Implementing pagination

Test: go/vts-web-staging/show_plan_release?plan=vts&type=suite&page=1
Bug: 77456536
Change-Id: I0e9c7ad04c8c832f4229d77c2840be813869d293

1 files changed, 78 insertions, 30 deletions

diff --git a/src/main/java/com/android/vts/util/Pagination.java b/src/main/java/com/android/vts/util/Pagination.java
index c8bec0f..6223c35 100644
--- a/src/main/java/com/android/vts/util/Pagination.java
+++ b/src/main/java/com/android/vts/util/Pagination.java
@@ -22,7 +22,9 @@ import com.googlecode.objectify.cmd.Query;
 
 import java.util.ArrayList;
 import java.util.Iterator;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.stream.Collectors;
 
 /** Helper class for pagination. */
 public class Pagination<T> implements Iterable<T> {
@@ -41,9 +43,18 @@ public class Pagination<T> implements Iterable<T> {
     /** the total number of found entities */
     private int totalCount;
 
-    /** the cursor string token where to start */
+    /** the previous cursor string token where to start */
+    private String previousPageCountToken = "";
+
+    /** the previous cursor string token where to start */
+    private String currentPageCountToken = "";
+
+    /** the next cursor string token where to start */
     private String nextPageCountToken = "";
 
+    /** the previous cursor string token list where to start */
+    private LinkedHashSet<String> pageCountTokenSet;
+
     /** the maximum number of pages */
     private int maxPages;
 
@@ -57,33 +68,53 @@ public class Pagination<T> implements Iterable<T> {
         this.totalCount = totalCount;
     }
 
-    public Pagination(Query<T> query, int page, int pageSize, String nextPageToken) {
+    public Pagination(
+            Query<T> query,
+            int page,
+            int pageSize,
+            String startPageToken,
+            LinkedHashSet<String> pageCountTokenSet) {
         this.page = page;
         this.pageSize = pageSize;
+        this.pageCountTokenSet = pageCountTokenSet;
+        this.currentPageCountToken = startPageToken;
+
+        List<String> pageCountTokenList =
+                this.pageCountTokenSet.stream().collect(Collectors.toList());
+        if (pageCountTokenList.size() > 1) {
+            int foundIndex = pageCountTokenList.indexOf(startPageToken);
+            if (foundIndex <= 0) {
+                this.previousPageCountToken = "";
+            } else {
+                this.previousPageCountToken = pageCountTokenList.get(foundIndex - 1);
+            }
+        }
 
-        int limitValue = pageSize * DEFAULT_PAGE_WINDOW + pageSize;
+        int limitValue = pageSize * DEFAULT_PAGE_WINDOW + pageSize / 2;
         query = query.limit(limitValue);
-        if (nextPageToken.equals("")) {
+        if (startPageToken.equals("")) {
             this.totalCount = query.count();
         } else {
-            query = query.startAt(Cursor.fromWebSafeString(nextPageToken));
+            query = query.startAt(Cursor.fromWebSafeString(startPageToken));
             this.totalCount = query.count();
         }
 
-        this.maxPages = this.totalCount / this.pageSize + (this.totalCount % this.pageSize == 0 ? 0 : 1);
+        this.maxPages =
+                this.totalCount / this.pageSize + (this.totalCount % this.pageSize == 0 ? 0 : 1);
+
+        int iteratorIndex = 0;
+        int startIndex = (page % pageSize == 0 ? 1 : page % pageSize - 1) * pageSize;
 
         QueryResultIterator<T> resultIterator = query.iterator();
-        int iteratorIndex = 1;
-        int startIndex = page / pageSize * pageSize;
         while (resultIterator.hasNext()) {
             if (startIndex <= iteratorIndex && iteratorIndex < startIndex + this.pageSize)
                 this.list.add(resultIterator.next());
-            else
-                resultIterator.next();
+            else resultIterator.next();
+            if (iteratorIndex == DEFAULT_PAGE_SIZE * this.pageSize) {
+                this.nextPageCountToken = resultIterator.getCursor().toWebSafeString();
+            }
             iteratorIndex++;
         }
-
-        this.nextPageCountToken = resultIterator.getCursor().toWebSafeString();
     }
 
     public Iterator<T> iterator() {
@@ -93,7 +124,7 @@ public class Pagination<T> implements Iterable<T> {
     /**
      * Gets the total number of objects.
      *
-     * @return  the total number of objects as an int
+     * @return the total number of objects as an int
      */
     public int getTotalCount() {
         return totalCount;
@@ -102,7 +133,7 @@ public class Pagination<T> implements Iterable<T> {
     /**
      * Gets the number of page window.
      *
-     * @return  the number of page window as an int
+     * @return the number of page window as an int
      */
     public int getPageSize() {
         return pageSize;
@@ -111,7 +142,7 @@ public class Pagination<T> implements Iterable<T> {
     /**
      * Gets the maximum number of pages.
      *
-     * @return  the maximum number of pages as an int
+     * @return the maximum number of pages as an int
      */
     public int getMaxPages() {
         return this.maxPages;
@@ -120,7 +151,7 @@ public class Pagination<T> implements Iterable<T> {
     /**
      * Gets the page.
      *
-     * @return  the page as an int
+     * @return the page as an int
      */
     public int getPage() {
         return page;
@@ -129,49 +160,66 @@ public class Pagination<T> implements Iterable<T> {
     /**
      * Gets the minimum page in the window.
      *
-     * @return  the page number
+     * @return the page number
      */
     public int getMinPageRange() {
-        if (this.getPage() < DEFAULT_PAGE_WINDOW) {
+        if (this.getPage() <= this.getPageSize()) {
             return 1;
         } else {
-            return this.getPage() / DEFAULT_PAGE_WINDOW * DEFAULT_PAGE_WINDOW;
+            if ((this.getPage() % this.getPageSize()) == 0) {
+                return (this.getPage() / this.getPageSize() - 1) * this.getPageSize() + 1;
+            } else {
+                return this.getPage() / this.getPageSize() * this.getPageSize() + 1;
+            }
         }
     }
 
     /**
      * Gets the maximum page in the window.
      *
-     * @return  the page number
+     * @return the page number
      */
     public int getMaxPageRange() {
-        if (this.getPage() < DEFAULT_PAGE_WINDOW) {
-            return DEFAULT_PAGE_WINDOW;
+        if (this.getMaxPages() > this.getPageSize()) {
+            return getMinPageRange() + this.getPageSize() - 1;
         } else {
-            if (this.getMaxPages() > DEFAULT_PAGE_WINDOW) {
-                return this.getPage() / DEFAULT_PAGE_WINDOW * DEFAULT_PAGE_WINDOW + this.pageSize;
-            } else {
-                return this.getMinPageRange() + this.getMaxPages();
-            }
+            return this.getMinPageRange() + this.getMaxPages() - 1;
         }
     }
 
     /**
      * Gets the subset of the list for the current page.
      *
-     * @return  a List
+     * @return a List
      */
     public List<T> getList() {
         return this.list;
     }
 
     /**
+     * Gets the cursor token for the previous page starting point.
+     *
+     * @return a string of cursor of previous starting point
+     */
+    public String getPreviousPageCountToken() {
+        return this.previousPageCountToken;
+    }
+
+    /**
+     * Gets the cursor token for the current page starting point.
+     *
+     * @return a string of cursor of current starting point
+     */
+    public String getCurrentPageCountToken() {
+        return this.currentPageCountToken;
+    }
+
+    /**
      * Gets the cursor token for the next page starting point.
      *
-     * @return  a string of cursor of next starting point
+     * @return a string of cursor of next starting point
      */
     public String getNextPageCountToken() {
         return this.nextPageCountToken;
     }
-
 }