// 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 perform

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"github.com/matrix-org/dendrite/internal/eventutil"
	"github.com/matrix-org/dendrite/roomserver/api"
	"github.com/matrix-org/dendrite/roomserver/internal/input"
	"github.com/matrix-org/dendrite/roomserver/internal/query"
	"github.com/matrix-org/dendrite/roomserver/storage"
	"github.com/matrix-org/dendrite/setup/config"
	"github.com/matrix-org/gomatrixserverlib"
)

type Admin struct {
	DB      storage.Database
	Cfg     *config.RoomServer
	Queryer *query.Queryer
	Inputer *input.Inputer
}

// PerformEvacuateRoom will remove all local users from the given room.
func (r *Admin) PerformAdminEvacuateRoom(
	ctx context.Context,
	req *api.PerformAdminEvacuateRoomRequest,
	res *api.PerformAdminEvacuateRoomResponse,
) {
	roomInfo, err := r.DB.RoomInfo(ctx, req.RoomID)
	if err != nil {
		res.Error = &api.PerformError{
			Code: api.PerformErrorBadRequest,
			Msg:  fmt.Sprintf("r.DB.RoomInfo: %s", err),
		}
		return
	}
	if roomInfo == nil || roomInfo.IsStub {
		res.Error = &api.PerformError{
			Code: api.PerformErrorNoRoom,
			Msg:  fmt.Sprintf("Room %s not found", req.RoomID),
		}
		return
	}

	memberNIDs, err := r.DB.GetMembershipEventNIDsForRoom(ctx, roomInfo.RoomNID, true, true)
	if err != nil {
		res.Error = &api.PerformError{
			Code: api.PerformErrorBadRequest,
			Msg:  fmt.Sprintf("r.DB.GetMembershipEventNIDsForRoom: %s", err),
		}
		return
	}

	memberEvents, err := r.DB.Events(ctx, memberNIDs)
	if err != nil {
		res.Error = &api.PerformError{
			Code: api.PerformErrorBadRequest,
			Msg:  fmt.Sprintf("r.DB.Events: %s", err),
		}
		return
	}

	inputEvents := make([]api.InputRoomEvent, 0, len(memberEvents))
	res.Affected = make([]string, 0, len(memberEvents))
	latestReq := &api.QueryLatestEventsAndStateRequest{
		RoomID: req.RoomID,
	}
	latestRes := &api.QueryLatestEventsAndStateResponse{}
	if err = r.Queryer.QueryLatestEventsAndState(ctx, latestReq, latestRes); err != nil {
		res.Error = &api.PerformError{
			Code: api.PerformErrorBadRequest,
			Msg:  fmt.Sprintf("r.Queryer.QueryLatestEventsAndState: %s", err),
		}
		return
	}

	prevEvents := latestRes.LatestEvents
	for _, memberEvent := range memberEvents {
		if memberEvent.StateKey() == nil {
			continue
		}

		var memberContent gomatrixserverlib.MemberContent
		if err = json.Unmarshal(memberEvent.Content(), &memberContent); err != nil {
			res.Error = &api.PerformError{
				Code: api.PerformErrorBadRequest,
				Msg:  fmt.Sprintf("json.Unmarshal: %s", err),
			}
			return
		}
		memberContent.Membership = gomatrixserverlib.Leave

		stateKey := *memberEvent.StateKey()
		fledglingEvent := &gomatrixserverlib.EventBuilder{
			RoomID:     req.RoomID,
			Type:       gomatrixserverlib.MRoomMember,
			StateKey:   &stateKey,
			Sender:     stateKey,
			PrevEvents: prevEvents,
		}

		if fledglingEvent.Content, err = json.Marshal(memberContent); err != nil {
			res.Error = &api.PerformError{
				Code: api.PerformErrorBadRequest,
				Msg:  fmt.Sprintf("json.Marshal: %s", err),
			}
			return
		}

		eventsNeeded, err := gomatrixserverlib.StateNeededForEventBuilder(fledglingEvent)
		if err != nil {
			res.Error = &api.PerformError{
				Code: api.PerformErrorBadRequest,
				Msg:  fmt.Sprintf("gomatrixserverlib.StateNeededForEventBuilder: %s", err),
			}
			return
		}

		event, err := eventutil.BuildEvent(ctx, fledglingEvent, r.Cfg.Matrix, time.Now(), &eventsNeeded, latestRes)
		if err != nil {
			res.Error = &api.PerformError{
				Code: api.PerformErrorBadRequest,
				Msg:  fmt.Sprintf("eventutil.BuildEvent: %s", err),
			}
			return
		}

		inputEvents = append(inputEvents, api.InputRoomEvent{
			Kind:         api.KindNew,
			Event:        event,
			Origin:       r.Cfg.Matrix.ServerName,
			SendAsServer: string(r.Cfg.Matrix.ServerName),
		})
		res.Affected = append(res.Affected, stateKey)
		prevEvents = []gomatrixserverlib.EventReference{
			event.EventReference(),
		}
	}

	inputReq := &api.InputRoomEventsRequest{
		InputRoomEvents: inputEvents,
		Asynchronous:    true,
	}
	inputRes := &api.InputRoomEventsResponse{}
	r.Inputer.InputRoomEvents(ctx, inputReq, inputRes)
}