Add GitHub corner component to display repository link

Author: Trikolon

src/app.ts

@@ -6,6 +6,9 @@ import { LitElement, html, css } from "lit";
 import { customElement, state } from "lit/decorators.js";
 import { ExceptionListEntry } from "./types";
 import "./exceptions-table";
+import "./github-corner";
+
+const GITHUB_URL = "https://github.com/Trikolon/url-classifier-exceptions-ui";
 
 const RS_ENDPOINTS = {
   prod: "https://firefox.settings.services.mozilla.com",
@@ -223,6 +226,8 @@ export class App extends LitElement {
             >.
           </p>
         </footer>
+        <!-- Show a link to the repository in the top right corner -->
+        <github-corner repoUrl=${GITHUB_URL}></github-corner>
       </div>
     `;
   }

src/github-corner.ts

@@ -0,0 +1,94 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import { LitElement, html, css } from "lit";
+import { customElement, property } from "lit/decorators.js";
+
+/**
+ * A simple component that displays octocat in the corner of the page linking to
+ * a GitHub repo.
+ */
+@customElement("github-corner")
+export class GitHubCorner extends LitElement {
+  @property({ type: String }) repoUrl = "";
+
+  static styles = css`
+    :host {
+      position: absolute;
+      top: 0;
+      border: 0;
+      right: 0;
+    }
+
+    .github-corner svg {
+      color: white;
+      fill: black;
+    }
+
+    @media (prefers-color-scheme: dark) {
+      .github-corner svg {
+        filter: invert(1);
+      }
+    }
+
+    @keyframes octocat-wave {
+      0%,
+      100% {
+        transform: rotate(0);
+      }
+      20%,
+      60% {
+        transform: rotate(-25deg);
+      }
+      40%,
+      80% {
+        transform: rotate(10deg);
+      }
+    }
+
+    .github-corner:hover .octo-arm {
+      animation: octocat-wave 560ms ease-in-out;
+    }
+
+    @media (prefers-reduced-motion: reduce) {
+      .github-corner:hover .octo-arm {
+        animation: none;
+      }
+    }
+  `;
+
+  render() {
+    return html`
+      <div class="github-corner">
+        <a
+          href="${this.repoUrl}"
+          target="_blank"
+          rel="noopener noreferrer"
+          aria-label="View source on GitHub"
+        >
+          <svg
+            width="80"
+            height="80"
+            viewBox="0 0 250 250"
+            class="github-corner-svg"
+            aria-hidden="true"
+          >
+            <path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path>
+            <path
+              d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2"
+              fill="currentColor"
+              style="transform-origin: 130px 106px;"
+              class="octo-arm"
+            ></path>
+            <path
+              d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z"
+              fill="currentColor"
+              class="octo-body"
+            ></path>
+          </svg>
+        </a>
+      </div>
+    `;
+  }
+}