fix: unify chat process and reply presentation

src/shared/ai-elements/paragraph-copy.ts

@@ -0,0 +1,51 @@
+import type { ClipboardEvent } from "react";
+
+export function copySelectedText(event: ClipboardEvent<HTMLElement>) {
+  if (event.defaultPrevented) return;
+  const target = event.target instanceof Element ? event.target : null;
+  if (target?.closest("input, textarea, [contenteditable]:not([contenteditable=false])")) return;
+  const selection = event.currentTarget.ownerDocument.defaultView?.getSelection();
+  if (!selection || selection.isCollapsed || selection.rangeCount !== 1) return;
+  const range = selection.getRangeAt(0);
+  const text = selection.toString();
+  const suffix = text.match(/\n+$/)?.[0].length ?? 0;
+  const sourceSuffix = range.toString().match(/\n+$/)?.[0].length ?? 0;
+  // Chromium includes the block boundary when selecting an entire paragraph.
+  // Keep native internal paragraphs, table tabs and code indentation, removing
+  // only the trailing boundary that is absent from the selected source.
+  if (suffix < 2 || suffix <= sourceSuffix) return;
+  event.clipboardData.setData("text/plain", text.slice(0, text.length - suffix + sourceSuffix));
+  event.preventDefault();
+}
+
+export function copySelectedParagraph(event: ClipboardEvent<HTMLElement>, paragraph: HTMLParagraphElement, hasNonSelectableControls = false) {
+  const selection = paragraph.ownerDocument.defaultView?.getSelection();
+  if (!selection || selection.isCollapsed || selection.rangeCount !== 1) return;
+
+  const selected = selection.getRangeAt(0);
+  if (!selected.intersectsNode(paragraph)) return;
+
+  const contents = paragraph.ownerDocument.createRange();
+  contents.selectNodeContents(paragraph);
+  const bounded = selected.cloneRange();
+  if (bounded.compareBoundaryPoints(Range.START_TO_START, contents) < 0) {
+    bounded.setStart(contents.startContainer, contents.startOffset);
+  }
+  if (bounded.compareBoundaryPoints(Range.END_TO_END, contents) > 0) {
+    bounded.setEnd(contents.endContainer, contents.endOffset);
+  }
+
+  // Native paragraph selection can extend to the next message and serialize
+  // the paragraph boundary as extra newlines. Range text preserves the actual
+  // selected source, including intentional whitespace inside the message.
+  const text = bounded.toString();
+  if (!text) return;
+  if (hasNonSelectableControls) {
+    // DOM ranges can include adjacent user-select:none toolbar labels, while
+    // the rendered selection contains only this paragraph and its boundary.
+    if (selection.toString() !== `${text}\n\n`) return;
+  } else if (selected.toString() !== text || selection.toString() === text) return;
+
+  event.clipboardData.setData("text/plain", text);
+  event.preventDefault();
+}