Fix copy buttons on non-secure (plain http) deployments

`navigator.clipboard` only exists in secure contexts, so every copy button
threw on plain-http LAN/IP deployments and falsely reported failure.

Add copyTextToClipboard(), which uses the Clipboard API on secure origins
and falls back to a hidden textarea + `execCommand("copy")` otherwise
(restoring focus/selection and always cleaning the element up). CopyButton
now reports success only when the text actually reached the clipboard.

installClipboardFallback() polyfills a working `navigator.clipboard` on
insecure pages so twui's CodeBlock/CopySlug/Input copy icons work too,
without editing twui sources. It is installed once from AppProviders.

src/components/general/app-providers.tsx

@@ -1,8 +1,12 @@
 import type { PropsWithChildren } from "react";
 import ToastProvider from "./toast/toast-provider";
 import ConfirmProvider from "./confirm/confirm-provider";
+import useClipboardFallback from "@/src/hooks/use-clipboard-fallback";
 
 export default function AppProviders({ children }: PropsWithChildren) {
+    // Plain-http (non-localhost) deployments have no `navigator.clipboard`.
+    useClipboardFallback();
+
     return (
         <ToastProvider>
             <ConfirmProvider>{children}</ConfirmProvider>

src/components/general/copy-button.tsx

@@ -1,5 +1,6 @@
 import Button from "@/src/components/twui/layout/Button";
 import useToast from "@/src/hooks/use-toast";
+import { copyTextToClipboard } from "@/src/utils/copy-text-to-clipboard";
 import { Check, Copy } from "lucide-react";
 import { useState } from "react";
 import { twMerge } from "tailwind-merge";
@@ -18,14 +19,16 @@ export default function CopyButton({ value, label, show_text, className }: Props
     const [copied, setCopied] = useState(false);
 
     async function copy() {
-        try {
+        const copied_ok = await copyTextToClipboard({ text: value });
-            await navigator.clipboard.writeText(value);
+
+        if (!copied_ok) {
+            toast({ msg: `Couldn't copy ${label.toLowerCase()}`, color: "error" });
+            return;
+        }
+
         setCopied(true);
         toast({ msg: `${label} copied`, color: "success" });
         setTimeout(() => setCopied(false), 1500);
-        } catch {
-            toast({ msg: `Couldn't copy ${label.toLowerCase()}`, color: "error" });
-        }
     }
 
     const Icon = copied ? Check : Copy;

src/hooks/use-clipboard-fallback.ts

@@ -0,0 +1,13 @@
+import { useEffect } from "react";
+import { installClipboardFallback } from "../utils/copy-text-to-clipboard";
+
+/**
+ * Installs the insecure-context clipboard fallback once the app mounts, so
+ * twui components calling `navigator.clipboard` directly also work over plain
+ * http on a LAN IP.
+ */
+export default function useClipboardFallback() {
+    useEffect(() => {
+        installClipboardFallback();
+    }, []);
+}

src/utils/copy-text-to-clipboard.test.ts

@@ -0,0 +1,259 @@
+import { afterEach, describe, expect, test } from "bun:test";
+import { copyTextToClipboard, installClipboardFallback } from "./copy-text-to-clipboard";
+
+type FakeElement = {
+    tag: string;
+    value: string;
+    style: Record<string, string>;
+    attrs: Record<string, string>;
+    focused: boolean;
+    setAttribute: (key: string, value: string) => void;
+    focus: () => void;
+    select: () => void;
+    setSelectionRange: (start: number, end: number) => void;
+    remove: () => void;
+};
+
+type FakeDom = {
+    document: unknown;
+    /** Text the fake `execCommand("copy")` "wrote" to the clipboard. */
+    copied: string[];
+    /** Textareas currently attached to `body`. */
+    attached: FakeElement[];
+};
+
+const Originals = {
+    document: Object.getOwnPropertyDescriptor(globalThis, "document"),
+    navigator: Object.getOwnPropertyDescriptor(globalThis, "navigator"),
+};
+
+function createFakeElement({ tag, on_remove }: { tag: string; on_remove: () => void }): FakeElement {
+    const element: FakeElement = {
+        tag,
+        value: "",
+        style: {},
+        attrs: {},
+        focused: false,
+        setAttribute: (key, value) => {
+            element.attrs[key] = value;
+        },
+        focus: () => {
+            element.focused = true;
+        },
+        select: () => {},
+        setSelectionRange: () => {},
+        remove: on_remove,
+    };
+
+    return element;
+}
+
+/** jsdom-free stand-in for the handful of DOM APIs the fallback touches. */
+function installFakeDom({ exec_command_result = true } = {}): FakeDom {
+    const dom: FakeDom = { document: null, copied: [], attached: [] };
+
+    const fake_document = {
+        body: {
+            appendChild: (element: FakeElement) => {
+                dom.attached.push(element);
+                return element;
+            },
+        },
+        activeElement: null,
+        getSelection: () => null,
+        createElement: (tag: string) => {
+            const element: FakeElement = createFakeElement({
+                tag,
+                on_remove: () => {
+                    dom.attached = dom.attached.filter((item) => item !== element);
+                },
+            });
+
+            return element;
+        },
+        execCommand: (command: string) => {
+            if (command != "copy") {
+                return false;
+            }
+
+            const selected = dom.attached.at(-1);
+
+            if (exec_command_result && selected) {
+                dom.copied.push(selected.value);
+            }
+
+            return exec_command_result;
+        },
+    };
+
+    dom.document = fake_document;
+
+    Object.defineProperty(globalThis, "document", {
+        value: fake_document,
+        configurable: true,
+        writable: true,
+    });
+
+    return dom;
+}
+
+function setNavigator(value: unknown) {
+    Object.defineProperty(globalThis, "navigator", {
+        value,
+        configurable: true,
+        writable: true,
+    });
+}
+
+type FakeClipboard = {
+    writeText: (text: string) => Promise<void>;
+};
+
+function grabFakeClipboard() {
+    return (globalThis.navigator as unknown as { clipboard: FakeClipboard }).clipboard;
+}
+
+function setWindow(value: unknown) {
+    Object.defineProperty(globalThis, "window", {
+        value,
+        configurable: true,
+        writable: true,
+    });
+}
+
+afterEach(() => {
+    for (const [key, descriptor] of Object.entries(Originals)) {
+        if (descriptor) {
+            Object.defineProperty(globalThis, key, descriptor);
+            continue;
+        }
+
+        // Not present originally (e.g. `document` under bun) → remove it again.
+        delete (globalThis as Record<string, unknown>)[key];
+    }
+
+    delete (globalThis as Record<string, unknown>)["window"];
+});
+
+describe("copyTextToClipboard", () => {
+    test("uses the native Clipboard API when it is available", async () => {
+        const written: string[] = [];
+        const dom = installFakeDom();
+
+        setNavigator({
+            clipboard: {
+                writeText: async (text: string) => {
+                    written.push(text);
+                },
+            },
+        });
+
+        expect(await copyTextToClipboard({ text: "wg-pubkey" })).toBe(true);
+        expect(written).toEqual(["wg-pubkey"]);
+        expect(dom.copied).toEqual([]);
+    });
+
+    test("falls back to execCommand when navigator.clipboard is missing (plain http)", async () => {
+        const dom = installFakeDom();
+
+        // Insecure contexts expose `navigator` but no `clipboard` property.
+        setNavigator({});
+
+        expect(await copyTextToClipboard({ text: "10.0.0.2" })).toBe(true);
+        expect(dom.copied).toEqual(["10.0.0.2"]);
+        // The helper textarea must be cleaned up afterwards.
+        expect(dom.attached).toEqual([]);
+    });
+
+    test("falls back to execCommand when the native API rejects", async () => {
+        const dom = installFakeDom();
+
+        setNavigator({
+            clipboard: {
+                writeText: async () => {
+                    throw new Error("NotAllowedError");
+                },
+            },
+        });
+
+        expect(await copyTextToClipboard({ text: "key" })).toBe(true);
+        expect(dom.copied).toEqual(["key"]);
+    });
+
+    test("skips the Clipboard API on an insecure origin", async () => {
+        const dom = installFakeDom();
+        let native_calls = 0;
+
+        setNavigator({
+            clipboard: {
+                writeText: async () => {
+                    native_calls += 1;
+                },
+            },
+        });
+        setWindow({ isSecureContext: false });
+
+        expect(await copyTextToClipboard({ text: "plain-http" })).toBe(true);
+        expect(native_calls).toEqual(0);
+        expect(dom.copied).toEqual(["plain-http"]);
+    });
+
+    test("reports failure instead of pretending the copy worked", async () => {
+        installFakeDom({ exec_command_result: false });
+
+        setNavigator({});
+
+        expect(await copyTextToClipboard({ text: "key" })).toBe(false);
+    });
+});
+
+describe("installClipboardFallback", () => {
+    test("polyfills navigator.clipboard on an insecure origin", async () => {
+        const dom = installFakeDom();
+
+        setNavigator({});
+        setWindow({ isSecureContext: false });
+
+        installClipboardFallback();
+
+        const clipboard = grabFakeClipboard();
+
+        expect(typeof clipboard.writeText).toEqual("function");
+
+        await clipboard.writeText("copied-via-polyfill");
+
+        expect(dom.copied).toEqual(["copied-via-polyfill"]);
+    });
+
+    test("leaves the native clipboard untouched on a secure origin", () => {
+        const native_write_text = async () => {};
+
+        setNavigator({ clipboard: { writeText: native_write_text } });
+        setWindow({ isSecureContext: true });
+
+        installClipboardFallback();
+
+        expect(grabFakeClipboard().writeText).toBe(native_write_text);
+    });
+
+    test("is idempotent", async () => {
+        const dom = installFakeDom();
+
+        setNavigator({});
+        setWindow({ isSecureContext: false });
+
+        installClipboardFallback();
+
+        const first = grabFakeClipboard();
+
+        installClipboardFallback();
+
+        const second = grabFakeClipboard();
+
+        expect(second.writeText).toBe(first.writeText);
+
+        await second.writeText("once");
+
+        expect(dom.copied).toEqual(["once"]);
+    });
+});

src/utils/copy-text-to-clipboard.ts

@@ -0,0 +1,166 @@
+/**
+ * `navigator.clipboard` only exists in secure contexts (https, localhost,
+ * 127.0.0.1). Deployments served over plain http on a LAN IP have no
+ * clipboard API at all, so every copy button needs a fallback.
+ *
+ * `document.execCommand("copy")` is deprecated but still the only option
+ * there, and it works from any origin as long as it runs inside a user
+ * gesture.
+ */
+
+/** Marker so the fallback never re-enters itself through `navigator.clipboard`. */
+const FallbackMark = "__wgui_clipboard_fallback";
+
+type CopyParams = {
+    text: string;
+};
+
+function copyViaExecCommand({ text }: CopyParams): boolean {
+    if (typeof document === "undefined" || !document.body) {
+        return false;
+    }
+
+    const holder = document.createElement("textarea");
+    holder.value = text;
+    holder.setAttribute("readonly", "");
+    holder.setAttribute("aria-hidden", "true");
+    // Must stay rendered (not `display: none`) for selection to work.
+    holder.style.position = "fixed";
+    holder.style.top = "0";
+    holder.style.left = "0";
+    holder.style.width = "1px";
+    holder.style.height = "1px";
+    holder.style.padding = "0";
+    holder.style.border = "none";
+    holder.style.opacity = "0";
+    holder.style.pointerEvents = "none";
+
+    const previous_focus = document.activeElement as HTMLElement | null;
+    const selection = document.getSelection();
+    const previous_range =
+        selection && selection.rangeCount > 0 ? selection.getRangeAt(0) : null;
+
+    document.body.appendChild(holder);
+
+    let copied = false;
+
+    try {
+        holder.focus();
+        holder.select();
+        // iOS ignores `select()` on a readonly textarea without a range.
+        holder.setSelectionRange(0, holder.value.length);
+        copied = document.execCommand("copy");
+    } catch {
+        copied = false;
+    } finally {
+        holder.remove();
+
+        try {
+            previous_focus?.focus?.();
+
+            if (selection && previous_range) {
+                selection.removeAllRanges();
+                selection.addRange(previous_range);
+            }
+        } catch {
+            // Restoring selection/focus is cosmetic — never fail the copy on it.
+        }
+    }
+
+    return copied;
+}
+
+function isFallback(write_text: unknown) {
+    return (
+        typeof write_text === "function" &&
+        (write_text as unknown as Record<string, unknown>)[FallbackMark] === true
+    );
+}
+
+function createFallbackWriteText() {
+    // Mirrors the native signature so third-party call sites need no change.
+    const write_text = async (text: string) => {
+        if (!copyViaExecCommand({ text: String(text ?? "") })) {
+            throw new Error("Clipboard is unavailable in this context");
+        }
+    };
+
+    return Object.assign(write_text, { [FallbackMark]: true });
+}
+
+/**
+ * Copies `text`, using the async Clipboard API when the page is a secure
+ * context and falling back to `execCommand` everywhere else.
+ *
+ * Resolves `true` when the text reached the clipboard, `false` otherwise —
+ * callers should never assume success from a resolved promise alone.
+ */
+export async function copyTextToClipboard({ text }: CopyParams): Promise<boolean> {
+    // On a plain-http origin the Clipboard API is absent, and awaiting
+    // anything first would also break the user-gesture requirement — so go
+    // straight to the synchronous fallback.
+    const insecure = typeof window !== "undefined" && window.isSecureContext === false;
+    const clipboard = typeof navigator === "undefined" ? undefined : navigator.clipboard;
+
+    if (
+        !insecure &&
+        clipboard &&
+        typeof clipboard.writeText === "function" &&
+        !isFallback(clipboard.writeText)
+    ) {
+        try {
+            await clipboard.writeText(text);
+            return true;
+        } catch {
+            // Permission denied or a partially-supported stub → fall back.
+        }
+    }
+
+    return copyViaExecCommand({ text });
+}
+
+/**
+ * Gives insecure-context pages a working `navigator.clipboard`, so third-party
+ * components (twui `CodeBlock`, `CopySlug`, `Input`) that call it directly keep
+ * working without patching their source. Safe to call more than once.
+ */
+export function installClipboardFallback() {
+    if (typeof window === "undefined" || typeof navigator === "undefined") {
+        return;
+    }
+
+    // Keep the native implementation unless the page is definitely insecure
+    // (`isSecureContext` is `undefined` on very old browsers).
+    if (window.isSecureContext !== false && navigator.clipboard) {
+        return;
+    }
+
+    const fallback_write_text = createFallbackWriteText();
+    const clipboard = navigator.clipboard ?? ({} as Clipboard);
+
+    try {
+        Object.defineProperty(clipboard, "writeText", {
+            value: fallback_write_text,
+            configurable: true,
+            writable: true,
+        });
+    } catch {
+        // Frozen/exotic implementations: leave them alone.
+        return;
+    }
+
+    // The property already existed → it was patched in place.
+    if (clipboard === navigator.clipboard) {
+        return;
+    }
+
+    try {
+        Object.defineProperty(navigator, "clipboard", {
+            value: clipboard,
+            configurable: true,
+            writable: true,
+        });
+    } catch {
+        // Nothing else we can do; `copyTextToClipboard` still works directly.
+    }
+}