package main

import (
	"context"
	"database/sql"
	"encoding/hex"
	"errors"
	"fmt"
	"net"
	"sync"
	"time"

	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/google/uuid"
	"github.com/libp2p/go-libp2p/core/peer"
	"github.com/libp2p/go-libp2p/core/peerstore"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/waku-org/go-waku/waku/v2/dnsdisc"
	"github.com/waku-org/go-waku/waku/v2/node"
	"github.com/waku-org/go-waku/waku/v2/protocol"
	"github.com/waku-org/go-waku/waku/v2/protocol/pb"
	"github.com/waku-org/go-waku/waku/v2/protocol/store"
	"github.com/waku-org/storenode-messages/internal/logging"
	"github.com/waku-org/storenode-messages/internal/metrics"
	"github.com/waku-org/storenode-messages/internal/persistence"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
	"google.golang.org/protobuf/proto"
)

type MessageExistence int

const (
	Unknown MessageExistence = iota
	Exists
	DoesNotExist
)

const timeInterval = 2 * time.Minute
const delay = 5 * time.Minute
const maxAttempts = 3

type Application struct {
	node    *node.WakuNode
	metrics metrics.Metrics
	db      *persistence.DBStore
}

func Execute(ctx context.Context, options Options) error {
	// Set encoding for logs (console, json, ...)
	// Note that libp2p reads the encoding from GOLOG_LOG_FMT env var.
	logging.InitLogger(options.LogEncoding, options.LogOutput)

	logger := logging.Logger()

	var metricsServer *metrics.Server
	if options.EnableMetrics {
		metricsServer = metrics.NewMetricsServer(options.MetricsAddress, options.MetricsPort, logger)
		go metricsServer.Start()
	}

	var db *sql.DB
	var migrationFn func(*sql.DB, *zap.Logger) error
	db, migrationFn, err := persistence.ParseURL(options.DatabaseURL, logger)
	if err != nil {
		return err
	}

	dbStore, err := persistence.NewDBStore(logger, persistence.WithDB(db), persistence.WithMigrations(migrationFn), persistence.WithRetentionPolicy(options.RetentionPolicy))
	if err != nil {
		return err
	}
	defer dbStore.Stop()

	var discoveredNodes []dnsdisc.DiscoveredNode
	if len(options.DNSDiscoveryURLs.Value()) != 0 {
		discoveredNodes = node.GetNodesFromDNSDiscovery(logger, ctx, options.DNSDiscoveryNameserver, options.DNSDiscoveryURLs.Value())
	}

	var storenodes []peer.AddrInfo
	for _, node := range discoveredNodes {
		if len(node.PeerInfo.Addrs) == 0 {
			continue
		}
		storenodes = append(storenodes, node.PeerInfo)
	}

	for _, node := range options.StoreNodes {
		pInfo, err := peer.AddrInfosFromP2pAddrs(node)
		if err != nil {
			return err
		}

		storenodes = append(storenodes, pInfo...)
	}

	if len(storenodes) == 0 {
		return errors.New("no storenodes specified")
	}

	hostAddr, err := net.ResolveTCPAddr("tcp", fmt.Sprintf("%s:%d", options.Address, options.Port))
	if err != nil {
		return err
	}

	lvl, err := zapcore.ParseLevel(options.LogLevel)
	if err != nil {
		return err
	}

	wakuNode, err := node.New(
		node.WithLogLevel(lvl),
		node.WithNTP(),
		node.WithClusterID(uint16(options.ClusterID)),
		node.WithHostAddress(hostAddr),
	)
	if err != nil {
		return err
	}

	metrics := metrics.NewMetrics(prometheus.DefaultRegisterer, logger)

	err = wakuNode.Start(ctx)
	if err != nil {
		return err
	}
	defer wakuNode.Stop()

	for _, s := range storenodes {
		wakuNode.Host().Peerstore().AddAddrs(s.ID, s.Addrs, peerstore.PermanentAddrTTL)
	}

	err = dbStore.Start(ctx, wakuNode.Timesource())
	if err != nil {
		return err
	}

	application := &Application{
		node:    wakuNode,
		metrics: metrics,
		db:      dbStore,
	}

	timer := time.NewTimer(0)
	defer timer.Stop()
	for {
		select {
		case <-ctx.Done():
			return nil
		case <-timer.C:
			tmpUUID := uuid.New()
			runId := hex.EncodeToString(tmpUUID[:])
			runIdLogger := logger.With(zap.String("runId", runId))

			runIdLogger.Info("verifying message history...")
			err := application.verifyHistory(ctx, runId, storenodes, runIdLogger)
			if err != nil {
				return err
			}
			runIdLogger.Info("verification complete")

			timer.Reset(timeInterval)
		}
	}
}

var msgMapLock sync.Mutex
var msgMap map[pb.MessageHash]map[peer.ID]MessageExistence
var msgPubsubTopic map[pb.MessageHash]string

func (app *Application) verifyHistory(ctx context.Context, runId string, storenodes []peer.AddrInfo, logger *zap.Logger) error {

	// [MessageHash][StoreNode] = exists?
	msgMapLock.Lock()
	msgMap = make(map[pb.MessageHash]map[peer.ID]MessageExistence)
	msgPubsubTopic = make(map[pb.MessageHash]string)
	msgMapLock.Unlock()

	topicSyncStatus, err := app.db.GetTopicSyncStatus(ctx, options.ClusterID, options.PubSubTopics.Value())
	if err != nil {
		return err
	}

	tx, err := app.db.GetTrx(ctx)
	if err != nil {
		return err
	}

	defer func() {
		if err == nil {
			err = tx.Commit()
			return
		}
		// don't shadow original error
		_ = tx.Rollback()
	}()

	wg := sync.WaitGroup{}
	for topic, lastSyncTimestamp := range topicSyncStatus {
		wg.Add(1)
		go func(topic string, lastSyncTimestamp *time.Time) {
			defer wg.Done()
			app.retrieveHistory(ctx, runId, storenodes, topic, lastSyncTimestamp, tx, logger)
		}(topic, lastSyncTimestamp)
	}
	wg.Wait()

	// Verify for each storenode which messages are not available, and query
	// for their existence using message hash
	// ========================================================================
	msgsToVerify := make(map[peer.ID][]pb.MessageHash) // storenode -> msgHash
	msgMapLock.Lock()
	for msgHash, nodes := range msgMap {
		for _, node := range storenodes {
			if nodes[node.ID] != Exists {
				msgsToVerify[node.ID] = append(msgsToVerify[node.ID], msgHash)
			}
		}
	}
	msgMapLock.Unlock()

	wg = sync.WaitGroup{}
	for peerID, messageHashes := range msgsToVerify {
		wg.Add(1)
		go func(peerID peer.ID, messageHashes []pb.MessageHash) {
			defer wg.Done()
			app.verifyMessageExistence(ctx, runId, peerID, messageHashes, logger)
		}(peerID, messageHashes)
	}
	wg.Wait()

	// If a message is not available, store in DB in which store nodes it wasnt
	// available
	// ========================================================================
	msgMapLock.Lock()
	defer msgMapLock.Unlock()

	missingInSummary := make(map[peer.ID]int)
	unknownInSummary := make(map[peer.ID]int)
	totalMissingMessages := 0

	for msgHash, nodes := range msgMap {
		var missingIn []peer.ID
		var unknownIn []peer.ID

		for _, node := range storenodes {
			if nodes[node.ID] == DoesNotExist {
				missingIn = append(missingIn, node.ID)
				missingInSummary[node.ID]++
			} else if nodes[node.ID] == Unknown {
				unknownIn = append(unknownIn, node.ID)
				unknownInSummary[node.ID]++
			}
		}

		if len(missingIn) != 0 {
			logger.Info("missing message identified", zap.Stringer("hash", msgHash), zap.String("pubsubTopic", msgPubsubTopic[msgHash]), zap.Int("num_nodes", len(missingIn)))
			err := app.db.RecordMessage(runId, tx, msgHash, options.ClusterID, msgPubsubTopic[msgHash], missingIn, "does_not_exist")
			if err != nil {
				return err
			}
			totalMissingMessages++
		}

		if len(unknownIn) != 0 {
			logger.Info("message with unknown state identified", zap.Stringer("hash", msgHash), zap.String("pubsubTopic", msgPubsubTopic[msgHash]), zap.Int("num_nodes", len(missingIn)))
			err = app.db.RecordMessage(runId, tx, msgHash, options.ClusterID, msgPubsubTopic[msgHash], unknownIn, "unknown")
			if err != nil {
				return err
			}
		}
	}

	for _, s := range storenodes {
		missingCnt := missingInSummary[s.ID]
		app.metrics.RecordMissingMessages(s.ID, "does_not_exist", missingCnt)
		logger.Info("missing message summary", zap.Stringer("storenode", s.ID), zap.Int("numMsgs", missingCnt))

		unknownCnt := unknownInSummary[s.ID]
		app.metrics.RecordMissingMessages(s.ID, "unknown", unknownCnt)
		logger.Info("messages that could not be verified summary", zap.Stringer("storenode", s.ID), zap.Int("numMsgs", missingCnt))
	}

	logger.Info("total missing messages", zap.Int("total", totalMissingMessages))
	app.metrics.RecordTotalMissingMessages(totalMissingMessages)

	return nil
}

func (app *Application) fetchStoreNodeMessages(ctx context.Context, runId string, storenodeID peer.ID, topic string, startTime time.Time, endTime time.Time, logger *zap.Logger) {
	var result *store.Result
	var err error

	queryLogger := logger.With(zap.Stringer("storenode", storenodeID), zap.Int64("startTime", startTime.UnixNano()), zap.Int64("endTime", endTime.UnixNano()))

	retry := true
	success := false
	count := 1
	for retry && count <= maxAttempts {
		queryLogger.Info("retrieving message history for topic!", zap.Int("attempt", count))

		tCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
		result, err = app.node.Store().Query(tCtx, store.FilterCriteria{
			ContentFilter: protocol.NewContentFilter(topic),
			TimeStart:     proto.Int64(startTime.UnixNano()),
			TimeEnd:       proto.Int64(endTime.UnixNano()),
		}, store.WithPeer(storenodeID), store.WithPaging(false, 100), store.IncludeData(false))
		cancel()

		if err != nil {
			queryLogger.Error("could not query storenode", zap.Error(err), zap.Int("attempt", count))
			time.Sleep(2 * time.Second)
		} else {
			queryLogger.Info("messages available", zap.Int("len", len(result.Messages())))
			retry = false
			success = true
		}
		count++
	}

	if !success {
		queryLogger.Error("storenode not available")
		err := app.db.RecordStorenodeUnavailable(runId, storenodeID)
		if err != nil {
			queryLogger.Error("could not store node unavailable", zap.Error(err))
		}
		app.metrics.RecordStorenodeAvailability(storenodeID, false)
		return
	}

	app.metrics.RecordStorenodeAvailability(storenodeID, true)

	for !result.IsComplete() {
		msgMapLock.Lock()
		for _, mkv := range result.Messages() {
			hash := mkv.WakuMessageHash()
			_, ok := msgMap[hash]
			if !ok {
				msgMap[hash] = make(map[peer.ID]MessageExistence)
			}
			msgMap[hash][storenodeID] = Exists
			msgPubsubTopic[hash] = mkv.GetPubsubTopic()
		}
		msgMapLock.Unlock()

		retry := true
		success := false
		count := 1
		cursorLogger := queryLogger.With(zap.String("cursor", hex.EncodeToString(result.Cursor())))
		for retry && count <= maxAttempts {
			cursorLogger.Info("retrieving next page")
			tCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
			err = result.Next(tCtx)
			cancel()
			if err != nil {
				cursorLogger.Error("could not query storenode", zap.Error(err))
				time.Sleep(2 * time.Second)
			} else {
				cursorLogger.Info("more messages available", zap.Int("len", len(result.Messages())))
				retry = false
				success = true
			}
			count++
		}

		if !success {
			cursorLogger.Error("storenode not available")
			err := app.db.RecordStorenodeUnavailable(runId, storenodeID)
			if err != nil {
				cursorLogger.Error("could not store recordnode unavailable", zap.Error(err))
			}
			app.metrics.RecordStorenodeAvailability(storenodeID, false)
			return
		}

		app.metrics.RecordStorenodeAvailability(storenodeID, true)
	}
}

func (app *Application) retrieveHistory(ctx context.Context, runId string, storenodes []peer.AddrInfo, topic string, lastSyncTimestamp *time.Time, tx *sql.Tx, logger *zap.Logger) {
	logger = logger.With(zap.String("topic", topic), zap.Timep("lastSyncTimestamp", lastSyncTimestamp))

	if lastSyncTimestamp != nil {
		app.metrics.RecordLastSyncDate(topic, *lastSyncTimestamp)
	}

	now := app.node.Timesource().Now()

	// Query is done with a delay
	startTime := now.Add(-(timeInterval + delay))
	if lastSyncTimestamp != nil {
		startTime = *lastSyncTimestamp
	}
	endTime := now.Add(-delay)

	if startTime.After(endTime) {
		logger.Warn("too soon to retrieve messages for topic")
		return
	}

	// Determine if the messages exist across all nodes
	wg := sync.WaitGroup{}
	for _, node := range storenodes {
		wg.Add(1)
		go func(peerID peer.ID) {
			defer wg.Done()
			app.fetchStoreNodeMessages(ctx, runId, peerID, topic, startTime, endTime, logger)
		}(node.ID)
	}

	wg.Wait()

	// Update db with last sync time
	err := app.db.UpdateTopicSyncState(tx, options.ClusterID, topic, endTime)
	if err != nil {
		logger.Panic("could not update topic sync state", zap.Error(err))
	}

	app.metrics.RecordLastSyncDate(topic, endTime)

}

func (app *Application) verifyMessageExistence(ctx context.Context, runId string, peerID peer.ID, messageHashes []pb.MessageHash, logger *zap.Logger) {
	var result *store.Result
	var err error

	peerInfo := app.node.Host().Peerstore().PeerInfo(peerID)

	queryLogger := logger.With(zap.Stringer("storenode", peerID))

	retry := true
	success := false
	count := 1
	for retry && count <= maxAttempts {
		queryLogger.Info("querying by hash", zap.Int("attempt", count))
		tCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
		result, err = app.node.Store().QueryByHash(tCtx, messageHashes, store.IncludeData(false), store.WithPeer(peerInfo.ID), store.WithPaging(false, 100))
		cancel()
		if err != nil {
			queryLogger.Error("could not query storenode", zap.Error(err), zap.Int("attempt", count))
			time.Sleep(2 * time.Second)
		} else {
			queryLogger.Info("hashes available", zap.Int("len", len(result.Messages())))
			retry = false
			success = true
		}
		count++
	}

	if !success {
		queryLogger.Error("storenode not available")
		err := app.db.RecordStorenodeUnavailable(runId, peerID)
		if err != nil {
			queryLogger.Error("could not store recordnode unavailable", zap.Error(err))
		}
		app.metrics.RecordStorenodeAvailability(peerID, false)
		return
	}

	app.metrics.RecordStorenodeAvailability(peerID, true)

	for !result.IsComplete() {
		msgMapLock.Lock()
		for _, mkv := range result.Messages() {
			hash := mkv.WakuMessageHash()
			_, ok := msgMap[hash]
			if !ok {
				msgMap[hash] = make(map[peer.ID]MessageExistence)
			}
			msgMap[hash][peerInfo.ID] = Exists
		}

		for _, msgHash := range messageHashes {
			if msgMap[msgHash][peerInfo.ID] != Exists {
				msgMap[msgHash][peerInfo.ID] = DoesNotExist
			}
		}

		msgMapLock.Unlock()

		retry := true
		success := false
		count := 1
		for retry && count <= maxAttempts {
			queryLogger.Info("executing next while querying hashes", zap.String("cursor", hexutil.Encode(result.Cursor())), zap.Int("attempt", count))
			tCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
			err = result.Next(tCtx)
			cancel()
			if err != nil {
				queryLogger.Error("could not query storenode", zap.String("cursor", hexutil.Encode(result.Cursor())), zap.Error(err), zap.Int("attempt", count))
				time.Sleep(2 * time.Second)
			} else {
				queryLogger.Info("more hashes available", zap.String("cursor", hex.EncodeToString(result.Cursor())), zap.Int("len", len(result.Messages())))
				retry = false
				success = true
			}
			count++
		}

		if !success {
			queryLogger.Error("storenode not available", zap.String("cursor", hexutil.Encode(result.Cursor())))
			err := app.db.RecordStorenodeUnavailable(runId, peerID)
			if err != nil {
				logger.Error("could not store recordnode unavailable", zap.Error(err), zap.String("cursor", hex.EncodeToString(result.Cursor())), zap.Stringer("storenode", peerInfo))
			}
			app.metrics.RecordStorenodeAvailability(peerID, false)
			return
		}

		app.metrics.RecordStorenodeAvailability(peerID, true)
	}
}