diffusion/src/node_modules/topic-update/update-stream-factory.js

Diffusion JavaScript client

var UpdateStream = require('topic-update/update-stream');

var NewUpdateStream = require('topic-update/new-update-stream');
var NewAddTopicAndUpdateStream = require('topic-update/new-add-topic-and-update-stream');
var TopicType = require('../../topics/topics').TopicType;

var requireNonNull = require('util/require-non-null');

var UpdateStreamFactory = function(streamServices) {

    var getValueCheckOperation = function(dataType) {
        if (['int64', 'double', 'string'].includes(dataType.name())) {
            return function() {};
        }
        else {
            return function(value) {
                requireNonNull(value, "null can only be passed for int64, double or string topics");
            };
        }
    };

    var getChangeService = function(deltaType) {
        return (deltaType === undefined)?
                streamServices.STREAM_SET_TOPIC_SERVICE:
                streamServices.STREAM_APPLY_DELTA_SERVICE;
    };

    var getToBytesFunction = function(dataType, deltaType) {
        if (deltaType === undefined) {
            return function(oldValue, newValue) {
                return dataType.from(newValue).asBuffer();
            };
        }
        else {
            return function(oldValue, newValue) {
                var delta = deltaType.diff(oldValue, newValue);
                return delta.$buffer.slice(delta.$offset, delta.$offset + delta.$length);
            };
        }
    };

    var binaryDeltaType = function(dataType) {
        try {
            return dataType.binaryDeltaType();
        }
        catch (e) {
            // catch the error and return undefined to signal that no delta type is available
            return;
        }
    };

    this.createUpdateStream = function(path, dataType, constraint) {
        var deltaType = binaryDeltaType(dataType);
        var options = {
            dataType: dataType,
            checkOperation: getValueCheckOperation(dataType),
            toBuffer: getToBytesFunction(dataType, deltaType),
            deltaService: getChangeService(deltaType)
        };
        var topicType = TopicType[dataType.name().toUpperCase()];

        return new UpdateStream(
            function(updateStreamImpl) {
                return new NewUpdateStream(streamServices, options, updateStreamImpl, path, topicType, constraint);
            }
        );
    };

    this.createUpdateStreamThatAddsTopic = function(path, specification, dataType, constraint) {
        var deltaType = binaryDeltaType(dataType);
        var options = {
            dataType: dataType,
            checkOperation: getValueCheckOperation(dataType),
            toBuffer: getToBytesFunction(dataType, deltaType),
            deltaService: getChangeService(deltaType)
        };
        return new UpdateStream(
            function(updateStreamImpl) {
                return new NewAddTopicAndUpdateStream(streamServices,
                                                      options,
                                                      updateStreamImpl,
                                                      path,
                                                      specification,
                                                      constraint);
            }
        );
    };
};

module.exports = UpdateStreamFactory;