feat: create LibreTranslateTranslator class that implements DittoTranslator

src/translators/LibreTranslateTranslator.ts

@@ -0,0 +1,147 @@
+import { z } from 'zod';
+
+import {
+  DittoTranslator,
+  MastodonTranslation,
+  Provider,
+  SourceLanguage,
+  TargetLanguage,
+} from '@/translators/translator.ts';
+
+interface LibreTranslateTranslatorOpts {
+  /** Libretranslate endpoint to use. Default: 'https://libretranslate.com' */
+  endpoint?: string;
+  /** Libretranslate API key. */
+  apiKey: string;
+  /** Custom fetch implementation. */
+  fetch?: typeof fetch;
+}
+
+export class LibreTranslateTranslator implements DittoTranslator {
+  private readonly endpoint: string;
+  private readonly apiKey: string;
+  private readonly fetch: typeof fetch;
+  private readonly provider: Provider;
+
+  constructor(opts: LibreTranslateTranslatorOpts) {
+    this.endpoint = opts.endpoint ?? 'https://libretranslate.com';
+    this.fetch = opts.fetch ?? globalThis.fetch;
+    this.provider = 'libretranslate.com';
+    this.apiKey = opts.apiKey;
+  }
+
+  async translate(
+    contentHTMLencoded: string,
+    spoilerText: string,
+    mediaAttachments: { id: string; description: string }[],
+    poll: { id: string; options: { title: string }[] } | null,
+    sourceLanguage: SourceLanguage | undefined,
+    targetLanguage: TargetLanguage,
+    opts?: { signal?: AbortSignal },
+  ) {
+    const mastodonTranslation: MastodonTranslation = {
+      content: '',
+      spoiler_text: '',
+      media_attachments: [],
+      poll: null,
+      detected_source_language: 'en',
+      provider: this.provider,
+    };
+
+    const translatedContent = await this.makeRequest(contentHTMLencoded, sourceLanguage, targetLanguage, 'html', {
+      signal: opts?.signal,
+    });
+    mastodonTranslation.content = translatedContent;
+
+    if (spoilerText.length) {
+      const translatedSpoilerText = await this.makeRequest(spoilerText, sourceLanguage, targetLanguage, 'text', {
+        signal: opts?.signal,
+      });
+      mastodonTranslation.spoiler_text = translatedSpoilerText;
+    }
+
+    if (mediaAttachments) {
+      for (const media of mediaAttachments) {
+        const translatedDescription = await this.makeRequest(
+          media.description,
+          sourceLanguage,
+          targetLanguage,
+          'text',
+          {
+            signal: opts?.signal,
+          },
+        );
+        mastodonTranslation.media_attachments.push({
+          id: media.id,
+          description: translatedDescription,
+        });
+      }
+    }
+
+    if (poll) {
+      mastodonTranslation.poll = {
+        id: poll.id,
+        options: [],
+      };
+
+      for (const option of poll.options) {
+        const translatedTitle = await this.makeRequest(
+          option.title,
+          sourceLanguage,
+          targetLanguage,
+          'text',
+          {
+            signal: opts?.signal,
+          },
+        );
+        mastodonTranslation.poll.options.push({
+          title: translatedTitle,
+        });
+      }
+    }
+
+    return {
+      data: mastodonTranslation,
+    };
+  }
+
+  private async makeRequest(
+    q: string,
+    sourceLanguage: string | undefined,
+    targetLanguage: string,
+    format: 'html' | 'text',
+    opts?: { signal?: AbortSignal },
+  ): Promise<string> {
+    const body = {
+      q,
+      source: sourceLanguage?.toLowerCase() ?? 'auto',
+      target: targetLanguage.toLowerCase(),
+      format,
+      api_key: this.apiKey,
+    };
+
+    const headers = new Headers();
+    headers.append('Content-Type', 'application/json');
+
+    const request = new Request(this.endpoint + '/translate', {
+      method: 'POST',
+      body: JSON.stringify(body),
+      headers,
+      signal: opts?.signal,
+    });
+
+    const response = await this.fetch(request);
+    const json = await response.json();
+    const data = LibreTranslateTranslator.schema().parse(json).translatedText;
+
+    return data;
+  }
+
+  /** Libretranslate response schema.
+   *  https://libretranslate.com/docs/#/translate/post_translate */
+  private static schema() {
+    return z.object({
+      translatedText: z.string(),
+    });
+  }
+}