Support pagination in query across all anchors(ep4)

Add pagination query parameters in query across all anchors API
pagination parameters (pageIndex and pageSize) are optional
default is to query all fragments
each pageSize represents number of records(number of anchors)
TotalRecords is returned in response header to find number of pages.

- If pagination option is provided in request then query number of
  anchors equal to pageSize. pageIndex is used for setting offset.

- return number of records(one anchor per record) as per pagesize
  and pageSize

Issue-ID: CPS-1605
Change-ID: I73f97f986a817d423f93a8d922dcd9647b2504bc
Signed-off-by: rajesh.kumar <rk00747546@techmahindra.com>

1 files changed, 45 insertions, 10 deletions

diff --git a/cps-rest/src/main/java/org/onap/cps/rest/controller/QueryRestController.java b/cps-rest/src/main/java/org/onap/cps/rest/controller/QueryRestController.java
index 1fc13fc522..5334b48143 100644
--- a/cps-rest/src/main/java/org/onap/cps/rest/controller/QueryRestController.java
+++ b/cps-rest/src/main/java/org/onap/cps/rest/controller/QueryRestController.java
@@ -25,12 +25,14 @@ package org.onap.cps.rest.controller;
 import io.micrometer.core.annotation.Timed;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import lombok.RequiredArgsConstructor;
 import org.onap.cps.api.CpsQueryService;
 import org.onap.cps.rest.api.CpsQueryApi;
 import org.onap.cps.spi.FetchDescendantsOption;
+import org.onap.cps.spi.PaginationOption;
 import org.onap.cps.spi.model.DataNode;
 import org.onap.cps.utils.DataMapUtils;
 import org.onap.cps.utils.JsonObjectMapper;
@@ -72,22 +74,55 @@ public class QueryRestController implements CpsQueryApi {
     }
 
     @Override
-    public ResponseEntity<Object> getNodesByDataspaceAndCpsPath(final String dataspaceName,
-        final String cpsPath, final String fetchDescendantsOptionAsString) {
+    @Timed(value = "cps.data.controller.datanode.query.across.anchors",
+            description = "Time taken to query data nodes across anchors")
+    public ResponseEntity<Object> getNodesByDataspaceAndCpsPath(final String dataspaceName, final String cpsPath,
+                                                                final String fetchDescendantsOptionAsString,
+                                                                final Integer pageIndex, final Integer pageSize) {
         final FetchDescendantsOption fetchDescendantsOption =
                 FetchDescendantsOption.getFetchDescendantsOption(fetchDescendantsOptionAsString);
-        final Collection<DataNode> dataNodes =
-                cpsQueryService.queryDataNodesAcrossAnchors(dataspaceName, cpsPath, fetchDescendantsOption);
-        final List<Map<String, Object>> dataMaps = new ArrayList<>(dataNodes.size());
+        final PaginationOption paginationOption = (pageIndex == null || pageSize == null)
+                ? PaginationOption.NO_PAGINATION : new PaginationOption(pageIndex, pageSize);
+        final Collection<DataNode> dataNodes = cpsQueryService.queryDataNodesAcrossAnchors(dataspaceName,
+                cpsPath, fetchDescendantsOption, paginationOption);
+        final List<Map<String, Object>> dataNodesAsListOfMaps = new ArrayList<>(dataNodes.size());
         String prefix = null;
-        for (final DataNode dataNode : dataNodes) {
+        final Map<String, List<DataNode>> anchorDataNodeListMap = prepareDataNodesForAnchor(dataNodes);
+        for (final Map.Entry<String, List<DataNode>> anchorDataNodesMapEntry : anchorDataNodeListMap.entrySet()) {
             if (prefix == null) {
-                prefix = prefixResolver.getPrefix(dataspaceName, dataNode.getAnchorName(), dataNode.getXpath());
+                prefix = prefixResolver.getPrefix(dataspaceName, anchorDataNodesMapEntry.getKey(),
+                        anchorDataNodesMapEntry.getValue().get(0).getXpath());
+            }
+            final Map<String, Object> dataMap = DataMapUtils.toDataMapWithIdentifierAndAnchor(
+                    anchorDataNodesMapEntry.getValue(), anchorDataNodesMapEntry.getKey(), prefix);
+            dataNodesAsListOfMaps.add(dataMap);
+        }
+        final Integer totalPages = getTotalPages(dataspaceName, cpsPath, paginationOption);
+        return ResponseEntity.ok().header("total-pages",
+                totalPages.toString()).body(jsonObjectMapper.asJsonString(dataNodesAsListOfMaps));
+    }
+
+    private Integer getTotalPages(final String dataspaceName, final String cpsPath,
+                                                          final PaginationOption paginationOption) {
+        if (paginationOption == PaginationOption.NO_PAGINATION) {
+            return 1;
+        }
+        final int totalAnchors =  cpsQueryService.countAnchorsForDataspaceAndCpsPath(dataspaceName, cpsPath);
+        return totalAnchors <= paginationOption.getPageSize() ? 1
+                : (int) Math.ceil((double) totalAnchors / paginationOption.getPageSize());
+    }
+
+    private Map<String, List<DataNode>> prepareDataNodesForAnchor(final Collection<DataNode> dataNodes) {
+        final Map<String, List<DataNode>> dataNodesMapForAnchor = new HashMap<>();
+        for (final DataNode dataNode : dataNodes) {
+            List<DataNode> dataNodesInAnchor = dataNodesMapForAnchor.get(dataNode.getAnchorName());
+            if (dataNodesInAnchor == null) {
+                dataNodesInAnchor = new ArrayList<>();
+                dataNodesMapForAnchor.put(dataNode.getAnchorName(), dataNodesInAnchor);
             }
-            final Map<String, Object> dataMap = DataMapUtils.toDataMapWithIdentifierAndAnchor(dataNode, prefix);
-            dataMaps.add(dataMap);
+            dataNodesInAnchor.add(dataNode);
         }
-        return new ResponseEntity<>(jsonObjectMapper.asJsonString(dataMaps), HttpStatus.OK);
+        return dataNodesMapForAnchor;
     }
 
     private ResponseEntity<Object> executeNodesByDataspaceQueryAndCreateResponse(final String dataspaceName,