feat(domains): migrate scroll with W3C deltaY semantics and dialog guard

1 files changed, 53 insertions, 0 deletions

diff --git a/src/domains/scroll.ts b/src/domains/scroll.ts
new file mode 100644
index 0000000..db80af7
--- /dev/null
+++ b/src/domains/scroll.ts
@@ -0,0 +1,53 @@
+import { Type } from "typebox";
+import { type Result, err, ok } from "../util/result";
+import { defineBrowserTool, type ToolErr, type ToolOk } from "../util/tool";
+
+const ScrollArgs = Type.Object({
+  x: Type.Optional(Type.Number({ description: "X coordinate where to scroll. Default: viewport center" })),
+  y: Type.Optional(Type.Number({ description: "Y coordinate where to scroll. Default: viewport center" })),
+  deltaX: Type.Optional(Type.Number({ default: 0, description: "Horizontal scroll delta (CSS pixels). Positive = right." })),
+  deltaY: Type.Optional(Type.Number({
+    default: -300,
+    description: "Vertical scroll delta (CSS pixels). Positive = up (matches W3C wheel events). Default: -300 (scroll down).",
+  })),
+});
+
+export const scrollTool = defineBrowserTool({
+  name: "browser_scroll",
+  label: "Browser Scroll",
+  description:
+    "Scroll the page at given coordinates. deltaY follows W3C wheel-event convention: positive = scroll up, negative = scroll down. Default scrolls down (deltaY = -300).",
+  promptSnippet: "Scroll the page (deltaY positive=up, negative=down)",
+  promptGuidelines: [
+    "Default behavior scrolls down 300px (deltaY=-300). Pass a positive deltaY to scroll up.",
+    "Pass x/y to target a specific scrollable region (e.g., a div with overflow); otherwise scrolls the page at viewport center.",
+  ],
+  parameters: ScrollArgs,
+  async handler(args, { client }): Promise<Result<ToolOk, ToolErr>> {
+    const info = await client.pageInfo();
+    if (!info.success) return err({ kind: "cdp_error", message: info.error.message });
+    if ("dialog" in info.data) {
+      return err({
+        kind: "invalid_state",
+        message: `Dialog open: ${info.data.dialog.type} — ${info.data.dialog.message}`,
+      });
+    }
+    const cx = args.x ?? Math.round(info.data.width / 2);
+    const cy = args.y ?? Math.round(info.data.height / 2);
+    const dx = args.deltaX ?? 0;
+    const dy = args.deltaY ?? -300;
+    // Establish compositor mouse position before mouseWheel; without this,
+    // CDP sometimes drops the wheel event with a timeout. Fix preserved
+    // from v0.2.0.
+    const moved = await client.session().call("Input.dispatchMouseEvent", { type: "mouseMoved", x: cx, y: cy });
+    if (!moved.success) return err({ kind: "cdp_error", message: moved.error.message });
+    const wheel = await client.session().call("Input.dispatchMouseEvent", {
+      type: "mouseWheel", x: cx, y: cy, deltaX: dx, deltaY: dy,
+    });
+    if (!wheel.success) return err({ kind: "cdp_error", message: wheel.error.message });
+    return ok({
+      text: `Scrolled at (${cx}, ${cy}) by (${dx}, ${dy})`,
+      details: { x: cx, y: cy, deltaX: dx, deltaY: dy },
+    });
+  },
+});