[Telemetry] Add metadata and formatter support

Add TelemetryMetadataManager which assists developers in interrogating
telemetry metadata to find values that are useful for them.

Add TelemetryValueFormatter to simplify the parsing (retrieval of numerical
values) and formatting (retrieval of displayable string value) of datums.

https://github.com/nasa/openmct/issues/1310

src/api/telemetry/TelemetryValueFormatter.js

@@ -0,0 +1,92 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2016, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is 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.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+
+define([
+    'lodash'
+], function (
+    _
+) {
+
+    // TODO: needs reference to formatService;
+    function TelemetryValueFormatter(valueMetadata, formatService) {
+        this.valueMetadata = valueMetadata;
+        this.parseCache = new WeakMap();
+        this.formatCache = new WeakMap();
+        try {
+            this.formatter = formatService
+                .getFormat(valueMetadata.format, valueMetadata);
+        } catch (e) {
+            // TODO: Better formatting
+            this.formatter = {
+                parse: function (x) { return Number(x); },
+                format: function (x) { return x; },
+                validate: function (x) { return true; }
+            };
+        }
+
+        if (valueMetadata.type === 'enum') {
+            this.formatter = {};
+            this.enumerations = valueMetadata.enumerations.reduce(function (vm, e) {
+                vm.byValue[e.value] = e.string;
+                vm.byString[e.string] = e.value;
+                return vm;
+            }, {byValue: {}, byString: {}});
+            this.formatter.format = function (value) {
+                return this.enumerations.byValue[value];
+            }.bind(this);
+            this.formatter.parse = function (string) {
+                if (typeof string === "string" && this.enumerations.hasOwnProperty(string)) {
+                    return this.enumerations.byString[string];
+                }
+                return Number(string);
+            }.bind(this);
+        }
+    }
+
+    TelemetryValueFormatter.prototype.parse = function (datum) {
+        if (_.isObject(datum)) {
+            if (!this.parseCache.has(datum)) {
+                this.parseCache.set(
+                    datum,
+                    this.formatter.parse(datum[this.valueMetadata.source])
+                );
+            }
+            return this.parseCache.get(datum);
+        }
+        return this.formatter.parse(datum);
+    };
+
+    TelemetryValueFormatter.prototype.format = function (datum) {
+        if (_.isObject(datum)) {
+            if (!this.formatCache.has(datum)) {
+                this.formatCache.set(
+                    datum,
+                    this.formatter.format(datum[this.valueMetadata.source])
+                );
+            }
+            return this.formatCache.get(datum);
+        }
+        return this.formatter.format(datum);
+    };
+
+    return TelemetryValueFormatter;
+});