[Time Conductor] Validate start/end times

Attach validation functions passed into mct-control instances
as custom validators (in the  object of ngModelController)
to integrate cleanly with normal Angular form validation.

Supports usage of comparative validation logic to visually display
form elements in the time conductor as invalid when bounds
overlap (e.g. start is before end.)

https://github.com/nasa/openmctweb/issues/325

platform/commonUI/general/res/templates/controls/time-controller.html

@@ -25,7 +25,7 @@
         <span class="l-time-range-inputs-elem ui-symbol type-icon">&#x43;</span>
         <span class="l-time-range-input">
             <mct-control key="'datetime-field'"
-                         structure="{ format: parameters.format }"
+                         structure="{ format: parameters.format, validate: validateStart }"
                          ng-model="formModel"
                          ng-blur="updateBoundsFromForm()"
                          field="'start'"
@@ -37,7 +37,7 @@
 
         <span class="l-time-range-input" ng-controller="ToggleController as t2">
             <mct-control key="'datetime-field'"
-                         structure="{ format: parameters.format }"
+                         structure="{ format: parameters.format, validate: validateEnd }"
                          ng-model="formModel"
                          ng-blur="updateBoundsFromForm()"
                          field="'end'"

platform/commonUI/general/src/controllers/TimeRangeController.js

@@ -240,6 +240,14 @@ define(
                 };
             }
 
+            function validateStart(startValue) {
+                return startValue <= $scope.ngModel.outer.end - outerMinimumSpan;
+            }
+
+            function validateEnd(endValue) {
+                return endValue >= $scope.ngModel.outer.start + outerMinimumSpan;
+            }
+
             $scope.startLeftDrag = startLeftDrag;
             $scope.startRightDrag = startRightDrag;
             $scope.startMiddleDrag = startMiddleDrag;
@@ -249,6 +257,9 @@ define(
 
             $scope.updateBoundsFromForm = updateBoundsFromForm;
 
+            $scope.validateStart = validateStart;
+            $scope.validateEnd = validateEnd;
+
             $scope.ticks = [];
 
             // Initialize scope to defaults

platform/forms/src/MCTControl.js

@@ -54,6 +54,13 @@ define(
                     // Pass the template URL to ng-include via scope.
                     scope.inclusion = controlMap[key];
                 });
+                scope.$watch("structure.validate", function (validate) {
+                    if (typeof validate === 'function') {
+                        ngModelController.$validators.custom = validate;
+                    } else {
+                        delete ngModelController.$validators.custom;
+                    }
+                });
                 scope.ngModelController = ngModelController;
             }