// Copyright 2017 New Vector 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 (
	"fmt"
	"net/http"
	"time"

	"github.com/matrix-org/dendrite/clientapi/jsonerror"
	"github.com/matrix-org/dendrite/clientapi/producers"
	"github.com/matrix-org/dendrite/common"
	"github.com/matrix-org/dendrite/common/config"
	"github.com/matrix-org/dendrite/roomserver/api"
	"github.com/matrix-org/gomatrixserverlib"
	"github.com/matrix-org/util"
)

// MakeJoin implements the /make_join API
func MakeJoin(
	httpReq *http.Request,
	request *gomatrixserverlib.FederationRequest,
	cfg *config.Dendrite,
	query api.RoomserverQueryAPI,
	roomID, userID string,
	remoteVersions []gomatrixserverlib.RoomVersion,
) util.JSONResponse {
	verReq := api.QueryRoomVersionForRoomRequest{RoomID: roomID}
	verRes := api.QueryRoomVersionForRoomResponse{}
	if err := query.QueryRoomVersionForRoom(httpReq.Context(), &verReq, &verRes); err != nil {
		return util.JSONResponse{
			Code: http.StatusInternalServerError,
			JSON: jsonerror.InternalServerError(),
		}
	}

	// Check that the room that the remote side is trying to join is actually
	// one of the room versions that they listed in their supported ?ver= in
	// the make_join URL.
	// https://matrix.org/docs/spec/server_server/r0.1.3#get-matrix-federation-v1-make-join-roomid-userid
	remoteSupportsVersion := false
	for _, v := range remoteVersions {
		if v == verRes.RoomVersion {
			remoteSupportsVersion = true
			break
		}
	}
	// If it isn't, stop trying to join the room.
	if !remoteSupportsVersion {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.UnsupportedRoomVersion(
				fmt.Sprintf("Joining server does not support room version %s", verRes.RoomVersion),
			),
		}
	}

	_, domain, err := gomatrixserverlib.SplitID('@', userID)
	if err != nil {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.BadJSON("Invalid UserID"),
		}
	}
	if domain != request.Origin() {
		return util.JSONResponse{
			Code: http.StatusForbidden,
			JSON: jsonerror.Forbidden("The join must be sent by the server of the user"),
		}
	}

	// Try building an event for the server
	builder := gomatrixserverlib.EventBuilder{
		Sender:   userID,
		RoomID:   roomID,
		Type:     "m.room.member",
		StateKey: &userID,
	}
	err = builder.SetContent(map[string]interface{}{"membership": gomatrixserverlib.Join})
	if err != nil {
		util.GetLogger(httpReq.Context()).WithError(err).Error("builder.SetContent failed")
		return jsonerror.InternalServerError()
	}

	queryRes := api.QueryLatestEventsAndStateResponse{
		RoomVersion: verRes.RoomVersion,
	}
	event, err := common.BuildEvent(httpReq.Context(), &builder, cfg, time.Now(), query, &queryRes)
	if err == common.ErrRoomNoExists {
		return util.JSONResponse{
			Code: http.StatusNotFound,
			JSON: jsonerror.NotFound("Room does not exist"),
		}
	} else if err != nil {
		util.GetLogger(httpReq.Context()).WithError(err).Error("common.BuildEvent failed")
		return jsonerror.InternalServerError()
	}

	// Check that the join is allowed or not
	stateEvents := make([]*gomatrixserverlib.Event, len(queryRes.StateEvents))
	for i := range queryRes.StateEvents {
		stateEvents[i] = &queryRes.StateEvents[i].Event
	}

	provider := gomatrixserverlib.NewAuthEvents(stateEvents)
	if err = gomatrixserverlib.Allowed(*event, &provider); err != nil {
		return util.JSONResponse{
			Code: http.StatusForbidden,
			JSON: jsonerror.Forbidden(err.Error()),
		}
	}

	return util.JSONResponse{
		Code: http.StatusOK,
		JSON: map[string]interface{}{
			"event":        builder,
			"room_version": verRes.RoomVersion,
		},
	}
}

// SendJoin implements the /send_join API
func SendJoin(
	httpReq *http.Request,
	request *gomatrixserverlib.FederationRequest,
	cfg *config.Dendrite,
	query api.RoomserverQueryAPI,
	producer *producers.RoomserverProducer,
	keys gomatrixserverlib.KeyRing,
	roomID, eventID string,
) util.JSONResponse {
	verReq := api.QueryRoomVersionForRoomRequest{RoomID: roomID}
	verRes := api.QueryRoomVersionForRoomResponse{}
	if err := query.QueryRoomVersionForRoom(httpReq.Context(), &verReq, &verRes); err != nil {
		util.GetLogger(httpReq.Context()).WithError(err).Error("query.QueryRoomVersionForRoom failed")
		return util.JSONResponse{
			Code: http.StatusInternalServerError,
			JSON: jsonerror.InternalServerError(),
		}
	}

	event, err := gomatrixserverlib.NewEventFromUntrustedJSON(request.Content(), verRes.RoomVersion)
	if err != nil {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.NotJSON("The request body could not be decoded into valid JSON. " + err.Error()),
		}
	}

	// Check that the room ID is correct.
	if event.RoomID() != roomID {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.BadJSON(
				fmt.Sprintf(
					"The room ID in the request path (%q) must match the room ID in the join event JSON (%q)",
					roomID, event.RoomID(),
				),
			),
		}
	}

	// Check that the event ID is correct.
	if event.EventID() != eventID {
		return util.JSONResponse{
			Code: http.StatusBadRequest,
			JSON: jsonerror.BadJSON(
				fmt.Sprintf(
					"The event ID in the request path (%q) must match the event ID in the join event JSON (%q)",
					eventID, event.EventID(),
				),
			),
		}
	}

	// Check that the event is from the server sending the request.
	if event.Origin() != request.Origin() {
		return util.JSONResponse{
			Code: http.StatusForbidden,
			JSON: jsonerror.Forbidden("The join must be sent by the server it originated on"),
		}
	}

	// Check that the event is signed by the server sending the request.
	redacted := event.Redact()
	verifyRequests := []gomatrixserverlib.VerifyJSONRequest{{
		ServerName:             event.Origin(),
		Message:                redacted.JSON(),
		AtTS:                   event.OriginServerTS(),
		StrictValidityChecking: true,
	}}
	verifyResults, err := keys.VerifyJSONs(httpReq.Context(), verifyRequests)
	if err != nil {
		util.GetLogger(httpReq.Context()).WithError(err).Error("keys.VerifyJSONs failed")
		return jsonerror.InternalServerError()
	}
	if verifyResults[0].Error != nil {
		return util.JSONResponse{
			Code: http.StatusForbidden,
			JSON: jsonerror.Forbidden("Signature check failed: " + verifyResults[0].Error.Error()),
		}
	}

	// Fetch the state and auth chain. We do this before we send the events
	// on, in case this fails.
	var stateAndAuthChainResponse api.QueryStateAndAuthChainResponse
	err = query.QueryStateAndAuthChain(httpReq.Context(), &api.QueryStateAndAuthChainRequest{
		PrevEventIDs: event.PrevEventIDs(),
		AuthEventIDs: event.AuthEventIDs(),
		RoomID:       roomID,
		ResolveState: true,
	}, &stateAndAuthChainResponse)
	if err != nil {
		util.GetLogger(httpReq.Context()).WithError(err).Error("query.QueryStateAndAuthChain failed")
		return jsonerror.InternalServerError()
	}

	if !stateAndAuthChainResponse.RoomExists {
		return util.JSONResponse{
			Code: http.StatusNotFound,
			JSON: jsonerror.NotFound("Room does not exist"),
		}
	}

	// Send the events to the room server.
	// We are responsible for notifying other servers that the user has joined
	// the room, so set SendAsServer to cfg.Matrix.ServerName
	_, err = producer.SendEvents(
		httpReq.Context(),
		[]gomatrixserverlib.HeaderedEvent{
			event.Headered(stateAndAuthChainResponse.RoomVersion),
		},
		cfg.Matrix.ServerName,
		nil,
	)
	if err != nil {
		util.GetLogger(httpReq.Context()).WithError(err).Error("producer.SendEvents failed")
		return jsonerror.InternalServerError()
	}

	return util.JSONResponse{
		Code: http.StatusOK,
		JSON: map[string]interface{}{
			"state":      gomatrixserverlib.UnwrapEventHeaders(stateAndAuthChainResponse.StateEvents),
			"auth_chain": gomatrixserverlib.UnwrapEventHeaders(stateAndAuthChainResponse.AuthChainEvents),
		},
	}
}