Preserve assistant message formatting on copy

2026-05-24 04:10:09 +00:00
parent 846c9b9da3
commit 83f205bd3d
5 changed files with 209 additions and 2 deletions
@@ -0,0 +1,81 @@
+import * as Clipboard from "expo-clipboard";
+import MarkdownIt from "markdown-it";
+import { isWeb } from "@/constants/platform";
+
+const markdownRenderer = new MarkdownIt({
+  html: false,
+  linkify: true,
+  typographer: true,
+});
+
+type ClipboardMimeType = "text/plain" | "text/html";
+
+export interface MarkdownClipboardContent {
+  plainText: string;
+  html: string;
+}
+
+export interface RichClipboardWriter {
+  supportsHtml: () => boolean;
+  write: (data: Record<ClipboardMimeType, Blob>) => Promise<void>;
+}
+
+export interface MarkdownClipboardEnvironment {
+  richWriter?: RichClipboardWriter | null;
+  writePlainText: (text: string) => Promise<unknown>;
+}
+
+export function createMarkdownClipboardContent(markdown: string): MarkdownClipboardContent {
+  return {
+    plainText: markdown,
+    html: `<meta charset="utf-8">${markdownRenderer.render(markdown)}`,
+  };
+}
+
+export async function writeMarkdownToRichClipboard(
+  markdown: string,
+  environment: MarkdownClipboardEnvironment = getDefaultMarkdownClipboardEnvironment(),
+): Promise<void> {
+  if (environment.richWriter?.supportsHtml()) {
+    const content = createMarkdownClipboardContent(markdown);
+    try {
+      await environment.richWriter.write({
+        "text/plain": new Blob([content.plainText], { type: "text/plain" }),
+        "text/html": new Blob([content.html], { type: "text/html" }),
+      });
+      return;
+    } catch {
+      // Fall through to the plain-text path. Some webviews expose rich clipboard
+      // APIs but deny writes depending on focus, permissions, or browser policy.
+    }
+  }
+
+  await environment.writePlainText(markdown);
+}
+
+function getDefaultMarkdownClipboardEnvironment(): MarkdownClipboardEnvironment {
+  return {
+    richWriter: getWebRichClipboardWriter(),
+    writePlainText: (text) => Clipboard.setStringAsync(text),
+  };
+}
+
+function getWebRichClipboardWriter(): RichClipboardWriter | null {
+  if (!isWeb) {
+    return null;
+  }
+  if (typeof navigator === "undefined" || typeof navigator.clipboard?.write !== "function") {
+    return null;
+  }
+  if (typeof ClipboardItem === "undefined") {
+    return null;
+  }
+
+  return {
+    supportsHtml: () =>
+      typeof ClipboardItem.supports !== "function" || ClipboardItem.supports("text/html"),
+    write: async (data) => {
+      await navigator.clipboard.write([new ClipboardItem(data)]);
+    },
+  };
+}