		delete(w.privateKeys, deterministicID)
		return true
	}
	return false
}

// AddKeyPair imports a asymmetric private key and returns it identifier.
func (w *Waku) AddKeyPair(key *ecdsa.PrivateKey) (string, error) {
	id, err := makeDeterministicID(hexutil.Encode(crypto.FromECDSAPub(&key.PublicKey)), common.KeyIDSize)
	if err != nil {
		return "", err
	}
	if w.HasKeyPair(id) {
		return id, nil // no need to re-inject
	}

	w.keyMu.Lock()
	w.privateKeys[id] = key
	w.keyMu.Unlock()

	return id, nil
}

// SelectKeyPair adds cryptographic identity, and makes sure
// that it is the only private key known to the node.
func (w *Waku) SelectKeyPair(key *ecdsa.PrivateKey) error {
	id, err := makeDeterministicID(hexutil.Encode(crypto.FromECDSAPub(&key.PublicKey)), common.KeyIDSize)
	if err != nil {
		return err
	}

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	w.privateKeys = make(map[string]*ecdsa.PrivateKey) // reset key store
	w.privateKeys[id] = key

	return nil
}

// DeleteKeyPairs removes all cryptographic identities known to the node
func (w *Waku) DeleteKeyPairs() error {
	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	w.privateKeys = make(map[string]*ecdsa.PrivateKey)

	return nil
}

// HasKeyPair checks if the waku node is configured with the private key
// of the specified public pair.
func (w *Waku) HasKeyPair(id string) bool {
	deterministicID, err := toDeterministicID(id, common.KeyIDSize)
	if err != nil {
		return false
	}

	w.keyMu.RLock()
	defer w.keyMu.RUnlock()
	return w.privateKeys[deterministicID] != nil
}

// GetPrivateKey retrieves the private key of the specified identity.
func (w *Waku) GetPrivateKey(id string) (*ecdsa.PrivateKey, error) {
	deterministicID, err := toDeterministicID(id, common.KeyIDSize)
	if err != nil {
		return nil, err
	}

	w.keyMu.RLock()
	defer w.keyMu.RUnlock()
	key := w.privateKeys[deterministicID]
	if key == nil {
		return nil, fmt.Errorf("invalid id")
	}
	return key, nil
}

// GenerateSymKey generates a random symmetric key and stores it under id,
// which is then returned. Will be used in the future for session key exchange.
func (w *Waku) GenerateSymKey() (string, error) {
	key, err := common.GenerateSecureRandomData(common.AESKeyLength)
	if err != nil {
		return "", err
	} else if !common.ValidateDataIntegrity(key, common.AESKeyLength) {
		return "", fmt.Errorf("error in GenerateSymKey: crypto/rand failed to generate random data")
	}

	id, err := common.GenerateRandomID()
	if err != nil {
		return "", fmt.Errorf("failed to generate ID: %s", err)
	}

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	if w.symKeys[id] != nil {
		return "", fmt.Errorf("failed to generate unique ID")
	}
	w.symKeys[id] = key
	return id, nil
}

// AddSymKey stores the key with a given id.
func (w *Waku) AddSymKey(id string, key []byte) (string, error) {
	deterministicID, err := toDeterministicID(id, common.KeyIDSize)
	if err != nil {
		return "", err
	}

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	if w.symKeys[deterministicID] != nil {
		return "", fmt.Errorf("key already exists: %v", id)
	}
	w.symKeys[deterministicID] = key
	return deterministicID, nil
}

// AddSymKeyDirect stores the key, and returns its id.
func (w *Waku) AddSymKeyDirect(key []byte) (string, error) {
	if len(key) != common.AESKeyLength {
		return "", fmt.Errorf("wrong key size: %d", len(key))
	}

	id, err := common.GenerateRandomID()
	if err != nil {
		return "", fmt.Errorf("failed to generate ID: %s", err)
	}

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	if w.symKeys[id] != nil {
		return "", fmt.Errorf("failed to generate unique ID")
	}
	w.symKeys[id] = key
	return id, nil
}

// AddSymKeyFromPassword generates the key from password, stores it, and returns its id.
func (w *Waku) AddSymKeyFromPassword(password string) (string, error) {
	id, err := common.GenerateRandomID()
	if err != nil {
		return "", fmt.Errorf("failed to generate ID: %s", err)
	}
	if w.HasSymKey(id) {
		return "", fmt.Errorf("failed to generate unique ID")
	}

	// kdf should run no less than 0.1 seconds on an average computer,
	// because it's an once in a session experience
	derived := pbkdf2.Key([]byte(password), nil, 65356, common.AESKeyLength, sha256.New)

	w.keyMu.Lock()
	defer w.keyMu.Unlock()

	// double check is necessary, because deriveKeyMaterial() is very slow
	if w.symKeys[id] != nil {
		return "", fmt.Errorf("critical error: failed to generate unique ID")
	}
	w.symKeys[id] = derived
	return id, nil
}

// HasSymKey returns true if there is a key associated with the given id.
// Otherwise returns false.
func (w *Waku) HasSymKey(id string) bool {
	w.keyMu.RLock()
	defer w.keyMu.RUnlock()
	return w.symKeys[id] != nil
}

// DeleteSymKey deletes the key associated with the name string if it exists.
func (w *Waku) DeleteSymKey(id string) bool {
	w.keyMu.Lock()
	defer w.keyMu.Unlock()
	if w.symKeys[id] != nil {
		delete(w.symKeys, id)
		return true
	}
	return false
}

// GetSymKey returns the symmetric key associated with the given id.
func (w *Waku) GetSymKey(id string) ([]byte, error) {
	w.keyMu.RLock()
	defer w.keyMu.RUnlock()
	if w.symKeys[id] != nil {
		return w.symKeys[id], nil
	}
	return nil, fmt.Errorf("non-existent key ID")
}

// Subscribe installs a new message handler used for filtering, decrypting
// and subsequent storing of incoming messages.
func (w *Waku) Subscribe(f *common.Filter) (string, error) {
	s, err := w.filters.Install(f)
	if err != nil {
		return s, err
	}

	return s, nil
}

// GetFilter returns the filter by id.
func (w *Waku) GetFilter(id string) *common.Filter {
	return w.filters.Get(id)
}

// Unsubscribe removes an installed message handler.
// TODO: This does not seem to update the bloom filter, but does update
// the topic interest map
func (w *Waku) Unsubscribe(id string) error {
	ok := w.filters.Uninstall(id)
	if !ok {
		return fmt.Errorf("failed to unsubscribe: invalid ID '%s'", id)
	}
	return nil
}

// Unsubscribe removes an installed message handler.
// TODO: This does not seem to update the bloom filter, but does update
// the topic interest map
func (w *Waku) UnsubscribeMany(ids []string) error {
	for _, id := range ids {
		w.logger.Debug("cleaning up filter", zap.String("id", id))
		ok := w.filters.Uninstall(id)
		if !ok {
			w.logger.Warn("could not remove filter with id", zap.String("id", id))
		}
	}
	return nil
}

// Send injects a message into the waku send queue, to be distributed in the
// network in the coming cycles.
func (w *Waku) Send(msg *pb.WakuMessage) ([]byte, error) {
	return w.node.Publish(context.Background(), msg, nil)
}

func (w *Waku) Query(topics []types.TopicType, from uint64, to uint64, opts []store.HistoryRequestOption) (cursor *pb.Index, err error) {
	strTopics := make([]string, len(topics))
	for i, t := range topics {
		strTopics[i] = t.String()
	}

	result, err := w.node.Query(context.Background(), strTopics, float64(from), float64(to), opts...)

	for _, msg := range result.Messages {
		envelope := wakuprotocol.NewEnvelope(msg, string(relay.DefaultWakuTopic))
		_, err = w.OnNewEnvelopes(envelope)
		if err != nil {
			return nil, err
		}
	}

	if len(result.Messages) != 0 {
		cursor = result.PagingInfo.Cursor
	}

	return
}

// Start implements node.Service, starting the background data propagation thread
// of the Waku protocol.
func (w *Waku) Start() error {
	numCPU := runtime.NumCPU()
	for i := 0; i < numCPU; i++ {
		go w.processQueue()
	}

	return nil
}

// Stop implements node.Service, stopping the background data propagation thread
// of the Waku protocol.
func (w *Waku) Stop() error {
	w.node.Stop()
	close(w.quit)
	return nil
}

func (w *Waku) OnNewEnvelopes(envelope *wakuprotocol.Envelope) ([]common.EnvelopeError, error) {
	recvMessage := common.NewReceivedMessage(envelope)
	envelopeErrors := make([]common.EnvelopeError, 0)

	w.logger.Debug("received new envelope")

	trouble := false

	_, err := w.add(recvMessage)
	if err != nil {
		w.logger.Info("invalid envelope received", zap.Error(err))
	}

	common.EnvelopesValidatedCounter.Inc()

	if trouble {
		return envelopeErrors, errors.New("received invalid envelope")
	}

	return envelopeErrors, nil
}

// addEnvelope adds an envelope to the envelope map, used for sending
func (w *Waku) addEnvelope(envelope *common.ReceivedMessage) {
	hash := envelope.Hash()

	w.poolMu.Lock()
	w.envelopes[hash] = envelope
	w.poolMu.Unlock()
}

func (w *Waku) add(recvMessage *common.ReceivedMessage) (bool, error) {
	common.EnvelopesReceivedCounter.Inc()

	hash := recvMessage.Hash()

	w.poolMu.Lock()
	_, alreadyCached := w.envelopes[hash]
	w.poolMu.Unlock()
	if !alreadyCached {
		w.addEnvelope(recvMessage)
	}

	if alreadyCached {
		log.Trace("w envelope already cached", "hash", recvMessage.Hash().Hex())
		common.EnvelopesCachedCounter.WithLabelValues("hit").Inc()
	} else {
		log.Trace("cached w envelope", "hash", recvMessage.Hash().Hex())
		common.EnvelopesCachedCounter.WithLabelValues("miss").Inc()
		common.EnvelopesSizeMeter.Observe(float64(recvMessage.Envelope.Size()))
		w.postEvent(recvMessage) // notify the local node about the new message
	}
	return true, nil
}

// postEvent queues the message for further processing.
func (w *Waku) postEvent(envelope *common.ReceivedMessage) {
	w.msgQueue <- envelope
}

// processQueue delivers the messages to the watchers during the lifetime of the waku node.
func (w *Waku) processQueue() {
	for {
		select {
		case <-w.quit:
			return
		case e := <-w.msgQueue:
			w.filters.NotifyWatchers(e)
			w.envelopeFeed.Send(common.EnvelopeEvent{
				Topic: e.Topic,
				Hash:  e.Hash(),
				Event: common.EventEnvelopeAvailable,
			})
		}
	}
}

// Envelopes retrieves all the messages currently pooled by the node.
func (w *Waku) Envelopes() []*common.ReceivedMessage {
	w.poolMu.RLock()
	defer w.poolMu.RUnlock()

	all := make([]*common.ReceivedMessage, 0, len(w.envelopes))
	for _, envelope := range w.envelopes {
		all = append(all, envelope)
	}
	return all
}

// GetEnvelope retrieves an envelope from the message queue by its hash.
// It returns nil if the envelope can not be found.
func (w *Waku) GetEnvelope(hash gethcommon.Hash) *common.ReceivedMessage {
	w.poolMu.RLock()
	defer w.poolMu.RUnlock()
	return w.envelopes[hash]
}

// isEnvelopeCached checks if envelope with specific hash has already been received and cached.
func (w *Waku) IsEnvelopeCached(hash gethcommon.Hash) bool {
	w.poolMu.Lock()
	defer w.poolMu.Unlock()

	_, exist := w.envelopes[hash]
	return exist
}

// validatePrivateKey checks the format of the given private key.
func validatePrivateKey(k *ecdsa.PrivateKey) bool {
	if k == nil || k.D == nil || k.D.Sign() == 0 {
		return false
	}
	return common.ValidatePublicKey(&k.PublicKey)
}

// makeDeterministicID generates a deterministic ID, based on a given input
func makeDeterministicID(input string, keyLen int) (id string, err error) {
	buf := pbkdf2.Key([]byte(input), nil, 4096, keyLen, sha256.New)
	if !common.ValidateDataIntegrity(buf, common.KeyIDSize) {
		return "", fmt.Errorf("error in GenerateDeterministicID: failed to generate key")
	}
	id = gethcommon.Bytes2Hex(buf)
	return id, err
}

// toDeterministicID reviews incoming id, and transforms it to format
// expected internally be private key store. Originally, public keys
// were used as keys, now random keys are being used. And in order to
// make it easier to consume, we now allow both random IDs and public
// keys to be passed.
func toDeterministicID(id string, expectedLen int) (string, error) {
	if len(id) != (expectedLen * 2) { // we received hex key, so number of chars in id is doubled
		var err error
		id, err = makeDeterministicID(id, expectedLen)
		if err != nil {
			return "", err
		}
	}

	return id, nil
}