// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// 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 consumers

import (
	"context"
	"encoding/json"

	"github.com/matrix-org/dendrite/eduserver/api"
	"github.com/matrix-org/dendrite/federationsender/queue"
	"github.com/matrix-org/dendrite/federationsender/storage"
	"github.com/matrix-org/dendrite/setup/config"
	"github.com/matrix-org/dendrite/setup/jetstream"
	"github.com/matrix-org/dendrite/setup/process"
	"github.com/matrix-org/gomatrixserverlib"
	"github.com/matrix-org/util"
	"github.com/nats-io/nats.go"
	log "github.com/sirupsen/logrus"
)

// OutputEDUConsumer consumes events that originate in EDU server.
type OutputEDUConsumer struct {
	jetstream         nats.JetStreamContext
	db                storage.Database
	queues            *queue.OutgoingQueues
	ServerName        gomatrixserverlib.ServerName
	typingTopic       string
	sendToDeviceTopic string
	receiptTopic      string
}

// NewOutputEDUConsumer creates a new OutputEDUConsumer. Call Start() to begin consuming from EDU servers.
func NewOutputEDUConsumer(
	process *process.ProcessContext,
	cfg *config.FederationSender,
	js nats.JetStreamContext,
	queues *queue.OutgoingQueues,
	store storage.Database,
) *OutputEDUConsumer {
	return &OutputEDUConsumer{
		jetstream:         js,
		queues:            queues,
		db:                store,
		ServerName:        cfg.Matrix.ServerName,
		typingTopic:       cfg.Matrix.JetStream.TopicFor(jetstream.OutputTypingEvent),
		sendToDeviceTopic: cfg.Matrix.JetStream.TopicFor(jetstream.OutputSendToDeviceEvent),
		receiptTopic:      cfg.Matrix.JetStream.TopicFor(jetstream.OutputReceiptEvent),
	}
}

// Start consuming from EDU servers
func (t *OutputEDUConsumer) Start() error {
	if _, err := t.jetstream.Subscribe(t.typingTopic, t.onTypingEvent); err != nil {
		return err
	}
	if _, err := t.jetstream.Subscribe(t.sendToDeviceTopic, t.onSendToDeviceEvent); err != nil {
		return err
	}
	if _, err := t.jetstream.Subscribe(t.receiptTopic, t.onReceiptEvent); err != nil {
		return err
	}
	return nil
}

// onSendToDeviceEvent is called in response to a message received on the
// send-to-device events topic from the EDU server.
func (t *OutputEDUConsumer) onSendToDeviceEvent(msg *nats.Msg) {
	// Extract the send-to-device event from msg.
	var ote api.OutputSendToDeviceEvent
	if err := json.Unmarshal(msg.Data, &ote); err != nil {
		log.WithError(err).Errorf("eduserver output log: message parse failed (expected send-to-device)")
		_ = msg.Ack()
		return
	}

	// only send send-to-device events which originated from us
	_, originServerName, err := gomatrixserverlib.SplitID('@', ote.Sender)
	if err != nil {
		log.WithError(err).WithField("user_id", ote.Sender).Error("Failed to extract domain from send-to-device sender")
		_ = msg.Ack()
		return
	}
	if originServerName != t.ServerName {
		log.WithField("other_server", originServerName).Info("Suppressing send-to-device: originated elsewhere")
		_ = msg.Ack()
		return
	}

	_, destServerName, err := gomatrixserverlib.SplitID('@', ote.UserID)
	if err != nil {
		log.WithError(err).WithField("user_id", ote.UserID).Error("Failed to extract domain from send-to-device destination")
		_ = msg.Ack()
		return
	}

	// Pack the EDU and marshal it
	edu := &gomatrixserverlib.EDU{
		Type:   gomatrixserverlib.MDirectToDevice,
		Origin: string(t.ServerName),
	}
	tdm := gomatrixserverlib.ToDeviceMessage{
		Sender:    ote.Sender,
		Type:      ote.Type,
		MessageID: util.RandomString(32),
		Messages: map[string]map[string]json.RawMessage{
			ote.UserID: {
				ote.DeviceID: ote.Content,
			},
		},
	}
	if edu.Content, err = json.Marshal(tdm); err != nil {
		log.WithError(err).Error("failed to marshal EDU JSON")
		_ = msg.Ack()
		return
	}

	log.Infof("Sending send-to-device message into %q destination queue", destServerName)
	if err := t.queues.SendEDU(edu, t.ServerName, []gomatrixserverlib.ServerName{destServerName}); err != nil {
		log.WithError(err).Error("failed to send EDU")
	}

	_ = msg.Ack()
}

// onTypingEvent is called in response to a message received on the typing
// events topic from the EDU server.
func (t *OutputEDUConsumer) onTypingEvent(msg *nats.Msg) {
	// Extract the typing event from msg.
	var ote api.OutputTypingEvent
	if err := json.Unmarshal(msg.Data, &ote); err != nil {
		// Skip this msg but continue processing messages.
		log.WithError(err).Errorf("eduserver output log: message parse failed (expected typing)")
		_ = msg.Ack()
		return
	}

	// only send typing events which originated from us
	_, typingServerName, err := gomatrixserverlib.SplitID('@', ote.Event.UserID)
	if err != nil {
		log.WithError(err).WithField("user_id", ote.Event.UserID).Error("Failed to extract domain from typing sender")
		_ = msg.Ack()
		return
	}
	if typingServerName != t.ServerName {
		return
	}

	joined, err := t.db.GetJoinedHosts(context.TODO(), ote.Event.RoomID)
	if err != nil {
		log.WithError(err).WithField("room_id", ote.Event.RoomID).Error("failed to get joined hosts for room")
		return
	}

	names := make([]gomatrixserverlib.ServerName, len(joined))
	for i := range joined {
		names[i] = joined[i].ServerName
	}

	edu := &gomatrixserverlib.EDU{Type: ote.Event.Type}
	if edu.Content, err = json.Marshal(map[string]interface{}{
		"room_id": ote.Event.RoomID,
		"user_id": ote.Event.UserID,
		"typing":  ote.Event.Typing,
	}); err != nil {
		log.WithError(err).Error("failed to marshal EDU JSON")
		_ = msg.Ack()
		return
	}

	if err := t.queues.SendEDU(edu, t.ServerName, names); err != nil {
		log.WithError(err).Error("failed to send EDU")
	}

	_ = msg.Ack()
}

// onReceiptEvent is called in response to a message received on the receipt
// events topic from the EDU server.
func (t *OutputEDUConsumer) onReceiptEvent(msg *nats.Msg) {
	// Extract the typing event from msg.
	var receipt api.OutputReceiptEvent
	if err := json.Unmarshal(msg.Data, &receipt); err != nil {
		// Skip this msg but continue processing messages.
		log.WithError(err).Errorf("eduserver output log: message parse failed (expected receipt)")
		_ = msg.Ack()
		return
	}

	// only send receipt events which originated from us
	_, receiptServerName, err := gomatrixserverlib.SplitID('@', receipt.UserID)
	if err != nil {
		log.WithError(err).WithField("user_id", receipt.UserID).Error("failed to extract domain from receipt sender")
		_ = msg.Ack()
		return
	}
	if receiptServerName != t.ServerName {
		_ = msg.Ack()
		return // don't log, very spammy as it logs for each remote receipt
	}

	joined, err := t.db.GetJoinedHosts(context.TODO(), receipt.RoomID)
	if err != nil {
		log.WithError(err).WithField("room_id", receipt.RoomID).Error("failed to get joined hosts for room")
		return
	}

	names := make([]gomatrixserverlib.ServerName, len(joined))
	for i := range joined {
		names[i] = joined[i].ServerName
	}

	content := map[string]api.FederationReceiptMRead{}
	content[receipt.RoomID] = api.FederationReceiptMRead{
		User: map[string]api.FederationReceiptData{
			receipt.UserID: {
				Data: api.ReceiptTS{
					TS: receipt.Timestamp,
				},
				EventIDs: []string{receipt.EventID},
			},
		},
	}

	edu := &gomatrixserverlib.EDU{
		Type:   gomatrixserverlib.MReceipt,
		Origin: string(t.ServerName),
	}
	if edu.Content, err = json.Marshal(content); err != nil {
		log.WithError(err).Error("failed to marshal EDU JSON")
		_ = msg.Ack()
		return
	}

	if err := t.queues.SendEDU(edu, t.ServerName, names); err != nil {
		log.WithError(err).Error("failed to send EDU")
	}

	_ = msg.Ack()
}