Move to lambda at edge based routing

Author: James Bray

README.md

@@ -1,10 +1,11 @@
 # adapter-lambda for SvelteKit
 
 An adapter to build a [SvelteKit](https://kit.svelte.dev/) app into a lambda ready for deployment with lambda proxy.
+
+## Installation
 ```
 npm install --save-dev @yarbsemaj/adapter-lambda
 ```
-
 ## Usage
 
 In your `svelte.config.cjs` configure the adapter as bellow;
@@ -24,5 +25,11 @@ const config = {
 
 };
 ```
-## A note on static assets
-Precompiled pages, client and static resources should be served independently of your dynamic content. One solution to this could be to upload the `build/assets/` directory to S3 and using its static site hosting functionality. Then, by using a CDN like CloudFront, requests could be routed to the correct origin.
+Copy `serverless.yml` from the root of this repo to the root of your project
+
+After building your app run `sls deploy` to deploy code to AWS.
+
+Your app can then be accessed via the CloudFront distribution created as aprt of the stack.
+
+## Static Assets and precompiled pages
+To server static assets and precompiled pages this adapter makes use of S3. In order to route traffic the correct destination a Lambda@edge fuction is used to perfrom a origin rewrite is used to redirect traffic to the S3 Bucket.

index.js

@@ -1,4 +1,4 @@
-const { copyFileSync, unlinkSync, existsSync, mkdirSync } = require('fs');
+const { copyFileSync, unlinkSync, existsSync, mkdirSync, statSync, readdirSync, writeFileSync } = require('fs');
 const { join } = require('path');
 
 const esbuild = require('esbuild');
@@ -24,6 +24,11 @@ module.exports = function ({ out = 'build' } = {}) {
         mkdirSync(server_directory, { recursive: true });
       }
 
+      const edge_directory = join(out, 'edge');
+      if (!existsSync(edge_directory)) {
+        mkdirSync(edge_directory, { recursive: true });
+      }
+
       builder.log.minor('Copying assets');
       builder.writeClient(static_directory);
       builder.writeStatic(static_directory);
@@ -51,11 +56,42 @@ module.exports = function ({ out = 'build' } = {}) {
         dest: `${static_directory}`,
       });
 
+      console.log('Building router');
+      copyFileSync(`${__dirname}/files/router.js`, `${edge_directory}/_router.js`);
+      writeFileSync(`${edge_directory}/static.js`, `export default ${JSON.stringify(getAllFiles(static_directory))}`)
+
+      esbuild.buildSync({
+        entryPoints: [`${edge_directory}/_router.js`],
+        outfile: `${edge_directory}/router.js`,
+        format: 'cjs',
+        bundle: true,
+        platform: 'node',
+      });
+
+
       builder.log.minor('Cleanup');
       unlinkSync(`${server_directory}/_serverless.js`);
+      unlinkSync(`${edge_directory}/_router.js`);
       unlinkSync(`${out}/app.js`);
     },
   };
 
   return adapter;
 };
+
+const getAllFiles = function (dirPath, basePath, arrayOfFiles) {
+  files = readdirSync(dirPath)
+
+  arrayOfFiles = arrayOfFiles || []
+  basePath = basePath || dirPath
+
+  files.forEach(function (file) {
+    if (statSync(dirPath + "/" + file).isDirectory()) {
+      arrayOfFiles = getAllFiles(dirPath + "/" + file, basePath, arrayOfFiles)
+    } else {
+      arrayOfFiles.push(join("/", dirPath.replace(basePath, ''), "/", file))
+    }
+  })
+
+  return arrayOfFiles
+}