Replace 404 page with general error page

src/content/end.ts

@@ -1,7 +1,7 @@
 import { MessageType } from "../messages";
 import { ExtensionSettings } from "../settings";
 import { Course } from "./pages/Course/Course";
-import { Err404 } from "./pages/Err404";
+import { ErrorPage } from "./pages/Error/Error";
 import { Exam } from "./pages/Exam";
 import { Logged } from "./pages/Logged";
 import { Login } from "./pages/Login";
@@ -38,65 +38,72 @@ const main = async (settings: ExtensionSettings) => {
     document.body.removeAttribute("text");
 
     let page: Page;
-    if (document.body.innerHTML == "") {
-        page = new Err404(settings);
-    } else if (document.querySelector("select[name=UID_UNIVERSITY]") != null) {
-        page = new Login();
-    } else if (args.has("X")) {
-        switch (args.get("X")) {
-            case "FAQ":
-            case "Preset":
-            case "CompilersDryRuns":
-            case "Extra":
-            case "KNT":
-            case "TaskGrp": {
-                page = new Logged(settings);
-                break;
-            }
-            case "KNTQ": {
-                page = new Exam(settings);
-                break;
-            }
-            case "Course": {
-                page = new Course(settings);
-                break;
-            }
-            case "Results": {
-                page = new Results(settings);
-                break;
-            }
-            case "Compiler":
-            case "DryRun":
-            case "Task":
-            case "TaskU": {
-                page = new Task(settings);
-                break;
-            }
-            case "Main": {
-                page = new Main(settings);
-                break;
-            }
-            default: {
-                // determine if site is really main
-                const navlink =
-                    document.querySelector<HTMLSpanElement>("span.navlink"); // first time login
-                if (
-                    document.querySelector(
-                        'span.navLink > a.navLink[href="?X=Main"]',
-                    ) ||
-                    (navlink && navlink.innerText.includes("Než"))
-                ) {
+    try {
+        if (document.querySelector("select[name=UID_UNIVERSITY]") != null) {
+            page = new Login();
+        } else if (args.has("X")) {
+            switch (args.get("X")) {
+                case "FAQ":
+                case "Preset":
+                case "CompilersDryRuns":
+                case "Extra":
+                case "KNT":
+                case "TaskGrp": {
                     page = new Logged(settings);
-                } else {
+                    break;
+                }
+                case "KNTQ": {
+                    page = new Exam(settings);
+                    break;
+                }
+                case "Course": {
+                    page = new Course(settings);
+                    break;
+                }
+                case "Results": {
+                    page = new Results(settings);
+                    break;
+                }
+                case "Compiler":
+                case "DryRun":
+                case "Task":
+                case "TaskU": {
+                    page = new Task(settings);
+                    break;
+                }
+                case "Main": {
                     page = new Main(settings);
+                    break;
+                }
+                default: {
+                    // determine if site is really main
+                    const navlink =
+                        document.querySelector<HTMLSpanElement>("span.navlink"); // first time login
+                    if (
+                        document.querySelector(
+                            'span.navLink > a.navLink[href="?X=Main"]',
+                        ) ||
+                        (navlink && navlink.innerText.includes("Než"))
+                    ) {
+                        page = new Logged(settings);
+                    } else {
+                        page = new Main(settings);
+                    }
                 }
             }
+        } else {
+            page = new Main(settings);
         }
-    } else {
-        page = new Main(settings);
-    }
 
-    await page.initialise();
+        await page.initialise();
+    } catch (e) {
+        if (e instanceof Error) {
+            page = new ErrorPage(e);
+            await page.initialise();
+        } else {
+            throw e;
+        }
+    }
     return page;
 };
 

src/content/pages/Error/Error.svelte

@@ -0,0 +1,38 @@
+<script lang="ts">
+    export let error: Error;
+
+    const goBack = () => {
+        history.back();
+        return false;
+    };
+</script>
+
+<main>
+    <h1>An unexpected error occurred</h1>
+    <p>The following error has occurred:</p>
+    <code>{error.toString()}</code>
+    {#if error.stack}
+        {#each error.stack.split("\n") as line}
+            <code>{line}</code>
+        {/each}
+    {/if}
+    <p>
+        Try <a href={document.referrer} on:click={goBack}>going back</a>, if
+        that doesn't help,
+        <a href="https://github.com/keombre/progtest-theme/issues"
+            >file an issue on GitHub</a
+        >.
+    </p>
+</main>
+
+<style>
+    code {
+        display: block;
+    }
+
+    main {
+        font-size: 14px;
+        max-width: 640px;
+        margin: 0 auto;
+    }
+</style>

src/content/pages/Error/Error.ts

@@ -0,0 +1,22 @@
+import { Page } from "../Page";
+import ErrorComponent from "./Error.svelte";
+
+export class ErrorPage implements Page {
+    constructor(private error: Error) {}
+
+    async initialise() {
+        document.title = "Error | ProgTest";
+
+        const center = document.querySelector<HTMLElement>("body > center");
+        if (center) {
+            center.style.display = "none";
+        }
+
+        const container = document.createElement("div");
+        document.body.insertBefore(container, center);
+        new ErrorComponent({
+            target: container,
+            props: { error: this.error },
+        });
+    }
+}