package internal

import (
	"context"
	"fmt"
	"time"

	"github.com/matrix-org/dendrite/federationsender/api"
	"github.com/matrix-org/dendrite/federationsender/internal/perform"
	"github.com/matrix-org/dendrite/roomserver/version"
	"github.com/matrix-org/gomatrixserverlib"
	"github.com/matrix-org/util"
	"github.com/sirupsen/logrus"
)

// PerformLeaveRequest implements api.FederationSenderInternalAPI
func (r *FederationSenderInternalAPI) PerformDirectoryLookup(
	ctx context.Context,
	request *api.PerformDirectoryLookupRequest,
	response *api.PerformDirectoryLookupResponse,
) (err error) {
	dir, err := r.federation.LookupRoomAlias(
		ctx,
		request.ServerName,
		request.RoomAlias,
	)
	if err != nil {
		return err
	}
	response.RoomID = dir.RoomID
	response.ServerNames = dir.Servers
	return nil
}

// PerformJoinRequest implements api.FederationSenderInternalAPI
func (r *FederationSenderInternalAPI) PerformJoin(
	ctx context.Context,
	request *api.PerformJoinRequest,
	response *api.PerformJoinResponse,
) (err error) {
	// Look up the supported room versions.
	var supportedVersions []gomatrixserverlib.RoomVersion
	for version := range version.SupportedRoomVersions() {
		supportedVersions = append(supportedVersions, version)
	}

	// Deduplicate the server names we were provided.
	util.Unique(request.ServerNames)

	// Try each server that we were provided until we land on one that
	// successfully completes the make-join send-join dance.
	for _, serverName := range request.ServerNames {
		// Try to perform a make_join using the information supplied in the
		// request.
		respMakeJoin, err := r.federation.MakeJoin(
			ctx,
			serverName,
			request.RoomID,
			request.UserID,
			supportedVersions,
		)
		if err != nil {
			// TODO: Check if the user was not allowed to join the room.
			return fmt.Errorf("r.federation.MakeJoin: %w", err)
		}

		// Set all the fields to be what they should be, this should be a no-op
		// but it's possible that the remote server returned us something "odd"
		respMakeJoin.JoinEvent.Type = gomatrixserverlib.MRoomMember
		respMakeJoin.JoinEvent.Sender = request.UserID
		respMakeJoin.JoinEvent.StateKey = &request.UserID
		respMakeJoin.JoinEvent.RoomID = request.RoomID
		respMakeJoin.JoinEvent.Redacts = ""
		if request.Content == nil {
			request.Content = map[string]interface{}{}
		}
		request.Content["membership"] = "join"
		if err = respMakeJoin.JoinEvent.SetContent(request.Content); err != nil {
			return fmt.Errorf("respMakeJoin.JoinEvent.SetContent: %w", err)
		}
		if err = respMakeJoin.JoinEvent.SetUnsigned(struct{}{}); err != nil {
			return fmt.Errorf("respMakeJoin.JoinEvent.SetUnsigned: %w", err)
		}

		// Work out if we support the room version that has been supplied in
		// the make_join response.
		if respMakeJoin.RoomVersion == "" {
			respMakeJoin.RoomVersion = gomatrixserverlib.RoomVersionV1
		}
		if _, err = respMakeJoin.RoomVersion.EventFormat(); err != nil {
			return fmt.Errorf("respMakeJoin.RoomVersion.EventFormat: %w", err)
		}

		// Build the join event.
		event, err := respMakeJoin.JoinEvent.Build(
			time.Now(),
			r.cfg.Matrix.ServerName,
			r.cfg.Matrix.KeyID,
			r.cfg.Matrix.PrivateKey,
			respMakeJoin.RoomVersion,
		)
		if err != nil {
			return fmt.Errorf("respMakeJoin.JoinEvent.Build: %w", err)
		}

		// Try to perform a send_join using the newly built event.
		respSendJoin, err := r.federation.SendJoin(
			ctx,
			serverName,
			event,
			respMakeJoin.RoomVersion,
		)
		if err != nil {
			logrus.WithError(err).Warnf("r.federation.SendJoin failed")
			continue
		}

		// Check that the send_join response was valid.
		joinCtx := perform.JoinContext(r.federation, r.keyRing)
		if err = joinCtx.CheckSendJoinResponse(
			ctx, event, serverName, respMakeJoin, respSendJoin,
		); err != nil {
			logrus.WithError(err).Warnf("joinCtx.CheckSendJoinResponse failed")
			continue
		}

		// If we successfully performed a send_join above then the other
		// server now thinks we're a part of the room. Send the newly
		// returned state to the roomserver to update our local view.
		if err = r.producer.SendEventWithState(
			ctx,
			respSendJoin.ToRespState(),
			event.Headered(respMakeJoin.RoomVersion),
		); err != nil {
			logrus.WithError(err).Warnf("r.producer.SendEventWithState failed")
			continue
		}

		// We're all good.
		return nil
	}

	// If we reach here then we didn't complete a join for some reason.
	return fmt.Errorf(
		"failed to join user %q to room %q through %d server(s)",
		request.UserID, request.RoomID, len(request.ServerNames),
	)
}

// PerformLeaveRequest implements api.FederationSenderInternalAPI
func (r *FederationSenderInternalAPI) PerformLeave(
	ctx context.Context,
	request *api.PerformLeaveRequest,
	response *api.PerformLeaveResponse,
) (err error) {
	return nil
}