Update to add external hook for page size for paginated results

Adds header and check to response to react to external page size changes. This removes any coupling that the core module could have to the persistence module. Added a call in the persistence module to handle adding the headers to the response.

core/src/main/java/org/eclipsefoundation/core/response/PaginatedResultsFilter.java

@@ -4,9 +4,11 @@ import java.io.IOException;
 import java.util.List;
 
 import javax.enterprise.inject.Instance;
+import javax.servlet.http.HttpServletResponse;
 import javax.ws.rs.container.ContainerRequestContext;
 import javax.ws.rs.container.ContainerResponseContext;
 import javax.ws.rs.container.ContainerResponseFilter;
+import javax.ws.rs.core.Context;
 import javax.ws.rs.core.MultivaluedMap;
 import javax.ws.rs.core.UriBuilder;
 import javax.ws.rs.core.UriInfo;
@@ -18,15 +20,20 @@ import org.jboss.resteasy.core.ResteasyContext;
 import org.jboss.resteasy.spi.LinkHeader;
 
 /**
- * Adds pagination and Link headers to the response by slicing the response entity if its a list
- * entity. This will not dig into complex entities to avoid false positives.
+ * Adds pagination and Link headers to the response by slicing the response
+ * entity if its a list entity. This will not dig into complex entities to avoid
+ * false positives.
  *
  * @author Martin Lowe
  */
 @Provider
 public class PaginatedResultsFilter implements ContainerResponseFilter {
-  // should be set whenever we pass a limited subset to the response to be paginated of a larger subset
+  // should be set whenever we pass a limited subset to the response to be
+  // paginated of a larger subset
   public static final String MAX_RESULTS_SIZE_HEADER = "X-Max-Result-Size";
+  // should be set whenever we request data that has a maximum page size that is
+  // different than the default here
+  public static final String MAX_PAGE_SIZE_HEADER = "X-Max-Page-Size";
 
   @ConfigProperty(name = "eclipse.pagination.enabled", defaultValue = "true")
   Instance<Boolean> enablePagination;
@@ -40,29 +47,30 @@ public class PaginatedResultsFilter implements ContainerResponseFilter {
   @ConfigProperty(name = "eclipse.pagination.scheme.value", defaultValue = "https")
   Instance<String> linkScheme;
 
+  @Context
+  HttpServletResponse response;
+
   @Override
-  public void filter(
-      ContainerRequestContext requestContext, ContainerResponseContext responseContext)
+  public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext)
       throws IOException {
     if (enablePagination.get()) {
-
-      int pageSize = defaultPageSize.get();
+      int pageSize = getCurrentLimit(responseContext);
       Object entity = responseContext.getEntity();
       // only try and paginate if there are multiple entities
       if (entity instanceof List) {
         List<?> listEntity = (List<?>) entity;
-        int page = getRequestedPage(listEntity);
+        int page = getRequestedPage(listEntity, pageSize);
         // if available, use max results header value
-        String rawMaxSize = responseContext.getHeaderString(MAX_RESULTS_SIZE_HEADER);
+        String rawMaxSize = response.getHeader(MAX_RESULTS_SIZE_HEADER);
         int maxSize = listEntity.size();
         if (StringUtils.isNumeric(rawMaxSize)) {
-            maxSize = Integer.valueOf(rawMaxSize);
+          maxSize = Integer.valueOf(rawMaxSize);
         }
+
         int lastPage = (int) Math.ceil((double) maxSize / pageSize);
         // set the sliced array as the entity
-        responseContext.setEntity(
-            listEntity.subList(
-                getArrayLimitedNumber(listEntity, Math.max(0, page - 1) * pageSize),
+        responseContext
+            .setEntity(listEntity.subList(getArrayLimitedNumber(listEntity, Math.max(0, page - 1) * pageSize),
                 getArrayLimitedNumber(listEntity, pageSize * page)));
 
         // set the link header to the response
@@ -73,6 +81,7 @@ public class PaginatedResultsFilter implements ContainerResponseFilter {
 
   private LinkHeader createLinkHeader(int page, int lastPage) {
     // add link headers for paginated page hints
+
     UriBuilder builder = getUriInfo().getRequestUriBuilder();
     LinkHeader lh = new LinkHeader();
     // add first + last page link headers
@@ -90,19 +99,21 @@ public class PaginatedResultsFilter implements ContainerResponseFilter {
   }
 
   /**
-   * Gets the current requested page, rounding down to max if larger than the max page number, and
-   * up if below 1.
+   * Gets the current requested page, rounding down to max if larger than the max
+   * page number, and up if below 1.
    *
-   * @param listEntity list entity used to determine the number of pages present for current call.
-   * @return the current page number if set, the last page if greater, or 1 if not set or negative.
+   * @param listEntity list entity used to determine the number of pages present
+   *                   for current call.
+   * @return the current page number if set, the last page if greater, or 1 if not
+   *         set or negative.
    */
-  private int getRequestedPage(List<?> listEntity) {
+  private int getRequestedPage(List<?> listEntity, int pageSize) {
     MultivaluedMap<String, String> params = getUriInfo().getQueryParameters();
     if (params.containsKey("page")) {
       try {
         int page = Integer.parseInt(params.getFirst("page"));
         // use double cast int to allow ceil call to round up for pages
-        int maxPage = (int) Math.ceil((double) listEntity.size() / defaultPageSize.get());
+        int maxPage = (int) Math.ceil((double) listEntity.size() / pageSize);
         // get page, with min of 1 and max of last page
         return Math.min(Math.max(1, page), maxPage);
       } catch (NumberFormatException e) {
@@ -114,11 +125,29 @@ public class PaginatedResultsFilter implements ContainerResponseFilter {
   }
 
   /**
-   * Builds an href for a paginated link using the BaseUri UriBuilder from the UriInfo object,
-   * replacing just the page query parameter.
+   * Allows for external bindings to affect the current page size, defaulting to
+   * the internal set configuration.
+   * 
+   * @param responseContext
+   * @return
+   */
+  private int getCurrentLimit(ContainerResponseContext responseContext) {
+    if (response.getHeaderNames().contains(MAX_PAGE_SIZE_HEADER)) {
+      try {
+        return Integer.parseInt(response.getHeader(MAX_PAGE_SIZE_HEADER));
+      } catch (NumberFormatException e) {
+        // page size isn't a number, allow to return default outside current scope
+      }
+    }
+    return defaultPageSize.get();
+  }
+
+  /**
+   * Builds an href for a paginated link using the BaseUri UriBuilder from the
+   * UriInfo object, replacing just the page query parameter.
    *
    * @param builder base URI builder from the UriInfo object.
-   * @param page the page to link to in the returned link
+   * @param page    the page to link to in the returned link
    * @return fully qualified HREF for the paginated results
    */
   private String buildHref(UriBuilder builder, int page) {
@@ -132,9 +161,10 @@ public class PaginatedResultsFilter implements ContainerResponseFilter {
    * Gets an int bound by the size of a list.
    *
    * @param list the list to bind the number by
-   * @param num the number to check for exceeding bounds.
-   * @return the passed number if its within the size of the given array, 0 if the number is
-   *     negative, and the array size if greater than the maximum bounds.
+   * @param num  the number to check for exceeding bounds.
+   * @return the passed number if its within the size of the given array, 0 if the
+   *         number is negative, and the array size if greater than the maximum
+   *         bounds.
    */
   private int getArrayLimitedNumber(List<?> list, int num) {
     if (num < 0) {