Redesigned the paging in the Grid widget.

rapidoid-commons/src/main/java/org/rapidoid/commons/Coll.java

@@ -286,7 +286,7 @@ public Set<V> map(K src) throws Exception {
 		});
 	}
 
-	public static <T> Iterable<T> range(Iterable<T> items, int from, int to) {
+	public static <T> List<T> range(Iterable<T> items, int from, int to) {
 		U.must(from <= to, "'from' must be <= 'to'!");
 
 		if (from == to) {

rapidoid-commons/src/main/java/org/rapidoid/util/Msc.java

@@ -21,6 +21,7 @@
 import org.rapidoid.log.Log;
 import org.rapidoid.u.U;
 import org.rapidoid.validation.InvalidData;
+import org.rapidoid.wrap.BoolWrap;
 
 import javax.validation.ConstraintViolation;
 import javax.validation.ConstraintViolationException;
@@ -820,19 +821,26 @@ public static ErrCodeAndMsg getErrorCodeAndMsg(Throwable err) {
 		return new ErrCodeAndMsg(code, msg);
 	}
 
-	public static <T> List<T> range(Iterable<T> items, int fromIndex, int toIndex) {
-		// TODO more efficient implementation
-		List<T> list = U.list(items);
+	public static <T> List<T> page(Iterable<T> items, int page, int pageSize) {
+		return Coll.range(items, (page - 1) * pageSize, page * pageSize);
+	}
 
-		fromIndex = U.limit(0, fromIndex, list.size());
-		toIndex = U.limit(fromIndex, toIndex, list.size());
+	public static List<?> getPage(Iterable<?> items, int page, int pageSize, Integer size, BoolWrap isLastPage) {
+		int pageFrom = Math.max((page - 1) * pageSize, 0);
+		int pageTo = (page) * pageSize + 1;
 
-		return U.list(list.subList(fromIndex, toIndex));
-	}
+		if (size != null) {
+			pageTo = Math.min(pageTo, size);
+		}
 
-	public static <T> List<T> page(Iterable<T> items, int page, int pageSize) {
-		return range(items, (page - 1) * pageSize, page * pageSize);
-	}
+		List<?> range = Coll.range(items, pageFrom, pageTo);
+		isLastPage.value = range.size() < pageSize + 1;
+
+		if (!isLastPage.value && !range.isEmpty()) {
+			range.remove(range.size() - 1);
+		}
 
+		return range; // 1 item extra, to test if there are more results
+	}
 
 }

rapidoid-gui/src/main/java/org/rapidoid/gui/GUI.java

@@ -401,7 +401,7 @@ public static HtmlPage page(Object... contents) {
 		return Cls.customizable(HtmlPage.class, new Object[]{AnyObj.flat(contents)});
 	}
 
-	public static <T> Grid grid(Iterable<T> items) {
+	public static Grid grid(Iterable<?> items) {
 		return Cls.customizable(Grid.class).items(items);
 	}
 
@@ -954,7 +954,7 @@ public static String uriFor(String baseUri, Object target) {
 		}
 
 		Object id = getIdentifier(target);
-		return id != null ? Msc.uri(baseUri, id + "", "view") : "";
+		return id != null ? Msc.uri(baseUri, id + "") : "";
 	}
 
 	public static String typeUri(Class<?> entityType) {

rapidoid-gui/src/main/java/org/rapidoid/gui/Grid.java

@@ -2,6 +2,7 @@
 
 import org.rapidoid.annotation.Authors;
 import org.rapidoid.annotation.Since;
+import org.rapidoid.commons.Coll;
 import org.rapidoid.gui.base.AbstractWidget;
 import org.rapidoid.html.Tag;
 import org.rapidoid.html.tag.TdTag;
@@ -12,7 +13,9 @@
 import org.rapidoid.model.Models;
 import org.rapidoid.model.Property;
 import org.rapidoid.u.U;
+import org.rapidoid.util.Msc;
 import org.rapidoid.var.Var;
+import org.rapidoid.wrap.BoolWrap;
 
 import java.util.Iterator;
 import java.util.List;
@@ -52,51 +55,76 @@ public class Grid extends AbstractWidget<Grid> {
 	private volatile Mapper<Object, String> toUri;
 
 	@Override
-	protected Tag render() {
+	protected Object render() {
 
-		Iterator<?> it = items.iterator();
-		Class<?> type = it.hasNext() ? it.next().getClass() : Object.class;
+		Pager pager = noPager();
+		boolean paging = pageSize > 0;
+		Iterable<?> rows;
+
+		BoolWrap isLastPage = new BoolWrap();
+
+		if (paging) {
+			String pageParam = "_p" + seq("pager");
+			pager = GUI.pager(pageParam).min(1);
+
+			Integer size = Coll.getSizeOrNull(items);
+
+			if (size != null) {
+				int pages = (int) Math.ceil(size / (double) pageSize);
+				pager.max(pages);
+			}
+
+			rows = Msc.getPage(items, pager.pageNumber(), pageSize, size, isLastPage);
 
-		Items itemsModel;
-		if (items instanceof Items) {
-			itemsModel = (Items) items;
 		} else {
-			itemsModel = Models.beanItems(type, U.array(items));
+			rows = items;
 		}
 
-		final List<Property> props = itemsModel.properties(columns);
+		return renderGridPage(pager, rows, isLastPage.value);
+	}
 
-		int total = itemsModel.size();
-		int pages = (int) Math.ceil(total / (double) pageSize);
+	private Object renderGridPage(Pager pager, Iterable<?> rows, boolean isLastPage) {
+		Iterator<?> it = rows.iterator();
+		boolean hasData = it.hasNext();
 
-		boolean ordered = !U.isEmpty(orderBy);
-		Var<String> order = null;
+		if (isLastPage || !hasData) {
+			pager.max(pager.pageNumber());
+		}
 
-		Items slice = itemsModel;
+		if (!hasData) {
+			return U.list(noDataAvailable(), pager); // no data
+		}
 
-		String currentOrder = orderBy;
+		Class<?> type = it.next().getClass();
 
-		if (ordered) {
-			order = GUI.local("_order_" + widgetId(), orderBy);
-			currentOrder = order.get();
-			slice = slice.orderedBy(currentOrder);
+		Items itemsModel;
+		if (rows instanceof Items) {
+			itemsModel = (Items) rows;
+		} else {
+			itemsModel = Models.beanItems(type, U.array(rows));
 		}
 
-		boolean paging = pageSize > 0;
-		Var<Integer> pageNumber = null;
+		final List<Property> props = itemsModel.properties(columns);
+		boolean ordered = !U.isEmpty(orderBy);
+		Var<String> order = null;
+		String currentOrder = orderBy;
 
-		if (paging) {
-			pageNumber = GUI.local("_page_" + widgetId(), 1, 1, pages);
-			slice = getPage(slice, pageNumber.get());
+		if (ordered) {
+			order = GUI.local("_o" + seq("order"), orderBy);
+			currentOrder = order.get();
+			itemsModel = itemsModel.orderedBy(currentOrder);
 		}
 
 		Tag header = tableHeader(props, order);
-		Tag body = tableBody(props, slice);
-		Pager pager = paging ? GUI.pager(pageNumber.name()).min(1).max(pages) : noPager();
+		Tag body = tableBody(props, itemsModel);
 
 		return fullTable(header, body, pager);
 	}
 
+	protected Tag noDataAvailable() {
+		return GUI.h4("No data available!");
+	}
+
 	protected Pager noPager() {
 		return null;
 	}
@@ -105,15 +133,6 @@ protected Tag fullTable(Tag header, Tag body, Pager pager) {
 		return GUI.row(GUI.table_(GUI.thead(header), body), pager);
 	}
 
-	protected Items getPage(Items items, Integer pageN) {
-		Items pageOrAll;
-		int pageFrom = Math.max((pageN - 1) * pageSize, 0);
-		int pageTo = Math.min((pageN) * pageSize, items.size());
-
-		pageOrAll = items.range(pageFrom, pageTo);
-		return pageOrAll;
-	}
-
 	protected Tag tableBody(final List<Property> props, Items pageOrAll) {
 		Tag body = GUI.tbody();
 
@@ -181,7 +200,16 @@ protected Tag itemRow(List<Property> properties, Item item) {
 	}
 
 	protected String onClickScript(Item item) {
-		String uri = toUri != null ? Lmbd.eval(toUri, item.value()) : GUI.uriFor(item.value());
+		String uri;
+		if (toUri != null) {
+			uri = Lmbd.eval(toUri, item.value());
+		} else {
+			uri = GUI.uriFor(item.value());
+			if (U.notEmpty(uri)) {
+				uri = Msc.uri(uri, "view");
+			}
+		}
+
 		return U.notEmpty(uri) ? U.frmt("Rapidoid.goAt('%s');", uri) : null;
 	}
 
@@ -194,6 +222,7 @@ public Iterable<?> items() {
 	}
 
 	public Grid items(Iterable<?> items) {
+		U.must(!(items instanceof Items));
 		this.items = items;
 		return this;
 	}

rapidoid-gui/src/main/java/org/rapidoid/gui/Pager.java

@@ -62,7 +62,7 @@ protected String pageUri(int pageN) {
 	}
 
 	protected boolean shouldDisplay() {
-		return U.neq(min, max);
+		return U.neq(min, max) || max == null || min == null;
 	}
 
 	protected Tag pagination() {

rapidoid-gui/src/main/java/org/rapidoid/gui/base/AbstractWidget.java

@@ -12,10 +12,9 @@
 import org.rapidoid.html.tag.ATag;
 import org.rapidoid.html.tag.TdTag;
 import org.rapidoid.html.tag.ThTag;
+import org.rapidoid.u.U;
 import org.rapidoid.util.Constants;
 
-import java.util.UUID;
-
 /*
  * #%L
  * rapidoid-gui
@@ -62,7 +61,18 @@ public final Object render(Object extra) {
 	}
 
 	public String widgetId() {
-		return getClass().getSimpleName() + "-" + UUID.randomUUID();
+		String type = getClass().getSimpleName().toLowerCase();
+		return type + seq(type);
+	}
+
+	public String seq(String seqName) {
+		String seq = "__seq_" + seqName;
+		int seqNum = (Integer) U.or(req().attrs().get(seq), 0);
+
+		seqNum++;
+		req().attrs().put(seq, seqNum);
+
+		return "" + seqNum;
 	}
 
 	public boolean visible() {

rapidoid-gui/src/test/java/org/rapidoid/widget/TableWidgetTest.java → rapidoid-gui/src/test/java/org/rapidoid/widget/GridWidgetTest.java

@@ -25,13 +25,11 @@
 import org.rapidoid.annotation.Since;
 import org.rapidoid.gui.GUI;
 import org.rapidoid.gui.Grid;
-import org.rapidoid.model.Items;
-import org.rapidoid.model.Models;
 import org.rapidoid.u.U;
 
 @Authors("Nikolche Mihajlovski")
-@Since("2.0.0")
-public class TableWidgetTest extends WidgetTestCommons {
+@Since("5.1.0")
+public class GridWidgetTest extends WidgetTestCommons {
 
 	@Test
 	public void testTableWidget() {
@@ -41,9 +39,7 @@ public void testTableWidget() {
 		Person rambo = new Person("Rambo", 50);
 		rambo.id = 2;
 
-		Items items = Models.beanItemsInfer(john, rambo);
-
-		Grid table = GUI.grid(items).pageSize(10);
+		Grid table = GUI.grid(U.list(john, rambo)).pageSize(10);
 		verifyGUI("persons-grid", table);
 
 		verifyGUI("map-grid", GUI.grid(U.map("name", "Foo", "year", "2016")));

rapidoid-web/src/main/java/org/rapidoid/goodies/ClasspathHandler.java

@@ -47,11 +47,11 @@ public Object call() throws Exception {
 
 		info.add(h3("Classpath folders:"));
 
-		info.add(grid(ClasspathUtil.getClasspathFolders()).columns("trim").headers("Classpath entries (folders)"));
+		info.add(grid(ClasspathUtil.getClasspathFolders()).columns("trim").headers("Classpath entries (folders)").pageSize(0));
 
 		info.add(h3("Classpath JARs:"));
 
-		info.add(grid(ClasspathUtil.getClasspathJars()).columns("trim").headers("Classpath entries (JARs)"));
+		info.add(grid(ClasspathUtil.getClasspathJars()).columns("trim").headers("Classpath entries (JARs)").pageSize(0));
 
 		return info;
 	}

rapidoid-web/src/main/java/org/rapidoid/goodies/X.java

@@ -13,12 +13,10 @@
 import org.rapidoid.http.ReqRespHandler;
 import org.rapidoid.http.Resp;
 import org.rapidoid.jpa.JPA;
-import org.rapidoid.lambda.Mapper;
 import org.rapidoid.setup.On;
 import org.rapidoid.setup.Setup;
 import org.rapidoid.sql.JDBC;
 import org.rapidoid.u.U;
-import org.rapidoid.util.Msc;
 
 import javax.persistence.metamodel.EntityType;
 import java.util.List;
@@ -136,12 +134,7 @@ public Object execute(Req req, Resp resp) throws Exception {
 				IRange range = Range.of((page - 1) * pageSize, pageSize);
 				List<?> records = JPA.of(entityType).page(range.start(), range.length());
 
-				Grid grid = GUI.grid(records).toUri(new Mapper<Object, String>() {
-					@Override
-					public String map(Object target) throws Exception {
-						return Msc.uri(GUI.uriFor(baseUri, target), "view");
-					}
-				});
+				Grid grid = GUI.grid(records);
 
 				Btn add = GUI.btn("Add " + name(entityType)).primary().go(baseUri + "/add");