// Copyright 2022 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/federationapi/queue"
	"github.com/matrix-org/dendrite/federationapi/storage"
	"github.com/matrix-org/dendrite/setup/config"
	"github.com/matrix-org/dendrite/setup/jetstream"
	"github.com/matrix-org/dendrite/setup/process"
	syncTypes "github.com/matrix-org/dendrite/syncapi/types"
	"github.com/matrix-org/gomatrixserverlib"
	"github.com/matrix-org/util"
	"github.com/nats-io/nats.go"
	log "github.com/sirupsen/logrus"
)

// OutputSendToDeviceConsumer consumes events that originate in the clientapi.
type OutputSendToDeviceConsumer struct {
	ctx        context.Context
	jetstream  nats.JetStreamContext
	durable    string
	db         storage.Database
	queues     *queue.OutgoingQueues
	ServerName gomatrixserverlib.ServerName
	topic      string
}

// NewOutputSendToDeviceConsumer creates a new OutputSendToDeviceConsumer. Call Start() to begin consuming send-to-device events.
func NewOutputSendToDeviceConsumer(
	process *process.ProcessContext,
	cfg *config.FederationAPI,
	js nats.JetStreamContext,
	queues *queue.OutgoingQueues,
	store storage.Database,
) *OutputSendToDeviceConsumer {
	return &OutputSendToDeviceConsumer{
		ctx:        process.Context(),
		jetstream:  js,
		queues:     queues,
		db:         store,
		ServerName: cfg.Matrix.ServerName,
		durable:    cfg.Matrix.JetStream.Durable("FederationAPIESendToDeviceConsumer"),
		topic:      cfg.Matrix.JetStream.Prefixed(jetstream.OutputSendToDeviceEvent),
	}
}

// Start consuming from the client api
func (t *OutputSendToDeviceConsumer) Start() error {
	return jetstream.JetStreamConsumer(
		t.ctx, t.jetstream, t.topic, t.durable, 1,
		t.onMessage, nats.DeliverAll(), nats.ManualAck(),
	)
}

// onMessage is called in response to a message received on the
// send-to-device events topic from the client api.
func (t *OutputSendToDeviceConsumer) onMessage(ctx context.Context, msgs []*nats.Msg) bool {
	msg := msgs[0] // Guaranteed to exist if onMessage is called
	// only send send-to-device events which originated from us
	sender := msg.Header.Get("sender")
	_, originServerName, err := gomatrixserverlib.SplitID('@', sender)
	if err != nil {
		log.WithError(err).WithField("user_id", sender).Error("Failed to extract domain from send-to-device sender")
		return true
	}
	if originServerName != t.ServerName {
		return true
	}
	// Extract the send-to-device event from msg.
	var ote syncTypes.OutputSendToDeviceEvent
	if err = json.Unmarshal(msg.Data, &ote); err != nil {
		log.WithError(err).Errorf("output log: message parse failed (expected send-to-device)")
		return true
	}

	_, 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")
		return true
	}

	// The SyncAPI is already handling sendToDevice for the local server
	if destServerName == t.ServerName {
		return true
	}

	// 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")
		return true
	}

	log.Debugf("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")
		return false
	}

	return true
}