package xmpp

import (
	"github.com/pkg/errors"
	"regexp"
	"strconv"
	"sync"
	"time"

	"dev.narayana.im/narayana/telegabber/badger"
	"dev.narayana.im/narayana/telegabber/config"
	"dev.narayana.im/narayana/telegabber/persistence"
	"dev.narayana.im/narayana/telegabber/telegram"
	"dev.narayana.im/narayana/telegabber/xmpp/gateway"

	log "github.com/sirupsen/logrus"
	"gosrc.io/xmpp"
	"gosrc.io/xmpp/stanza"
)

var tgConf config.TelegramConfig
var sessions map[string]*telegram.Client
var db *persistence.SessionsYamlDB
var sessionLock sync.Mutex

const (
	B  uint64 = 1
	KB        = B << 10
	MB        = KB << 10
	GB        = MB << 10
	TB        = GB << 10
	PB        = TB << 10
	EB        = PB << 10

	maxUint64 uint64 = (1 << 64) - 1
)

var sizeRegex = regexp.MustCompile("\\A([0-9]+) ?([KMGTPE]?B?)\\z")

// NewComponent starts a new component and wraps it in
// a stream manager that you should start yourself
func NewComponent(conf config.XMPPConfig, tc config.TelegramConfig, idsPath string) (*xmpp.StreamManager, *xmpp.Component, error) {
	var err error

	gateway.Jid, err = stanza.NewJid(conf.Jid)
	if err != nil {
		return nil, nil, err
	}
	if gateway.Jid.Resource == "" {
		if tc.Tdlib.Client.DeviceModel != "" {
			gateway.Jid.Resource = tc.Tdlib.Client.DeviceModel
		} else {
			gateway.Jid.Resource = "telegabber"
		}
	}

	gateway.IdsDB = badger.IdsDBOpen(idsPath)

	tgConf = tc

	if tc.Content.Quota != "" {
		gateway.StorageQuota, err = parseSize(tc.Content.Quota)
		if err != nil {
			log.Warnf("Error parsing the storage quota: %v; the cleaner is disabled", err)
		}
	}

	options := xmpp.ComponentOptions{
		TransportConfiguration: xmpp.TransportConfiguration{
			Address: conf.Host + ":" + conf.Port,
			Domain:  conf.Jid,
		},
		Domain: conf.Jid,
		Secret: conf.Password,
		Name:   "telegabber",
	}

	router := xmpp.NewRouter()
	router.HandleFunc("iq", HandleIq)
	router.HandleFunc("presence", HandlePresence)
	router.HandleFunc("message", HandleMessage)

	component, err := xmpp.NewComponent(options, router, func(err error) {
		log.Error(err)
	})
	if err != nil {
		return nil, nil, err
	}

	// probe all known sessions
	err = loadSessions(conf.Db, component)
	if err != nil {
		return nil, nil, err
	}

	sm := xmpp.NewStreamManager(component, func(s xmpp.Sender) {
		go heartbeat(component)
	})

	return sm, component, nil
}

func heartbeat(component *xmpp.Component) {
	var err error
	probeType := gateway.SPType("probe")

	sessionLock.Lock()
	for jid := range sessions {
		err = gateway.SendPresence(component, jid, probeType)
		if err != nil {
			log.Error(err)
		}
	}
	sessionLock.Unlock()

	quotaLowThreshold := gateway.StorageQuota / 10 * 9

	log.Info("Starting heartbeat queue")

	// status updater thread
	for {
		gateway.StorageLock.Lock()
		if quotaLowThreshold > 0 && tgConf.Content.Path != "" {
			gateway.MeasureStorageSize(tgConf.Content.Path)

			if gateway.CachedStorageSize > quotaLowThreshold {
				gateway.CleanOldFiles(tgConf.Content.Path, quotaLowThreshold)
			}
		}
		gateway.StorageLock.Unlock()

		time.Sleep(60e9)
		now := time.Now().Unix()

		sessionLock.Lock()
		for _, session := range sessions {
			session.DelayedStatusesLock.Lock()
			for chatID, delayedStatus := range session.DelayedStatuses {
				if delayedStatus.TimestampExpired <= now {
					go session.ProcessStatusUpdate(
						chatID,
						session.LastSeenStatus(delayedStatus.TimestampOnline),
						"away",
					)
					delete(session.DelayedStatuses, chatID)
				}
			}
			session.DelayedStatusesLock.Unlock()
		}
		sessionLock.Unlock()

		for key, presence := range gateway.Queue {
			err = gateway.ResumableSend(component, presence)
			if err != nil {
				gateway.LogBadPresence(presence)
			} else {
				gateway.QueueLock.Lock()
				delete(gateway.Queue, key)
				gateway.QueueLock.Unlock()
			}
		}

		if gateway.DirtySessions {
			gateway.DirtySessions = false
			// no problem if a dirty flag gets set again here,
			// it would be resolved on the next iteration
			SaveSessions()
		}

		gateway.IdsDB.Gc()
	}
}

func loadSessions(dbPath string, component *xmpp.Component) error {
	var err error

	sessions = make(map[string]*telegram.Client)

	db, err = persistence.LoadSessions(dbPath)
	if err != nil {
		return err
	}

	db.Transaction(func() bool {
		for jid, session := range db.Data.Sessions {
			// copy the session struct, otherwise all of them would reference
			// the same temporary range variable
			currentSession := session
			getTelegramInstance(jid, &currentSession, component)
		}

		return false
	}, persistence.SessionMarshaller)

	return nil
}

func getTelegramInstance(jid string, savedSession *persistence.Session, component *xmpp.Component) (*telegram.Client, bool) {
	var err error
	session, ok := sessions[jid]
	if !ok {
		session, err = telegram.NewClient(tgConf, jid, component, savedSession)
		if err != nil {
			log.Error(errors.Wrap(err, "TDlib initialization failure"))
			return session, false
		}
		if savedSession.KeepOnline {
			if err = session.Connect(""); err != nil {
				log.Error(err)
				return session, false
			}
		}
		sessionLock.Lock()
		sessions[jid] = session
		sessionLock.Unlock()
	}

	return session, true
}

// SaveSessions dumps current sessions to the file
func SaveSessions() {
	sessionLock.Lock()
	defer sessionLock.Unlock()
	db.Transaction(func() bool {
		for jid, session := range sessions {
			db.Data.Sessions[jid] = *session.Session
		}

		return true
	}, persistence.SessionMarshaller)
}

// Close gracefully terminates the component and saves active sessions
func Close(component *xmpp.Component) {
	log.Error("Disconnecting...")

	sessionLock.Lock()
	// close all sessions
	for _, session := range sessions {
		session.Disconnect("", true)
	}
	sessionLock.Unlock()

	// save sessions
	SaveSessions()

	// flush the ids database
	gateway.IdsDB.Close()

	// close stream
	component.Disconnect()
}

// based on https://github.com/c2h5oh/datasize/blob/master/datasize.go
func parseSize(sSize string) (uint64, error) {
	sizeParts := sizeRegex.FindStringSubmatch(sSize)

	if len(sizeParts) > 2 {
		numPart, err := strconv.ParseInt(sizeParts[1], 10, 64)
		if err != nil {
			return 0, err
		}

		var divisor uint64
		val := uint64(numPart)

		if len(sizeParts[2]) > 0 {
			switch sizeParts[2][0] {
			case 'B':
				divisor = 1
			case 'K':
				divisor = KB
			case 'M':
				divisor = MB
			case 'G':
				divisor = GB
			case 'T':
				divisor = TB
			case 'P':
				divisor = PB
			case 'E':
				divisor = EB
			}
		}

		if divisor == 0 {
			return 0, &strconv.NumError{"Wrong suffix", sSize, strconv.ErrSyntax}
		}
		if val > maxUint64/divisor {
			return 0, &strconv.NumError{"Overflow", sSize, strconv.ErrRange}
		}
		return val * divisor, nil
	}

	return 0, &strconv.NumError{"Not enough parts", sSize, strconv.ErrSyntax}
}