Microsoft Teams bot with a personal static tab for DeepL translation and ChatGPT chat, plus bot messaging that routes either to DeepL (when you use a language prefix) or OpenAI (rewrite / answer without a prefix).

• Personal tab (/tabs/translate-chat):
  • Translate (DeepL) — pick a target language, send text, see source → target pairs.
  • Chat (ChatGPT) — multi-turn chat; only prior chat messages are sent as context (DeepL turns stay out of the model context).
  • Thread items are labeled DeepL vs ChatGPT (data-kind on each card for styling).
• Bot (1:1 / channel):
  • Message with a language prefix (e.g. en Wie heißt du) → translate via DeepL.
  • Message without a prefix → OpenAI prompt (rewrite / assist).
  • Send tr help (or tr hlep) for a full list of DeepL prefixes and usage (tr help is handled locally, no AI call).
• HTTP APIs used by the tab (JSON under /api* is parsed by the Teams app host).

• Node.js 18+ (recommended 20+)
• A registered Microsoft Teams app / Bot Framework registration (see appPackage/manifest.json)
• Optional: DeepL API key, OpenAI API key

Create a .env in this folder for local development (npm run dev loads it via dotenv).

If OPENAI_API_KEY or DEEPL_API_KEY is missing while the corresponding _MODE opts in, adapter creation fails gracefully and that integration is disabled (null in the container) instead of crashing the process.

npm install
npm run dev      # watch + dotenv — src/index.ts
npm run build    # tsup → dist/
npm start        # node . (uses dist/)
npm test         # vitest (unit tests in test/)
npm run test:watch

Unit tests use Vitest (vitest.config.ts). They live under test/ and cover:

• envMode, chatLimits, mapApiFailure, parseChatRequestBody, targetLanguageMapper (including tr help help text)
• TeamsBotMessageService, TranslateTabService, ChatTabService with mocked adapters

• Manifest: appPackage/manifest.json
• Static tab URL: https://<BOT_DOMAIN>/tabs/translate-chat
• After changing URLs or entityId, repackage and update the app in Teams.

Query parameters:

• text — required (non-empty after trim)
• targetLanguage — DeepL target code (e.g. EN-US, DE)

200 — { translatedText, targetLanguage, detectedSourceLanguage? }
400 — empty text
500 — e.g. DeepL not configured or translation error

JSON body:

{
  "messages": [
    { "role": "user", "content": "Hello" },
    { "role": "assistant", "content": "Hi there!" },
    { "role": "user", "content": "Follow-up…" }
  ]
}

Rules enforced server-side:

• messages is a non-empty array.
• Each item: role is user or assistant, content is a non-empty string.
• Last message must be user.
• Limits: up to 50 messages, 24 000 characters total (approximate guardrail).

200 — { reply: string }
400 — invalid body
413 — over limits
501 — OpenAI not configured
500 — upstream / internal error

Prefixes map to DeepL target codes (examples: en, english → EN-US; de, german → DE). See src/mappers/targetLanguageMapper.ts for the full map. In chat, send tr help to print every prefix grouped by target code (same source as the mapper).

src/
  index.ts                    # App construction, composeApp, start
  composeApp.ts               # buildContainer + registerTabAndBotHandlers; returns AppContainer
  api/types.ts                # Tab API result types
  config/envMode.ts           # OPENAI_MODE / DEEPL_MODE opt-in parsing
  config/chatLimits.ts        # Chat payload limits from env
  validation/parseChatRequestBody.ts
  http/                       # registerApiRoutes, registerStaticTabs, mapApiFailure, resolveTabFilePath
  services/
    TranslateTabService.ts    # GET /api/translate
    ChatTabService.ts         # POST /api/chat
    TeamsBotMessageService.ts # Bot 1:1 / channel messages
  tabs/translate-chat.html
  adapters/deepl/
  adapters/openai/
  container/buildContainer.ts # Adapters + TranslateTabService, ChatTabService, TeamsBotMessageService; `get()` accessor
  factories/
appPackage/manifest.json

At runtime the server prefers dist/tabs/translate-chat.html if it exists, otherwise src/tabs/translate-chat.html. tsup bundles app code to dist/index.js; HTML stays under src/tabs unless you copy it into dist/tabs/ during deploy.

MIT (see package.json).