function FirebaseConnection(connection, connectCallback) {
    function isData(session) {
        return !session.audio && !session.video && !session.screen && session.data;
    }

    connection.firebase = connection.firebase || 'webrtc';
    var channelId = connection.channel;

    connection.socket = new Firebase('https://' + connection.firebase + '.firebaseio.com/' + channelId);

    connection.socket.on('child_added', function(snap) {
        var data = JSON.parse(snap.val());

        if (data.eventName === connection.socketMessageEvent) {
            onMessagesCallback(data.data);
        }

        snap.ref().remove(); // for socket.io live behavior
    });

    connection.socket.onDisconnect().remove();

    connection.socket.emit = function(eventName, data, callback) {
        if (eventName === 'changed-uuid') return;
        if (data.message && data.message.shiftedModerationControl) return;

        connection.socket.push(JSON.stringify({
            eventName: eventName,
            data: data
        }));

        if (callback) {
            callback();
        }
    };

    var mPeer = connection.multiPeersHandler;

    function onMessagesCallback(message) {
        if (message.remoteUserId != connection.userid) return;

        if (connection.peers[message.sender] && connection.peers[message.sender].extra != message.message.extra) {
            connection.peers[message.sender].extra = message.message.extra;
            connection.onExtraDataUpdated({
                userid: message.sender,
                extra: message.message.extra
            });
        }

        if (message.message.streamSyncNeeded && connection.peers[message.sender]) {
            var stream = connection.streamEvents[message.message.streamid];
            if (!stream || !stream.stream) {
                return;
            }

            var action = message.message.action;

            if (action === 'ended' || action === 'stream-removed') {
                connection.onstreamended(stream);
                return;
            }

            var type = message.message.type != 'both' ? message.message.type : null;
            stream.stream[action](type);
            return;
        }

        if (message.message === 'connectWithAllParticipants') {
            if (connection.broadcasters.indexOf(message.sender) === -1) {
                connection.broadcasters.push(message.sender);
            }

            mPeer.onNegotiationNeeded({
                allParticipants: connection.getAllParticipants(message.sender)
            }, message.sender);
            return;
        }

        if (message.message === 'removeFromBroadcastersList') {
            if (connection.broadcasters.indexOf(message.sender) !== -1) {
                delete connection.broadcasters[connection.broadcasters.indexOf(message.sender)];
                connection.broadcasters = removeNullEntries(connection.broadcasters);
            }
            return;
        }

        if (message.message === 'dropPeerConnection') {
            connection.deletePeer(message.sender);
            return;
        }

        if (message.message.allParticipants) {
            if (message.message.allParticipants.indexOf(message.sender) === -1) {
                message.message.allParticipants.push(message.sender);
            }

            message.message.allParticipants.forEach(function(participant) {
                mPeer[!connection.peers[participant] ? 'createNewPeer' : 'renegotiatePeer'](participant, {
                    localPeerSdpConstraints: {
                        OfferToReceiveAudio: connection.sdpConstraints.mandatory.OfferToReceiveAudio,
                        OfferToReceiveVideo: connection.sdpConstraints.mandatory.OfferToReceiveVideo
                    },
                    remotePeerSdpConstraints: {
                        OfferToReceiveAudio: connection.session.oneway ? !!connection.session.audio : connection.sdpConstraints.mandatory.OfferToReceiveAudio,
                        OfferToReceiveVideo: connection.session.oneway ? !!connection.session.video || !!connection.session.screen : connection.sdpConstraints.mandatory.OfferToReceiveVideo
                    },
                    isOneWay: !!connection.session.oneway || connection.direction === 'one-way',
                    isDataOnly: isData(connection.session)
                });
            });
            return;
        }

        if (message.message.newParticipant) {
            if (message.message.newParticipant == connection.userid) return;
            if (!!connection.peers[message.message.newParticipant]) return;

            mPeer.createNewPeer(message.message.newParticipant, message.message.userPreferences || {
                localPeerSdpConstraints: {
                    OfferToReceiveAudio: connection.sdpConstraints.mandatory.OfferToReceiveAudio,
                    OfferToReceiveVideo: connection.sdpConstraints.mandatory.OfferToReceiveVideo
                },
                remotePeerSdpConstraints: {
                    OfferToReceiveAudio: connection.session.oneway ? !!connection.session.audio : connection.sdpConstraints.mandatory.OfferToReceiveAudio,
                    OfferToReceiveVideo: connection.session.oneway ? !!connection.session.video || !!connection.session.screen : connection.sdpConstraints.mandatory.OfferToReceiveVideo
                },
                isOneWay: !!connection.session.oneway || connection.direction === 'one-way',
                isDataOnly: isData(connection.session)
            });
            return;
        }

        if (message.message.readyForOffer || message.message.addMeAsBroadcaster) {
            connection.addNewBroadcaster(message.sender);
        }

        if (message.message.newParticipationRequest && message.sender !== connection.userid) {
            if (connection.peers[message.sender]) {
                connection.deletePeer(message.sender);
            }

            var userPreferences = {
                extra: message.message.extra || {},
                localPeerSdpConstraints: message.message.remotePeerSdpConstraints || {
                    OfferToReceiveAudio: connection.sdpConstraints.mandatory.OfferToReceiveAudio,
                    OfferToReceiveVideo: connection.sdpConstraints.mandatory.OfferToReceiveVideo
                },
                remotePeerSdpConstraints: message.message.localPeerSdpConstraints || {
                    OfferToReceiveAudio: connection.session.oneway ? !!connection.session.audio : connection.sdpConstraints.mandatory.OfferToReceiveAudio,
                    OfferToReceiveVideo: connection.session.oneway ? !!connection.session.video || !!connection.session.screen : connection.sdpConstraints.mandatory.OfferToReceiveVideo
                },
                isOneWay: typeof message.message.isOneWay !== 'undefined' ? message.message.isOneWay : !!connection.session.oneway || connection.direction === 'one-way',
                isDataOnly: typeof message.message.isDataOnly !== 'undefined' ? message.message.isDataOnly : isData(connection.session),
                dontGetRemoteStream: typeof message.message.isOneWay !== 'undefined' ? message.message.isOneWay : !!connection.session.oneway || connection.direction === 'one-way',
                dontAttachLocalStream: !!message.message.dontGetRemoteStream,
                connectionDescription: message,
                successCallback: function() {
                    // if its oneway----- todo: THIS SEEMS NOT IMPORTANT.
                    if (typeof message.message.isOneWay !== 'undefined' ? message.message.isOneWay : !!connection.session.oneway || connection.direction === 'one-way') {
                        connection.addNewBroadcaster(message.sender, userPreferences);
                    }

                    if (!!connection.session.oneway || connection.direction === 'one-way' || isData(connection.session)) {
                        connection.addNewBroadcaster(message.sender, userPreferences);
                    }
                }
            };

            connection.onNewParticipant(message.sender, userPreferences);
            return;
        }

        if (message.message.shiftedModerationControl) {
            connection.onShiftedModerationControl(message.sender, message.message.broadcasters);
            return;
        }

        if (message.message.changedUUID) {
            if (connection.peers[message.message.oldUUID]) {
                connection.peers[message.message.newUUID] = connection.peers[message.message.oldUUID];
                delete connection.peers[message.message.oldUUID];
            }
        }

        if (message.message.userLeft) {
            mPeer.onUserLeft(message.sender);

            if (!!message.message.autoCloseEntireSession) {
                connection.leave();
            }

            return;
        }

        mPeer.addNegotiatedMessage(message.message, message.sender);
    }

    new Firebase('https://' + connection.firebase + '.firebaseio.com/.info/connected').on('value', function(snap) {
        if (snap.val()) {
            if (connection.enableLogs) {
                console.info('Firebase connection is opened.');
            }

            if (connectCallback) connectCallback(connection.socket);
        }
    });
}
