diffusion/src/node_modules/features/topics/value-stream-adapter.js

Diffusion JavaScript client

var DataTypes = require('data/datatypes');

/**
 * Adapter for transforming the type of the emitted value to the datatype of
 * the ValueStream.
 *
 * @param {ValueStreamProxy} stream - The stream that is wrapped
 * @param {DataType} datatype - The data type of the value stream
 * @param {TopicType} topictype - The topic type
 */
module.exports = function ValueStreamAdapter(stream, datatype, topictype) {
    var sourceDatatype = DataTypes.getByValue(topictype);

    this.subscription = stream.subscription;
    this.emitter = stream.emitter;

    this.selects = function(specification) {
        return stream.selects(specification);
    };

    this.onOpen = function() {
        return stream.onOpen();
    };

    this.onDelta = function(topic, details, specification, received, delta, oldValue, newValue) {
        return stream.onDelta(topic, details, specification, received, delta,
            sourceDatatype.readAs(datatype.valueClass, datatype.writeValue(oldValue)),
            sourceDatatype.readAs(datatype.valueClass, datatype.writeValue(newValue))
        );
    };

    this.onValue = function(topic, details, specification, received, oldValue, newValue) {
        return stream.onValue(topic, details, specification, received,
            sourceDatatype.readAs(datatype.valueClass, datatype.writeValue(oldValue)),
            sourceDatatype.readAs(datatype.valueClass, datatype.writeValue(newValue))
        );
    };

    this.onSubscription = function(topic, details, specification) {
        return stream.onSubscription(topic, details, specification);
    };

    this.onUnsubscription = function(topic, details, specification, reason) {
        return stream.onUnsubscription(topic, details, specification, reason);
    };

    this.onSubscriptionError = function(error) {
        return stream.onSubscriptionError(error);
    };

};