From eb2b2d4d7a57095b17f17eb6cfc084cbaa37ea90 Mon Sep 17 00:00:00 2001
From: Joe Wreschnig <joe.wreschnig@gmail.com>
Date: Mon, 19 May 2014 10:22:38 +0200
Subject: [PATCH] Split diffLerp into basic and astral helpers for type
 uniformity.

---
 string-lerp.js | 49 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 19 deletions(-)

diff --git a/string-lerp.js b/string-lerp.js
index 6c240e4..114bebd 100644
--- a/string-lerp.js
+++ b/string-lerp.js
@@ -120,16 +120,7 @@
 
     var GLYPH = /([\0-\u02FF\u0370-\u1DBF\u1E00-\u20CF\u2100-\uD7FF\uDC00-\uFE1F\uFE30-\uFFFF]|[\uD800-\uDBFF][\uDC00-\uDFFF]|[\uD800-\uDBFF])([\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uFE20-\uFE2F]*)/g;
 
-    function diffLerp(source, target, amount ) {
-        /** Interpolate between two strings using edit operations
-
-            This interpolation algorithm applys a partial edit of one
-            string into the other. This produces nice looking results,
-            but can take a significant amount of time and memory to
-            compute the edits. It is not recommended for strings
-            longer than a few hundred characters.
-        */
-
+    function diffLerpAstral(source, target, amount) {
         // If given strings with astral codepoints or combining
         // characters, split them into arrays of "glyphs" first,
         // do the edit on the list of "glyphs", and rejoin them.
@@ -137,21 +128,41 @@
         // This split is not perfect for all languages, but at least
         // it won't create invalid surrogate pairs or orphaned
         // combining characters.
-        //
-        // TODO: The way this is called is a hack.
-        if (source.match && (source.match(MULTI) || target.match(MULTI))) {
-            var sourceGlyphs = source.match(GLYPH) || [];
-            var targetGlyphs = target.match(GLYPH) || [];
-            return diffLerp(sourceGlyphs, targetGlyphs, amount).join("");
-        }
-
+        var sourceGlyphs = source.match(GLYPH) || [];
+        var targetGlyphs = target.match(GLYPH) || [];
+        var edits = diff(targetGlyphs, sourceGlyphs, 2, 2, 3);
         // The edit path works from the string end, forwards, because
         // that's how Levenshtein edits work. To match LTR reading
         // direction (and the behavior of fastLerp), swap the strings
         // and invert the parameter when editing.
+        var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
+        return patchArray(partial, targetGlyphs).join("");
+    }
+
+    function diffLerpBasic(source, target, amount) {
         var edits = diff(target, source, 2, 2, 3);
+        // The edit path works from the string end, forwards, because
+        // that's how Levenshtein edits work. To match LTR reading
+        // direction (and the behavior of fastLerp), swap the strings
+        // and invert the parameter when editing.
         var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
-        return patch(partial, target);
+        return patchString(partial, target);
+    }
+
+    function diffLerp(source, target, amount) {
+        /** Interpolate between two strings using edit operations
+
+            This interpolation algorithm applys a partial edit of one
+            string into the other. This produces nice looking results,
+            but can take a significant amount of time and memory to
+            compute the edits. It is not recommended for strings
+            longer than a few hundred characters.
+        */
+
+        if (source.match(MULTI) || target.match(MULTI))
+            return diffLerpAstral(source, target, amount);
+        else
+            return diffLerpBasic(source, target, amount);
     }
 
     var NUMBERS = /(-?\d{1,20}(?:\.\d{1,20})?)/g;
-- 
2.20.1