1 files changed, 55 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/timeline/Diff.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/timeline/Diff.java
new file mode 100644
index 00000000..cec6049e
--- /dev/null
+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/timeline/Diff.java
@@ -0,0 +1,55 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2019, Tamas Szabo, itemis AG, Gabor Bergmann, IncQuery Labs Ltd.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.matchers.util.timeline;
+
+import java.util.ArrayList;
+
+import tools.refinery.viatra.runtime.matchers.util.Signed;
+
+/**
+ * The description of a delta that specifies how a {@link Timeline} changes. It consists of {@link Signed} timestamps that
+ * depict the moments of insertions and deletions on the timeline.
+ * 
+ * @author Tamas Szabo
+ * @since 2.4
+ * @param <Timestamp>
+ *            the type representing the timestamps
+ */
+public class Diff<Timestamp extends Comparable<Timestamp>> extends ArrayList<Signed<Timestamp>> {
+
+    private static final long serialVersionUID = 3853460426655994160L;
+
+    public Diff() {
+
+    }
+
+    public void appendWithCancellation(Signed<Timestamp> item) {
+        if (this.isEmpty()) {
+            this.add(item);
+        } else {
+            final Signed<Timestamp> last = this.get(this.size() - 1);
+            final int lastMinusItem = last.getPayload().compareTo(item.getPayload());
+            if (lastMinusItem == 0) {
+                if (last.getDirection() != item.getDirection()) {
+                    // cancellation
+                    this.remove(this.size() - 1);
+                } else {
+                    throw new IllegalStateException(
+                            "Trying to insert or delete for the second time at the same timestamp! " + item);
+                }
+            } else if (lastMinusItem > 0) {
+                throw new IllegalStateException(
+                        "Trying to append a timestamp that is smaller than the last one! " + last + " " + item);
+            } else {
+                this.add(item);
+            }
+        }
+    }
+
+}
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