From 9469fff6ac4cd95bdb99a0c37b763c6c32af392f Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Thu, 10 Oct 2024 13:48:50 -0500
Subject: [PATCH 1/6] Rename translation variables from _ENDPOINT to _BASE_URL

---
 src/config.ts                                 | 12 +++---
 src/middleware/translatorMiddleware.ts        | 37 +++++++------------
 src/translators/DeepLTranslator.test.ts       | 19 ++++++----
 src/translators/DeepLTranslator.ts            | 37 +++++++++----------
 .../LibreTranslateTranslator.test.ts          | 19 ++++++----
 src/translators/LibreTranslateTranslator.ts   | 16 +++-----
 src/translators/translator.ts                 |  3 +-
 7 files changed, 66 insertions(+), 77 deletions(-)

diff --git a/src/config.ts b/src/config.ts
index 0e4fc816..806fe196 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -276,19 +276,19 @@ class Conf {
     return Deno.env.get('TRANSLATION_PROVIDER');
   }
   /** DeepL URL endpoint. */
-  static get deepLendpoint(): string | undefined {
-    return Deno.env.get('DEEPL_ENDPOINT');
+  static get deeplBaseUrl(): string | undefined {
+    return Deno.env.get('DEEPL_BASE_URL');
   }
   /** DeepL API KEY. */
-  static get deepLapiKey(): string | undefined {
+  static get deeplApiKey(): string | undefined {
     return Deno.env.get('DEEPL_API_KEY');
   }
   /** LibreTranslate URL endpoint. */
-  static get libreTranslateEndpoint(): string | undefined {
-    return Deno.env.get('LIBRETRANSLATE_ENDPOINT');
+  static get libretranslateBaseUrl(): string | undefined {
+    return Deno.env.get('LIBRETRANSLATE_BASE_URL');
   }
   /** LibreTranslate API KEY. */
-  static get libreTranslateApiKey(): string | undefined {
+  static get libretranslateApiKey(): string | undefined {
     return Deno.env.get('LIBRETRANSLATE_API_KEY');
   }
   /** Cache settings. */
diff --git a/src/middleware/translatorMiddleware.ts b/src/middleware/translatorMiddleware.ts
index b8a07686..f5a6baa2 100644
--- a/src/middleware/translatorMiddleware.ts
+++ b/src/middleware/translatorMiddleware.ts
@@ -6,33 +6,22 @@ import { LibreTranslateTranslator } from '@/translators/LibreTranslateTranslator
 
 /** Set the translator used for translating posts. */
 export const translatorMiddleware: AppMiddleware = async (c, next) => {
-  const deepLendpoint = Conf.deepLendpoint;
-  const deepLapiKey = Conf.deepLapiKey;
-  const libreTranslateEndpoint = Conf.libreTranslateEndpoint;
-  const libreTranslateApiKey = Conf.libreTranslateApiKey;
-  const translationProvider = Conf.translationProvider;
+  switch (Conf.translationProvider) {
+    case 'deepl': {
+      const { deeplApiKey: apiKey, deeplBaseUrl: baseUrl } = Conf;
+      if (apiKey) {
+        c.set('translator', new DeepLTranslator({ baseUrl, apiKey, fetch: fetchWorker }));
+      }
+      break;
+    }
 
-  switch (translationProvider) {
-    case 'deepl':
-      if (deepLapiKey) {
-        c.set(
-          'translator',
-          new DeepLTranslator({ endpoint: deepLendpoint, apiKey: deepLapiKey, fetch: fetchWorker }),
-        );
-      }
-      break;
-    case 'libretranslate':
-      if (libreTranslateApiKey) {
-        c.set(
-          'translator',
-          new LibreTranslateTranslator({
-            endpoint: libreTranslateEndpoint,
-            apiKey: libreTranslateApiKey,
-            fetch: fetchWorker,
-          }),
-        );
+    case 'libretranslate': {
+      const { libretranslateApiKey: apiKey, libretranslateBaseUrl: baseUrl } = Conf;
+      if (apiKey) {
+        c.set('translator', new LibreTranslateTranslator({ baseUrl, apiKey, fetch: fetchWorker }));
       }
       break;
+    }
   }
 
   await next();
diff --git a/src/translators/DeepLTranslator.test.ts b/src/translators/DeepLTranslator.test.ts
index 385c10fc..d78c0a0a 100644
--- a/src/translators/DeepLTranslator.test.ts
+++ b/src/translators/DeepLTranslator.test.ts
@@ -4,15 +4,18 @@ import { Conf } from '@/config.ts';
 import { DeepLTranslator } from '@/translators/DeepLTranslator.ts';
 import { getLanguage } from '@/test.ts';
 
-const endpoint = Conf.deepLendpoint;
-const apiKey = Conf.deepLapiKey;
-const translationProvider = Conf.translationProvider;
-const deepL = 'deepl';
+const {
+  deeplBaseUrl: baseUrl,
+  deeplApiKey: apiKey,
+  translationProvider,
+} = Conf;
+
+const deepl = 'deepl';
 
 Deno.test('DeepL translation with source language omitted', {
-  ignore: !(translationProvider === deepL && apiKey),
+  ignore: !(translationProvider === deepl && apiKey),
 }, async () => {
-  const translator = new DeepLTranslator({ fetch: fetch, endpoint, apiKey: apiKey as string });
+  const translator = new DeepLTranslator({ fetch: fetch, baseUrl, apiKey: apiKey! });
 
   const data = await translator.translate(
     [
@@ -31,9 +34,9 @@ Deno.test('DeepL translation with source language omitted', {
 });
 
 Deno.test('DeepL translation with source language set', {
-  ignore: !(translationProvider === deepL && apiKey),
+  ignore: !(translationProvider === deepl && apiKey),
 }, async () => {
-  const translator = new DeepLTranslator({ fetch: fetch, endpoint, apiKey: apiKey as string });
+  const translator = new DeepLTranslator({ fetch: fetch, baseUrl, apiKey: apiKey as string });
 
   const data = await translator.translate(
     [
diff --git a/src/translators/DeepLTranslator.ts b/src/translators/DeepLTranslator.ts
index f30d414a..2b4da175 100644
--- a/src/translators/DeepLTranslator.ts
+++ b/src/translators/DeepLTranslator.ts
@@ -5,8 +5,8 @@ import { DittoTranslator, SourceLanguage, TargetLanguage } from '@/translators/t
 import { languageSchema } from '@/schema.ts';
 
 interface DeepLTranslatorOpts {
-  /** DeepL endpoint to use. Default: 'https://api.deepl.com' */
-  endpoint?: string;
+  /** DeepL base URL to use. Default: 'https://api.deepl.com' */
+  baseUrl?: string;
   /** DeepL API key. */
   apiKey: string;
   /** Custom fetch implementation. */
@@ -14,13 +14,14 @@ interface DeepLTranslatorOpts {
 }
 
 export class DeepLTranslator implements DittoTranslator {
-  private readonly endpoint: string;
+  private readonly baseUrl: string;
   private readonly apiKey: string;
   private readonly fetch: typeof fetch;
-  private static provider = 'DeepL.com';
+
+  readonly provider = 'DeepL.com';
 
   constructor(opts: DeepLTranslatorOpts) {
-    this.endpoint = opts.endpoint ?? 'https://api.deepl.com';
+    this.baseUrl = opts.baseUrl ?? 'https://api.deepl.com';
     this.fetch = opts.fetch ?? globalThis.fetch;
     this.apiKey = opts.apiKey;
   }
@@ -31,11 +32,11 @@ export class DeepLTranslator implements DittoTranslator {
     dest: TargetLanguage,
     opts?: { signal?: AbortSignal },
   ) {
-    const data = (await this.translateMany(texts, source, dest, opts)).translations;
+    const { translations } = await this.translateMany(texts, source, dest, opts);
 
     return {
-      results: data.map((value) => value.text),
-      source_lang: data[0].detected_source_language as LanguageCode,
+      results: translations.map((value) => value.text),
+      source_lang: translations[0]?.detected_source_language as LanguageCode,
     };
   }
 
@@ -56,25 +57,26 @@ export class DeepLTranslator implements DittoTranslator {
       body.source_lang = source.toUpperCase();
     }
 
-    const headers = new Headers();
-    headers.append('Authorization', 'DeepL-Auth-Key' + ' ' + this.apiKey);
-    headers.append('Content-Type', 'application/json');
+    const url = new URL('/v2/translate', this.baseUrl);
 
-    const request = new Request(this.endpoint + '/v2/translate', {
+    const request = new Request(url, {
       method: 'POST',
       body: JSON.stringify(body),
-      headers,
+      headers: {
+        'Authorization': `DeepL-Auth-Key ${this.apiKey}`,
+        'Content-Type': 'application/json',
+      },
       signal: opts?.signal,
     });
 
     const response = await this.fetch(request);
     const json = await response.json();
+
     if (!response.ok) {
       throw new Error(json['message']);
     }
-    const data = DeepLTranslator.schema().parse(json);
 
-    return data;
+    return DeepLTranslator.schema().parse(json);
   }
 
   /** DeepL response schema.
@@ -89,9 +91,4 @@ export class DeepLTranslator implements DittoTranslator {
       ),
     });
   }
-
-  /** DeepL provider. */
-  getProvider(): string {
-    return DeepLTranslator.provider;
-  }
 }
diff --git a/src/translators/LibreTranslateTranslator.test.ts b/src/translators/LibreTranslateTranslator.test.ts
index 6b87cc91..edda3039 100644
--- a/src/translators/LibreTranslateTranslator.test.ts
+++ b/src/translators/LibreTranslateTranslator.test.ts
@@ -4,15 +4,18 @@ import { Conf } from '@/config.ts';
 import { LibreTranslateTranslator } from '@/translators/LibreTranslateTranslator.ts';
 import { getLanguage } from '@/test.ts';
 
-const endpoint = Conf.libreTranslateEndpoint;
-const apiKey = Conf.libreTranslateApiKey;
-const translationProvider = Conf.translationProvider;
-const libreTranslate = 'libretranslate';
+const {
+  libretranslateBaseUrl: baseUrl,
+  libretranslateApiKey: apiKey,
+  translationProvider,
+} = Conf;
+
+const libretranslate = 'libretranslate';
 
 Deno.test('LibreTranslate translation with source language omitted', {
-  ignore: !(translationProvider === libreTranslate && apiKey),
+  ignore: !(translationProvider === libretranslate && apiKey),
 }, async () => {
-  const translator = new LibreTranslateTranslator({ fetch: fetch, endpoint, apiKey: apiKey as string });
+  const translator = new LibreTranslateTranslator({ fetch: fetch, baseUrl, apiKey: apiKey! });
 
   const data = await translator.translate(
     [
@@ -31,9 +34,9 @@ Deno.test('LibreTranslate translation with source language omitted', {
 });
 
 Deno.test('LibreTranslate translation with source language set', {
-  ignore: !(translationProvider === libreTranslate && apiKey),
+  ignore: !(translationProvider === libretranslate && apiKey),
 }, async () => {
-  const translator = new LibreTranslateTranslator({ fetch: fetch, endpoint, apiKey: apiKey as string });
+  const translator = new LibreTranslateTranslator({ fetch: fetch, baseUrl, apiKey: apiKey! });
 
   const data = await translator.translate(
     [
diff --git a/src/translators/LibreTranslateTranslator.ts b/src/translators/LibreTranslateTranslator.ts
index 2c201575..bd2850ff 100644
--- a/src/translators/LibreTranslateTranslator.ts
+++ b/src/translators/LibreTranslateTranslator.ts
@@ -6,7 +6,7 @@ import { languageSchema } from '@/schema.ts';
 
 interface LibreTranslateTranslatorOpts {
   /** Libretranslate endpoint to use. Default: 'https://libretranslate.com' */
-  endpoint?: string;
+  baseUrl?: string;
   /** Libretranslate API key. */
   apiKey: string;
   /** Custom fetch implementation. */
@@ -14,13 +14,14 @@ interface LibreTranslateTranslatorOpts {
 }
 
 export class LibreTranslateTranslator implements DittoTranslator {
-  private readonly endpoint: string;
+  private readonly baseUrl: string;
   private readonly apiKey: string;
   private readonly fetch: typeof fetch;
-  private static provider = 'libretranslate.com';
+
+  readonly provider = 'libretranslate.com';
 
   constructor(opts: LibreTranslateTranslatorOpts) {
-    this.endpoint = opts.endpoint ?? 'https://libretranslate.com';
+    this.baseUrl = opts.baseUrl ?? 'https://libretranslate.com';
     this.fetch = opts.fetch ?? globalThis.fetch;
     this.apiKey = opts.apiKey;
   }
@@ -59,7 +60,7 @@ export class LibreTranslateTranslator implements DittoTranslator {
     const headers = new Headers();
     headers.append('Content-Type', 'application/json');
 
-    const request = new Request(this.endpoint + '/translate', {
+    const request = new Request(new URL('/translate', this.baseUrl), {
       method: 'POST',
       body: JSON.stringify(body),
       headers,
@@ -87,9 +88,4 @@ export class LibreTranslateTranslator implements DittoTranslator {
       }).optional(),
     });
   }
-
-  /** LibreTranslate provider. */
-  getProvider(): string {
-    return LibreTranslateTranslator.provider;
-  }
 }
diff --git a/src/translators/translator.ts b/src/translators/translator.ts
index 98adf5ee..df3c7929 100644
--- a/src/translators/translator.ts
+++ b/src/translators/translator.ts
@@ -41,7 +41,8 @@ export interface DittoTranslator {
     /** Custom options. */
     opts?: { signal?: AbortSignal },
   ): Promise<{ results: string[]; source_lang: SourceLanguage }>;
-  getProvider(): string;
+  /** Provider name, eg `DeepL.com` */
+  provider: string;
 }
 
 /** Includes the TARGET language and the status id.

From 874da1baad5bac890431ae9de1462a3673038b1c Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Thu, 10 Oct 2024 14:01:18 -0500
Subject: [PATCH 2/6] Delete unused cacheMiddleware and ExpiringCache module

---
 src/middleware/cacheMiddleware.ts | 28 -------------
 src/utils/expiring-cache.test.ts  | 18 --------
 src/utils/expiring-cache.ts       | 68 -------------------------------
 3 files changed, 114 deletions(-)
 delete mode 100644 src/middleware/cacheMiddleware.ts
 delete mode 100644 src/utils/expiring-cache.test.ts
 delete mode 100644 src/utils/expiring-cache.ts

diff --git a/src/middleware/cacheMiddleware.ts b/src/middleware/cacheMiddleware.ts
deleted file mode 100644
index baa4976d..00000000
--- a/src/middleware/cacheMiddleware.ts
+++ /dev/null
@@ -1,28 +0,0 @@
-import Debug from '@soapbox/stickynotes/debug';
-import { type MiddlewareHandler } from 'hono';
-
-import ExpiringCache from '@/utils/expiring-cache.ts';
-
-const debug = Debug('ditto:middleware:cache');
-
-export const cacheMiddleware = (options: {
-  cacheName: string;
-  expires?: number;
-}): MiddlewareHandler => {
-  return async (c, next) => {
-    const key = c.req.url.replace('http://', 'https://');
-    const cache = new ExpiringCache(await caches.open(options.cacheName));
-    const response = await cache.match(key);
-    if (!response) {
-      debug('Building cache for page', c.req.url);
-      await next();
-      const response = c.res.clone();
-      if (response.status < 500) {
-        await cache.putExpiring(key, response, options.expires ?? 0);
-      }
-    } else {
-      debug('Serving page from cache', c.req.url);
-      return response;
-    }
-  };
-};
diff --git a/src/utils/expiring-cache.test.ts b/src/utils/expiring-cache.test.ts
deleted file mode 100644
index 8c6d7b18..00000000
--- a/src/utils/expiring-cache.test.ts
+++ /dev/null
@@ -1,18 +0,0 @@
-import { assert } from '@std/assert';
-
-import ExpiringCache from './expiring-cache.ts';
-
-Deno.test('ExpiringCache', async () => {
-  const cache = new ExpiringCache(await caches.open('test'));
-
-  await cache.putExpiring('http://mostr.local/1', new Response('hello world'), 300);
-  await cache.putExpiring('http://mostr.local/2', new Response('hello world'), -1);
-
-  // const resp1 = await cache.match('http://mostr.local/1');
-  const resp2 = await cache.match('http://mostr.local/2');
-
-  // assert(resp1!.headers.get('Expires'));
-  assert(!resp2);
-
-  // await resp1!.text();
-});
diff --git a/src/utils/expiring-cache.ts b/src/utils/expiring-cache.ts
deleted file mode 100644
index ebb5d2ee..00000000
--- a/src/utils/expiring-cache.ts
+++ /dev/null
@@ -1,68 +0,0 @@
-class ExpiringCache implements Cache {
-  #cache: Cache;
-
-  constructor(cache: Cache) {
-    this.#cache = cache;
-  }
-
-  add(request: RequestInfo | URL): Promise<void> {
-    return this.#cache.add(request);
-  }
-
-  addAll(requests: RequestInfo[]): Promise<void> {
-    return this.#cache.addAll(requests);
-  }
-
-  keys(request?: RequestInfo | URL | undefined, options?: CacheQueryOptions | undefined): Promise<readonly Request[]> {
-    return this.#cache.keys(request, options);
-  }
-
-  matchAll(
-    request?: RequestInfo | URL | undefined,
-    options?: CacheQueryOptions | undefined,
-  ): Promise<readonly Response[]> {
-    return this.#cache.matchAll(request, options);
-  }
-
-  put(request: RequestInfo | URL, response: Response): Promise<void> {
-    return this.#cache.put(request, response);
-  }
-
-  putExpiring(request: RequestInfo | URL, response: Response, expiresIn: number): Promise<void> {
-    const expires = Date.now() + expiresIn;
-
-    const clone = new Response(response.body, {
-      status: response.status,
-      headers: {
-        expires: new Date(expires).toUTCString(),
-        ...Object.fromEntries(response.headers.entries()),
-      },
-    });
-
-    return this.#cache.put(request, clone);
-  }
-
-  async match(request: RequestInfo | URL, options?: CacheQueryOptions | undefined): Promise<Response | undefined> {
-    const response = await this.#cache.match(request, options);
-    const expires = response?.headers.get('Expires');
-
-    if (response && expires) {
-      if (new Date(expires).getTime() > Date.now()) {
-        return response;
-      } else {
-        await Promise.all([
-          this.delete(request),
-          response.text(), // Prevent memory leaks
-        ]);
-      }
-    } else if (response) {
-      return response;
-    }
-  }
-
-  delete(request: RequestInfo | URL, options?: CacheQueryOptions | undefined): Promise<boolean> {
-    return this.#cache.delete(request, options);
-  }
-}
-
-export default ExpiringCache;

From d639d9a14d1cbae36b00c360b571217e9676f7d8 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Thu, 10 Oct 2024 14:06:04 -0500
Subject: [PATCH 3/6] Reorganize translation interfaces/files

---
 src/app.ts                                  |  2 +-
 src/caches/translationCache.ts              | 16 ++++++
 src/controllers/api/translate.ts            | 21 ++++----
 src/entities/MastodonTranslation.ts         | 17 ++++++
 src/interfaces/DittoTranslator.ts           | 18 +++++++
 src/translators/DeepLTranslator.ts          | 10 ++--
 src/translators/LibreTranslateTranslator.ts |  6 +--
 src/translators/translator.ts               | 57 ---------------------
 8 files changed, 71 insertions(+), 76 deletions(-)
 create mode 100644 src/caches/translationCache.ts
 create mode 100644 src/entities/MastodonTranslation.ts
 create mode 100644 src/interfaces/DittoTranslator.ts
 delete mode 100644 src/translators/translator.ts

diff --git a/src/app.ts b/src/app.ts
index 3f6f7413..ad80cbb1 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -120,6 +120,7 @@ import { indexController } from '@/controllers/site.ts';
 import { manifestController } from '@/controllers/manifest.ts';
 import { nodeInfoController, nodeInfoSchemaController } from '@/controllers/well-known/nodeinfo.ts';
 import { nostrController } from '@/controllers/well-known/nostr.ts';
+import { DittoTranslator } from '@/interfaces/DittoTranslator.ts';
 import { auth98Middleware, requireProof, requireRole } from '@/middleware/auth98Middleware.ts';
 import { cspMiddleware } from '@/middleware/cspMiddleware.ts';
 import { metricsMiddleware } from '@/middleware/metricsMiddleware.ts';
@@ -129,7 +130,6 @@ import { requireSigner } from '@/middleware/requireSigner.ts';
 import { signerMiddleware } from '@/middleware/signerMiddleware.ts';
 import { storeMiddleware } from '@/middleware/storeMiddleware.ts';
 import { uploaderMiddleware } from '@/middleware/uploaderMiddleware.ts';
-import { DittoTranslator } from '@/translators/translator.ts';
 import { translatorMiddleware } from '@/middleware/translatorMiddleware.ts';
 
 interface AppEnv extends HonoEnv {
diff --git a/src/caches/translationCache.ts b/src/caches/translationCache.ts
new file mode 100644
index 00000000..88121c1f
--- /dev/null
+++ b/src/caches/translationCache.ts
@@ -0,0 +1,16 @@
+import { LanguageCode } from 'iso-639-1';
+import { LRUCache } from 'lru-cache';
+
+import { MastodonTranslation } from '@/entities/MastodonTranslation.ts';
+import { Time } from '@/utils/time.ts';
+
+/** Entity returned by DittoTranslator and LRUCache */
+interface DittoTranslation {
+  data: MastodonTranslation;
+}
+
+/** Translations LRU cache. */
+export const translationCache = new LRUCache<`${LanguageCode}-${string}`, DittoTranslation>({
+  max: 1000,
+  ttl: Time.hours(6),
+});
diff --git a/src/controllers/api/translate.ts b/src/controllers/api/translate.ts
index e1577478..56bd1b8d 100644
--- a/src/controllers/api/translate.ts
+++ b/src/controllers/api/translate.ts
@@ -2,10 +2,11 @@ import { LanguageCode } from 'iso-639-1';
 import { z } from 'zod';
 
 import { AppController } from '@/app.ts';
-import { localeSchema } from '@/schema.ts';
-import { dittoTranslations, dittoTranslationsKey, MastodonTranslation } from '@/translators/translator.ts';
-import { parseBody } from '@/utils/api.ts';
+import { translationCache } from '@/caches/translationCache.ts';
+import { MastodonTranslation } from '@/entities/MastodonTranslation.ts';
 import { getEvent } from '@/queries.ts';
+import { localeSchema } from '@/schema.ts';
+import { parseBody } from '@/utils/api.ts';
 import { renderStatus } from '@/views/mastodon/statuses.ts';
 
 const translateSchema = z.object({
@@ -45,11 +46,11 @@ const translateController: AppController = async (c) => {
     return c.json({ error: 'Bad request.', schema: result.error }, 400);
   }
 
-  const translatedId = `${lang}-${id}` as dittoTranslationsKey;
-  const translationCache = dittoTranslations.get(translatedId);
+  const cacheKey: `${LanguageCode}-${string}` = `${lang}-${id}`;
+  const cached = translationCache.get(cacheKey);
 
-  if (translationCache) {
-    return c.json(translationCache.data, 200);
+  if (cached) {
+    return c.json(cached.data, 200);
   }
 
   const mediaAttachments = status?.media_attachments.map((value) => {
@@ -68,7 +69,7 @@ const translateController: AppController = async (c) => {
       media_attachments: [],
       poll: null,
       detected_source_language: event.language ?? 'en',
-      provider: translator.getProvider(),
+      provider: translator.provider,
     };
 
     if ((status?.poll as MastodonTranslation['poll'])?.options) {
@@ -130,10 +131,10 @@ const translateController: AppController = async (c) => {
 
     mastodonTranslation.detected_source_language = data.source_lang;
 
-    dittoTranslations.set(translatedId, { data: mastodonTranslation });
+    translationCache.set(cacheKey, { data: mastodonTranslation });
     return c.json(mastodonTranslation, 200);
   } catch (e) {
-    if (e instanceof Error && e.message?.includes('not supported')) {
+    if (e instanceof Error && e.message.includes('not supported')) {
       return c.json({ error: `Translation of source language '${event.language}' not supported` }, 422);
     }
     return c.json({ error: 'Service Unavailable' }, 503);
diff --git a/src/entities/MastodonTranslation.ts b/src/entities/MastodonTranslation.ts
new file mode 100644
index 00000000..d59b9aad
--- /dev/null
+++ b/src/entities/MastodonTranslation.ts
@@ -0,0 +1,17 @@
+import { LanguageCode } from 'iso-639-1';
+
+/** https://docs.joinmastodon.org/entities/Translation/ */
+export interface MastodonTranslation {
+  /** HTML-encoded translated content of the status. */
+  content: string;
+  /** The translated spoiler warning of the status. */
+  spoiler_text: string;
+  /** The translated media descriptions of the status. */
+  media_attachments: { id: string; description: string }[];
+  /** The translated poll of the status. */
+  poll: { id: string; options: { title: string }[] } | null;
+  //** The language of the source text, as auto-detected by the machine translation provider. */
+  detected_source_language: LanguageCode;
+  /** The service that provided the machine translation. */
+  provider: string;
+}
diff --git a/src/interfaces/DittoTranslator.ts b/src/interfaces/DittoTranslator.ts
new file mode 100644
index 00000000..426e1428
--- /dev/null
+++ b/src/interfaces/DittoTranslator.ts
@@ -0,0 +1,18 @@
+import type { LanguageCode } from 'iso-639-1';
+
+/** DittoTranslator class, used for status translation. */
+export interface DittoTranslator {
+  /** Translate the 'content' into 'targetLanguage'. */
+  translate(
+    /** Texts to translate. */
+    texts: string[],
+    /** The language of the source texts. */
+    sourceLanguage: LanguageCode | undefined,
+    /** The texts will be translated into this language. */
+    targetLanguage: LanguageCode,
+    /** Custom options. */
+    opts?: { signal?: AbortSignal },
+  ): Promise<{ results: string[]; source_lang: LanguageCode }>;
+  /** Provider name, eg `DeepL.com` */
+  provider: string;
+}
diff --git a/src/translators/DeepLTranslator.ts b/src/translators/DeepLTranslator.ts
index 2b4da175..b856d1ec 100644
--- a/src/translators/DeepLTranslator.ts
+++ b/src/translators/DeepLTranslator.ts
@@ -1,7 +1,7 @@
 import { LanguageCode } from 'iso-639-1';
 import { z } from 'zod';
 
-import { DittoTranslator, SourceLanguage, TargetLanguage } from '@/translators/translator.ts';
+import { DittoTranslator } from '@/interfaces/DittoTranslator.ts';
 import { languageSchema } from '@/schema.ts';
 
 interface DeepLTranslatorOpts {
@@ -28,8 +28,8 @@ export class DeepLTranslator implements DittoTranslator {
 
   async translate(
     texts: string[],
-    source: SourceLanguage | undefined,
-    dest: TargetLanguage,
+    source: LanguageCode | undefined,
+    dest: LanguageCode,
     opts?: { signal?: AbortSignal },
   ) {
     const { translations } = await this.translateMany(texts, source, dest, opts);
@@ -43,8 +43,8 @@ export class DeepLTranslator implements DittoTranslator {
   /** DeepL translate request. */
   private async translateMany(
     texts: string[],
-    source: SourceLanguage | undefined,
-    targetLanguage: TargetLanguage,
+    source: LanguageCode | undefined,
+    targetLanguage: LanguageCode,
     opts?: { signal?: AbortSignal },
   ) {
     const body: any = {
diff --git a/src/translators/LibreTranslateTranslator.ts b/src/translators/LibreTranslateTranslator.ts
index bd2850ff..b7a749cf 100644
--- a/src/translators/LibreTranslateTranslator.ts
+++ b/src/translators/LibreTranslateTranslator.ts
@@ -1,7 +1,7 @@
 import { LanguageCode } from 'iso-639-1';
 import { z } from 'zod';
 
-import { DittoTranslator, SourceLanguage, TargetLanguage } from '@/translators/translator.ts';
+import { DittoTranslator } from '@/interfaces/DittoTranslator.ts';
 import { languageSchema } from '@/schema.ts';
 
 interface LibreTranslateTranslatorOpts {
@@ -28,8 +28,8 @@ export class LibreTranslateTranslator implements DittoTranslator {
 
   async translate(
     texts: string[],
-    source: SourceLanguage | undefined,
-    dest: TargetLanguage,
+    source: LanguageCode | undefined,
+    dest: LanguageCode,
     opts?: { signal?: AbortSignal },
   ) {
     const translations = await Promise.all(
diff --git a/src/translators/translator.ts b/src/translators/translator.ts
deleted file mode 100644
index df3c7929..00000000
--- a/src/translators/translator.ts
+++ /dev/null
@@ -1,57 +0,0 @@
-import { LanguageCode } from 'iso-639-1';
-import { LRUCache } from 'lru-cache';
-
-import { Time } from '@/utils/time.ts';
-
-/** Original language of the post */
-export type SourceLanguage = LanguageCode;
-
-/** Content will be translated to this language */
-export type TargetLanguage = LanguageCode;
-
-/** Entity returned by DittoTranslator and LRUCache */
-type DittoTranslation = {
-  data: MastodonTranslation;
-};
-
-export type MastodonTranslation = {
-  /** HTML-encoded translated content of the status. */
-  content: string;
-  /** The translated spoiler warning of the status. */
-  spoiler_text: string;
-  /** The translated media descriptions of the status. */
-  media_attachments: { id: string; description: string }[];
-  /** The translated poll of the status. */
-  poll: { id: string; options: { title: string }[] } | null;
-  //** The language of the source text, as auto-detected by the machine translation provider. */
-  detected_source_language: SourceLanguage;
-  /** The service that provided the machine translation. */
-  provider: string;
-};
-
-/** DittoTranslator class, used for status translation. */
-export interface DittoTranslator {
-  /** Translate the 'content' into 'targetLanguage'. */
-  translate(
-    texts: string[],
-    /** The language of the source text/status. */
-    sourceLanguage: SourceLanguage | undefined,
-    /** The status content will be translated into this language. */
-    targetLanguage: TargetLanguage,
-    /** Custom options. */
-    opts?: { signal?: AbortSignal },
-  ): Promise<{ results: string[]; source_lang: SourceLanguage }>;
-  /** Provider name, eg `DeepL.com` */
-  provider: string;
-}
-
-/** Includes the TARGET language and the status id.
- *  Example: en-390f5b01b49a8ee6e13fe917420c023d889b3da8e983a14c9e84587e43d12c15
- *  The example above means:
- *  I want the status 390f5b01b49a8ee6e13fe917420c023d889b3da8e983a14c9e84587e43d12c15 translated to english (if it exists in the LRUCache). */
-export type dittoTranslationsKey = `${TargetLanguage}-${string}`;
-
-export const dittoTranslations = new LRUCache<dittoTranslationsKey, DittoTranslation>({
-  max: 1000,
-  ttl: Time.hours(6),
-});

From 12d643e150edef61916d35a85cab92e1ffe4af3e Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Thu, 10 Oct 2024 14:12:20 -0500
Subject: [PATCH 4/6] Add translation cache metrics, let the cache be
 configurable

---
 src/caches/translationCache.ts   | 13 ++++---------
 src/config.ts                    |  7 +++++++
 src/controllers/api/translate.ts |  7 +++++--
 src/metrics.ts                   |  5 +++++
 4 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/caches/translationCache.ts b/src/caches/translationCache.ts
index 88121c1f..7bd27946 100644
--- a/src/caches/translationCache.ts
+++ b/src/caches/translationCache.ts
@@ -1,16 +1,11 @@
 import { LanguageCode } from 'iso-639-1';
 import { LRUCache } from 'lru-cache';
 
+import { Conf } from '@/config.ts';
 import { MastodonTranslation } from '@/entities/MastodonTranslation.ts';
-import { Time } from '@/utils/time.ts';
-
-/** Entity returned by DittoTranslator and LRUCache */
-interface DittoTranslation {
-  data: MastodonTranslation;
-}
 
 /** Translations LRU cache. */
-export const translationCache = new LRUCache<`${LanguageCode}-${string}`, DittoTranslation>({
-  max: 1000,
-  ttl: Time.hours(6),
+export const translationCache = new LRUCache<`${LanguageCode}-${string}`, MastodonTranslation>({
+  max: Conf.caches.translation.max,
+  ttl: Conf.caches.translation.ttl,
 });
diff --git a/src/config.ts b/src/config.ts
index 806fe196..c0daf894 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -314,6 +314,13 @@ class Conf {
         ttl: Number(Deno.env.get('DITTO_CACHE_LINK_PREVIEW_TTL') || 12 * 60 * 60 * 1000),
       };
     },
+    /** Translation cache settings. */
+    get translation(): { max: number; ttl: number } {
+      return {
+        max: Number(Deno.env.get('DITTO_CACHE_TRANSLATION_MAX') || 1000),
+        ttl: Number(Deno.env.get('DITTO_CACHE_TRANSLATION_TTL') || 6 * 60 * 60 * 1000),
+      };
+    },
   };
 }
 
diff --git a/src/controllers/api/translate.ts b/src/controllers/api/translate.ts
index 56bd1b8d..d763c713 100644
--- a/src/controllers/api/translate.ts
+++ b/src/controllers/api/translate.ts
@@ -4,6 +4,7 @@ import { z } from 'zod';
 import { AppController } from '@/app.ts';
 import { translationCache } from '@/caches/translationCache.ts';
 import { MastodonTranslation } from '@/entities/MastodonTranslation.ts';
+import { cachedTranslationsSizeGauge } from '@/metrics.ts';
 import { getEvent } from '@/queries.ts';
 import { localeSchema } from '@/schema.ts';
 import { parseBody } from '@/utils/api.ts';
@@ -50,7 +51,7 @@ const translateController: AppController = async (c) => {
   const cached = translationCache.get(cacheKey);
 
   if (cached) {
-    return c.json(cached.data, 200);
+    return c.json(cached, 200);
   }
 
   const mediaAttachments = status?.media_attachments.map((value) => {
@@ -131,7 +132,9 @@ const translateController: AppController = async (c) => {
 
     mastodonTranslation.detected_source_language = data.source_lang;
 
-    translationCache.set(cacheKey, { data: mastodonTranslation });
+    translationCache.set(cacheKey, mastodonTranslation);
+    cachedTranslationsSizeGauge.set(translationCache.size);
+
     return c.json(mastodonTranslation, 200);
   } catch (e) {
     if (e instanceof Error && e.message.includes('not supported')) {
diff --git a/src/metrics.ts b/src/metrics.ts
index c005a6c7..2cb3eb2d 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -121,6 +121,11 @@ export const cachedLinkPreviewSizeGauge = new Gauge({
   help: 'Number of link previews in cache',
 });
 
+export const cachedTranslationsSizeGauge = new Gauge({
+  name: 'ditto_cached_translations_size',
+  help: 'Number of translated statuses in cache',
+});
+
 export const internalSubscriptionsSizeGauge = new Gauge({
   name: 'ditto_internal_subscriptions_size',
   help: "Number of active subscriptions to Ditto's internal relay",

From 655e94ef91941d93e5362cb0998726ca44ddfb5c Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Thu, 10 Oct 2024 14:14:29 -0500
Subject: [PATCH 5/6] DittoTranslator: move `provider` to top of interface

---
 src/interfaces/DittoTranslator.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/interfaces/DittoTranslator.ts b/src/interfaces/DittoTranslator.ts
index 426e1428..7e5e1d50 100644
--- a/src/interfaces/DittoTranslator.ts
+++ b/src/interfaces/DittoTranslator.ts
@@ -2,6 +2,8 @@ import type { LanguageCode } from 'iso-639-1';
 
 /** DittoTranslator class, used for status translation. */
 export interface DittoTranslator {
+  /** Provider name, eg `DeepL.com` */
+  provider: string;
   /** Translate the 'content' into 'targetLanguage'. */
   translate(
     /** Texts to translate. */
@@ -13,6 +15,4 @@ export interface DittoTranslator {
     /** Custom options. */
     opts?: { signal?: AbortSignal },
   ): Promise<{ results: string[]; source_lang: LanguageCode }>;
-  /** Provider name, eg `DeepL.com` */
-  provider: string;
 }

From df3b8863df6ff7e54467ca7850d48c98680a9e19 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Thu, 10 Oct 2024 14:16:29 -0500
Subject: [PATCH 6/6] LibreTranslateTranslator: move headers to plain object,
 add url variable

---
 src/translators/LibreTranslateTranslator.ts | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/translators/LibreTranslateTranslator.ts b/src/translators/LibreTranslateTranslator.ts
index b7a749cf..ef7fb1f8 100644
--- a/src/translators/LibreTranslateTranslator.ts
+++ b/src/translators/LibreTranslateTranslator.ts
@@ -57,13 +57,14 @@ export class LibreTranslateTranslator implements DittoTranslator {
       api_key: this.apiKey,
     };
 
-    const headers = new Headers();
-    headers.append('Content-Type', 'application/json');
+    const url = new URL('/translate', this.baseUrl);
 
-    const request = new Request(new URL('/translate', this.baseUrl), {
+    const request = new Request(url, {
       method: 'POST',
       body: JSON.stringify(body),
-      headers,
+      headers: {
+        'Content-Type': 'application/json',
+      },
       signal: opts?.signal,
     });