From d7f49f973b5ac7ccbf043e73c7ac4f2eba1539fe Mon Sep 17 00:00:00 2001
From: Doug Parker <dgp1130@users.noreply.github.com>
Date: Sat, 30 Apr 2022 16:19:24 -0700
Subject: [PATCH] Updates resource injector to inject inline styles.

Refs #41.

The resource injector now processes the input HTML to look for any inline style annotations replaces them with a `<style />` tag containing the contents of the file.
---
 packages/resource_injector/BUILD.bazel      |  3 +
 packages/resource_injector/injector.ts      | 31 +++++++-
 packages/resource_injector/injector_test.ts | 85 +++++++++++++++++++++
 3 files changed, 118 insertions(+), 1 deletion(-)

diff --git a/packages/resource_injector/BUILD.bazel b/packages/resource_injector/BUILD.bazel
index 7677accc..c138792f 100644
--- a/packages/resource_injector/BUILD.bazel
+++ b/packages/resource_injector/BUILD.bazel
@@ -57,6 +57,8 @@ ts_library(
     deps = [
         ":config",
         "//common:fs",
+        "//common:prerender_annotation_walker",
+        "//common/models:prerender_annotation",
         "@npm//node-html-parser",
     ],
 )
@@ -69,6 +71,7 @@ ts_library(
         ":config",
         ":injector",
         "//common:fs",
+        "//common/models:prerender_annotation",
         "@npm//@types/jasmine",
     ],
 )
diff --git a/packages/resource_injector/injector.ts b/packages/resource_injector/injector.ts
index 752a38e5..84cf321a 100644
--- a/packages/resource_injector/injector.ts
+++ b/packages/resource_injector/injector.ts
@@ -1,6 +1,8 @@
 import * as fs from 'rules_prerender/common/fs';
 import { HTMLElement, parse } from 'node-html-parser';
 import { InjectorConfig, InjectScript, InjectStyle } from 'rules_prerender/packages/resource_injector/config';
+import { isInlineStyle } from 'rules_prerender/common/models/prerender_annotation';
+import { AnnotationNode, walkAllAnnotations } from 'rules_prerender/common/prerender_annotation_walker';
 
 /**
  * Parses the given HTML document and injects all the resources specified by the
@@ -26,7 +28,7 @@ export async function inject(html: string, config: InjectorConfig):
         },
     });
 
-    // Inject all resources.
+    // Inject all static resources.
     for (const action of config) {
         switch (action.type) {
             case 'script': {
@@ -41,6 +43,9 @@ export async function inject(html: string, config: InjectorConfig):
         }
     }
 
+    // Inject `<style />` tags for each inline style annotation in the document.
+    await replaceInlineStyleAnnotations(walkAllAnnotations(root));
+
     // Return the new document.
     return root.toString();
 }
@@ -115,6 +120,30 @@ async function injectStyle(root: HTMLElement, { path }: InjectStyle):
     style.insertAdjacentHTML('afterend', '\n');
 }
 
+/**
+ * Replaces all inline style annotations with real `<style />` tags for the referenced
+ * file.
+ */
+async function replaceInlineStyleAnnotations(
+    nodes: Generator<AnnotationNode, void, void>,
+): Promise<void> {
+    for (const node of nodes) {
+        const { annotation } = node;
+
+        // Only inline styles should still be in the HTML, everything else should have
+        // been extracted already.
+        if (!isInlineStyle(annotation)){
+            throw new Error(`Injector found an annotation which is not an inline style (actually ${
+                annotation.type}). This should have been handled earlier in the pipeline.\n${
+                JSON.stringify(annotation, null, 4)}`);
+        }
+
+        const inlineStyle = new HTMLElement('style', {});
+        inlineStyle.set_content(await fs.readFile(annotation.path, 'utf-8'));
+        node.replace(inlineStyle);
+    }
+}
+
 function assertNever(value: never): never {
     throw new Error(`Unexpected call to \`assertNever()\` with value: ${
         JSON.stringify(value)}`);
diff --git a/packages/resource_injector/injector_test.ts b/packages/resource_injector/injector_test.ts
index 86f8f23a..212d49bd 100644
--- a/packages/resource_injector/injector_test.ts
+++ b/packages/resource_injector/injector_test.ts
@@ -1,6 +1,7 @@
 import 'jasmine';
 
 import * as fs from 'rules_prerender/common/fs';
+import { createAnnotation, StyleScope } from 'rules_prerender/common/models/prerender_annotation';
 import { InjectorConfig } from 'rules_prerender/packages/resource_injector/config';
 import { inject } from 'rules_prerender/packages/resource_injector/injector';
 
@@ -195,5 +196,89 @@ describe('injector', () => {
 </html>
             `.trim());
         });
+
+        it('inlines style annotations', async () => {
+            const annotation = createAnnotation({
+                type: 'style',
+                path: 'foo.css',
+                scope: StyleScope.Inline,
+            });
+
+            const input = `
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Some title</title>
+    </head>
+    <body>
+        <h2>Hello, World!</h2>
+        <!-- ${annotation} -->
+    </body>
+</html>
+            `.trim();
+
+            spyOn(fs, 'readFile').and.resolveTo('.foo { color: red; }');
+
+            const injected = await inject(input, []);
+            expect(fs.readFile).toHaveBeenCalledWith('foo.css', 'utf-8');
+
+            expect(injected).toBe(`
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Some title</title>
+    </head>
+    <body>
+        <h2>Hello, World!</h2>
+        <style>.foo { color: red; }</style>
+    </body>
+</html>
+            `.trim());
+        });
+
+        it('throws on any annotations other than inline style annotations', async () => {
+            // Should fail when given a script annotation.
+            const scriptAnnotation = createAnnotation({
+                type: 'script',
+                path: 'foo.js',
+            });
+            const inputWithScriptAnnotation = `
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Some title</title>
+    </head>
+    <body>
+        <h2>Hello, World!</h2>
+        <!-- ${scriptAnnotation} -->
+    </body>
+</html>
+            `.trim();
+            await expectAsync(inject(inputWithScriptAnnotation, []))
+                .toBeRejectedWithError(
+                    /Injector found an annotation which is not an inline style/);
+
+            // Should fail when given a global style annotation.
+            const globalStyleAnnotation = createAnnotation({
+                type: 'style',
+                path: 'foo.css',
+                scope: StyleScope.Global,
+            });
+            const inputWithGlobalStyleAnnotation = `
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Some title</title>
+    </head>
+    <body>
+        <h2>Hello, World!</h2>
+        <!-- ${globalStyleAnnotation} -->
+    </body>
+</html>
+            `.trim();
+            await expectAsync(inject(inputWithGlobalStyleAnnotation, []))
+                .toBeRejectedWithError(
+                    /Injector found an annotation which is not an inline style/);
+        });
     });
 });