feat(web): add surround selection in composer

apps/web/src/components/ChatView.browser.tsx

@@ -614,6 +614,167 @@ async function waitForComposerEditor(): Promise<HTMLElement> {
   );
 }
 
+async function pressComposerKey(key: string): Promise<void> {
+  const composerEditor = await waitForComposerEditor();
+  composerEditor.focus();
+  const keydownEvent = new KeyboardEvent("keydown", {
+    key,
+    bubbles: true,
+    cancelable: true,
+  });
+  composerEditor.dispatchEvent(keydownEvent);
+  if (keydownEvent.defaultPrevented) {
+    await waitForLayout();
+    return;
+  }
+
+  const beforeInputEvent = new InputEvent("beforeinput", {
+    data: key,
+    inputType: "insertText",
+    bubbles: true,
+    cancelable: true,
+  });
+  composerEditor.dispatchEvent(beforeInputEvent);
+  if (beforeInputEvent.defaultPrevented) {
+    await waitForLayout();
+    return;
+  }
+
+  if (
+    typeof document.execCommand === "function" &&
+    document.execCommand("insertText", false, key)
+  ) {
+    await waitForLayout();
+    return;
+  }
+
+  const selection = window.getSelection();
+  if (!selection || selection.rangeCount === 0) {
+    throw new Error("Unable to resolve composer selection for text input.");
+  }
+  const range = selection.getRangeAt(0);
+  range.deleteContents();
+  const textNode = document.createTextNode(key);
+  range.insertNode(textNode);
+  range.setStartAfter(textNode);
+  range.collapse(true);
+  selection.removeAllRanges();
+  selection.addRange(range);
+  composerEditor.dispatchEvent(
+    new InputEvent("input", {
+      data: key,
+      inputType: "insertText",
+      bubbles: true,
+    }),
+  );
+  await waitForLayout();
+}
+
+async function waitForComposerText(expectedText: string): Promise<void> {
+  await vi.waitFor(
+    () => {
+      expect(useComposerDraftStore.getState().draftsByThreadId[THREAD_ID]?.prompt ?? "").toBe(
+        expectedText,
+      );
+    },
+    { timeout: 8_000, interval: 16 },
+  );
+}
+
+async function setComposerSelectionByTextOffsets(options: {
+  start: number;
+  end: number;
+  direction?: "forward" | "backward";
+}): Promise<void> {
+  const composerEditor = await waitForComposerEditor();
+  composerEditor.focus();
+  const resolvePoint = (targetOffset: number) => {
+    const traversedRef = { value: 0 };
+
+    const visitNode = (node: Node): { node: Node; offset: number } | null => {
+      if (node.nodeType === Node.TEXT_NODE) {
+        const textLength = node.textContent?.length ?? 0;
+        if (targetOffset <= traversedRef.value + textLength) {
+          return {
+            node,
+            offset: Math.max(0, Math.min(targetOffset - traversedRef.value, textLength)),
+          };
+        }
+        traversedRef.value += textLength;
+        return null;
+      }
+
+      if (node instanceof HTMLBRElement) {
+        const parent = node.parentNode;
+        if (!parent) {
+          return null;
+        }
+        const siblingIndex = Array.prototype.indexOf.call(parent.childNodes, node);
+        if (targetOffset <= traversedRef.value) {
+          return { node: parent, offset: siblingIndex };
+        }
+        if (targetOffset <= traversedRef.value + 1) {
+          return { node: parent, offset: siblingIndex + 1 };
+        }
+        traversedRef.value += 1;
+        return null;
+      }
+
+      if (node instanceof Element || node instanceof DocumentFragment) {
+        for (const child of node.childNodes) {
+          const point = visitNode(child);
+          if (point) {
+            return point;
+          }
+        }
+      }
+
+      return null;
+    };
+
+    return (
+      visitNode(composerEditor) ?? {
+        node: composerEditor,
+        offset: composerEditor.childNodes.length,
+      }
+    );
+  };
+
+  const startPoint = resolvePoint(options.start);
+  const endPoint = resolvePoint(options.end);
+  const selection = window.getSelection();
+  if (!selection) {
+    throw new Error("Unable to resolve window selection.");
+  }
+  selection.removeAllRanges();
+
+  if (options.direction === "backward" && "setBaseAndExtent" in selection) {
+    selection.setBaseAndExtent(endPoint.node, endPoint.offset, startPoint.node, startPoint.offset);
+    await waitForLayout();
+    return;
+  }
+
+  const range = document.createRange();
+  range.setStart(startPoint.node, startPoint.offset);
+  range.setEnd(endPoint.node, endPoint.offset);
+  selection.addRange(range);
+  await waitForLayout();
+}
+
+async function selectAllComposerContent(): Promise<void> {
+  const composerEditor = await waitForComposerEditor();
+  composerEditor.focus();
+  const selection = window.getSelection();
+  if (!selection) {
+    throw new Error("Unable to resolve window selection.");
+  }
+  selection.removeAllRanges();
+  const range = document.createRange();
+  range.selectNodeContents(composerEditor);
+  selection.addRange(range);
+  await waitForLayout();
+}
+
 async function waitForSendButton(): Promise<HTMLButtonElement> {
   return waitForElement(
     () => document.querySelector<HTMLButtonElement>('button[aria-label="Send message"]'),
@@ -1582,6 +1743,155 @@ describe("ChatView timeline estimator parity (full app)", () => {
     }
   });
 
+  it("surrounds selected plain text and preserves the inner selection for repeated wrapping", async () => {
+    const mounted = await mountChatView({
+      viewport: DEFAULT_VIEWPORT,
+      snapshot: createSnapshotForTargetUser({
+        targetMessageId: "msg-user-surround-basic" as MessageId,
+        targetText: "surround basic",
+      }),
+    });
+
+    try {
+      useComposerDraftStore.getState().setPrompt(THREAD_ID, "selected");
+      await waitForComposerText("selected");
+      await setComposerSelectionByTextOffsets({ start: 0, end: "selected".length });
+      await pressComposerKey("(");
+      await waitForComposerText("(selected)");
+
+      await pressComposerKey("[");
+      await waitForComposerText("([selected])");
+    } finally {
+      await mounted.cleanup();
+    }
+  });
+
+  it("leaves collapsed-caret typing unchanged for surround symbols", async () => {
+    useComposerDraftStore.getState().setPrompt(THREAD_ID, "selected");
+
+    const mounted = await mountChatView({
+      viewport: DEFAULT_VIEWPORT,
+      snapshot: createSnapshotForTargetUser({
+        targetMessageId: "msg-user-surround-collapsed" as MessageId,
+        targetText: "surround collapsed",
+      }),
+    });
+
+    try {
+      await waitForComposerText("selected");
+      await setComposerSelectionByTextOffsets({
+        start: "selected".length,
+        end: "selected".length,
+      });
+      await pressComposerKey("(");
+      await waitForComposerText("selected(");
+    } finally {
+      await mounted.cleanup();
+    }
+  });
+
+  it("supports symmetric and backward-selection surrounds", async () => {
+    useComposerDraftStore.getState().setPrompt(THREAD_ID, "backward");
+
+    const mounted = await mountChatView({
+      viewport: DEFAULT_VIEWPORT,
+      snapshot: createSnapshotForTargetUser({
+        targetMessageId: "msg-user-surround-backward" as MessageId,
+        targetText: "surround backward",
+      }),
+    });
+
+    try {
+      await waitForComposerText("backward");
+      await setComposerSelectionByTextOffsets({
+        start: 0,
+        end: "backward".length,
+        direction: "backward",
+      });
+      await pressComposerKey("*");
+      await waitForComposerText("*backward*");
+    } finally {
+      await mounted.cleanup();
+    }
+  });
+
+  it("supports option-produced surround symbols like guillemets", async () => {
+    useComposerDraftStore.getState().setPrompt(THREAD_ID, "quoted");
+
+    const mounted = await mountChatView({
+      viewport: DEFAULT_VIEWPORT,
+      snapshot: createSnapshotForTargetUser({
+        targetMessageId: "msg-user-surround-guillemet" as MessageId,
+        targetText: "surround guillemet",
+      }),
+    });
+
+    try {
+      await waitForComposerText("quoted");
+      await setComposerSelectionByTextOffsets({ start: 0, end: "quoted".length });
+      await pressComposerKey("«");
+      await waitForComposerText("«quoted»");
+    } finally {
+      await mounted.cleanup();
+    }
+  });
+
+  it("surrounds text after a mention using the correct expanded offsets", async () => {
+    useComposerDraftStore.getState().setPrompt(THREAD_ID, "hi @package.json there");
+
+    const mounted = await mountChatView({
+      viewport: DEFAULT_VIEWPORT,
+      snapshot: createSnapshotForTargetUser({
+        targetMessageId: "msg-user-surround-after-mention" as MessageId,
+        targetText: "surround after mention",
+      }),
+    });
+
+    try {
+      await vi.waitFor(
+        () => {
+          expect(document.body.textContent).toContain("package.json");
+        },
+        { timeout: 8_000, interval: 16 },
+      );
+      await waitForComposerText("hi @package.json there");
+      await setComposerSelectionByTextOffsets({
+        start: "hi package.json ".length,
+        end: "hi package.json there".length,
+      });
+      await pressComposerKey("(");
+      await waitForComposerText("hi @package.json (there)");
+    } finally {
+      await mounted.cleanup();
+    }
+  });
+
+  it("falls back to normal replacement when the selection includes a mention token", async () => {
+    useComposerDraftStore.getState().setPrompt(THREAD_ID, "hi @package.json there ");
+
+    const mounted = await mountChatView({
+      viewport: DEFAULT_VIEWPORT,
+      snapshot: createSnapshotForTargetUser({
+        targetMessageId: "msg-user-surround-token" as MessageId,
+        targetText: "surround token",
+      }),
+    });
+
+    try {
+      await vi.waitFor(
+        () => {
+          expect(document.body.textContent).toContain("package.json");
+        },
+        { timeout: 8_000, interval: 16 },
+      );
+      await selectAllComposerContent();
+      await pressComposerKey("(");
+      await waitForComposerText("(");
+    } finally {
+      await mounted.cleanup();
+    }
+  });
+
   it("keeps removed terminal context pills removed when a new one is added", async () => {
     const removedLabel = "Terminal 1 lines 1-2";
     const addedLabel = "Terminal 2 lines 9-10";