CDP: implement LP.getSemanticTree for native semantic DOM extraction

src/cdp/domains/lp.zig

@@ -18,19 +18,53 @@
 
 const std = @import("std");
 const lp = @import("lightpanda");
+const log = @import("../../log.zig");
 const markdown = lp.markdown;
 const Node = @import("../Node.zig");
+const DOMNode = @import("../../browser/webapi/Node.zig");
+const SemanticTree = @import("../semantic_tree.zig");
 
 pub fn processMessage(cmd: anytype) !void {
     const action = std.meta.stringToEnum(enum {
         getMarkdown,
+        getSemanticTree,
     }, cmd.input.action) orelse return error.UnknownMethod;
 
     switch (action) {
         .getMarkdown => return getMarkdown(cmd),
+        .getSemanticTree => return getSemanticTree(cmd),
     }
 }
 
+const SemanticTreeResult = struct {
+    dom_node: *DOMNode,
+    registry: *Node.Registry,
+    page: *lp.Page,
+    arena: std.mem.Allocator,
+
+    pub fn jsonStringify(self: @This(), jw: *std.json.Stringify) error{WriteFailed}!void {
+        SemanticTree.dump(self.dom_node, self.registry, jw, self.page, self.arena) catch |err| {
+            log.err(.cdp, "semantic tree dump failed", .{ .err = err });
+            return error.WriteFailed;
+        };
+    }
+};
+
+fn getSemanticTree(cmd: anytype) !void {
+    const bc = cmd.browser_context orelse return error.NoBrowserContext;
+    const page = bc.session.currentPage() orelse return error.PageNotLoaded;
+    const dom_node = page.document.asNode();
+
+    return cmd.sendResult(.{
+        .semanticTree = .{
+            .dom_node = dom_node,
+            .registry = &bc.node_registry,
+            .page = page,
+            .arena = cmd.arena,
+        },
+    }, .{});
+}
+
 fn getMarkdown(cmd: anytype) !void {
     const Params = struct {
         nodeId: ?Node.Id = null,
@@ -45,7 +79,7 @@ fn getMarkdown(cmd: anytype) !void {
     else
         page.document.asNode();
 
-    var aw = std.Io.Writer.Allocating.init(cmd.arena);
+    var aw: std.Io.Writer.Allocating = .init(cmd.arena);
     defer aw.deinit();
     try markdown.dump(dom_node, .{}, &aw.writer, page);