Add a method to register custom message providers

src/__tests__/I18nProvider.test.ts

@@ -44,4 +44,17 @@ describe('I18nProvider', () => {
             expect(provider.__(key, replacements)).toBe(expected);
         }
     );
+
+    describe('Dynamic message providers', () => {
+        it('should register and use a message provider of an existing key', () => {
+            provider['localeData'] = { 'game.load': 'default message' };
+            const message = 'Another game loading message';
+            provider.addProvider('game.load', () => message);
+            expect(provider.__('game.load')).toBe(message);
+        });
+
+        it('should throw an error if the key does not exist', () => {
+            expect(() => provider.addProvider('unknown_key', () => 'hello world')).toThrow();
+        });
+    });
 });

src/__tests__/index.test.ts

@@ -100,4 +100,11 @@ describe('TicTacToe', () => {
         expect(eventHandler.registerListener).toHaveBeenCalledTimes(1);
         expect(eventHandler.registerListener).toHaveBeenCalledWith('tie', listener);
     });
+
+    test('should call addProvider from localize', () => {
+        const messageProvider = () => 'my message';
+        tictactoe.addMessageProvider('game.load', messageProvider);
+        expect(localize.addProvider).toHaveBeenCalledTimes(1);
+        expect(localize.addProvider).toHaveBeenCalledWith('game.load', messageProvider);
+    });
 });

src/i18n/I18nProvider.ts

@@ -1,6 +1,16 @@
 import fs from 'fs';
 import path from 'path';
 
+/**
+ * Represents a collection of replacements when translating a text.
+ */
+export type Replacements = { [key: string]: string | number | string[] };
+
+/**
+ * Represents a message provider added programmatically.
+ */
+export type MessageProvider = () => string;
+
 /**
  * Default implementation to translate messages.
  * Can load messages from integrated or external locale files.
@@ -20,10 +30,17 @@ export class I18nProvider {
 
     /**
      * Collection with paths of integrated locales in the module
+     * @private
+     */
+    private readonly availableLocales: Map<string, string>;
+    /**
+     * Collection of message providers added programmatically
+     * @private
      */
-    private availableLocales: Map<string, string>;
+    private readonly messageProviders: Map<string, MessageProvider>;
     /**
      * Collection of all locale messages loaded from a language file
+     * @private
      */
     private localeData?: Record<string, string>;
 
@@ -36,14 +53,15 @@ export class I18nProvider {
                 .readdirSync(localesPath)
                 .map(file => [path.basename(file, '.json'), path.resolve(localesPath, file)])
         );
+        this.messageProviders = new Map<string, MessageProvider>();
     }
 
     /**
      * Loads module messages from an internal or external file.
      *
      * @param locale locale key or language file to load
      */
-    loadFromLocale(locale?: string): void {
+    public loadFromLocale(locale?: string): void {
         let filepath = this.availableLocales.get(locale ?? I18nProvider.DEFAULT_LOCALE);
         let loaded = filepath !== undefined;
 
@@ -79,9 +97,9 @@ export class I18nProvider {
      * @param replacements collection of replacement to operate on the message
      * @returns translated message using replacements
      */
-    __(key: string, replacements?: Replacements): string {
+    public __(key: string, replacements?: Replacements): string {
         if (this.localeData && this.localeData[key]) {
-            let message = this.localeData[key];
+            let message = this.messageProviders.get(key)?.() ?? this.localeData[key];
 
             if (replacements) {
                 Object.entries(replacements).forEach(replacement => {
@@ -95,6 +113,20 @@ export class I18nProvider {
         }
     }
 
+    /**
+     * Adds a message provider for a given key.
+     * Key must already exist in the cache, otherwise an error will be thrown.
+     *
+     * @param key key corresponding to the added provider
+     * @param provider function that dynamically supplies the message
+     */
+    public addProvider(key: string, provider: MessageProvider): void {
+        if (this.localeData?.[key] == null) {
+            throw new Error(`Cannot register message provider because key "${key}" does not exist`);
+        }
+        this.messageProviders.set(key, provider);
+    }
+
     private static flatten<T extends Record<string, any>>(
         object: T,
         objectPath: string | null = null,
@@ -108,10 +140,3 @@ export class I18nProvider {
         }, {} as T);
     }
 }
-
-/**
- * Allows to define some replacements when translating a text.
- */
-export interface Replacements {
-    [key: string]: string | number | string[];
-}

src/i18n/localize.ts

@@ -1,8 +1,10 @@
-import { I18nProvider, Replacements } from '@i18n/I18nProvider';
+import { I18nProvider, MessageProvider, Replacements } from '@i18n/I18nProvider';
 
 const provider = new I18nProvider();
 
 const loadFromLocale = (locale?: string): void => provider.loadFromLocale(locale);
 const __ = (id: string, replacements?: Replacements): string => provider.__(id, replacements);
+const addProvider = (id: string, messageProvider: MessageProvider): void =>
+    provider.addProvider(id, messageProvider);
 
-export default { loadFromLocale, __ };
+export default { loadFromLocale, __, addProvider };

src/index.ts

@@ -3,6 +3,7 @@ import TicTacToeBot from '@bot/TicTacToeBot';
 import Config from '@config/Config';
 import localize from '@i18n/localize';
 import { Client, CommandInteraction, Intents, Message } from 'discord.js';
+import { MessageProvider } from '@i18n/I18nProvider';
 
 /**
  * Controls all interactions between modules of the bot.
@@ -103,6 +104,17 @@ class TicTacToe {
     ): void {
         this.eventHandler.registerListener(eventName, listener);
     }
+
+    /**
+     * Adds a message provider for a given key.
+     * Key must exist, otherwise an error will be thrown.
+     *
+     * @param key key corresponding to the added provider
+     * @param provider function that dynamically supplies the message
+     */
+    public addMessageProvider(key: string, provider: MessageProvider): void {
+        localize.addProvider(key, provider);
+    }
 }
 
 export = TicTacToe;