From d117052ca47948cf1c92c33267f2dbe0454ab02c Mon Sep 17 00:00:00 2001
From: kske <kai@kske.dev>
Date: Fri, 11 Feb 2022 09:48:41 +0100
Subject: [PATCH] Aggregate Change

The aggregate change combines multiple changes into one while
implementing the Change interface.
---
 .../kske/undoredo/core/AggregateChange.java   | 47 +++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 core/src/main/java/dev/kske/undoredo/core/AggregateChange.java

diff --git a/core/src/main/java/dev/kske/undoredo/core/AggregateChange.java b/core/src/main/java/dev/kske/undoredo/core/AggregateChange.java
new file mode 100644
index 0000000..06ca427
--- /dev/null
+++ b/core/src/main/java/dev/kske/undoredo/core/AggregateChange.java
@@ -0,0 +1,47 @@
+package dev.kske.undoredo.core;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * @author Kai S. K. Engelbart
+ * @since 0.2.0
+ */
+public final class AggregateChange<C extends Change> implements Change {
+
+	private final List<C> changes = new ArrayList<>();
+
+	@SafeVarargs
+	public AggregateChange(C... changes) {
+		this(Arrays.asList(changes));
+	}
+
+	public AggregateChange(Collection<C> changes) {
+		changes.addAll(changes);
+	}
+
+	@Override
+	public void apply() {
+		changes.forEach(Change::apply);
+	}
+
+	@Override
+	public Change invert() {
+		List<Change> invertedChanges =
+			changes
+				.parallelStream()
+				.map(Change::invert)
+				.collect(Collectors.toList());
+		Collections.reverse(invertedChanges);
+		return new AggregateChange<>(invertedChanges);
+	}
+
+	@Override
+	public boolean isIdentity() {
+		return changes.stream().allMatch(Change::isIdentity);
+	}
+
+	public List<C> changes() {
+		return Collections.unmodifiableList(changes);
+	}
+}