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frontend/app/utils/languages.ts

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+/**
+ * The languages an article can be written in: an ISO 639-1 code with the
+ * name of the language in its own script, as the editor's picker lists them.
+ */
+export const LANGUAGES: ReadonlyArray<{ code: string; name: string }> = [
+  { code: 'en', name: 'English' },
+  { code: 'fr', name: 'Français' },
+  { code: 'de', name: 'Deutsch' },
+  { code: 'es', name: 'Español' },
+  { code: 'ca', name: 'Català' },
+  { code: 'pt', name: 'Português' },
+  { code: 'it', name: 'Italiano' },
+  { code: 'nl', name: 'Nederlands' },
+  { code: 'pl', name: 'Polski' },
+  { code: 'ru', name: 'Русский' },
+  { code: 'uk', name: 'Українська' },
+  { code: 'tr', name: 'Türkçe' },
+  { code: 'ar', name: 'العربية' },
+  { code: 'fa', name: 'فارسی' },
+  { code: 'hi', name: 'हिन्दी' },
+  { code: 'zh', name: '中文' },
+  { code: 'ja', name: '日本語' },
+  { code: 'ko', name: '한국어' },
+]
+
+export const DEFAULT_LANGUAGE = 'en'
+
+/** The language an article is written in; articles predating the field are English. */
+export function articleLanguage(article: { language?: string }): string {
+  return article.language?.trim().toLowerCase() || DEFAULT_LANGUAGE
+}
+
+/** Display name for a code — the code itself in upper case if it is unfamiliar. */
+export function languageName(code: string): string {
+  return LANGUAGES.find((l) => l.code === code)?.name ?? code.toUpperCase()
+}
+
+/** The first language no version of an article has been written in yet. */
+export function nextFreeLanguage(taken: readonly string[]): string {
+  const takenCodes = taken.map((c) => c.trim().toLowerCase())
+  return LANGUAGES.find((l) => !takenCodes.includes(l.code))?.code ?? DEFAULT_LANGUAGE
+}