feat(router): basePath util to add base for routes

Author: dangreen

packages/kida-router/README.md

@@ -233,6 +233,20 @@ paths.post({ id: '456', slug: 'hello-world' }) // '/posts/456/hello-world'
 paths.admin({ wildcard: 'settings/profile' }) // '/admin/settings/profile'
 ```
 
+### `basePath`
+
+The `basePath` function allows you to set a base path for all routes in navigation:
+
+```ts
+import { browserNavigation, basePath } from '@kidajs/router'
+
+const routes = basePath('/github-pages', {
+  home: '/',
+  user: '/users/:id'
+})
+const [$location, navigation] = browserNavigation(routes)
+```
+
 ### `updateHref`
 
 The `updateHref` function allows you to update parts of a URL string easily:

packages/kida-router/src/paths.ts

@@ -61,3 +61,27 @@ export function buildPaths<const R extends Routes>(routes: R) {
     {}
   ) as Paths<R>
 }
+
+/**
+ * Adds a base path to all route patterns.
+ * @param base - The base path to prepend.
+ * @param routes - The original route patterns.
+ * @returns New route patterns with the base path prepended.
+ */
+/* @__NO_SIDE_EFFECTS__ */
+export function basePath<const R extends Routes>(base: string, routes: R): R {
+  const normalizedBase = removeTrailingSlash(base).replace(/^\.\//, '/')
+
+  if (normalizedBase === '' || normalizedBase === '/') {
+    return routes
+  }
+
+  return Object.entries(routes).reduce<Record<string, string>>(
+    (paths, [route, pattern]) => {
+      paths[route] = removeTrailingSlash(`${normalizedBase}${pattern}`)
+
+      return paths
+    },
+    {}
+  ) as R
+}

packages/kida-router/src/utils.ts

@@ -150,4 +150,3 @@ export function updateLocation(
     action
   }
 }
-