From 976505222683234b11505191394f9e046c7cfbdd Mon Sep 17 00:00:00 2001
From: Tobias Warneke <t.warneke@gmx.net>
Date: Thu, 8 Jul 2021 22:42:53 +0200
Subject: [PATCH] first implementation of meyers diff with linear space

---
 .../com/github/difflib/algorithm/Change.java    |  8 ++++++++
 .../myers/MeyersDiffWithLinearSpace.java        | 17 ++++++++++++++---
 .../WithMeyersDiffWithLinearSpacePatchTest.java |  2 +-
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/java-diff-utils/src/main/java/com/github/difflib/algorithm/Change.java b/java-diff-utils/src/main/java/com/github/difflib/algorithm/Change.java
index 57fbb78..9b6f1df 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/algorithm/Change.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/algorithm/Change.java
@@ -36,4 +36,12 @@ public class Change {
         this.startRevised = startRevised;
         this.endRevised = endRevised;
     }
+    
+    public Change withEndOriginal(int endOriginal) {
+        return new Change(deltaType, startOriginal, endOriginal, startRevised, endRevised);
+    }
+    
+    public Change withEndRevised(int endRevised) {
+        return new Change(deltaType, startOriginal, endOriginal, startRevised, endRevised);
+    }
 }
diff --git a/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MeyersDiffWithLinearSpace.java b/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MeyersDiffWithLinearSpace.java
index 1dcae64..98a49dc 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MeyersDiffWithLinearSpace.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MeyersDiffWithLinearSpace.java
@@ -65,11 +65,22 @@ public class MeyersDiffWithLinearSpace<T> implements DiffAlgorithmI<T> {
                     //TODO: compress these commands.
                     if (end1 - start1 > end2 - start2) {
                         //script.append(new DeleteCommand<>(left.charAt(i)));
-                        data.script.add(new Change(DeltaType.DELETE, i, i + 1, j, j));
+                        if (data.script.isEmpty()
+                                || data.script.get(data.script.size() - 1).endOriginal != i
+                                || data.script.get(data.script.size() - 1).deltaType != DeltaType.DELETE) {
+                            data.script.add(new Change(DeltaType.DELETE, i, i + 1, j, j));
+                        } else {
+                            data.script.set(data.script.size() - 1, data.script.get(data.script.size() - 1).withEndOriginal(i + 1));
+                        }
                         ++i;
                     } else {
-                        //script.append(new InsertCommand<>(right.charAt(j)));
-                        data.script.add(new Change(DeltaType.INSERT, i, i, j, j + 1));
+                        if (data.script.isEmpty()
+                                || data.script.get(data.script.size() - 1).endRevised != j
+                                || data.script.get(data.script.size() - 1).deltaType != DeltaType.INSERT) {
+                            data.script.add(new Change(DeltaType.INSERT, i, i, j, j + 1));
+                        } else {
+                            data.script.set(data.script.size() - 1, data.script.get(data.script.size() - 1).withEndRevised(j + 1));
+                        }
                         ++j;
                     }
                 }
diff --git a/java-diff-utils/src/test/java/com/github/difflib/algorithm/myers/WithMeyersDiffWithLinearSpacePatchTest.java b/java-diff-utils/src/test/java/com/github/difflib/algorithm/myers/WithMeyersDiffWithLinearSpacePatchTest.java
index 2b06001..d2a02ca 100644
--- a/java-diff-utils/src/test/java/com/github/difflib/algorithm/myers/WithMeyersDiffWithLinearSpacePatchTest.java
+++ b/java-diff-utils/src/test/java/com/github/difflib/algorithm/myers/WithMeyersDiffWithLinearSpacePatchTest.java
@@ -93,7 +93,7 @@ public class WithMeyersDiffWithLinearSpacePatchTest {
 
         try {
             List<String> data = DiffUtils.patch(changeTest_from, patch);
-            assertEquals(9, data.size());
+            assertEquals(11, data.size());
             
             assertEquals(Arrays.asList("aaa", "<<<<<< HEAD", "bbb", "CDC", "======", "bbb", "ccc", ">>>>>>> PATCH", "ddd"), data);