clean up and reduce repetition in validation code

- factor out checks against arrays of valid values
- use Arrays.toString, List.of, Ints.contains, static imports

Author: abyrd

src/main/java/com/conveyal/analysis/controllers/RegionalAnalysisController.java

@@ -60,6 +60,9 @@
 import static com.conveyal.analysis.util.JsonUtil.toJson;
 import static com.conveyal.file.FileCategory.BUNDLES;
 import static com.conveyal.file.FileCategory.RESULTS;
+import static com.conveyal.file.FileStorageFormat.GEOTIFF;
+import static com.conveyal.file.FileStorageFormat.GRID;
+import static com.conveyal.file.FileStorageFormat.PNG;
 import static com.conveyal.file.UrlWithHumanName.filenameCleanString;
 import static com.conveyal.r5.transit.TransportNetworkCache.getScenarioFilename;
 import static com.google.common.base.Preconditions.checkArgument;
@@ -308,7 +311,7 @@ private Object getAllRegionalResults (Request req, Response res) throws IOExcept
                     for (int threshold : getValidThresholds(analysis)) {
                         for (int percentile : analysis.travelTimePercentiles) {
                             HumanKey gridKey = getSingleCutoffGrid(
-                                analysis, destinations, threshold, percentile, gridResultType, FileStorageFormat.GEOTIFF
+                                analysis, destinations, threshold, percentile, gridResultType, GEOTIFF
                             );
                             humanKeys.add(gridKey);
                             progressListener.increment();
@@ -384,38 +387,17 @@ private UrlWithHumanName getRegionalResults (Request req, Response res) throws I
         // expected to have no gridded results and cleanly return a 404?
         final String regionalAnalysisId = req.params("_id");
         FileStorageFormat format = FileStorageFormat.valueOf(req.params("format").toUpperCase());
-        if (!FileStorageFormat.GRID.equals(format) && !FileStorageFormat.PNG.equals(format) && !FileStorageFormat.GEOTIFF.equals(format)) {
-            throw AnalysisServerException.badRequest("Format \"" + format + "\" is invalid. Request format must be \"grid\", \"png\", or \"geotiff\".");
+        if (!List.of(GRID, PNG, GEOTIFF).contains(format)) {
+            throw AnalysisServerException.badRequest("Parameter 'format' must be one of [grid, png, geotiff].");
         }
         final UserPermissions userPermissions = UserPermissions.from(req);
         RegionalAnalysis analysis = getAnalysis(regionalAnalysisId, userPermissions);
         GridResultType gridResultType = determineGridResultType(analysis);
         // The threshold parameter holds the value in minutes, not the position in the array of thresholds.
-        int threshold = getIntQueryParameter(req, "threshold");
-        int[] thresholds = getValidThresholds(analysis);
-        checkState(thresholds != null && thresholds.length > 0, "Regional analysis lacks thresholds for " + gridResultType);
-        checkArgument(Ints.contains(thresholds, threshold),
-              "Threshold parameter for this regional analysis must be taken from this list: (%s)",
-              Ints.join(", ", thresholds)
-        );
-        int percentile = getIntQueryParameter(req, "percentile");
-        int [] percentiles = analysis.travelTimePercentiles;
-        checkState(percentiles != null && percentiles.length > 0, "Regional analysis lacks percentiles.");
-        checkArgument(Ints.contains(percentiles, percentile),
-                "Percentile for this regional analysis must be taken from this list: (%s)",
-                Ints.join(", ", percentiles)
-        );
-        // Handle regional analyses with multiple destination pointsets per analysis.
-        int nGrids = analysis.destinationPointSetIds.length;
-        checkState(nGrids > 0, "Regional analysis has no grids.");
-        String destinationPointSetId = req.queryParams("destinationPointSetId");
-        if (destinationPointSetId == null) {
-            destinationPointSetId = analysis.destinationPointSetIds[0];
-        }
-        checkArgument(Arrays.asList(analysis.destinationPointSetIds).contains(destinationPointSetId),
-                "Destination gridId must be one of: %s",
-                String.join(",", analysis.destinationPointSetIds)
-        );
+        int threshold = getAndValidateIntParameter(req, "threshold", getValidThresholds(analysis));
+        int percentile = getAndValidateIntParameter(req, "percentile", analysis.travelTimePercentiles);
+        String destinationPointSetId = getAndValidateStringParameter(
+              req, "destinationPointSetId", analysis.destinationPointSetIds);
         // We started implementing the ability to retrieve and display partially completed analyses.
         // We eventually decided these should not be available here at the same endpoint as complete, immutable results.
         if (broker.findJob(regionalAnalysisId) != null) {
@@ -441,6 +423,28 @@ private GridResultType determineGridResultType (RegionalAnalysis analysis) {
         return analysis.request.includeTemporalDensity ? GridResultType.DUAL_ACCESS : GridResultType.ACCESS;
     }
 
+    /// Get the value for a given query parameter name, check that it's non-null and can be parsed
+    /// as an integer, and check that the value is present in an array of valid values.
+    private int getAndValidateIntParameter (Request req, String parameterName, int[] allowedValues) {
+        int value = getIntQueryParameter(req, parameterName);
+        checkState(allowedValues != null && allowedValues.length > 0, "Lacking values for " + parameterName);
+        checkArgument(Ints.contains(allowedValues, value), "Parameter '%s' must be one of: %s",
+              parameterName, Arrays.toString(allowedValues));
+        return value;
+    }
+
+    /// Should behave identically to getAndValidateIntParameter, but for Strings.
+    private String getAndValidateStringParameter (Request req, String parameterName, String[] allowedValues) {
+        checkState(allowedValues != null && allowedValues.length > 0, "Lacking values for " + parameterName);
+        String value = req.queryParams(parameterName);
+        if (value == null || value.isEmpty()) {
+            throw new IllegalArgumentException("Must provide query parameter " + parameterName);
+        }
+        checkArgument(List.of(allowedValues).contains(value), "Parameter '%s' must be one of: %s",
+              parameterName, Arrays.toString(allowedValues));
+        return value;
+    }
+
     private Object getCsvResults (Request req, Response res) {
         final String regionalAnalysisId = req.params("_id");
         final CsvResultType resultType = CsvResultType.valueOf(req.params("resultType").toUpperCase());