1 files changed, 88 insertions, 0 deletions
diff --git a/src/modification.hh b/src/modification.hh
new file mode 100644
index 00000000..103a7520
--- /dev/null
+++ b/src/modification.hh
@@ -0,0 +1,88 @@
+#ifndef modification_hh_INCLUDED
+#define modification_hh_INCLUDED
+
+#include "coord.hh"
+#include "utils.hh"
+#include "buffer.hh"
+
+namespace Kakoune
+{
+
+struct Modification
+{
+    ByteCoord old_coord;
+    ByteCoord new_coord;
+    ByteCoord num_removed;
+    ByteCoord num_added;
+
+    ByteCoord added_end() const
+    {
+        if (num_added.line)
+            return { new_coord.line + num_added.line, num_added.column };
+        else
+            return { new_coord.line, new_coord.column + num_added.column };
+    }
+
+    ByteCoord get_old_coord(ByteCoord coord) const
+    {
+        if (coord.line == new_coord.line)
+        {
+            if (num_added.line == 0)
+                coord.column -= new_coord.column - old_coord.column + num_added.column - num_removed.column;
+            else
+                coord.column -= num_added.column - num_removed.column;
+        }
+        coord.line -= new_coord.line - old_coord.line + num_added.line - num_removed.line;
+        return coord;
+    }
+
+    ByteCoord get_new_coord(ByteCoord coord, bool& deleted) const
+    {
+        deleted = false;
+        if (coord < old_coord)
+            return coord;
+
+        // apply remove
+        if (coord.line < old_coord.line + num_removed.line or
+            (coord.line == old_coord.line + num_removed.line and
+             coord.column < old_coord.column + num_removed.column))
+        {
+            deleted = true;
+            coord = old_coord;
+        }
+        else if (coord.line == old_coord.line + num_removed.line)
+        {
+            coord.line = old_coord.line;
+            coord.column -= num_removed.column;
+        }
+
+        // apply move
+        coord.line += new_coord.line - old_coord.line;
+        coord.column += new_coord.column - old_coord.column;
+
+        // apply add
+        if (coord.line == new_coord.line)
+        {
+            if (num_added.line == 0)
+                coord.column += num_added.column;
+            else
+                coord.column += num_added.column - new_coord.column;
+        }
+        coord.line += num_added.line;
+
+        return coord;
+    }
+
+    ByteCoord get_new_coord(ByteCoord coord) const
+    {
+        bool dummy;
+        return get_new_coord(coord, dummy);
+    }
+};
+
+std::vector<Modification> compute_modifications(const Buffer& buffer, size_t timestamp);
+std::vector<Modification> compute_modifications(memoryview<Buffer::Change> changes);
+
+}
+
+#endif // modification_hh_INCLUDED