From 6d325f56e17605477449527f496d5b9e5b4eac41 Mon Sep 17 00:00:00 2001
From: Sebastian Sdorra <sebastian.sdorra@cloudogu.com>
Date: Tue, 7 May 2019 10:11:26 +0200
Subject: [PATCH] adds option to render markdown headings with anchor links

---
 .../src/MarkdownHeadingRenderer.js            | 35 +++++++++++++++++++
 .../src/MarkdownHeadingRenderer.test.js       | 18 ++++++++++
 .../ui-components/src/MarkdownView.js         | 16 ++++++++-
 3 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.js
 create mode 100644 scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.test.js

diff --git a/scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.js b/scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.js
new file mode 100644
index 0000000000..d7268c2861
--- /dev/null
+++ b/scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.js
@@ -0,0 +1,35 @@
+// @flow
+import * as React from "react";
+
+/**
+ * Adds anchor links to markdown headings.
+ *
+ * @see <a href="https://github.com/rexxars/react-markdown/issues/69">Headings are missing anchors / ids</a>
+ */
+
+type Props = {
+  children: React.Node,
+  level: number
+};
+
+function flatten(text: string, child: any) {
+  return typeof child === "string"
+    ? text + child
+    : React.Children.toArray(child.props.children).reduce(flatten, text);
+}
+
+/**
+ * Turns heading text into a anchor id
+ *
+ * @VisibleForTesting
+ */
+export function headingToAnchorId(heading: string) {
+  return heading.toLowerCase().replace(/\W/g, "-");
+}
+
+export default function MarkdownHeadingRenderer(props: Props) {
+  const children = React.Children.toArray(props.children);
+  const heading = children.reduce(flatten, "");
+  const anchorId = headingToAnchorId(heading);
+  return React.createElement("h" + props.level, {id: anchorId}, props.children);
+}
diff --git a/scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.test.js b/scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.test.js
new file mode 100644
index 0000000000..4fd8428e98
--- /dev/null
+++ b/scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.test.js
@@ -0,0 +1,18 @@
+// @flow
+import React from "react";
+import { headingToAnchorId } from "./MarkdownHeadingRenderer";
+
+describe("headingToAnchorId tests", () => {
+
+  it("should lower case the text", () => {
+    expect(headingToAnchorId("Hello")).toBe("hello");
+    expect(headingToAnchorId("HeLlO")).toBe("hello");
+    expect(headingToAnchorId("HELLO")).toBe("hello");
+  });
+
+  it("should replace spaces with hyphen", () => {
+    expect(headingToAnchorId("awesome stuff")).toBe("awesome-stuff");
+    expect(headingToAnchorId("a b c d e f")).toBe("a-b-c-d-e-f");
+  });
+
+});
diff --git a/scm-ui-components/packages/ui-components/src/MarkdownView.js b/scm-ui-components/packages/ui-components/src/MarkdownView.js
index 4d2b2de92f..164c06b84a 100644
--- a/scm-ui-components/packages/ui-components/src/MarkdownView.js
+++ b/scm-ui-components/packages/ui-components/src/MarkdownView.js
@@ -3,17 +3,27 @@ import React from "react";
 import SyntaxHighlighter from "./SyntaxHighlighter";
 import Markdown from "react-markdown/with-html";
 import {binder} from "@scm-manager/ui-extensions";
+import MarkdownHeadingRenderer from "./MarkdownHeadingRenderer";
 
 type Props = {
   content: string,
   renderContext?: Object,
   renderers?: Object,
+  enableAnchorHeadings: boolean
 };
 
 class MarkdownView extends React.Component<Props> {
 
+  static defaultProps = {
+    enableAnchorHeadings: false
+  };
+
+  constructor(props: Props) {
+    super(props);
+  }
+
   render() {
-    const {content, renderers, renderContext} = this.props;
+    const {content, renderers, renderContext, enableAnchorHeadings} = this.props;
 
     const rendererFactory = binder.getExtension("markdown-renderer-factory");
     let rendererList = renderers;
@@ -26,6 +36,10 @@ class MarkdownView extends React.Component<Props> {
       rendererList = {};
     }
 
+    if (enableAnchorHeadings) {
+      rendererList.heading = MarkdownHeadingRenderer;
+    }
+
     if (!rendererList.code){
       rendererList.code = SyntaxHighlighter;
     }