refactor: Align EJS engine with Handlebars.

src/util/templates/EjsTemplateEngine.ts

@@ -0,0 +1,28 @@
+/* eslint-disable tsdoc/syntax */
+// tsdoc/syntax cannot handle `@range`
+import type { TemplateFunction } from 'ejs';
+import { compile, render } from 'ejs';
+import type { TemplateEngine, Template } from './TemplateEngine';
+import { readTemplate } from './TemplateEngine';
+import Dict = NodeJS.Dict;
+
+/**
+ * Fills in EJS templates.
+ */
+export class EjsTemplateEngine<T extends Dict<any> = Dict<any>> implements TemplateEngine<T> {
+  private readonly applyTemplate: Promise<TemplateFunction>;
+
+  /**
+   * @param template - The default template @range {json}
+   */
+  public constructor(template?: Template) {
+    this.applyTemplate = readTemplate(template)
+      .then((templateString: string): TemplateFunction => compile(templateString));
+  }
+
+  public async render(contents: T): Promise<string>;
+  public async render<TCustom = T>(contents: TCustom, template: Template): Promise<string>;
+  public async render<TCustom = T>(contents: TCustom, template?: Template): Promise<string> {
+    return template ? render(await readTemplate(template), contents) : (await this.applyTemplate)(contents);
+  }
+}

src/util/templates/HandlebarsTemplateEngine.ts

@@ -1,5 +1,5 @@
 /* eslint-disable tsdoc/syntax */
-// tsdoc/syntax can't handle {json} parameter
+// tsdoc/syntax cannot handle `@range`
 import type { TemplateDelegate } from 'handlebars';
 import { compile } from 'handlebars';
 import type { TemplateEngine, Template } from './TemplateEngine';

src/util/templates/TemplateEngine.ts

@@ -2,7 +2,9 @@ import { promises as fsPromises } from 'fs';
 import { joinFilePath, resolveAssetPath } from '../PathUtil';
 import Dict = NodeJS.Dict;
 
-export type Template = TemplateString | TemplatePath;
+export type Template = TemplateFileName | TemplateString | TemplatePath;
+
+export type TemplateFileName = string;
 
 export interface TemplateString {
   // String contents of the template
@@ -38,6 +40,10 @@ export interface TemplateEngine<T extends Dict<any> = Dict<any>> {
  * Reads the template and returns it as a string.
  */
 export async function readTemplate(template: Template = { templateString: '' }): Promise<string> {
+  // The template has been passed as a filename
+  if (typeof template === 'string') {
+    return readTemplate({ templateFile: template });
+  }
   // The template has already been given as a string
   if ('templateString' in template) {
     return template.templateString;