More things

frontend/app/utils/languages.ts

@@ -35,6 +35,22 @@ export function languageName(code: string): string {
   return LANGUAGES.find((l) => l.code === code)?.name ?? code.toUpperCase()
 }
 
+/**
+ * Which language version to open an article in when the address asks for
+ * none: the reader's own language when the article speaks it, else English
+ * as the wiki's common tongue, else null — nothing to pick, so whatever
+ * version already stands for the article answers.
+ */
+export function preferredLanguage(
+  available: readonly (string | undefined)[],
+  reader: string
+): string | null {
+  const codes = new Set(available.map((c) => (c ?? '').trim().toLowerCase()))
+  const wanted = reader.trim().toLowerCase()
+  if (codes.has(wanted)) return wanted
+  return codes.has(DEFAULT_LANGUAGE) ? DEFAULT_LANGUAGE : null
+}
+
 /** 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())

frontend/app/utils/routes.ts

@@ -3,15 +3,21 @@
    An article route is a page of the open book drawn by ArticleBookStack —
    pages laid out side by side, older ones parked with their spines showing —
    while the article edit page and the new-article page remain plain,
-   full-height pages. An article lives at /wiki/<slug>; one of its language
-   versions at /wiki/<lang>/<slug>, e.g. /wiki/fr/bayes-theorem. */
+   full-height pages. Every language version of an article has an address of
+   its own — /wiki/<lang>/<identity>, English no different from the rest, so
+   /wiki/en/bayes-theorem and /wiki/fr/bayes-theorem sit side by side. The one
+   short form, /wiki/<slug> (what a wiki link to [[Bayes Theorem]] writes, and
+   what an old bookmark holds), names no language: the open-article middleware
+   reads which document the slug speaks and turns the address into that
+   version's own. */
 
 const READER_PATH = /^\/wiki\/([^/]+?)\/?$/
 const VERSION_READER_PATH = /^\/wiki\/([a-z]{2})\/([^/]+?)\/?$/
 const WIKI_SUB_PATH = /^\/wiki\/[^/]+\/[^/]+/
 
 /** What a reader address names: the article's identity, and which language
- *  version the address asks for (null for the article's own version). */
+ *  version the address asks for (null for the short form, which asks for
+ *  whichever version the slug itself speaks). */
 export interface ReaderLocation {
   identity: string
   lang: string | null
@@ -37,12 +43,15 @@ export function wikiSlugFromPath(path: string): string | null {
 }
 
 /**
- * The address of one language version: the canonical document lives at the
- * article's own URL, translations at /wiki/<lang>/<identity>.
+ * The address one language version lives at: /wiki/<lang>/<identity>, the
+ * article's identity being the canonical version's slug — so every version of
+ * one article shares the last part of its address and differs only by the
+ * language in front. Documents carry their own stored slug, which no address
+ * needs: the wiki finds a version by (identity, language).
  */
-export function versionHref(identity: string, version: { language?: string; slug: string }): string {
-  if (version.slug === identity) return `/wiki/${encodeURIComponent(identity)}`
-  return `/wiki/${encodeURIComponent(version.language ?? 'en')}/${encodeURIComponent(identity)}`
+export function versionHref(identity: string, language?: string): string {
+  const code = language?.trim().toLowerCase() || DEFAULT_LANGUAGE
+  return `/wiki/${encodeURIComponent(code)}/${encodeURIComponent(identity)}`
 }
 
 /**