From d80dd94e906529a2e9ea0d2e720bf262d111a8dd Mon Sep 17 00:00:00 2001
From: kske <kai@kske.dev>
Date: Sun, 12 Dec 2021 05:49:47 +0100
Subject: [PATCH] Allow retrieving the last change from a change manager

---
 .../dev/kske/undoredo/core/ChangeManager.java |  8 ++++++-
 .../undoredo/core/UnlimitedChangeManager.java |  5 ++++
 .../kske/undoredo/core/ChangeManagerTest.java | 23 +++++++++++++++----
 3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/core/src/main/java/dev/kske/undoredo/core/ChangeManager.java b/core/src/main/java/dev/kske/undoredo/core/ChangeManager.java
index 7b887e7..be9424b 100644
--- a/core/src/main/java/dev/kske/undoredo/core/ChangeManager.java
+++ b/core/src/main/java/dev/kske/undoredo/core/ChangeManager.java
@@ -1,6 +1,6 @@
 package dev.kske.undoredo.core;
 
-import java.util.List;
+import java.util.*;
 
 /**
  * A change manager keeps track of subsequent changes and allows un- and redoing them. A specific
@@ -22,6 +22,12 @@ public interface ChangeManager<C extends Change> {
 	 */
 	void addChange(C change);
 
+	/**
+	 * @return the change that was applied last
+	 * @since 0.0.1
+	 */
+	Optional<Change> getLastChange();
+
 	/**
 	 * Undoes the current change.
 	 *
diff --git a/core/src/main/java/dev/kske/undoredo/core/UnlimitedChangeManager.java b/core/src/main/java/dev/kske/undoredo/core/UnlimitedChangeManager.java
index 8a0ff35..b353a7d 100644
--- a/core/src/main/java/dev/kske/undoredo/core/UnlimitedChangeManager.java
+++ b/core/src/main/java/dev/kske/undoredo/core/UnlimitedChangeManager.java
@@ -22,6 +22,11 @@ public final class UnlimitedChangeManager<C extends Change> implements ChangeMan
 		++index;
 	}
 
+	@Override
+	public Optional<Change> getLastChange() {
+		return index == -1 ? Optional.empty() : Optional.of(changes.get(index));
+	}
+
 	@Override
 	public boolean undo() {
 		if (isUndoAvailable()) {
diff --git a/core/src/test/java/dev/kske/undoredo/core/ChangeManagerTest.java b/core/src/test/java/dev/kske/undoredo/core/ChangeManagerTest.java
index 4643970..2508b56 100644
--- a/core/src/test/java/dev/kske/undoredo/core/ChangeManagerTest.java
+++ b/core/src/test/java/dev/kske/undoredo/core/ChangeManagerTest.java
@@ -35,12 +35,25 @@ class ChangeManagerTest {
 	}
 
 	/**
-	 * Tests the consistency of the change list.
+	 * Tests retrieving the last change.
 	 *
 	 * @since 0.0.1
 	 */
 	@Test
 	@Order(2)
+	void testLastChange() {
+		assertTrue(manager.getLastChange().isEmpty());
+		manager.addChange(change);
+		assertEquals(change, manager.getLastChange().get());
+	}
+
+	/**
+	 * Tests the consistency of the change list.
+	 *
+	 * @since 0.0.1
+	 */
+	@Test
+	@Order(3)
 	void testGetChanges() {
 		assertTrue(manager.getChanges().isEmpty());
 		manager.addChange(change);
@@ -54,7 +67,7 @@ class ChangeManagerTest {
 	 * @since 0.0.1
 	 */
 	@Test
-	@Order(2)
+	@Order(4)
 	void testUndo() {
 		assertFalse(manager.isUndoAvailable());
 		assertFalse(manager.undo());
@@ -63,6 +76,7 @@ class ChangeManagerTest {
 		assertTrue(manager.undo());
 		assertFalse(manager.isUndoAvailable());
 		assertFalse(manager.undo());
+		assertTrue(manager.getLastChange().isEmpty());
 	}
 
 	/**
@@ -71,7 +85,7 @@ class ChangeManagerTest {
 	 * @since 0.0.1
 	 */
 	@Test
-	@Order(4)
+	@Order(5)
 	void testRedo() {
 		assertFalse(manager.isRedoAvailable());
 		assertFalse(manager.redo());
@@ -83,6 +97,7 @@ class ChangeManagerTest {
 		assertTrue(manager.redo());
 		assertFalse(manager.isRedoAvailable());
 		assertFalse(manager.redo());
+		assertEquals(change, manager.getLastChange().get());
 	}
 
 	/**
@@ -91,7 +106,7 @@ class ChangeManagerTest {
 	 * @since 0.0.1
 	 */
 	@Test
-	@Order(5)
+	@Order(6)
 	void testMark() {
 		assertTrue(manager.isAtMarkedIndex());
 		manager.addChange(change);