[Plot] Suppress plot for non-numeric telemetry

Avoids plot views becoming erroneously available for image
telemetry, WTD-1170.

platform/features/plot/src/policies/PlotViewPolicy.js

@@ -0,0 +1,65 @@
+/*****************************************************************************
+ * Open MCT Web, Copyright (c) 2014-2015, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT Web 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 Web 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.
+ *****************************************************************************/
+/*global define*/
+
+define(
+    function () {
+        "use strict";
+
+        /**
+         * Policy preventing the Plot view from being made available for
+         * domain objects which have non-numeric telemetry.
+         * @implements {Policy}
+         */
+        function PlotViewPolicy() {
+            function hasImageTelemetry(domainObject) {
+                var telemetry = domainObject &&
+                        domainObject.getCapability('telemetry'),
+                    metadata = telemetry ? telemetry.getMetadata() : {},
+                    ranges = metadata.ranges || [];
+
+                // Generally, we want to allow Plot for telemetry-providing
+                // objects (most telemetry is plottable.) We only want to
+                // suppress this for telemetry which only has explicitly
+                // non-numeric values.
+                return ranges.length === 0 || ranges.some(function (range) {
+                    // Assume format is numeric if it is undefined
+                    // (numeric telemetry is the common case)
+                    return range.format === undefined ||
+                            range.format === 'number';
+                });
+            }
+
+            return {
+                allow: function (view, domainObject) {
+                    if (view.key === 'plot') {
+                        return hasImageTelemetry(domainObject);
+                    }
+
+                    return true;
+                }
+            };
+        }
+
+        return PlotViewPolicy;
+    }
+);