tannerlinsley · December 29, 2021 16:11 · Dec 29, 2021
diff --git a/treeFromPathMap.ts b/treeFromPathMap.ts
@@ -0,0 +1,110 @@
+import { multiSortBy } from 'src/shared/utils'
+
+export type PathNode<T> = {
+  id: string
+  path: string
+  parentId: string
+  meta: T
+  children?: PathNode<T>[]
+}
+
+export function treeFromPathMap<TMeta>(
+  rootMeta: TMeta,
+  flatRouteDefs: Record<string, TMeta>
+): [PathNode<TMeta>, PathNode<TMeta>[], Record<string, PathNode<TMeta>>] {
+  // We need to go from a flat pathMap to a tree-like structure:
+
+  // {
+  //   index: index.js
+  //   a: a.js
+  //   b: b.js
+  //   c: c.js
+  //   c/index: c/index.js
+  //   c/d: c/d.js
+  // }
+
+  // Becomes
+
+  // {
+  //   path: '/',
+  //   meta: 'index.js',
+  //   children: [{
+  //     path: 'a',
+  //     meta: 'a.js'
+  //   }, {
+  //     path: 'b',
+  //     meta: 'b.js'
+  //   }, {
+  //     path: 'c',
+  //     meta: 'c.js',
+  //     children: [{
+  //       path: '/',
+  //       meta: 'c/index.js'
+  //     }, {
+  //       path: 'd',
+  //       meta: 'c/d.js'
+  //     }]
+  //   }]
+  // }
+
+  // Make sure the paths are in order from root to leaf
+  let sortedRouteDefs = multiSortBy(Object.keys(flatRouteDefs), [
+    (d) => d.split('/').length,
+    (d) => (d.endsWith('index') ? -1 : 1),
+    (d) => d,
+  ]).map((id) => {
+    return {
+      id,
+      file: flatRouteDefs[id],
+    }
+  })
+
+  // The root node
+  let root: PathNode<TMeta> = {
+    id: 'root',
+    path: '/',
+    parentId: '',
+    meta: rootMeta,
+    children: [],
+  }
+
+  // A flat list of the final node objects
+  let flatRoutes: PathNode<TMeta>[] = [root]
+
+  sortedRouteDefs.forEach(({ id, file }) => {
+    // Reduce each node's full path to build the sub-tre
+    const parts = id === '/' ? ['/'] : id.split('/')
+
+    parts.reduce((parent, pathPart) => {
+      const found = parent.children?.find((d) => d.path === pathPart)
+
+      if (found) {
+        return found
+      }
+
+      parent.children = parent.children ?? []
+
+      const resolvedPath = pathPart === 'index' ? '/' : pathPart
+
+      const pathNode: PathNode<TMeta> = {
+        path: resolvedPath,
+        id: [parent.id, pathPart].join('/'),
+        parentId: parent.id,
+        meta: file,
+      }
+
+      flatRoutes.push(pathNode)
+      parent.children.push(pathNode)
+
+      return pathNode
+    }, root)
+  })
+
+  //
+  const nodesByPath = flatRoutes.filter(Boolean).reduce((obj, node) => {
+    obj[node.path] = node
+    return obj
+  }, {} as Record<string, PathNode<TMeta>>)
+
+  return [root, flatRoutes, nodesByPath]
+}