Fix furigana distribution when source/expression kana differs (#1532)

* Fix furigana distribution when source/expression kana differs

* Add an additional test

2 files changed, 16 insertions, 1 deletions

diff --git a/ext/js/language/japanese-util.js b/ext/js/language/japanese-util.js
index aa1e3f00..cade393b 100644
--- a/ext/js/language/japanese-util.js
+++ b/ext/js/language/japanese-util.js
@@ -475,13 +475,15 @@ const JapaneseUtil = (() => {
 
             // Check if source is derived from the reading instead of the expression
             const readingStemLength = this._getStemLength(readingNormalized, sourceNormalized);
-            if (readingStemLength > stemLength) {
+            if (readingStemLength > 0 && readingStemLength >= stemLength) {
                 mainText = reading;
                 stemLength = readingStemLength;
+                reading = `${source.substring(0, stemLength)}${reading.substring(stemLength)}`;
             }
 
             const segments = [];
             if (stemLength > 0) {
+                mainText = `${source.substring(0, stemLength)}${mainText.substring(stemLength)}`;
                 const segments2 = this.distributeFurigana(mainText, reading);
                 let consumed = 0;
                 for (const segment of segments2) {
diff --git a/test/test-japanese.js b/test/test-japanese.js
index 8e8078d1..978f4b9c 100644
--- a/test/test-japanese.js
+++ b/test/test-japanese.js
@@ -750,6 +750,19 @@ function testDistributeFuriganaInflected() {
             [
                 {text: 'おこなわなかった', furigana: ''}
             ]
+        ],
+        [
+            ['いい', 'いい', 'イイ'],
+            [
+                {text: 'イイ', furigana: ''}
+            ]
+        ],
+        [
+            ['否か', 'いなか', '否カ'],
+            [
+                {text: '否', furigana: 'いな'},
+                {text: 'カ', furigana: 'か'}
+            ]
         ]
     ];