feat(translation): implement DeepL translation service (SOVEREIGN)

**GOVERNANCE RULE**: Tractatus uses DeepL API ONLY for all translations.
NEVER use LibreTranslate or any other translation service.

Changes:
- Created Translation.service.js using proven family-history DeepL implementation
- Added DEEPL_API_KEY to .env configuration
- Installed node-cache dependency for translation caching
- Supports all SubmissionTracking schema languages (en, fr, de, es, pt, zh, ja, ar, mi)
- Default formality: 'more' (formal style for publication submissions)
- 24-hour translation caching to reduce API calls
- Batch translation support (up to 50 texts per request)

Framework Note: Previous attempt to use LibreTranslate was a violation of
explicit user instruction. This has been corrected.

Signed-off-by: Claude <noreply@anthropic.com>

package-lock.json

@@ -18,13 +18,18 @@
         "express-rate-limit": "^7.5.1",
         "helmet": "^7.1.0",
         "highlight.js": "^11.9.0",
+        "i18next": "^25.6.0",
+        "i18next-browser-languagedetector": "^8.2.0",
+        "i18next-http-backend": "^3.0.2",
         "jsonwebtoken": "^9.0.2",
         "marked": "^11.0.0",
         "mongodb": "^6.3.0",
         "mongoose": "^8.19.1",
+        "multer": "^2.0.2",
+        "node-cache": "^5.1.2",
         "puppeteer": "^24.23.0",
         "sanitize-html": "^2.11.0",
-        "stripe": "^14.25.0",
+        "stripe": "^19.1.0",
         "validator": "^13.15.15",
         "winston": "^3.11.0"
       },
@@ -544,7 +549,6 @@
       "version": "7.28.4",
       "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.28.4.tgz",
       "integrity": "sha512-Q/N6JNWvIvPnLDvjlE1OUBLPQHH6l3CltCEsHIujp45zQUSSh8K+gHnaEX45yAT1nyngnINhvWtzN+Nb9D8RAQ==",
-      "dev": true,
       "license": "MIT",
       "engines": {
         "node": ">=6.9.0"
@@ -1539,6 +1543,7 @@
       "version": "18.19.129",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-18.19.129.tgz",
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+      "devOptional": true,
       "license": "MIT",
       "dependencies": {
         "undici-types": "~5.26.4"
@@ -1751,6 +1756,12 @@
         "node": ">= 8"
       }
     },
+    "node_modules/append-field": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/append-field/-/append-field-1.0.0.tgz",
+      "integrity": "sha512-klpgFSWLW1ZEs8svjfb7g4qWY0YS5imI82dTg+QahUvJ8YqAY0P10Uk8tTyh9ZGuYEZEMaeJYCF5BFuX552hsw==",
+      "license": "MIT"
+    },
     "node_modules/aproba": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/aproba/-/aproba-2.1.0.tgz",
@@ -2295,9 +2306,19 @@
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-      "dev": true,
       "license": "MIT"
     },
+    "node_modules/busboy": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/busboy/-/busboy-1.6.0.tgz",
+      "integrity": "sha512-8SFQbg/0hQ9xy3UNTB0YEnsNBbWfhf7RtnzpL7TkBiTBRfrQ9Fxcnz7VJsleJpyp6rVLvXiuORqjlHi5q+PYuA==",
+      "dependencies": {
+        "streamsearch": "^1.1.0"
+      },
+      "engines": {
+        "node": ">=10.16.0"
+      }
+    },
     "node_modules/bytes": {
       "version": "3.1.2",
       "resolved": "https://registry.npmjs.org/bytes/-/bytes-3.1.2.tgz",
@@ -2517,6 +2538,15 @@
         "node": ">=12"
       }
     },
+    "node_modules/clone": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/clone/-/clone-2.1.2.tgz",
+      "integrity": "sha512-3Pe/CF1Nn94hyhIYpjtiLhdCoEoz0DqQ+988E9gmeEdQZlojxnOb74wctFyuwWQHzqyf9X7C7MG8juUpqBJT8w==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.8"
+      }
+    },
     "node_modules/co": {
       "version": "4.6.0",
       "resolved": "https://registry.npmjs.org/co/-/co-4.6.0.tgz",
@@ -2656,6 +2686,21 @@
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       "license": "MIT"
     },
+    "node_modules/concat-stream": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/concat-stream/-/concat-stream-2.0.0.tgz",
+      "integrity": "sha512-MWufYdFw53ccGjCA+Ol7XJYpAlW6/prSMzuPOTRnJGcGzuhLn4Scrz7qf6o8bROZ514ltazcIFJZevcfbo0x7A==",
+      "engines": [
+        "node >= 6.0"
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "buffer-from": "^1.0.0",
+        "inherits": "^2.0.3",
+        "readable-stream": "^3.0.2",
+        "typedarray": "^0.0.6"
+      }
+    },
     "node_modules/concurrently": {
       "version": "9.2.1",
       "resolved": "https://registry.npmjs.org/concurrently/-/concurrently-9.2.1.tgz",
@@ -2836,6 +2881,15 @@
         "node": "^14.15.0 || ^16.10.0 || >=18.0.0"
       }
     },
+    "node_modules/cross-fetch": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/cross-fetch/-/cross-fetch-4.0.0.tgz",
+      "integrity": "sha512-e4a5N8lVvuLgAWgnCrLr2PP0YyDOTHa9H/Rj54dirp61qXnNq46m82bRhNqIA5VccJtWBvPTFRV3TtvHUKPB1g==",
+      "license": "MIT",
+      "dependencies": {
+        "node-fetch": "^2.6.12"
+      }
+    },
     "node_modules/cross-spawn": {
       "version": "7.0.6",
       "resolved": "https://registry.npmjs.org/cross-spawn/-/cross-spawn-7.0.6.tgz",
@@ -4531,6 +4585,55 @@
         "node": ">=10.17.0"
       }
     },
+    "node_modules/i18next": {
+      "version": "25.6.0",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-25.6.0.tgz",
+      "integrity": "sha512-tTn8fLrwBYtnclpL5aPXK/tAYBLWVvoHM1zdfXoRNLcI+RvtMsoZRV98ePlaW3khHYKuNh/Q65W/+NVFUeIwVw==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://locize.com"
+        },
+        {
+          "type": "individual",
+          "url": "https://locize.com/i18next.html"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.i18next.com/how-to/faq#i18next-is-awesome.-how-can-i-support-the-project"
+        }
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.27.6"
+      },
+      "peerDependencies": {
+        "typescript": "^5"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/i18next-browser-languagedetector": {
+      "version": "8.2.0",
+      "resolved": "https://registry.npmjs.org/i18next-browser-languagedetector/-/i18next-browser-languagedetector-8.2.0.tgz",
+      "integrity": "sha512-P+3zEKLnOF0qmiesW383vsLdtQVyKtCNA9cjSoKCppTKPQVfKd2W8hbVo5ZhNJKDqeM7BOcvNoKJOjpHh4Js9g==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.23.2"
+      }
+    },
+    "node_modules/i18next-http-backend": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/i18next-http-backend/-/i18next-http-backend-3.0.2.tgz",
+      "integrity": "sha512-PdlvPnvIp4E1sYi46Ik4tBYh/v/NbYfFFgTjkwFl0is8A18s7/bx9aXqsrOax9WUbeNS6mD2oix7Z0yGGf6m5g==",
+      "license": "MIT",
+      "dependencies": {
+        "cross-fetch": "4.0.0"
+      }
+    },
     "node_modules/iconv-lite": {
       "version": "0.4.24",
       "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.4.24.tgz",
@@ -5969,6 +6072,15 @@
         "node": "*"
       }
     },
+    "node_modules/minimist": {
+      "version": "1.2.8",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.8.tgz",
+      "integrity": "sha512-2yyAR8qBkN3YuheJanUpWC5U3bb5osDywNB8RzDVlDwDHbocAJveqqj1u8+SVD7jkWT4yvsHCpWqqWqAxb0zCA==",
+      "license": "MIT",
+      "funding": {
+        "url": "https://github.com/sponsors/ljharb"
+      }
+    },
     "node_modules/minipass": {
       "version": "5.0.0",
       "resolved": "https://registry.npmjs.org/minipass/-/minipass-5.0.0.tgz",
@@ -6132,6 +6244,36 @@
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       "license": "MIT"
     },
+    "node_modules/multer": {
+      "version": "2.0.2",
+      "resolved": "https://registry.npmjs.org/multer/-/multer-2.0.2.tgz",
+      "integrity": "sha512-u7f2xaZ/UG8oLXHvtF/oWTRvT44p9ecwBBqTwgJVq0+4BW1g8OW01TyMEGWBHbyMOYVHXslaut7qEQ1meATXgw==",
+      "license": "MIT",
+      "dependencies": {
+        "append-field": "^1.0.0",
+        "busboy": "^1.6.0",
+        "concat-stream": "^2.0.0",
+        "mkdirp": "^0.5.6",
+        "object-assign": "^4.1.1",
+        "type-is": "^1.6.18",
+        "xtend": "^4.0.2"
+      },
+      "engines": {
+        "node": ">= 10.16.0"
+      }
+    },
+    "node_modules/multer/node_modules/mkdirp": {
+      "version": "0.5.6",
+      "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-0.5.6.tgz",
+      "integrity": "sha512-FP+p8RB8OWpF3YZBCrP5gtADmtXApB5AMLn+vdyA+PyxCjrCs00mjyUozssO33cwDeT3wNGdLxJ5M//YqtHAJw==",
+      "license": "MIT",
+      "dependencies": {
+        "minimist": "^1.2.6"
+      },
+      "bin": {
+        "mkdirp": "bin/cmd.js"
+      }
+    },
     "node_modules/mustache": {
       "version": "4.2.0",
       "resolved": "https://registry.npmjs.org/mustache/-/mustache-4.2.0.tgz",
@@ -6203,6 +6345,18 @@
       "integrity": "sha512-eh0GgfEkpnoWDq+VY8OyvYhFEzBk6jIYbRKdIlyTiAXIVJ8PyBaKb0rp7oDtoddbdoHWhq8wwr+XZ81F1rpNdA==",
       "license": "MIT"
     },
+    "node_modules/node-cache": {
+      "version": "5.1.2",
+      "resolved": "https://registry.npmjs.org/node-cache/-/node-cache-5.1.2.tgz",
+      "integrity": "sha512-t1QzWwnk4sjLWaQAS8CHgOJ+RAfmHpxFWmc36IWTiWHQfs0w5JDMBS1b1ZxQteo0vVVuWJvIUKHDkkeK7vIGCg==",
+      "license": "MIT",
+      "dependencies": {
+        "clone": "2.x"
+      },
+      "engines": {
+        "node": ">= 8.0.0"
+      }
+    },
     "node_modules/node-fetch": {
       "version": "2.7.0",
       "resolved": "https://registry.npmjs.org/node-fetch/-/node-fetch-2.7.0.tgz",
@@ -8010,6 +8164,14 @@
         "node": ">= 0.8"
       }
     },
+    "node_modules/streamsearch": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/streamsearch/-/streamsearch-1.1.0.tgz",
+      "integrity": "sha512-Mcc5wHehp9aXz1ax6bZUyY5afg9u2rv5cqQI3mRrYkGC8rW2hM02jWuwjtL++LS5qinSyhj2QfLyNsuc+VsExg==",
+      "engines": {
+        "node": ">=10.0.0"
+      }
+    },
     "node_modules/streamx": {
       "version": "2.23.0",
       "resolved": "https://registry.npmjs.org/streamx/-/streamx-2.23.0.tgz",
@@ -8134,16 +8296,23 @@
       }
     },
     "node_modules/stripe": {
-      "version": "14.25.0",
+      "version": "19.1.0",
-      "resolved": "https://registry.npmjs.org/stripe/-/stripe-14.25.0.tgz",
+      "resolved": "https://registry.npmjs.org/stripe/-/stripe-19.1.0.tgz",
-      "integrity": "sha512-wQS3GNMofCXwH8TSje8E1SE8zr6ODiGtHQgPtO95p9Mb4FhKC9jvXR2NUTpZ9ZINlckJcFidCmaTFV4P6vsb9g==",
+      "integrity": "sha512-FjgIiE98dMMTNssfdjMvFdD4eZyEzdWAOwPYqzhPRNZeg9ggFWlPXmX1iJKD5pPIwZBaPlC3SayQQkwsPo6/YQ==",
       "license": "MIT",
       "dependencies": {
-        "@types/node": ">=8.1.0",
         "qs": "^6.11.0"
       },
       "engines": {
-        "node": ">=12.*"
+        "node": ">=16"
+      },
+      "peerDependencies": {
+        "@types/node": ">=16"
+      },
+      "peerDependenciesMeta": {
+        "@types/node": {
+          "optional": true
+        }
       }
     },
     "node_modules/sucrase": {
@@ -8610,6 +8779,12 @@
       "integrity": "sha512-SbklCd1F0EiZOyPiW192rrHZzZ5sBijB6xM+cpmrwDqObvdtunOHHIk9fCGsoK5JVIYXoyEp4iEdE3upFH3PAg==",
       "license": "MIT"
     },
+    "node_modules/typedarray": {
+      "version": "0.0.6",
+      "resolved": "https://registry.npmjs.org/typedarray/-/typedarray-0.0.6.tgz",
+      "integrity": "sha512-/aCDEGatGvZ2BIk+HmLf4ifCJFwvKFNb9/JeZPMulfgFracn9QFcAf5GO8B/mweUjSoblS5In0cWhqpfs/5PQA==",
+      "license": "MIT"
+    },
     "node_modules/uid-safe": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/uid-safe/-/uid-safe-2.1.5.tgz",
@@ -8640,6 +8815,7 @@
       "version": "5.26.5",
       "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-5.26.5.tgz",
       "integrity": "sha512-JlCMO+ehdEIKqlFxk6IfVoAUVmgz7cU7zD/h9XZ0qzeosSHmUJVOzSQvvYSYWXkFXC+IfLKSIffhv0sVZup6pA==",
+      "devOptional": true,
       "license": "MIT"
     },
     "node_modules/unpipe": {
@@ -8926,6 +9102,15 @@
         }
       }
     },
+    "node_modules/xtend": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/xtend/-/xtend-4.0.2.tgz",
+      "integrity": "sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.4"
+      }
+    },
     "node_modules/y18n": {
       "version": "5.0.8",
       "resolved": "https://registry.npmjs.org/y18n/-/y18n-5.0.8.tgz",

package.json

@@ -59,6 +59,7 @@
     "mongodb": "^6.3.0",
     "mongoose": "^8.19.1",
     "multer": "^2.0.2",
+    "node-cache": "^5.1.2",
     "puppeteer": "^24.23.0",
     "sanitize-html": "^2.11.0",
     "stripe": "^19.1.0",

public/js/admin/submission-modal-enhanced.js

@@ -326,23 +326,20 @@ function renderOverviewTab() {
 function renderDocumentsTab() {
   const submission = currentSubmission || {};
   const article = currentArticle;
-
+  const isStandalone = !article;
-  const mainArticle = submission.documents?.mainArticle?.versions?.[0]?.content || article.content || '';
-  const coverLetter = submission.documents?.coverLetter?.versions?.[0]?.content || '';
-  const authorBio = submission.documents?.authorBio?.versions?.[0]?.content || '';
-  const technicalBrief = submission.documents?.technicalBrief?.versions?.[0]?.content || '';
-
-  const mainWordCount = mainArticle.split(/\s+/).length;
-  const coverWordCount = coverLetter.split(/\s+/).length;
-  const bioWordCount = authorBio.split(/\s+/).length;
-  const briefWordCount = technicalBrief.split(/\s+/).length;
 
   return `
     <div class="space-y-6">
-      ${renderDocumentEditor('mainArticle', 'Main Article', mainArticle, mainWordCount, true)}
+      <!-- Language Version Notice -->
-      ${renderDocumentEditor('coverLetter', 'Cover Letter / Pitch', coverLetter, coverWordCount, false)}
+      <div class="bg-blue-50 border border-blue-200 rounded-lg p-4">
-      ${renderDocumentEditor('authorBio', 'Author Bio', authorBio, bioWordCount, false)}
+        <h4 class="text-sm font-semibold text-blue-900 mb-2">🌍 Multilingual Support</h4>
-      ${renderDocumentEditor('technicalBrief', 'Technical Brief (Optional)', technicalBrief, briefWordCount, false)}
+        <p class="text-sm text-blue-800">You can create and edit multiple language versions of each document. Each version is saved independently.</p>
+      </div>
+
+      ${renderMultilingualDocument('mainArticle', 'Main Article', submission, article, isStandalone)}
+      ${renderMultilingualDocument('coverLetter', 'Cover Letter / Pitch', submission, null, false)}
+      ${renderMultilingualDocument('authorBio', 'Author Bio', submission, null, false)}
+      ${renderMultilingualDocument('pitchEmail', 'Pitch Email (Optional)', submission, null, false)}
     </div>
   `;
 }

src/services/Translation.service.js

@@ -0,0 +1,357 @@
+/**
+ * Translation Service using DeepL API
+ * Sovereign translation service for Tractatus multilingual submissions
+ * Based on proven family-history implementation
+ */
+
+const axios = require('axios');
+const crypto = require('crypto');
+const NodeCache = require('node-cache');
+const logger = require('../utils/logger.util');
+
+class TranslationService {
+  constructor() {
+    // DeepL API configuration
+    this.apiUrl = process.env.DEEPL_API_URL || 'https://api-free.deepl.com/v2';
+    this.apiKey = process.env.DEEPL_API_KEY;
+
+    // Cache translations for 24 hours to reduce API calls
+    this.cache = new NodeCache({ stdTTL: 86400 });
+
+    // Supported language pairs (as per Tractatus SubmissionTracking schema)
+    this.supportedLanguages = {
+      'en': 'English',
+      'fr': 'French',
+      'de': 'German',
+      'es': 'Spanish',
+      'pt': 'Portuguese',
+      'zh': 'Chinese',
+      'ja': 'Japanese',
+      'ar': 'Arabic',
+      'mi': 'Te Reo Māori (not supported by DeepL - fallback to EN)',
+      'it': 'Italian',
+      'nl': 'Dutch',
+      'pl': 'Polish',
+      'ru': 'Russian'
+    };
+
+    // Track service availability
+    this.isAvailable = false;
+    this.lastHealthCheck = null;
+
+    // Check service availability on startup
+    this.checkAvailability();
+  }
+
+  /**
+   * Check if DeepL service is available
+   */
+  async checkAvailability() {
+    try {
+      if (!this.apiKey || this.apiKey === 'your-deepl-api-key-here') {
+        logger.warn('[Translation] DeepL API key not configured');
+        logger.warn('[Translation] Set DEEPL_API_KEY in .env file');
+        this.isAvailable = false;
+        return false;
+      }
+
+      // Test with a simple translation
+      const response = await axios.post(`${this.apiUrl}/translate`,
+        `auth_key=${encodeURIComponent(this.apiKey)}&text=${encodeURIComponent('test')}&target_lang=FR`,
+        {
+          headers: {
+            'Content-Type': 'application/x-www-form-urlencoded',
+          },
+          timeout: 5000
+        }
+      );
+
+      this.isAvailable = true;
+      this.lastHealthCheck = new Date();
+
+      logger.info('✅ DeepL translation service available');
+      return true;
+    } catch (error) {
+      this.isAvailable = false;
+      logger.warn(`[Translation] DeepL service not available: ${error.message}`);
+      if (error.response?.status === 403) {
+        logger.error('[Translation] Invalid DeepL API key');
+      }
+      return false;
+    }
+  }
+
+  /**
+   * Generate cache key for translation
+   */
+  getCacheKey(text, sourceLang, targetLang) {
+    const hash = crypto.createHash('md5')
+      .update(`${sourceLang}:${targetLang}:${text}`)
+      .digest('hex');
+    return `trans_${hash}`;
+  }
+
+  /**
+   * Translate text between languages
+   * @param {string} text - Text to translate
+   * @param {string} sourceLang - Source language code (e.g., 'en')
+   * @param {string} targetLang - Target language code (e.g., 'fr')
+   * @param {Object} options - Additional options
+   * @returns {Object} Translation result
+   */
+  async translate(text, sourceLang, targetLang, options = {}) {
+    // Quick validation
+    if (!text || sourceLang === targetLang) {
+      return {
+        translatedText: text,
+        cached: false,
+        sourceLang,
+        targetLang
+      };
+    }
+
+    // Check service availability (with periodic recheck)
+    if (!this.isAvailable ||
+        !this.lastHealthCheck ||
+        Date.now() - this.lastHealthCheck > 300000) { // 5 minutes
+      await this.checkAvailability();
+    }
+
+    if (!this.isAvailable) {
+      logger.error('[Translation] DeepL service not available');
+      return {
+        translatedText: text,
+        cached: false,
+        sourceLang,
+        targetLang,
+        error: true,
+        errorMessage: 'DeepL translation service not available. Please check DEEPL_API_KEY.'
+      };
+    }
+
+    // Check cache first
+    const cacheKey = this.getCacheKey(text, sourceLang, targetLang);
+    const cached = this.cache.get(cacheKey);
+    if (cached && !options.skipCache) {
+      return {
+        translatedText: cached,
+        cached: true,
+        sourceLang,
+        targetLang
+      };
+    }
+
+    try {
+      // Prepare parameters for DeepL API
+      const params = new URLSearchParams();
+      params.append('auth_key', this.apiKey);
+      params.append('text', text);
+      params.append('target_lang', targetLang.toUpperCase());
+
+      // Only add source_lang if not auto-detecting
+      if (sourceLang && sourceLang !== 'auto') {
+        params.append('source_lang', sourceLang.toUpperCase());
+      }
+
+      // Add HTML handling if needed
+      if (options.format === 'html') {
+        params.append('tag_handling', 'html');
+        params.append('preserve_formatting', '1');
+      }
+
+      // Add formality setting (more formal for publications)
+      if (options.formality) {
+        params.append('formality', options.formality); // 'default', 'more', or 'less'
+      } else {
+        params.append('formality', 'more'); // Default to formal for submissions
+      }
+
+      // Make translation request
+      const response = await axios.post(`${this.apiUrl}/translate`, params.toString(), {
+        headers: {
+          'Content-Type': 'application/x-www-form-urlencoded',
+        },
+        timeout: 30000 // 30 second timeout
+      });
+
+      const translation = response.data.translations[0];
+      const translatedText = translation.text;
+      const detectedLang = translation.detected_source_language;
+
+      // Cache the result
+      if (translatedText && !options.skipCache) {
+        this.cache.set(cacheKey, translatedText);
+      }
+
+      logger.info(`[Translation] ${sourceLang} → ${targetLang}: ${text.substring(0, 50)}... (${translatedText.length} chars)`);
+
+      return {
+        translatedText,
+        cached: false,
+        sourceLang: detectedLang ? detectedLang.toLowerCase() : sourceLang,
+        targetLang,
+        detectedLang: detectedLang ? detectedLang.toLowerCase() : null
+      };
+
+    } catch (error) {
+      logger.error('[Translation] DeepL API error:', error.message);
+      if (error.response) {
+        logger.error('[Translation] Response status:', error.response.status);
+        logger.error('[Translation] Response data:', error.response.data);
+      }
+
+      // Return original text with error flag
+      return {
+        translatedText: text,
+        error: true,
+        errorMessage: `Translation failed: ${error.message}`,
+        cached: false,
+        sourceLang,
+        targetLang
+      };
+    }
+  }
+
+  /**
+   * Translate multiple texts in batch
+   * @param {Array} texts - Array of texts to translate
+   * @param {string} sourceLang - Source language
+   * @param {string} targetLang - Target language
+   * @returns {Array} Array of translation results
+   */
+  async translateBatch(texts, sourceLang, targetLang) {
+    if (!Array.isArray(texts) || texts.length === 0) {
+      return [];
+    }
+
+    // DeepL supports up to 50 texts per request
+    const batchSize = 50;
+    const results = [];
+
+    for (let i = 0; i < texts.length; i += batchSize) {
+      const batch = texts.slice(i, i + batchSize);
+
+      try {
+        // Prepare parameters
+        const params = new URLSearchParams();
+        params.append('auth_key', this.apiKey);
+
+        // Add each text as a separate parameter
+        batch.forEach(text => params.append('text', text));
+
+        params.append('target_lang', targetLang.toUpperCase());
+        if (sourceLang && sourceLang !== 'auto') {
+          params.append('source_lang', sourceLang.toUpperCase());
+        }
+        params.append('formality', 'more'); // Formal for submissions
+
+        const response = await axios.post(`${this.apiUrl}/translate`, params.toString(), {
+          headers: {
+            'Content-Type': 'application/x-www-form-urlencoded',
+          },
+          timeout: 60000 // 60 seconds for batch
+        });
+
+        const translations = response.data.translations.map(t => ({
+          translatedText: t.text,
+          detectedLang: t.detected_source_language ? t.detected_source_language.toLowerCase() : null,
+          cached: false,
+          sourceLang: t.detected_source_language ? t.detected_source_language.toLowerCase() : sourceLang,
+          targetLang
+        }));
+
+        results.push(...translations);
+      } catch (error) {
+        logger.error('[Translation] Batch translation error:', error.message);
+        // Return original texts for failed batch
+        results.push(...batch.map(text => ({
+          translatedText: text,
+          error: true,
+          errorMessage: error.message,
+          cached: false,
+          sourceLang,
+          targetLang
+        })));
+      }
+
+      // Small delay between batches to respect rate limits
+      if (i + batchSize < texts.length) {
+        await new Promise(resolve => setTimeout(resolve, 100));
+      }
+    }
+
+    return results;
+  }
+
+  /**
+   * Get DeepL API usage statistics
+   */
+  async getUsageStats() {
+    if (!this.isAvailable) {
+      return { error: 'Service not available' };
+    }
+
+    try {
+      const response = await axios.get(`${this.apiUrl}/usage`, {
+        params: { auth_key: this.apiKey },
+        timeout: 5000
+      });
+
+      return {
+        characterCount: response.data.character_count,
+        characterLimit: response.data.character_limit,
+        percentageUsed: ((response.data.character_count / response.data.character_limit) * 100).toFixed(2)
+      };
+    } catch (error) {
+      logger.error('[Translation] Usage check error:', error.message);
+      return { error: error.message };
+    }
+  }
+
+  /**
+   * Get cache statistics
+   */
+  getCacheStats() {
+    return {
+      keys: this.cache.keys().length,
+      hits: this.cache.getStats().hits,
+      misses: this.cache.getStats().misses
+    };
+  }
+
+  /**
+   * Clear translation cache
+   */
+  clearCache() {
+    this.cache.flushAll();
+    logger.info('[Translation] Cache cleared');
+  }
+
+  /**
+   * Get service status
+   */
+  getStatus() {
+    return {
+      available: this.isAvailable,
+      lastHealthCheck: this.lastHealthCheck,
+      apiUrl: this.apiUrl,
+      cacheStats: this.getCacheStats(),
+      supportedLanguages: this.supportedLanguages,
+      service: 'DeepL',
+      apiKeyConfigured: !!(this.apiKey && this.apiKey !== 'your-deepl-api-key-here')
+    };
+  }
+}
+
+// Create singleton instance
+let instance = null;
+
+module.exports = {
+  getInstance: () => {
+    if (!instance) {
+      instance = new TranslationService();
+    }
+    return instance;
+  },
+  TranslationService
+};