SemanticTree: unify tree traversal using visitor pattern

This commit is contained in:
Adrià Arrufat
2026-03-09 11:09:27 +09:00
parent 2a2b067633
commit d80e926015

View File

@@ -14,7 +14,7 @@
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// along with this program. See <https://www.gnu.org/licenses/>.
const std = @import("std");
@@ -37,19 +37,133 @@ page: *Page,
arena: std.mem.Allocator,
pub fn jsonStringify(self: @This(), jw: *std.json.Stringify) error{WriteFailed}!void {
self.dumpJson(self.dom_node, jw, "") catch |err| {
var visitor = JsonVisitor{ .jw = jw, .tree = self };
self.walk(self.dom_node, "", &visitor) catch |err| {
log.err(.app, "semantic tree json dump failed", .{ .err = err });
return error.WriteFailed;
};
}
pub fn textStringify(self: @This(), writer: *std.Io.Writer) error{WriteFailed}!void {
self.dumpText(self.dom_node, writer, 0) catch |err| {
var visitor = TextVisitor{ .writer = writer, .tree = self, .depth = 0 };
self.walk(self.dom_node, "", &visitor) catch |err| {
log.err(.app, "semantic tree text dump failed", .{ .err = err });
return error.WriteFailed;
};
}
const NodeData = struct {
id: u32,
axn: AXNode,
role: []const u8,
name: ?[]const u8,
value: ?[]const u8,
xpath: []const u8,
is_interactive: bool,
node_name: []const u8,
};
fn walk(self: @This(), node: *Node, parent_xpath: []const u8, visitor: anytype) !void {
// 1. Skip non-content nodes
if (node.is(Element)) |el| {
const tag = el.getTag();
if (tag.isMetadata() or tag == .svg) return;
// CSS display: none visibility check (inline style only for now)
if (el.getAttributeSafe(comptime lp.String.wrap("style"))) |style| {
if (std.mem.indexOf(u8, style, "display: none") != null or
std.mem.indexOf(u8, style, "display:none") != null)
{
return;
}
}
if (el.is(Element.Html)) |html_el| {
if (html_el.getHidden()) return;
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
const text = text_node.getWholeText();
if (isAllWhitespace(text)) {
return;
}
} else if (node._type != .document and node._type != .document_fragment) {
return;
}
const cdp_node = try self.registry.register(node);
const axn = AXNode.fromNode(node);
const role = try axn.getRole();
var is_interactive = false;
var value: ?[]const u8 = null;
var node_name: []const u8 = "text";
if (node.is(Element)) |el| {
node_name = el.getTagNameLower();
const ax_role = std.meta.stringToEnum(AXNode.AXRole, role) orelse .none;
is_interactive = ax_role.isInteractive();
const event_target = node.asEventTarget();
if (self.page._event_manager.hasListener(event_target, "click") or
self.page._event_manager.hasListener(event_target, "mousedown") or
self.page._event_manager.hasListener(event_target, "mouseup") or
self.page._event_manager.hasListener(event_target, "keydown") or
self.page._event_manager.hasListener(event_target, "change") or
self.page._event_manager.hasListener(event_target, "input"))
{
is_interactive = true;
}
if (el.is(Element.Html)) |html_el| {
if (html_el.hasAttributeFunction(.onclick, self.page) or
html_el.hasAttributeFunction(.onmousedown, self.page) or
html_el.hasAttributeFunction(.onmouseup, self.page) or
html_el.hasAttributeFunction(.onkeydown, self.page) or
html_el.hasAttributeFunction(.onchange, self.page) or
html_el.hasAttributeFunction(.oninput, self.page))
{
is_interactive = true;
}
}
if (el.is(Element.Html.Input)) |input| {
value = input.getValue();
} else if (el.is(Element.Html.TextArea)) |textarea| {
value = textarea.getValue();
} else if (el.is(Element.Html.Select)) |select| {
value = select.getValue(self.page);
}
} else if (node._type == .document or node._type == .document_fragment) {
node_name = "root";
}
const segment = try self.getXPathSegment(node);
const xpath = try std.mem.concat(self.arena, u8, &.{ parent_xpath, segment });
const name = try axn.getName(self.page, self.arena);
var data = NodeData{
.id = cdp_node.id,
.axn = axn,
.role = role,
.name = name,
.value = value,
.xpath = xpath,
.is_interactive = is_interactive,
.node_name = node_name,
};
if (try visitor.visit(node, &data)) {
var it = node.childrenIterator();
while (it.next()) |child| {
try self.walk(child, xpath, visitor);
}
try visitor.leave(node, &data);
}
}
fn getXPathSegment(self: @This(), node: *Node) ![]const u8 {
if (node.is(Element)) |el| {
const tag = el.getTagNameLower();
@@ -83,152 +197,78 @@ fn getXPathSegment(self: @This(), node: *Node) ![]const u8 {
return "";
}
fn dumpJson(self: Self, node: *Node, jw: *std.json.Stringify, parent_xpath: []const u8) !void {
// 1. Skip non-content nodes
if (node.is(Element)) |el| {
const tag = el.getTag();
if (tag.isMetadata() or tag == .svg) return;
const JsonVisitor = struct {
jw: *std.json.Stringify,
tree: Self,
// CSS display: none visibility check (inline style only for now)
if (el.getAttributeSafe(comptime lp.String.wrap("style"))) |style| {
if (std.mem.indexOf(u8, style, "display: none") != null or
std.mem.indexOf(u8, style, "display:none") != null)
{
return;
pub fn visit(self: *JsonVisitor, node: *Node, data: *NodeData) !bool {
try self.jw.beginObject();
try self.jw.objectField("nodeId");
try self.jw.write(try std.fmt.allocPrint(self.tree.arena, "{d}", .{data.id}));
try self.jw.objectField("backendDOMNodeId");
try self.jw.write(data.id);
try self.jw.objectField("nodeName");
try self.jw.write(data.node_name);
try self.jw.objectField("xpath");
try self.jw.write(data.xpath);
if (node.is(Element)) |el| {
try self.jw.objectField("nodeType");
try self.jw.write(1);
try self.jw.objectField("isInteractive");
try self.jw.write(data.is_interactive);
try self.jw.objectField("role");
try self.jw.write(data.role);
if (data.name) |name| {
if (name.len > 0) {
try self.jw.objectField("name");
try self.jw.write(name);
}
}
if (data.value) |value| {
try self.jw.objectField("value");
try self.jw.write(value);
}
if (el._attributes) |attrs| {
try self.jw.objectField("attributes");
try self.jw.beginObject();
var iter = attrs.iterator();
while (iter.next()) |attr| {
try self.jw.objectField(attr._name.str());
try self.jw.write(attr._value.str());
}
try self.jw.endObject();
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
try self.jw.objectField("nodeType");
try self.jw.write(3);
try self.jw.objectField("nodeValue");
try self.jw.write(text_node.getWholeText());
} else {
try self.jw.objectField("nodeType");
try self.jw.write(9);
}
if (el.is(Element.Html)) |html_el| {
if (html_el.getHidden()) return;
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
const text = text_node.getWholeText();
if (isAllWhitespace(text)) {
return;
}
} else if (node._type != .document and node._type != .document_fragment) {
return;
try self.jw.objectField("children");
try self.jw.beginArray();
return true;
}
const cdp_node = try self.registry.register(node);
const axn = AXNode.fromNode(node);
const role = try axn.getRole();
var is_interactive = false;
var node_name: []const u8 = "text";
if (node.is(Element)) |el| {
node_name = el.getTagNameLower();
const ax_role = std.meta.stringToEnum(AXNode.AXRole, role) orelse .none;
is_interactive = ax_role.isInteractive();
const event_target = node.asEventTarget();
if (self.page._event_manager.hasListener(event_target, "click") or
self.page._event_manager.hasListener(event_target, "mousedown") or
self.page._event_manager.hasListener(event_target, "mouseup") or
self.page._event_manager.hasListener(event_target, "keydown") or
self.page._event_manager.hasListener(event_target, "change") or
self.page._event_manager.hasListener(event_target, "input"))
{
is_interactive = true;
}
if (el.is(Element.Html)) |html_el| {
if (html_el.hasAttributeFunction(.onclick, self.page) or
html_el.hasAttributeFunction(.onmousedown, self.page) or
html_el.hasAttributeFunction(.onmouseup, self.page) or
html_el.hasAttributeFunction(.onkeydown, self.page) or
html_el.hasAttributeFunction(.onchange, self.page) or
html_el.hasAttributeFunction(.oninput, self.page))
{
is_interactive = true;
}
}
} else if (node._type == .document or node._type == .document_fragment) {
node_name = "root";
pub fn leave(self: *JsonVisitor, _: *Node, _: *NodeData) !void {
try self.jw.endArray();
try self.jw.endObject();
}
const segment = try self.getXPathSegment(node);
const xpath = try std.mem.concat(self.arena, u8, &.{ parent_xpath, segment });
try jw.beginObject();
try jw.objectField("nodeId");
try jw.write(try std.fmt.allocPrint(self.arena, "{d}", .{cdp_node.id}));
try jw.objectField("backendDOMNodeId");
try jw.write(cdp_node.id);
try jw.objectField("nodeName");
try jw.write(node_name);
try jw.objectField("xpath");
try jw.write(xpath);
if (node.is(Element)) |el| {
try jw.objectField("nodeType");
try jw.write(1);
try jw.objectField("isInteractive");
try jw.write(is_interactive);
try jw.objectField("role");
try jw.write(role);
// Add accessible name (e.g. button label, aria-label, etc.)
if (try axn.getName(self.page, self.arena)) |name| {
if (name.len > 0) {
try jw.objectField("name");
try jw.write(name);
}
}
// Add value for input elements
if (el.is(Element.Html.Input)) |input| {
try jw.objectField("value");
try jw.write(input.getValue());
} else if (el.is(Element.Html.TextArea)) |textarea| {
try jw.objectField("value");
try jw.write(textarea.getValue());
} else if (el.is(Element.Html.Select)) |select| {
try jw.objectField("value");
try jw.write(select.getValue(self.page));
}
if (el._attributes) |attrs| {
try jw.objectField("attributes");
try jw.beginObject();
var iter = attrs.iterator();
while (iter.next()) |attr| {
try jw.objectField(attr._name.str());
try jw.write(attr._value.str());
}
try jw.endObject();
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
try jw.objectField("nodeType");
try jw.write(3);
try jw.objectField("nodeValue");
try jw.write(text_node.getWholeText());
} else {
try jw.objectField("nodeType");
try jw.write(9);
}
try jw.objectField("children");
try jw.beginArray();
var it = node.childrenIterator();
while (it.next()) |child| {
try self.dumpJson(child, jw, xpath);
}
try jw.endArray();
try jw.endObject();
}
};
fn isStructuralRole(role: []const u8) bool {
return std.mem.eql(u8, role, "none") or
@@ -236,134 +276,74 @@ fn isStructuralRole(role: []const u8) bool {
std.mem.eql(u8, role, "InlineTextBox");
}
fn dumpText(self: Self, node: *Node, writer: *std.Io.Writer, depth: usize) !void {
// 1. Skip non-content nodes
if (node.is(Element)) |el| {
const tag = el.getTag();
if (tag.isMetadata() or tag == .svg) return;
const TextVisitor = struct {
writer: *std.Io.Writer,
tree: Self,
depth: usize,
// CSS display: none visibility check (inline style only for now)
if (el.getAttributeSafe(comptime lp.String.wrap("style"))) |style| {
if (std.mem.indexOf(u8, style, "display: none") != null or
std.mem.indexOf(u8, style, "display:none") != null)
{
return;
pub fn visit(self: *TextVisitor, node: *Node, data: *NodeData) !bool {
// Pruning Heuristic:
// If it's a structural node (none/generic) and has no unique label, unwrap it.
// We only keep 'none'/'generic' if they are interactive.
const structural = isStructuralRole(data.role);
const has_explicit_label = if (node.is(Element)) |el|
el.getAttributeSafe(.wrap("aria-label")) != null or el.getAttributeSafe(.wrap("title")) != null
else
false;
if (structural and !data.is_interactive and !has_explicit_label) {
// Just unwrap (don't print this node, but visit children at same depth)
return true;
}
// Skip redundant StaticText nodes if the parent already captures the text
if (std.mem.eql(u8, data.role, "StaticText") and node._parent != null) {
const parent_axn = AXNode.fromNode(node._parent.?);
const parent_name = try parent_axn.getName(self.tree.page, self.tree.arena);
if (parent_name != null and data.name != null and std.mem.indexOf(u8, parent_name.?, data.name.?) != null) {
return false;
}
}
if (el.is(Element.Html)) |html_el| {
if (html_el.getHidden()) return;
// Format: " [12] link: Hacker News (value)"
for (0..(self.depth * 2)) |_| {
try self.writer.writeByte(' ');
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
const text = text_node.getWholeText();
if (isAllWhitespace(text)) {
return;
}
} else if (node._type != .document and node._type != .document_fragment) {
return;
}
try self.writer.print("[{d}] {s}: ", .{ data.id, data.role });
const cdp_node = try self.registry.register(node);
const axn = AXNode.fromNode(node);
const role = try axn.getRole();
var is_interactive = false;
var value: ?[]const u8 = null;
if (node.is(Element)) |el| {
const ax_role = std.meta.stringToEnum(AXNode.AXRole, role) orelse .none;
is_interactive = ax_role.isInteractive();
const event_target = node.asEventTarget();
if (self.page._event_manager.hasListener(event_target, "click") or
self.page._event_manager.hasListener(event_target, "mousedown") or
self.page._event_manager.hasListener(event_target, "mouseup") or
self.page._event_manager.hasListener(event_target, "keydown") or
self.page._event_manager.hasListener(event_target, "change") or
self.page._event_manager.hasListener(event_target, "input"))
{
is_interactive = true;
}
if (el.is(Element.Html)) |html_el| {
if (html_el.hasAttributeFunction(.onclick, self.page) or
html_el.hasAttributeFunction(.onmousedown, self.page) or
html_el.hasAttributeFunction(.onmouseup, self.page) or
html_el.hasAttributeFunction(.onkeydown, self.page) or
html_el.hasAttributeFunction(.onchange, self.page) or
html_el.hasAttributeFunction(.oninput, self.page))
{
is_interactive = true;
if (data.name) |n| {
if (n.len > 0) {
try self.writer.writeAll(n);
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
const trimmed = std.mem.trim(u8, text_node.getWholeText(), " \t\r\n");
if (trimmed.len > 0) {
try self.writer.writeAll(trimmed);
}
}
if (el.is(Element.Html.Input)) |input| {
value = input.getValue();
} else if (el.is(Element.Html.TextArea)) |textarea| {
value = textarea.getValue();
} else if (el.is(Element.Html.Select)) |select| {
value = select.getValue(self.page);
if (data.value) |v| {
if (v.len > 0) {
try self.writer.print(" (value: {s})", .{v});
}
}
try self.writer.writeByte('\n');
self.depth += 1;
return true;
}
const name = try axn.getName(self.page, self.arena);
pub fn leave(self: *TextVisitor, node: *Node, data: *NodeData) !void {
const structural = isStructuralRole(data.role);
const has_explicit_label = if (node.is(Element)) |el|
el.getAttributeSafe(.wrap("aria-label")) != null or el.getAttributeSafe(.wrap("title")) != null
else
false;
// Pruning Heuristic:
// If it's a structural node (none/generic) and has no unique label, unwrap it.
// We only keep 'none'/'generic' if they are interactive.
const structural = isStructuralRole(role);
const has_explicit_label = if (node.is(Element)) |el|
el.getAttributeSafe(.wrap("aria-label")) != null or el.getAttributeSafe(.wrap("title")) != null
else
false;
if (structural and !is_interactive and !has_explicit_label) {
// Just unwrap and process children
var it = node.childrenIterator();
while (it.next()) |child| {
try self.dumpText(child, writer, depth);
}
return;
}
// Skip redundant StaticText nodes if the parent already captures the text
if (std.mem.eql(u8, role, "StaticText") and node._parent != null) {
const parent_axn = AXNode.fromNode(node._parent.?);
const parent_name = try parent_axn.getName(self.page, self.arena);
if (parent_name != null and name != null and std.mem.indexOf(u8, parent_name.?, name.?) != null) {
if (structural and !data.is_interactive and !has_explicit_label) {
return;
}
self.depth -= 1;
}
// Format: " [12] link: Hacker News (value)"
for (0..(depth * 2)) |_| {
try writer.writeByte(' ');
}
try writer.print("[{d}] {s}: ", .{ cdp_node.id, role });
if (name) |n| {
if (n.len > 0) {
try writer.writeAll(n);
}
} else if (node.is(CData.Text) != null) {
const text_node = node.is(CData.Text).?;
const trimmed = std.mem.trim(u8, text_node.getWholeText(), " \t\r\n");
if (trimmed.len > 0) {
try writer.writeAll(trimmed);
}
}
if (value) |v| {
if (v.len > 0) {
try writer.print(" (value: {s})", .{v});
}
}
try writer.writeByte('\n');
var it = node.childrenIterator();
while (it.next()) |child| {
try self.dumpText(child, writer, depth + 1);
}
}
};