init commit for iPAL-kit plugin

src/modules/pages/getSystemPagePath.ts

@@ -0,0 +1,66 @@
+import type { I18nConfig } from '../i18n/index.js'
+import type { SystemPageRole } from './types.js'
+
+import { buildLocalizedPath, getLocalizedSlugs } from '../i18n/index.js'
+
+/**
+ * The shape we need from an assigned system-page document: its localized slug
+ * field, as returned by Payload when the parent is read with `locale: 'all'`.
+ *
+ * The plugin doesn't know the client's Pages type, so it depends only on this
+ * minimal contract.
+ */
+type AssignedPage = {
+  slug?: null | Record<string, unknown>
+}
+
+type GetSystemPagePathArgs = {
+  config: I18nConfig
+  /**
+   * Slug that represents the site root. Defaults to 'home'. When the assigned
+   * page's slug in the target locale equals this, the path collapses to the
+   * locale root (/pl, /en).
+   */
+  homeSlug?: string
+  /** Target locale to build the path for. */
+  locale: string
+  /**
+   * The resolved system-page assignment from SiteSettings — the related
+   * document object (not just an ID), read with `locale: 'all'` so its slug
+   * is a locale→value map. Pass null/undefined if the role is unassigned.
+   */
+  page: AssignedPage | null | undefined
+}
+
+/**
+ * Resolves a system-page assignment to a locale-aware path.
+ *
+ * Bridges the Pages module (which document plays a role) and the i18n module
+ * (how that document's localized slug becomes a URL). This is what powers
+ * "visit /pl → serve the homepage": read SiteSettings.homepage, pass the
+ * related document here, get /pl/strona-glowna (or /pl if it's the home slug).
+ *
+ * Returns undefined when the role is unassigned or the assigned page has no
+ * slug in the target locale — the caller decides the fallback (e.g. 404,
+ * redirect to default locale).
+ *
+ * @example
+ * const settings = await payload.findGlobal({ slug: 'site-settings', locale: 'all', depth: 1 })
+ * getSystemPagePath({ page: settings.homepage, locale: 'pl', config })
+ * // → '/pl'  (home slug collapses to root)
+ * getSystemPagePath({ page: settings.privacyPolicy, locale: 'en', config })
+ * // → '/en/privacy-policy'
+ */
+export function getSystemPagePath({
+  config,
+  homeSlug = 'home',
+  locale,
+  page,
+}: GetSystemPagePathArgs): string | undefined {
+  if (!page?.slug) {
+    return undefined
+  }
+
+  const slugs = getLocalizedSlugs({ config, slugField: page.slug })
+  return buildLocalizedPath({ config, homeSlug, locale, slugs })
+}