Copy a message to the clipboard from the chat

Bot and user messages get a quiet copy button under them: the copy icon becomes a check for a moment after it copies the message's text as stored, markdown and refs included. A message still on its way to the server can be copied too, though reply and reactions wait for its id. The async clipboard API is used where it exists and a hidden textarea where a plain HTTP install has none.

src/data/app-data.ts

@@ -62,7 +62,7 @@ export const AppData = {
      * them.
      */
     LastVisitedBotCookieName: `${SiteData["SiteSlug"]}_last_visited_bot_id`,
-    LastVisitedWorkspaceCookieName: `${SiteData["SiteSlug"]}_last_visited_workspace_id`,
+    // LastVisitedWorkspaceCookieName: `${SiteData["SiteSlug"]}_last_visited_workspace_id`,
     LastVisitedCookieMaxAgeSeconds: 365 * 24 * 60 * 60,
     AuthExpiryDays: 60,
     APICrudBasePath: "/api/admin/crud",
@@ -395,6 +395,11 @@ export const AppData = {
      * Most bots or workspaces the composer's mention menu lists at once.
      */
     ComposerMentionMaxItems: 6,
+    /**
+     * How long a message's copy button shows a check after it copied the
+     * message, before it goes back to the copy icon.
+     */
+    CopyConfirmationMs: 1500,
     /**
      * Most of a bot message read aloud; the rest is cut.
      */

src/pages/admin/bots/[bot_id]/(partials)/copy-message-button.tsx

@@ -0,0 +1,55 @@
+import { useEffect, useRef, useState } from "react";
+import { Check, Copy } from "lucide-react";
+import { AppData } from "@/src/data/app-data";
+import copyText from "@/src/utils/copy-text";
+import MessageActionButton from "./message-action-button";
+
+type Props = {
+    text: string;
+};
+
+/**
+ * Copies a message's text as it is stored (markdown and all) and swaps
+ * its icon for a check for a moment, so it says it worked without a
+ * notification. Renders nothing for a message with no text.
+ */
+export default function CopyMessageButton({ text }: Props) {
+    const [copied, setCopied] = useState(false);
+    const timeout = useRef<ReturnType<typeof setTimeout> | null>(null);
+
+    useEffect(() => {
+        return () => {
+            if (timeout.current) clearTimeout(timeout.current);
+        };
+    }, []);
+
+    if (!text.trim()) return null;
+
+    const onCopy = async () => {
+        const worked = await copyText({ text });
+
+        if (!worked) return;
+
+        if (timeout.current) clearTimeout(timeout.current);
+
+        setCopied(true);
+        timeout.current = setTimeout(
+            () => setCopied(false),
+            AppData.CopyConfirmationMs,
+        );
+    };
+
+    return (
+        <MessageActionButton
+            title={copied ? "Copied" : "Copy"}
+            aria_label={copied ? "Copied to the clipboard" : "Copy this message"}
+            onClick={() => void onCopy()}
+        >
+            {copied ? (
+                <Check size={14} aria-hidden />
+            ) : (
+                <Copy size={14} aria-hidden />
+            )}
+        </MessageActionButton>
+    );
+}

src/pages/admin/bots/[bot_id]/(partials)/message-actions.tsx

@@ -3,6 +3,7 @@ import Row from "@moduletrace/twui/layout/Row";
 import { Reply } from "lucide-react";
 import type { BotMessageWithAttachments } from "@/src/types";
 import { BotMessageActionsContext } from "../(data)/message-actions-context";
+import CopyMessageButton from "./copy-message-button";
 import MessageActionButton from "./message-action-button";
 import MessageReactionPicker from "./message-reaction-picker";
 
@@ -11,15 +12,19 @@ type Props = {
 };
 
 /**
- * A message's reply and reaction actions, shown under it.
+ * A message's copy, reply and reaction actions, shown under it. A message
+ * still on its way to the server has no id yet, so it can only be copied.
  */
 export default function MessageActions({ message }: Props) {
     const { onReply, onReact } = useContext(BotMessageActionsContext);
 
-    if (!message.id) return null;
+    if (!message.id && !message.text?.trim()) return null;
 
     return (
         <Row className="gap-3! items-center">
+            <CopyMessageButton text={message.text || ""} />
+            {message.id ? (
+                <>
                     <MessageActionButton
                         title="Reply"
                         aria_label="Reply to this message"
@@ -27,7 +32,12 @@ export default function MessageActions({ message }: Props) {
                     >
                         <Reply size={14} aria-hidden />
                     </MessageActionButton>
-            <MessageReactionPicker message_id={message.id} onReact={onReact} />
+                    <MessageReactionPicker
+                        message_id={message.id}
+                        onReact={onReact}
+                    />
+                </>
+            ) : null}
         </Row>
     );
 }

src/pages/admin/bots/[bot_id]/(partials)/user-message.tsx

@@ -1,6 +1,8 @@
 import { memo } from "react";
+import Row from "@moduletrace/twui/layout/Row";
 import Stack from "@moduletrace/twui/layout/Stack";
 import type { BotMessageWithAttachments } from "@/src/types";
+import CopyMessageButton from "./copy-message-button";
 import MessageAttachments from "./message-attachments";
 import MessageReactions from "./message-reactions";
 import MessageReplyQuote from "./message-reply-quote";
@@ -14,8 +16,8 @@ type Props = {
 /**
  * One user message: the quoted message it answers, its files, then its
  * text (a file-only message has no bubble) and the bot's reactions to it.
- * The user doesn't reply to or react to their own messages. Memoized,
- * like `BotMessageLine`.
+ * The user doesn't reply to or react to their own messages, but they can
+ * copy one. Memoized, like `BotMessageLine`.
  */
 function UserMessage({ message, bot_name }: Props) {
     return (
@@ -35,6 +37,11 @@ function UserMessage({ message, bot_name }: Props) {
                     reactions={message.reactions}
                 />
             ) : null}
+            {message.text ? (
+                <Row className="gap-3! items-center">
+                    <CopyMessageButton text={message.text} />
+                </Row>
+            ) : null}
         </Stack>
     );
 }

src/utils/copy-text.ts

@@ -0,0 +1,49 @@
+type Params = {
+    text: string;
+};
+
+/**
+ * Copies text to the clipboard and says whether it worked. The async
+ * clipboard API needs a secure context, so a plain HTTP address (a VPN or
+ * LAN install) falls back to copying from a temporary textarea.
+ */
+export default async function copyText({ text }: Params): Promise<boolean> {
+    if (!text) {
+        return false;
+    }
+
+    if (navigator.clipboard?.writeText) {
+        try {
+            await navigator.clipboard.writeText(text);
+            return true;
+        } catch {
+            // Fall through to the textarea, which can still work.
+        }
+    }
+
+    return copyWithTextarea({ text });
+}
+
+/**
+ * The pre-clipboard-API way: select a hidden textarea and copy it. The
+ * element is off screen rather than hidden, since `display: none` is not
+ * selectable, and it is removed again either way.
+ */
+function copyWithTextarea({ text }: Params): boolean {
+    const textarea = document.createElement("textarea");
+
+    textarea.value = text;
+    textarea.setAttribute("readonly", "");
+    textarea.className = "sr-only";
+
+    document.body.appendChild(textarea);
+    textarea.select();
+
+    try {
+        return document.execCommand("copy");
+    } catch {
+        return false;
+    } finally {
+        textarea.remove();
+    }
+}