Template renderer class (#574)

* Convert handlebars.js to a class

* Move/rename function

* Update helper registration

* Rename helper functions

* Limit cache size

* Make render() async

* Rename and move

3 files changed, 205 insertions, 174 deletions

diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 0c7a0301..93ba620f 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -27,10 +27,10 @@
  * JsonSchema
  * Mecab
  * ObjectPropertyAccessor
+ * TemplateRenderer
  * Translator
  * conditionsTestValue
  * dictTermsSort
- * handlebarsRenderDynamic
  * jp
  * optionsLoad
  * optionsSave
@@ -63,6 +63,7 @@ class Backend {
             audioSystem: this.audioSystem,
             renderTemplate: this._renderTemplate.bind(this)
         });
+        this._templateRenderer = new TemplateRenderer();
 
         const url = (typeof window === 'object' && window !== null ? window.location.href : '');
         this.optionsContext = {depth: 0, url};
@@ -1230,7 +1231,7 @@ class Backend {
     }
 
     async _renderTemplate(template, data) {
-        return handlebarsRenderDynamic(template, data);
+        return await this._templateRenderer.render(template, data);
     }
 
     _getTemplates(options) {
diff --git a/ext/bg/js/handlebars.js b/ext/bg/js/handlebars.js
deleted file mode 100644
index 822174e2..00000000
--- a/ext/bg/js/handlebars.js
+++ /dev/null
@@ -1,172 +0,0 @@
-/*
- * Copyright (C) 2016-2020  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/>.
- */
-
-/* global
- * Handlebars
- * jp
- */
-
-function handlebarsEscape(text) {
-    return Handlebars.Utils.escapeExpression(text);
-}
-
-function handlebarsDumpObject(options) {
-    const dump = JSON.stringify(options.fn(this), null, 4);
-    return handlebarsEscape(dump);
-}
-
-function handlebarsFurigana(options) {
-    const definition = options.fn(this);
-    const segs = jp.distributeFurigana(definition.expression, definition.reading);
-
-    let result = '';
-    for (const seg of segs) {
-        if (seg.furigana) {
-            result += `<ruby>${seg.text}<rt>${seg.furigana}</rt></ruby>`;
-        } else {
-            result += seg.text;
-        }
-    }
-
-    return result;
-}
-
-function handlebarsFuriganaPlain(options) {
-    const definition = options.fn(this);
-    const segs = jp.distributeFurigana(definition.expression, definition.reading);
-
-    let result = '';
-    for (const seg of segs) {
-        if (seg.furigana) {
-            result += ` ${seg.text}[${seg.furigana}]`;
-        } else {
-            result += seg.text;
-        }
-    }
-
-    return result.trimLeft();
-}
-
-function handlebarsKanjiLinks(options) {
-    let result = '';
-    for (const c of options.fn(this)) {
-        if (jp.isCodePointKanji(c.codePointAt(0))) {
-            result += `<a href="#" class="kanji-link">${c}</a>`;
-        } else {
-            result += c;
-        }
-    }
-
-    return result;
-}
-
-function handlebarsMultiLine(options) {
-    return options.fn(this).split('\n').join('<br>');
-}
-
-function handlebarsSanitizeCssClass(options) {
-    return options.fn(this).replace(/[^_a-z0-9\u00a0-\uffff]/ig, '_');
-}
-
-function handlebarsRegexReplace(...args) {
-    // Usage:
-    // {{#regexReplace regex string [flags]}}content{{/regexReplace}}
-    // regex: regular expression string
-    // string: string to replace
-    // flags: optional flags for regular expression
-    //   e.g. "i" for case-insensitive, "g" for replace all
-    let value = args[args.length - 1].fn(this);
-    if (args.length >= 3) {
-        try {
-            const flags = args.length > 3 ? args[2] : 'g';
-            const regex = new RegExp(args[0], flags);
-            value = value.replace(regex, args[1]);
-        } catch (e) {
-            return `${e}`;
-        }
-    }
-    return value;
-}
-
-function handlebarsRegexMatch(...args) {
-    // Usage:
-    // {{#regexMatch regex [flags]}}content{{/regexMatch}}
-    // regex: regular expression string
-    // flags: optional flags for regular expression
-    //   e.g. "i" for case-insensitive, "g" for match all
-    let value = args[args.length - 1].fn(this);
-    if (args.length >= 2) {
-        try {
-            const flags = args.length > 2 ? args[1] : '';
-            const regex = new RegExp(args[0], flags);
-            const parts = [];
-            value.replace(regex, (g0) => parts.push(g0));
-            value = parts.join('');
-        } catch (e) {
-            return `${e}`;
-        }
-    }
-    return value;
-}
-
-function handlebarsMergeTags(object, isGroupMode, isMergeMode) {
-    const tagSources = [];
-    if (isGroupMode || isMergeMode) {
-        for (const definition of object.definitions) {
-            tagSources.push(definition.definitionTags);
-        }
-    } else {
-        tagSources.push(object.definitionTags);
-    }
-
-    const tags = new Set();
-    for (const tagSource of tagSources) {
-        for (const tag of tagSource) {
-            tags.add(tag.name);
-        }
-    }
-
-    return [...tags].join(', ');
-}
-
-function handlebarsRegisterHelpers() {
-    if (Handlebars.partials !== Handlebars.templates) {
-        Handlebars.partials = Handlebars.templates;
-        Handlebars.registerHelper('dumpObject', handlebarsDumpObject);
-        Handlebars.registerHelper('furigana', handlebarsFurigana);
-        Handlebars.registerHelper('furiganaPlain', handlebarsFuriganaPlain);
-        Handlebars.registerHelper('kanjiLinks', handlebarsKanjiLinks);
-        Handlebars.registerHelper('multiLine', handlebarsMultiLine);
-        Handlebars.registerHelper('sanitizeCssClass', handlebarsSanitizeCssClass);
-        Handlebars.registerHelper('regexReplace', handlebarsRegexReplace);
-        Handlebars.registerHelper('regexMatch', handlebarsRegexMatch);
-        Handlebars.registerHelper('mergeTags', handlebarsMergeTags);
-    }
-}
-
-function handlebarsRenderDynamic(template, data) {
-    handlebarsRegisterHelpers();
-    const cache = handlebarsRenderDynamic._cache;
-    let instance = cache.get(template);
-    if (typeof instance === 'undefined') {
-        instance = Handlebars.compile(template);
-        cache.set(template, instance);
-    }
-
-    return instance(data).trim();
-}
-handlebarsRenderDynamic._cache = new Map();
diff --git a/ext/bg/js/template-renderer.js b/ext/bg/js/template-renderer.js
new file mode 100644
index 00000000..f4b50c3d
--- /dev/null
+++ b/ext/bg/js/template-renderer.js
@@ -0,0 +1,202 @@
+/*
+ * Copyright (C) 2016-2020  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/>.
+ */
+
+/* global
+ * Handlebars
+ * jp
+ */
+
+class TemplateRenderer {
+    constructor() {
+        this._cache = new Map();
+        this._cacheMaxSize = 5;
+        this._helpersRegistered = false;
+    }
+
+    async render(template, data) {
+        if (!this._helpersRegistered) {
+            this._registerHelpers();
+            this._helpersRegistered = true;
+        }
+
+        const cache = this._cache;
+        let instance = cache.get(template);
+        if (typeof instance === 'undefined') {
+            this._updateCacheSize(this._cacheMaxSize - 1);
+            instance = Handlebars.compile(template);
+            cache.set(template, instance);
+        }
+
+        return instance(data).trim();
+    }
+
+    // Private
+
+    _updateCacheSize(maxSize) {
+        const cache = this._cache;
+        let removeCount = cache.size - maxSize;
+        if (removeCount <= 0) { return; }
+
+        for (const key of cache.keys()) {
+            cache.delete(key);
+            if (--removeCount <= 0) { break; }
+        }
+    }
+
+    _registerHelpers() {
+        Handlebars.partials = Handlebars.templates;
+
+        const helpers = [
+            ['dumpObject',       this._dumpObject.bind(this)],
+            ['furigana',         this._furigana.bind(this)],
+            ['furiganaPlain',    this._furiganaPlain.bind(this)],
+            ['kanjiLinks',       this._kanjiLinks.bind(this)],
+            ['multiLine',        this._multiLine.bind(this)],
+            ['sanitizeCssClass', this._sanitizeCssClass.bind(this)],
+            ['regexReplace',     this._regexReplace.bind(this)],
+            ['regexMatch',       this._regexMatch.bind(this)],
+            ['mergeTags',        this._mergeTags.bind(this)]
+        ];
+
+        for (const [name, helper] of helpers) {
+            Handlebars.registerHelper(name, helper);
+        }
+    }
+
+    _escape(text) {
+        return Handlebars.Utils.escapeExpression(text);
+    }
+
+    _dumpObject(options) {
+        const dump = JSON.stringify(options.fn(this), null, 4);
+        return this._escape(dump);
+    }
+
+    _furigana(options) {
+        const definition = options.fn(this);
+        const segs = jp.distributeFurigana(definition.expression, definition.reading);
+
+        let result = '';
+        for (const seg of segs) {
+            if (seg.furigana) {
+                result += `<ruby>${seg.text}<rt>${seg.furigana}</rt></ruby>`;
+            } else {
+                result += seg.text;
+            }
+        }
+
+        return result;
+    }
+
+    _furiganaPlain(options) {
+        const definition = options.fn(this);
+        const segs = jp.distributeFurigana(definition.expression, definition.reading);
+
+        let result = '';
+        for (const seg of segs) {
+            if (seg.furigana) {
+                result += ` ${seg.text}[${seg.furigana}]`;
+            } else {
+                result += seg.text;
+            }
+        }
+
+        return result.trimLeft();
+    }
+
+    _kanjiLinks(options) {
+        let result = '';
+        for (const c of options.fn(this)) {
+            if (jp.isCodePointKanji(c.codePointAt(0))) {
+                result += `<a href="#" class="kanji-link">${c}</a>`;
+            } else {
+                result += c;
+            }
+        }
+
+        return result;
+    }
+
+    _multiLine(options) {
+        return options.fn(this).split('\n').join('<br>');
+    }
+
+    _sanitizeCssClass(options) {
+        return options.fn(this).replace(/[^_a-z0-9\u00a0-\uffff]/ig, '_');
+    }
+
+    _regexReplace(...args) {
+        // Usage:
+        // {{#regexReplace regex string [flags]}}content{{/regexReplace}}
+        // regex: regular expression string
+        // string: string to replace
+        // flags: optional flags for regular expression
+        //   e.g. "i" for case-insensitive, "g" for replace all
+        let value = args[args.length - 1].fn(this);
+        if (args.length >= 3) {
+            try {
+                const flags = args.length > 3 ? args[2] : 'g';
+                const regex = new RegExp(args[0], flags);
+                value = value.replace(regex, args[1]);
+            } catch (e) {
+                return `${e}`;
+            }
+        }
+        return value;
+    }
+
+    _regexMatch(...args) {
+        // Usage:
+        // {{#regexMatch regex [flags]}}content{{/regexMatch}}
+        // regex: regular expression string
+        // flags: optional flags for regular expression
+        //   e.g. "i" for case-insensitive, "g" for match all
+        let value = args[args.length - 1].fn(this);
+        if (args.length >= 2) {
+            try {
+                const flags = args.length > 2 ? args[1] : '';
+                const regex = new RegExp(args[0], flags);
+                const parts = [];
+                value.replace(regex, (g0) => parts.push(g0));
+                value = parts.join('');
+            } catch (e) {
+                return `${e}`;
+            }
+        }
+        return value;
+    }
+
+    _mergeTags(object, isGroupMode, isMergeMode) {
+        const tagSources = [];
+        if (isGroupMode || isMergeMode) {
+            for (const definition of object.definitions) {
+                tagSources.push(definition.definitionTags);
+            }
+        } else {
+            tagSources.push(object.definitionTags);
+        }
+
+        const tags = new Set();
+        for (const tagSource of tagSources) {
+            for (const tag of tagSource) {
+                tags.add(tag.name);
+            }
+        }
+
+        return [...tags].join(', ');
+    }
+}