2 files changed, 108 insertions, 24 deletions

diff --git a/ext/bg/js/options.js b/ext/bg/js/options.js
index 02caa5a2..9e0e9cf0 100644
--- a/ext/bg/js/options.js
+++ b/ext/bg/js/options.js
@@ -17,11 +17,13 @@
 
 /* global
  * JsonSchemaValidator
+ * TemplatePatcher
  */
 
 class OptionsUtil {
     constructor() {
         this._schemaValidator = new JsonSchemaValidator();
+        this._templatePatcher = null;
         this._optionsSchema = null;
     }
 
@@ -381,32 +383,22 @@ class OptionsUtil {
 
     // Private
 
-    async _addFieldTemplatesToOptions(options, additionSourceUrl) {
-        let addition = null;
+    async _applyAnkiFieldTemplatesPatch(options, modificationsUrl) {
+        let patch = null;
         for (const {options: profileOptions} of options.profiles) {
             const fieldTemplates = profileOptions.anki.fieldTemplates;
-            if (fieldTemplates !== null) {
-                if (addition === null) {
-                    addition = await this._fetchAsset(additionSourceUrl);
+            if (fieldTemplates === null) { continue; }
+
+            if (patch === null) {
+                const content = await this._fetchAsset(modificationsUrl);
+                if (this._templatePatcher === null) {
+                    this._templatePatcher = new TemplatePatcher();
                 }
-                profileOptions.anki.fieldTemplates = this._addFieldTemplatesBeforeEnd(fieldTemplates, addition);
+                patch = this._templatePatcher.parsePatch(content);
             }
-        }
-    }
 
-    _addFieldTemplatesBeforeEnd(fieldTemplates, addition) {
-        const pattern = /[ \t]*\{\{~?>\s*\(\s*lookup\s*\.\s*"marker"\s*\)\s*~?\}\}/g;
-        const newline = '\n';
-        let replaced = false;
-        fieldTemplates = fieldTemplates.replace(pattern, (g0) => {
-            replaced = true;
-            return `${addition}${newline}${g0}`;
-        });
-        if (!replaced) {
-            fieldTemplates += newline;
-            fieldTemplates += addition;
+            profileOptions.anki.fieldTemplates = this._templatePatcher.applyPatch(fieldTemplates, patch);
         }
-        return fieldTemplates;
     }
 
     async _fetchAsset(url, json=false) {
@@ -495,7 +487,7 @@ class OptionsUtil {
     async _updateVersion3(options) {
         // Version 3 changes:
         //  Pitch accent Anki field templates added.
-        await this._addFieldTemplatesToOptions(options, '/bg/data/anki-field-templates-upgrade-v2.handlebars');
+        await this._applyAnkiFieldTemplatesPatch(options, '/bg/data/anki-field-templates-upgrade-v2.handlebars');
         return options;
     }
 
@@ -580,7 +572,7 @@ class OptionsUtil {
             });
             profileOptions.scanning.inputs = scanningInputs;
         }
-        await this._addFieldTemplatesToOptions(options, '/bg/data/anki-field-templates-upgrade-v4.handlebars');
+        await this._applyAnkiFieldTemplatesPatch(options, '/bg/data/anki-field-templates-upgrade-v4.handlebars');
         return options;
     }
 
@@ -600,7 +592,7 @@ class OptionsUtil {
         //  Added global option useSettingsV2.
         //  Added anki.checkForDuplicates.
         //  Added general.glossaryLayoutMode; removed general.compactGlossaries.
-        await this._addFieldTemplatesToOptions(options, '/bg/data/anki-field-templates-upgrade-v6.handlebars');
+        await this._applyAnkiFieldTemplatesPatch(options, '/bg/data/anki-field-templates-upgrade-v6.handlebars');
         options.global.showPopupPreview = false;
         options.global.useSettingsV2 = false;
         for (const profile of options.profiles) {
@@ -673,7 +665,7 @@ class OptionsUtil {
         //  Moved general.enableClipboardMonitor => clipboard.enableSearchPageMonitor. Forced value to false due to a bug which caused its value to not be read.
         //  Moved general.maximumClipboardSearchLength => clipboard.maximumSearchLength.
         //  Added clipboard.autoSearchContent.
-        await this._addFieldTemplatesToOptions(options, '/bg/data/anki-field-templates-upgrade-v8.handlebars');
+        await this._applyAnkiFieldTemplatesPatch(options, '/bg/data/anki-field-templates-upgrade-v8.handlebars');
         options.global.useSettingsV2 = true;
         for (const profile of options.profiles) {
             profile.options.translation.textReplacements = {
diff --git a/ext/bg/js/template-patcher.js b/ext/bg/js/template-patcher.js
new file mode 100644
index 00000000..57178957
--- /dev/null
+++ b/ext/bg/js/template-patcher.js
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2021  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+class TemplatePatcher {
+    constructor() {
+        this._diffPattern1 = /\n?\{\{<<<<<<<\}\}\n/g;
+        this._diffPattern2 = /\n\{\{=======\}\}\n/g;
+        this._diffPattern3 = /\n\{\{>>>>>>>\}\}\n*/g;
+        this._lookupMarkerPattern = /[ \t]*\{\{~?>\s*\(\s*lookup\s*\.\s*"marker"\s*\)\s*~?\}\}/g;
+    }
+
+    parsePatch(content) {
+        const diffPattern1 = this._diffPattern1;
+        const diffPattern2 = this._diffPattern2;
+        const diffPattern3 = this._diffPattern3;
+        const modifications = [];
+        let index = 0;
+
+        while (true) {
+            // Find modification boundaries
+            diffPattern1.lastIndex = index;
+            const m1 = diffPattern1.exec(content);
+            if (m1 === null) { break; }
+
+            diffPattern2.lastIndex = m1.index + m1[0].length;
+            const m2 = diffPattern2.exec(content);
+            if (m2 === null) { break; }
+
+            diffPattern3.lastIndex = m2.index + m2[0].length;
+            const m3 = diffPattern3.exec(content);
+            if (m3 === null) { break; }
+
+            // Construct
+            const current = content.substring(m1.index + m1[0].length, m2.index);
+            const replacement = content.substring(m2.index + m2[0].length, m3.index);
+
+            if (current.length > 0) {
+                modifications.push({current, replacement});
+            }
+
+            // Update
+            content = content.substring(0, m1.index) + content.substring(m3.index + m3[0].length);
+            index = m1.index;
+        }
+
+        return {addition: content, modifications};
+    }
+
+    applyPatch(template, patch) {
+        for (const {current, replacement} of patch.modifications) {
+            let fromIndex = 0;
+            while (true) {
+                const index = template.indexOf(current, fromIndex);
+                if (index < 0) { break; }
+                template = template.substring(0, index) + replacement + template.substring(index + current.length);
+                fromIndex = index + replacement.length;
+            }
+        }
+        template = this._addFieldTemplatesBeforeEnd(template, patch.addition);
+        return template;
+    }
+
+    // Private
+
+    _addFieldTemplatesBeforeEnd(template, addition) {
+        const newline = '\n';
+        let replaced = false;
+        template = template.replace(this._lookupMarkerPattern, (g0) => {
+            replaced = true;
+            return `${addition}${newline}${g0}`;
+        });
+        if (!replaced) {
+            template += newline;
+            template += addition;
+        }
+        return template;
+    }
+}