src/shared/seo/hreflang.test.ts

@@ -0,0 +1,71 @@
+import { describe, expect, it } from "vitest";
+import { buildHreflangSet } from "./hreflang.js";
+
+describe("buildHreflangSet", () => {
+  const LANGUAGES = ["ru", "en", "es", "fr", "it", "ja", "ko", "zh", "de"] as const;
+
+  it("returns entries for all 9 languages plus x-default", () => {
+    const result = buildHreflangSet({
+      canonicalOrigin: "https://www.aeroflot.ru",
+      pathWithoutLocale: "/onlineboard/flight/SU100-2025-01-15",
+    });
+
+    expect(result).toHaveLength(10); // 9 languages + x-default
+  });
+
+  it("includes all 9 languages", () => {
+    const result = buildHreflangSet({
+      canonicalOrigin: "https://www.aeroflot.ru",
+      pathWithoutLocale: "/smoke",
+    });
+
+    const langs = result.map((entry) => entry.lang);
+    for (const lang of LANGUAGES) {
+      expect(langs).toContain(lang);
+    }
+  });
+
+  it("x-default points to the ru variant", () => {
+    const result = buildHreflangSet({
+      canonicalOrigin: "https://www.aeroflot.ru",
+      pathWithoutLocale: "/smoke",
+    });
+
+    const xDefault = result.find((entry) => entry.lang === "x-default");
+    expect(xDefault).toBeDefined();
+    expect(xDefault?.href).toBe("https://www.aeroflot.ru/ru/smoke");
+  });
+
+  it("builds correct href for each language", () => {
+    const result = buildHreflangSet({
+      canonicalOrigin: "https://www.aeroflot.ru",
+      pathWithoutLocale: "/onlineboard",
+    });
+
+    const en = result.find((entry) => entry.lang === "en");
+    expect(en?.href).toBe("https://www.aeroflot.ru/en/onlineboard");
+
+    const ja = result.find((entry) => entry.lang === "ja");
+    expect(ja?.href).toBe("https://www.aeroflot.ru/ja/onlineboard");
+  });
+
+  it("preserves paths with nested segments", () => {
+    const result = buildHreflangSet({
+      canonicalOrigin: "https://www.aeroflot.ru",
+      pathWithoutLocale: "/onlineboard/flight/SU100-2025-01-15",
+    });
+
+    const fr = result.find((entry) => entry.lang === "fr");
+    expect(fr?.href).toBe("https://www.aeroflot.ru/fr/onlineboard/flight/SU100-2025-01-15");
+  });
+
+  it("handles root path", () => {
+    const result = buildHreflangSet({
+      canonicalOrigin: "https://www.aeroflot.ru",
+      pathWithoutLocale: "",
+    });
+
+    const ru = result.find((entry) => entry.lang === "ru");
+    expect(ru?.href).toBe("https://www.aeroflot.ru/ru");
+  });
+});

src/shared/seo/hreflang.ts

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+import type { Language } from "@/i18n/resolver";
+
+const LANGUAGES: readonly Language[] = ["ru", "en", "es", "fr", "it", "ja", "ko", "zh", "de"];
+const X_DEFAULT_LANGUAGE: Language = "ru";
+
+export interface HreflangEntry {
+  lang: Language | "x-default";
+  href: string;
+}
+
+/**
+ * Builds the full set of reciprocal hreflang links for a given path.
+ * Returns 9 language entries + 1 x-default entry (pointing to ru).
+ */
+export function buildHreflangSet(args: {
+  canonicalOrigin: string;
+  pathWithoutLocale: string;
+}): HreflangEntry[] {
+  const { canonicalOrigin, pathWithoutLocale } = args;
+
+  const entries: HreflangEntry[] = LANGUAGES.map((lang) => ({
+    lang,
+    href: `${canonicalOrigin}/${lang}${pathWithoutLocale}`,
+  }));
+
+  entries.push({
+    lang: "x-default",
+    href: `${canonicalOrigin}/${X_DEFAULT_LANGUAGE}${pathWithoutLocale}`,
+  });
+
+  return entries;
+}