Add PagedList

1 files changed, 135 insertions, 0 deletions

diff --git a/src/main/java/it/alessandroiezzi/util/PagedList.java b/src/main/java/it/alessandroiezzi/util/PagedList.java
new file mode 100644
index 0000000..5cfbe9b
--- /dev/null
+++ b/src/main/java/it/alessandroiezzi/util/PagedList.java
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2022  Alessandro Iezzi <aiezzi AT alessandroiezzi PERIOD it>
+ *
+ * This file is part of commons-page.
+ *
+ * commons-page is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * commons-page is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with commons-page.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package it.alessandroiezzi.util;
+
+import it.alessandroiezzi.commons.page.*;
+
+import java.util.*;
+
+public class PagedList<T> extends ArrayList<T> implements Page<T> {
+    private final int pageSize;
+    private int pageNumber;
+    private PageChangeListener<T> pageChangeListener;
+    boolean pageChanged = false;
+    private Page<T> currentPage;
+
+    public PagedList(List<T> elements, int pageSize) {
+        addAll(elements);
+        this.pageSize = pageSize;
+        this.pageNumber = 0;
+    }
+
+    public PagedList(List<T> elements) {
+        this(elements, 15);
+    }
+
+    public Page<T> firstPage() {
+        return toPage(0);
+    }
+
+    public Page<T> lastPage() {
+        return toPage(getTotalPages() - 1);
+    }
+
+    public Page<T> previousPage() {
+        return toPage(pageNumber - 1);
+    }
+
+    public Page<T> nextPage() {
+        return toPage(pageNumber + 1);
+    }
+
+    public Page<T> toPage(int page) {
+        if (page < 0) {
+            page = 0;
+        } else if (page >= getTotalPages()) {
+            page = getTotalPages() - 1;
+        }
+
+        int totalElements = getNumberOfElements();
+        int startIndex = page * pageSize;
+        if (startIndex > totalElements) {
+            startIndex = totalElements;
+        }
+
+        int count = startIndex + pageSize;
+        if (count > totalElements) {
+            count = totalElements;
+        }
+
+        pageChanged = page != pageNumber;
+        pageNumber = page;
+        List<T> subElements = subList(startIndex, count);
+        currentPage = Page.of(subElements, pageSize);
+
+        if (pageChangeListener != null && pageChanged) {
+            pageChangeListener.pageChanged(new ArrayList<>(subElements), pageSize);
+        }
+
+        return currentPage;
+    }
+
+    public Page<T> getCurrentPage() {
+        return currentPage;
+    }
+
+    public int getCurrentPageNumber() {
+        return pageNumber;
+    }
+
+    public void addPageChangeListener(PageChangeListener<T> pageChangeListener) {
+        this.pageChangeListener = pageChangeListener;
+    }
+
+    public boolean isPageChanged() {
+        return pageChanged;
+    }
+
+    public int firstRowNumber() {
+        return (pageNumber * pageSize) + 1;
+    }
+
+    public int lastRowNumber() {
+        int currentSize = getContent().size();
+        return currentSize < pageSize ? getNumberOfElements() : (pageNumber + 1) * currentSize;
+    }
+
+    public List<T> getContent() {
+        return getCurrentPage().getContent();
+    }
+
+    public int getPageSize() {
+        return pageSize;
+    }
+
+    public int getNumberOfElements() {
+        return size();
+    }
+
+    public int getTotalPages() {
+        double pages = (double) getNumberOfElements() / (double) getPageSize();
+        int pagesInt = (int) pages;
+
+        if (pages > pagesInt)
+            pagesInt++;
+
+        return pagesInt;
+    }
+}