Linguist custom translator for DeepL with Nynorsk support

lingust-deepl-translator.js

const deepLApiKey = '' // REQUIRED, Specify your DeepL API key here
const apiSubdomain = deepLApiKey.endsWith(':fx') ? 'api-free' : 'api'

class DeepLTranslator {
  async translate(text, from, to) {
    const deeplFrom = from === 'nn' ? 'nb' : from
    let deeplText = text

    // If from language is Nynorsk, convert to Bokmål using Apertium
    if (from === 'nn') {
      deeplText = await this.translateWithApertium(text, 'nno', 'nob')
    }

    const deeplTo = to === 'nn' ? 'nb' : to
    let translatedText =
      from === to ||
      (from === 'nb' && to === 'nn') ||
      (from === 'nn' && to === 'nb')
        ? deeplText
        : await this.translateWithDeepL(deeplText, deeplFrom, deeplTo)

    // If target language is Nynorsk, convert from Bokmål using Apertium
    if (to === 'nn') {
      translatedText = await this.translateWithApertium(
        translatedText,
        'nob',
        'nno'
      )
    }

    return translatedText
  }

  async translateBatch(texts, from, to) {
    return Promise.all(texts.map(text => this.translate(text, from, to)))
  }

  async translateWithDeepL(text, from, to) {
    const deepLData = JSON.stringify({
      text: [text],
      ...(from !== 'auto' && { source_lang: from }),
      target_lang: to
    })

    const deepLRes = await fetch(
      `https://${apiSubdomain}.deepl.com/v2/translate`,
      {
        method: 'POST',
        headers: {
          Authorization: `DeepL-Auth-Key ${deepLApiKey}`,
          'Content-Type': 'application/json'
        },
        body: deepLData
      }
    )

    const deepLJson = await deepLRes.json()

    return deepLJson.translations[0].text
  }

  async translateWithApertium(text, from, to) {
    const apertiumData = new URLSearchParams({
      langpair: `${from}|${to}`,
      markUnknown: 'no',
      prefs: '',
      q: text
    }).toString()

    const apertiumRes = await fetch('https://apertium.org/apy/translate', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded'
      },
      body: apertiumData
    })

    const apertiumJson = await apertiumRes.json()

    return apertiumJson.responseData.translatedText
  }

  getLengthLimit() {
    return 10000
  }

  getRequestsTimeout() {
    return 300
  }

  checkLimitExceeding(text) {
    return text.length - this.getLengthLimit()
  }

  static isSupportedAutoFrom() {
    return true
  }

  // Returns ISO 639-1 codes of supported languages
  static getSupportedLanguages() {
    // prettier-ignore
    return [
      'bg', 'cs', 'da', 'de', 'el', 'en', 'es', 'et', 'fi', 
      'fr', 'hu', 'id', 'it', 'ja', 'ko', 'lt', 'lv', 'nb', 
      'nn', 'nl', 'pl', 'pt', 'ro', 'ru', 'sk', 'sl', 'sv',
      'tr', 'uk', 'zh'
    ]
  }
}

DeepLTranslator