// Copyright 2017 Vector Creations Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package routing

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"sync"
	"time"

	"github.com/matrix-org/gomatrixserverlib"
	"github.com/matrix-org/util"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/sirupsen/logrus"

	"github.com/matrix-org/dendrite/clientapi/jsonerror"
	federationAPI "github.com/matrix-org/dendrite/federationapi/api"
	"github.com/matrix-org/dendrite/federationapi/producers"
	"github.com/matrix-org/dendrite/federationapi/types"
	"github.com/matrix-org/dendrite/internal"
	keyapi "github.com/matrix-org/dendrite/keyserver/api"
	"github.com/matrix-org/dendrite/roomserver/api"
	"github.com/matrix-org/dendrite/setup/config"
	syncTypes "github.com/matrix-org/dendrite/syncapi/types"
)

const (
	// Event was passed to the roomserver
	MetricsOutcomeOK = "ok"
	// Event failed to be processed
	MetricsOutcomeFail = "fail"
	// Event failed auth checks
	MetricsOutcomeRejected = "rejected"
	// Terminated the transaction
	MetricsOutcomeFatal = "fatal"
	// The event has missing auth_events we need to fetch
	MetricsWorkMissingAuthEvents = "missing_auth_events"
	// No work had to be done as we had all prev/auth events
	MetricsWorkDirect = "direct"
	// The event has missing prev_events we need to call /g_m_e for
	MetricsWorkMissingPrevEvents = "missing_prev_events"
)

var (
	pduCountTotal = prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Namespace: "dendrite",
			Subsystem: "federationapi",
			Name:      "recv_pdus",
			Help:      "Number of incoming PDUs from remote servers with labels for success",
		},
		[]string{"status"}, // 'success' or 'total'
	)
	eduCountTotal = prometheus.NewCounter(
		prometheus.CounterOpts{
			Namespace: "dendrite",
			Subsystem: "federationapi",
			Name:      "recv_edus",
			Help:      "Number of incoming EDUs from remote servers",
		},
	)
)

var inFlightTxnsPerOrigin sync.Map // transaction ID -> chan util.JSONResponse

// Send implements /_matrix/federation/v1/send/{txnID}
func Send(
	httpReq *http.Request,
	request *gomatrixserverlib.FederationRequest,
	txnID gomatrixserverlib.TransactionID,
	cfg *config.FederationAPI,
	rsAPI api.FederationRoomserverAPI,
	keyAPI keyapi.FederationKeyAPI,
	keys gomatrixserverlib.JSONVerifier,
	federation federationAPI.FederationClient,
	mu *internal.MutexByRoom,
	servers federationAPI.ServersInRoomProvider,
	producer *producers.SyncAPIProducer,
) util.JSONResponse {
	// First we should check if this origin has already submitted this
	// txn ID to us. If they have and the txnIDs map contains an entry,
	// the transaction is still being worked on. The new client can wait
	// for it to complete rather than creating more work.
	index := string(request.Origin()) + "\000" + string(txnID)
	v, ok := inFlightTxnsPerOrigin.LoadOrStore(index, make(chan util.JSONResponse, 1))
	ch := v.(chan util.JSONResponse)
	if ok {
		// This origin already submitted this txn ID to us, and the work
		// is still taking place, so we'll just wait for it to finish.
		ctx, cancel := context.WithTimeout(httpReq.Context(), time.Minute*5)
		defer cancel()
		select {
		case <-ctx.Done():
			// If the caller gives up then return straight away. We don't
			// want to attempt to process what they sent us any further.
			return util.JSONResponse{Code: http.StatusRequestTimeout}
		case res := <-ch:
			// The original task just finished processing so let's return
			// the result of it.
			if res.Code == 0 {
				return util.JSONResponse{Code: http.StatusAccepted}
			}
			return res
		}
	}
	// Otherwise, store that we're currently working on this txn from
	// this origin. When we're done processing, close the channel.
	defer close(ch)
	defer inFlightTxnsPerOrigin.Delete(index)

	t := txnReq{
		rsAPI:                  rsAPI,
		keys:                   keys,
		ourServerName:          cfg.Matrix.ServerName,
		federation:             federation,
		servers:                servers,
		keyAPI:                 keyAPI,
		roomsMu:                mu,
		producer:               producer,
		inboundPresenceEnabled: cfg.Matrix.Presence.EnableInbound,
	}

	var txnEvents struct {
		PDUs []json.RawMessage       `json:"pdus"`
		EDUs []gomatrixserverlib.EDU `json:"edus"`
	}

	if err := json.Unmarshal(request.Content(), &txnEvents); err != nil {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.NotJSON("The request body could not be decoded into valid JSON. " + err.Error()),
		}
	}
	// Transactions are limited in size; they can have at most 50 PDUs and 100 EDUs.
	// https://matrix.org/docs/spec/server_server/latest#transactions
	if len(txnEvents.PDUs) > 50 || len(txnEvents.EDUs) > 100 {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.BadJSON("max 50 pdus / 100 edus"),
		}
	}

	// TODO: Really we should have a function to convert FederationRequest to txnReq
	t.PDUs = txnEvents.PDUs
	t.EDUs = txnEvents.EDUs
	t.Origin = request.Origin()
	t.TransactionID = txnID
	t.Destination = cfg.Matrix.ServerName

	util.GetLogger(httpReq.Context()).Debugf("Received transaction %q from %q containing %d PDUs, %d EDUs", txnID, request.Origin(), len(t.PDUs), len(t.EDUs))

	resp, jsonErr := t.processTransaction(httpReq.Context())
	if jsonErr != nil {
		util.GetLogger(httpReq.Context()).WithField("jsonErr", jsonErr).Error("t.processTransaction failed")
		return *jsonErr
	}

	// https://matrix.org/docs/spec/server_server/r0.1.3#put-matrix-federation-v1-send-txnid
	// Status code 200:
	// The result of processing the transaction. The server is to use this response
	// even in the event of one or more PDUs failing to be processed.
	res := util.JSONResponse{
		Code: http.StatusOK,
		JSON: resp,
	}
	ch <- res
	return res
}

type txnReq struct {
	gomatrixserverlib.Transaction
	rsAPI                  api.FederationRoomserverAPI
	keyAPI                 keyapi.FederationKeyAPI
	ourServerName          gomatrixserverlib.ServerName
	keys                   gomatrixserverlib.JSONVerifier
	federation             txnFederationClient
	roomsMu                *internal.MutexByRoom
	servers                federationAPI.ServersInRoomProvider
	producer               *producers.SyncAPIProducer
	inboundPresenceEnabled bool
}

// A subset of FederationClient functionality that txn requires. Useful for testing.
type txnFederationClient interface {
	LookupState(ctx context.Context, s gomatrixserverlib.ServerName, roomID string, eventID string, roomVersion gomatrixserverlib.RoomVersion) (
		res gomatrixserverlib.RespState, err error,
	)
	LookupStateIDs(ctx context.Context, s gomatrixserverlib.ServerName, roomID string, eventID string) (res gomatrixserverlib.RespStateIDs, err error)
	GetEvent(ctx context.Context, s gomatrixserverlib.ServerName, eventID string) (res gomatrixserverlib.Transaction, err error)
	LookupMissingEvents(ctx context.Context, s gomatrixserverlib.ServerName, roomID string, missing gomatrixserverlib.MissingEvents,
		roomVersion gomatrixserverlib.RoomVersion) (res gomatrixserverlib.RespMissingEvents, err error)
}

func (t *txnReq) processTransaction(ctx context.Context) (*gomatrixserverlib.RespSend, *util.JSONResponse) {
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		t.processEDUs(ctx)
	}()

	results := make(map[string]gomatrixserverlib.PDUResult)
	roomVersions := make(map[string]gomatrixserverlib.RoomVersion)
	getRoomVersion := func(roomID string) gomatrixserverlib.RoomVersion {
		if v, ok := roomVersions[roomID]; ok {
			return v
		}
		verReq := api.QueryRoomVersionForRoomRequest{RoomID: roomID}
		verRes := api.QueryRoomVersionForRoomResponse{}
		if err := t.rsAPI.QueryRoomVersionForRoom(ctx, &verReq, &verRes); err != nil {
			util.GetLogger(ctx).WithError(err).Debug("Transaction: Failed to query room version for room", verReq.RoomID)
			return ""
		}
		roomVersions[roomID] = verRes.RoomVersion
		return verRes.RoomVersion
	}

	for _, pdu := range t.PDUs {
		pduCountTotal.WithLabelValues("total").Inc()
		var header struct {
			RoomID string `json:"room_id"`
		}
		if err := json.Unmarshal(pdu, &header); err != nil {
			util.GetLogger(ctx).WithError(err).Debug("Transaction: Failed to extract room ID from event")
			// We don't know the event ID at this point so we can't return the
			// failure in the PDU results
			continue
		}
		roomVersion := getRoomVersion(header.RoomID)
		event, err := gomatrixserverlib.NewEventFromUntrustedJSON(pdu, roomVersion)
		if err != nil {
			if _, ok := err.(gomatrixserverlib.BadJSONError); ok {
				// Room version 6 states that homeservers should strictly enforce canonical JSON
				// on PDUs.
				//
				// This enforces that the entire transaction is rejected if a single bad PDU is
				// sent. It is unclear if this is the correct behaviour or not.
				//
				// See https://github.com/matrix-org/synapse/issues/7543
				return nil, &util.JSONResponse{
					Code: 400,
					JSON: jsonerror.BadJSON("PDU contains bad JSON"),
				}
			}
			util.GetLogger(ctx).WithError(err).Debugf("Transaction: Failed to parse event JSON of event %s", string(pdu))
			continue
		}
		if event.Type() == gomatrixserverlib.MRoomCreate && event.StateKeyEquals("") {
			continue
		}
		if api.IsServerBannedFromRoom(ctx, t.rsAPI, event.RoomID(), t.Origin) {
			results[event.EventID()] = gomatrixserverlib.PDUResult{
				Error: "Forbidden by server ACLs",
			}
			continue
		}
		if err = event.VerifyEventSignatures(ctx, t.keys); err != nil {
			util.GetLogger(ctx).WithError(err).Debugf("Transaction: Couldn't validate signature of event %q", event.EventID())
			results[event.EventID()] = gomatrixserverlib.PDUResult{
				Error: err.Error(),
			}
			continue
		}

		// pass the event to the roomserver which will do auth checks
		// If the event fail auth checks, gmsl.NotAllowed error will be returned which we be silently
		// discarded by the caller of this function
		if err = api.SendEvents(
			ctx,
			t.rsAPI,
			api.KindNew,
			[]*gomatrixserverlib.HeaderedEvent{
				event.Headered(roomVersion),
			},
			t.Origin,
			api.DoNotSendToOtherServers,
			nil,
			true,
		); err != nil {
			util.GetLogger(ctx).WithError(err).Errorf("Transaction: Couldn't submit event %q to input queue: %s", event.EventID(), err)
			results[event.EventID()] = gomatrixserverlib.PDUResult{
				Error: err.Error(),
			}
			continue
		}

		results[event.EventID()] = gomatrixserverlib.PDUResult{}
		pduCountTotal.WithLabelValues("success").Inc()
	}

	wg.Wait()
	return &gomatrixserverlib.RespSend{PDUs: results}, nil
}

// nolint:gocyclo
func (t *txnReq) processEDUs(ctx context.Context) {
	for _, e := range t.EDUs {
		eduCountTotal.Inc()
		switch e.Type {
		case gomatrixserverlib.MTyping:
			// https://matrix.org/docs/spec/server_server/latest#typing-notifications
			var typingPayload struct {
				RoomID string `json:"room_id"`
				UserID string `json:"user_id"`
				Typing bool   `json:"typing"`
			}
			if err := json.Unmarshal(e.Content, &typingPayload); err != nil {
				util.GetLogger(ctx).WithError(err).Debug("Failed to unmarshal typing event")
				continue
			}
			if _, serverName, err := gomatrixserverlib.SplitID('@', typingPayload.UserID); err != nil {
				continue
			} else if serverName == t.ourServerName {
				continue
			} else if serverName != t.Origin {
				continue
			}
			if err := t.producer.SendTyping(ctx, typingPayload.UserID, typingPayload.RoomID, typingPayload.Typing, 30*1000); err != nil {
				util.GetLogger(ctx).WithError(err).Error("Failed to send typing event to JetStream")
			}
		case gomatrixserverlib.MDirectToDevice:
			// https://matrix.org/docs/spec/server_server/r0.1.3#m-direct-to-device-schema
			var directPayload gomatrixserverlib.ToDeviceMessage
			if err := json.Unmarshal(e.Content, &directPayload); err != nil {
				util.GetLogger(ctx).WithError(err).Debug("Failed to unmarshal send-to-device events")
				continue
			}
			if _, serverName, err := gomatrixserverlib.SplitID('@', directPayload.Sender); err != nil {
				continue
			} else if serverName == t.ourServerName {
				continue
			} else if serverName != t.Origin {
				continue
			}
			for userID, byUser := range directPayload.Messages {
				for deviceID, message := range byUser {
					// TODO: check that the user and the device actually exist here
					if err := t.producer.SendToDevice(ctx, directPayload.Sender, userID, deviceID, directPayload.Type, message); err != nil {
						util.GetLogger(ctx).WithError(err).WithFields(logrus.Fields{
							"sender":    directPayload.Sender,
							"user_id":   userID,
							"device_id": deviceID,
						}).Error("Failed to send send-to-device event to JetStream")
					}
				}
			}
		case gomatrixserverlib.MDeviceListUpdate:
			if err := t.producer.SendDeviceListUpdate(ctx, e.Content, e.Origin); err != nil {
				util.GetLogger(ctx).WithError(err).Error("failed to InputDeviceListUpdate")
			}
		case gomatrixserverlib.MReceipt:
			// https://matrix.org/docs/spec/server_server/r0.1.4#receipts
			payload := map[string]types.FederationReceiptMRead{}

			if err := json.Unmarshal(e.Content, &payload); err != nil {
				util.GetLogger(ctx).WithError(err).Debug("Failed to unmarshal receipt event")
				continue
			}

			for roomID, receipt := range payload {
				for userID, mread := range receipt.User {
					_, domain, err := gomatrixserverlib.SplitID('@', userID)
					if err != nil {
						util.GetLogger(ctx).WithError(err).Debug("Failed to split domain from receipt event sender")
						continue
					}
					if t.Origin != domain {
						util.GetLogger(ctx).Debugf("Dropping receipt event where sender domain (%q) doesn't match origin (%q)", domain, t.Origin)
						continue
					}
					if err := t.processReceiptEvent(ctx, userID, roomID, "m.read", mread.Data.TS, mread.EventIDs); err != nil {
						util.GetLogger(ctx).WithError(err).WithFields(logrus.Fields{
							"sender":  t.Origin,
							"user_id": userID,
							"room_id": roomID,
							"events":  mread.EventIDs,
						}).Error("Failed to send receipt event to JetStream")
						continue
					}
				}
			}
		case types.MSigningKeyUpdate:
			if err := t.producer.SendSigningKeyUpdate(ctx, e.Content, t.Origin); err != nil {
				logrus.WithError(err).Errorf("Failed to process signing key update")
			}
		case gomatrixserverlib.MPresence:
			if t.inboundPresenceEnabled {
				if err := t.processPresence(ctx, e); err != nil {
					logrus.WithError(err).Errorf("Failed to process presence update")
				}
			}
		default:
			util.GetLogger(ctx).WithField("type", e.Type).Debug("Unhandled EDU")
		}
	}
}

// processPresence handles m.receipt events
func (t *txnReq) processPresence(ctx context.Context, e gomatrixserverlib.EDU) error {
	payload := types.Presence{}
	if err := json.Unmarshal(e.Content, &payload); err != nil {
		return err
	}
	for _, content := range payload.Push {
		if _, serverName, err := gomatrixserverlib.SplitID('@', content.UserID); err != nil {
			continue
		} else if serverName == t.ourServerName {
			continue
		} else if serverName != t.Origin {
			continue
		}
		presence, ok := syncTypes.PresenceFromString(content.Presence)
		if !ok {
			continue
		}
		if err := t.producer.SendPresence(ctx, content.UserID, presence, content.StatusMsg, content.LastActiveAgo); err != nil {
			return err
		}
	}
	return nil
}

// processReceiptEvent sends receipt events to JetStream
func (t *txnReq) processReceiptEvent(ctx context.Context,
	userID, roomID, receiptType string,
	timestamp gomatrixserverlib.Timestamp,
	eventIDs []string,
) error {
	if _, serverName, err := gomatrixserverlib.SplitID('@', userID); err != nil {
		return nil
	} else if serverName == t.ourServerName {
		return nil
	} else if serverName != t.Origin {
		return nil
	}
	// store every event
	for _, eventID := range eventIDs {
		if err := t.producer.SendReceipt(ctx, userID, roomID, eventID, receiptType, timestamp); err != nil {
			return fmt.Errorf("unable to set receipt event: %w", err)
		}
	}

	return nil
}