feat: add bundlingComplete helper method

This method simplifies the process of checking whether bundling is
complete.

README.md

@@ -110,6 +110,13 @@ endpoint.
 GET http://<asset-server-url>/bundle/<hash>.js
 ```
 
+To make some of this a little easier, 2 helper methods exist on the client:
+
+* `bundleURL` - calculates the url location for a bundle based on a given array of asset hashes.
+* `bundlingComplete` - determines if bundling is complete for a given array of asset hashes.
+
+See API documentation below for more information.
+
 ## Installation
 
 ```bash
@@ -377,6 +384,34 @@ const { uri, id2 } = await client.publishAssets('podlet2', ['/path/to/file.js'])
 const url = await client.bundleURL([id1, id2]);
 ```
 
+### bundlingComplete(feedhashes, options)
+
+Calculates whether a bundling for the given `feedHashes` has been completed. The rules for this method are as follows:
+
+* If `feedHashes` is an empty array, this method resolves to `true` as no bundle needs to be built.
+* Otherwise, if `feedHashes` is not an empty array then a bundle url will be computed and a request made to check if the file exists on the server.
+
+* `hashes` - `string[]` - array of asset feed content hashes as returned by `client.publishAssets`
+* `options` - `object`
+  * `options.prefix` - `string` url prefix to use when building bundle url. Defaults to `${client.buildServerUri}/bundle/` which is the location on the asset server that a bundle can be located. Overwrite this if you use a CDN and need to point to that.
+  * `options.type` - `string` (`js`|`css`) - file type. Defaults to `js`
+
+`return` - `Promise<boolean>` - resolves to a boolean representing whether the bundling process for the given `feedHashes` is considered to be complete.
+
+**Example**
+
+```js
+// publish instructions
+await client.publishInstructions('layout', 'js', ['podlet1', 'podlet2']);
+
+// publish necessary assets
+const { uri, id1 } = await client.publishAssets('podlet1', ['/path/to/file.js']);
+const { uri, id2 } = await client.publishAssets('podlet2', ['/path/to/file.js']);
+
+// calculate the url of the finished bundle
+const isComplete = await client.bundlingComplete([id1, id2]);
+```
+
 ## Transpilers
 
 Since [asset-pipe][asset-pipe] is built on [browserify][browserify] under the

lib/main.js

@@ -69,6 +69,15 @@ function post(options) {
     });
 }
 
+function get(uri) {
+    return new Promise((resolve, reject) => {
+        request(uri, (error, response, body) => {
+            if (error) return reject(error);
+            resolve({ response, body });
+        });
+    });
+}
+
 module.exports = class Client {
     constructor({ serverId, buildServerUri, minify, sourceMaps } = {}) {
         assert(
@@ -370,6 +379,7 @@ module.exports = class Client {
     }
 
     async bundleURL(feedHashes, options = {}) {
+        if (feedHashes.length === 0) return null;
         const { type, prefix } = {
             prefix: url.resolve(this.buildServerUri, '/bundle/'),
             type: 'js',
@@ -379,4 +389,11 @@ module.exports = class Client {
         const filename = this.bundleFilename(hash, type);
         return url.resolve(prefix, filename);
     }
+
+    async bundlingComplete(feedHashes, options = {}) {
+        const uri = await this.bundleURL(feedHashes, options);
+        if (!uri) return true;
+        const { response } = await get(uri);
+        return response.statusCode >= 200 && response.statusCode < 300;
+    }
 };

test/unit/main.test.js

@@ -6,23 +6,26 @@ const buildServerUri = 'http://server.com:3000';
 
 function createRequestMock(error, response, body) {
     const { PassThrough } = require('stream');
-    return {
-        post(options, callback) {
-            const resolve = () => {
-                if (error) {
-                    return callback(error);
-                }
-                callback(null, response, body);
-            };
-            if (options.body) {
-                return resolve();
+    const mockRequest = (url, callback) => {
+        if (error) return callback(error);
+        callback(null, response, body);
+    };
+    mockRequest.post = (options, callback) => {
+        const resolve = () => {
+            if (error) {
+                return callback(error);
             }
-            const destination = new PassThrough();
-            destination.on('data', () => {});
-            destination.on('end', resolve);
-            return destination;
-        },
+            callback(null, response, body);
+        };
+        if (options.body) {
+            return resolve();
+        }
+        const destination = new PassThrough();
+        destination.on('data', () => {});
+        destination.on('end', resolve);
+        return destination;
     };
+    return mockRequest;
 }
 
 function createJsWriterMock() {
@@ -365,3 +368,48 @@ test('bundleURL(hashes, options) - js with prefix', async () => {
         'http://server/fb8e20fc2e4c3f248c60c39bd652f3c1347298bb977b8b4d5903b85055620603.js'
     );
 });
+
+test('bundleURL(hashes, options) - empty array returns null', async () => {
+    expect.assertions(1);
+    const client = new Client({ buildServerUri });
+    const url = await client.bundleURL([]);
+    expect(url).toBe(null);
+});
+
+test('bundlingComplete(hashes, options) - empty hashes array returns true', async () => {
+    expect.assertions(1);
+    const client = new Client({ buildServerUri });
+    const isComplete = await client.bundlingComplete([]);
+    expect(isComplete).toBe(true);
+});
+
+test('bundlingComplete(hashes, options) - empty hashes array returns true', async () => {
+    expect.assertions(1);
+    jest.resetModules();
+    jest.doMock('request', () => createRequestMock(null, { statusCode: 200 }));
+    Client = require('../../');
+    const client = new Client({ buildServerUri });
+    const isComplete = await client.bundlingComplete([]);
+    expect(isComplete).toBe(true);
+});
+
+test('bundlingComplete(hashes, options) - bundle does not exist returns false', async () => {
+    expect.assertions(1);
+    jest.resetModules();
+    jest.doMock('request', () => createRequestMock(null, { statusCode: 404 }));
+    Client = require('../../');
+    const client = new Client({ buildServerUri });
+    const isComplete = await client.bundlingComplete(['a12sd2s1a1a1323a']);
+    expect(isComplete).toBe(false);
+});
+
+test('bundlingComplete(hashes, options) - request throws', async () => {
+    expect.assertions(1);
+    jest.resetModules();
+    jest.doMock('request', () => createRequestMock(new Error('fake error')));
+    Client = require('../../');
+    const client = new Client({ buildServerUri });
+    await expect(client.bundlingComplete(['a12sd2s1a1a1323a'])).rejects.toEqual(
+        new Error('fake error')
+    );
+});