Introduce TerminalViewId instead of nullable id and secondaryId

Currently there is a pair of arguments in a number of signatures `String
id, String secondaryId` each of which may be `null`.

Instead of this pair a new type introduced that also handles the logic
of calculation for the next secondary id.

As a result the client code much be simplified to look like this:
`UIPlugin.getConsoleManager().showConsoleView(new
TerminalViewId().next());`

Author: ruspl-afed

terminal/bundles/org.eclipse.terminal.view.ui/src/org/eclipse/terminal/view/ui/TerminalViewId.java

@@ -0,0 +1,98 @@
+/*******************************************************************************
+ * Copyright (c) 2011, 2025 Wind River Systems, Inc. and others. All rights reserved.
+ * This program and the accompanying materials are made available under the terms
+ * of the Eclipse Public License 2.0 which accompanies this distribution, and is
+ * available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ * Wind River Systems - initial API and implementation
+ * Max Weninger (Wind River) - [361363] [TERMINALS] Implement "Pin&Clone" for the "Terminals" view
+ * Alexander Fedorov (ArSysOp) - further evolution
+ *******************************************************************************/
+package org.eclipse.terminal.view.ui;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import org.eclipse.ui.IViewReference;
+import org.eclipse.ui.IWorkbench;
+import org.eclipse.ui.IWorkbenchPage;
+import org.eclipse.ui.IWorkbenchWindow;
+import org.eclipse.ui.PlatformUI;
+
+/**
+ * Encapsulates the pair of mandatory primary terminal view id and optional secondary id
+ *
+ * @see IUIConstants#ID
+ * @see IViewReference#getSecondaryId()
+ */
+public record TerminalViewId(String primary, Optional<String> secondary) {
+
+	public TerminalViewId() {
+		this(IUIConstants.ID);
+	}
+
+	public TerminalViewId(String primary) {
+		this(primary, Optional.empty());
+	}
+
+	public TerminalViewId(String primary, String secondary) {
+		this(primary, Optional.ofNullable(secondary));
+	}
+
+	public TerminalViewId next() {
+		return new TerminalViewId(primary, nextSecondaryId(primary));
+	}
+
+	private static String nextSecondaryId(String primary) {
+		Map<String, IViewReference> terminalViews = new HashMap<>();
+		int maxNumber = 0;
+		for (IViewReference ref : viewReferences()) {
+			if (ref.getId().equals(primary)) {
+				if (ref.getSecondaryId() != null) {
+					terminalViews.put(ref.getSecondaryId(), ref);
+					int scondaryIdInt = Integer.parseInt(ref.getSecondaryId());
+					if (scondaryIdInt > maxNumber) {
+						maxNumber = scondaryIdInt;
+					}
+				} else {
+					// add the one with secondaryId == null with 0 by default
+					terminalViews.put(Integer.toString(0), ref);
+				}
+			}
+		}
+		if (terminalViews.size() == 0) {
+			return null;
+		}
+
+		int i = 0;
+		for (; i < maxNumber; i++) {
+			String secondaryIdStr = Integer.toString(i);
+			if (!terminalViews.keySet().contains(secondaryIdStr)) {
+				// found a free slot
+				if (i == 0) {
+					return null;
+				}
+				return Integer.toString(i);
+			}
+		}
+		// add a new one
+		return Integer.toString(i + 1);
+	}
+
+	private static List<IViewReference> viewReferences() {
+		if (!PlatformUI.isWorkbenchRunning()) {
+			return Collections.emptyList();
+		}
+		return Optional.of(PlatformUI.getWorkbench()).map(IWorkbench::getActiveWorkbenchWindow)
+				.map(IWorkbenchWindow::getActivePage).map(IWorkbenchPage::getViewReferences).map(Arrays::asList)
+				.orElseGet(Collections::emptyList);
+	}
+
+}