search resolution option (#436)

* add search resolution setting

* move finding next substring to method

* use regex literal

* fix comments

* fix comments

* add options update function

* update test

3 files changed, 37 insertions, 4 deletions

diff --git a/ext/js/background/backend.js b/ext/js/background/backend.js
index ae78a97b..68d4e0c8 100644
--- a/ext/js/background/backend.js
+++ b/ext/js/background/backend.js
@@ -2417,7 +2417,8 @@ export class Backend {
                 convertHiraganaToKatakana,
                 convertKatakanaToHiragana,
                 collapseEmphaticSequences,
-                textReplacements: textReplacementsOptions
+                textReplacements: textReplacementsOptions,
+                searchResolution
             }
         } = options;
         const textReplacements = this._getTranslatorTextReplacements(textReplacementsOptions);
@@ -2444,6 +2445,7 @@ export class Backend {
             convertHiraganaToKatakana,
             convertKatakanaToHiragana,
             collapseEmphaticSequences,
+            searchResolution,
             textReplacements,
             enabledDictionaryMap,
             excludeDictionaryDefinitions
diff --git a/ext/js/data/options-util.js b/ext/js/data/options-util.js
index c219bed3..eb9af9b6 100644
--- a/ext/js/data/options-util.js
+++ b/ext/js/data/options-util.js
@@ -555,7 +555,8 @@ export class OptionsUtil {
             {async: false, update: this._updateVersion18.bind(this)},
             {async: false, update: this._updateVersion19.bind(this)},
             {async: false, update: this._updateVersion20.bind(this)},
-            {async: true,  update: this._updateVersion21.bind(this)}
+            {async: true,  update: this._updateVersion21.bind(this)},
+            {async: false, update: this._updateVersion22.bind(this)}
         ];
         /* eslint-enable no-multi-spaces */
         if (typeof targetVersion === 'number' && targetVersion < result.length) {
@@ -1174,6 +1175,18 @@ export class OptionsUtil {
     }
 
     /**
+     * @type {import('options-util').ModernUpdateFunctionAsync}
+     */
+    _updateVersion22(options) {
+        //  Added translation.searchResolution
+        for (const {options: profileOptions} of options.profiles) {
+            profileOptions.translation.searchResolution = 'letter';
+        }
+
+        return options;
+    }
+
+    /**
      * @param {string} url
      * @returns {Promise<chrome.tabs.Tab>}
      */
diff --git a/ext/js/language/translator.js b/ext/js/language/translator.js
index 733955c2..36ed8b43 100644
--- a/ext/js/language/translator.js
+++ b/ext/js/language/translator.js
@@ -329,8 +329,12 @@ export class Translator {
                 text2 = jp.collapseEmphaticSequences(text2, collapseEmphaticFull, sourceMap);
             }
 
-            for (let i = text2.length; i > 0; --i) {
-                const source = text2.substring(0, i);
+            for (
+                let source = text2, i = text2.length;
+                i > 0;
+                i = this._getNextSubstringLength(options.searchResolution, i, source)
+            ) {
+                source = text2.substring(0, i);
                 if (used.has(source)) { break; }
                 used.add(source);
                 const rawSource = sourceMap.source.substring(0, sourceMap.getSourceLength(i));
@@ -343,6 +347,20 @@ export class Translator {
     }
 
     /**
+     * @param {string} searchResolution
+     * @param {number} currentLength
+     * @param {string} source
+     * @returns {number}
+     */
+    _getNextSubstringLength(searchResolution, currentLength, source) {
+        if (searchResolution === 'word') {
+            return source.search(/[^\p{Letter}][\p{Letter}\p{Number}]*$/u);
+        } else {
+            return currentLength - 1;
+        }
+    }
+
+    /**
      * @param {string} text
      * @param {TextSourceMap} sourceMap
      * @param {import('translation').FindTermsTextReplacement[]} replacements