From cc97d4ba41169a3a365922b05a30fdab88dbe688 Mon Sep 17 00:00:00 2001
From: Maxime Coste <frrrwww@gmail.com>
Date: Thu, 14 May 2015 13:57:03 +0100
Subject: [PATCH] Fix bugs in diff implementation

---
 src/diff.hh       |  5 +++++
 src/unit_tests.cc | 25 ++++++++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/diff.hh b/src/diff.hh
index bc9717083..e68ec10c4 100644
--- a/src/diff.hh
+++ b/src/diff.hh
@@ -14,6 +14,8 @@ struct MirroredArray : public ArrayView<T>
         : ArrayView<T>(data), size(size)
     {
         kak_assert(2 * size + 1 <= data.size());
+        for (int i = -size; i <= size; ++i)
+            (*this)[i] = 0;
     }
 
     T& operator[](int n) { return ArrayView<T>::operator[](n + size); }
@@ -118,6 +120,7 @@ void find_diff_rec(Iterator a, int offA, int lenA,
     if (lenA > 0 and lenB > 0)
     {
         auto middle_snake = find_middle_snake(a + offA, lenA, b + offB, lenB, data1, data2, eq);
+        kak_assert(middle_snake.u <= lenA and middle_snake.v <= lenB);
         if (middle_snake.d > 1)
         {
             find_diff_rec(a, offA, middle_snake.x,
@@ -145,6 +148,8 @@ void find_diff_rec(Iterator a, int offA, int lenA,
             else
                 diffs.push_back({Diff::Remove, 1, 0});
         }
+        else if (int len = middle_snake.u - middle_snake.x)
+            diffs.push_back({Diff::Keep, len, 0});
     }
     else if (lenB > 0)
         diffs.push_back({Diff::Add, lenB, offB});
diff --git a/src/unit_tests.cc b/src/unit_tests.cc
index e054ee411..29fd90f6c 100644
--- a/src/unit_tests.cc
+++ b/src/unit_tests.cc
@@ -242,10 +242,29 @@ void test_line_modifications()
 
 void test_diff()
 {
-    StringView s1 = "mais que fais la police";
-    StringView s2 = "mais ou va la police";
+    auto eq = [](const Diff& lhs, const Diff& rhs) {
+        return lhs.mode == rhs.mode and lhs.len == rhs.len and lhs.posB == rhs.posB;
+    };
 
-    auto diff = find_diff(s1.begin(), (int)s1.length(), s2.begin(), (int)s2.length());
+    {
+        StringView s1 = "mais que fais la police";
+        StringView s2 = "mais ou va la police";
+
+        auto diff = find_diff(s1.begin(), (int)s1.length(), s2.begin(), (int)s2.length());
+        kak_assert(diff.size() == 10);
+    }
+
+    {
+        StringView s1 = "a?";
+        StringView s2 = "!";
+
+        auto diff = find_diff(s1.begin(), (int)s1.length(), s2.begin(), (int)s2.length());
+
+        kak_assert(diff.size() == 3 and
+                   eq(diff[0], {Diff::Remove, 1, 0}) and
+                   eq(diff[1], {Diff::Add, 1, 0}) and
+                   eq(diff[2], {Diff::Remove, 1, 0}));
+    }
 }
 
 void run_unit_tests()