From 67b742bf3218ced0cc0471ae8615beed66fe2cd3 Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Mon, 25 May 2020 21:12:00 +0100
Subject: [PATCH] LibWeb: Add document.querySelector()

---
 .../anon/www/canvas-path-quadratic-curve.html |  2 +-
 Base/home/anon/www/canvas-path.html           |  2 +-
 Base/home/anon/www/img-canvas.html            |  4 ++--
 Base/home/anon/www/location.html              |  2 +-
 Libraries/LibWeb/Bindings/DocumentWrapper.cpp | 19 ++++++++++++++++++
 Libraries/LibWeb/Bindings/DocumentWrapper.h   |  1 +
 Libraries/LibWeb/DOM/Document.cpp             | 20 +++++++++++++++++++
 Libraries/LibWeb/DOM/Document.h               |  1 +
 8 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/Base/home/anon/www/canvas-path-quadratic-curve.html b/Base/home/anon/www/canvas-path-quadratic-curve.html
index 89c4a1d098..0985f97184 100644
--- a/Base/home/anon/www/canvas-path-quadratic-curve.html
+++ b/Base/home/anon/www/canvas-path-quadratic-curve.html
@@ -9,7 +9,7 @@
 
 function drawSomeCurves() {
 
-var canvas = document.querySelectorAll("canvas")[0];
+var canvas = document.querySelector("canvas");
 var ctx = canvas.getContext("2d");
 var x = 150;
 var y = 150;
diff --git a/Base/home/anon/www/canvas-path.html b/Base/home/anon/www/canvas-path.html
index 2f6c26c068..b44c7d655f 100644
--- a/Base/home/anon/www/canvas-path.html
+++ b/Base/home/anon/www/canvas-path.html
@@ -9,7 +9,7 @@
 
 function drawHouse() {
 
-var ctx = document.querySelectorAll("canvas")[0].getContext("2d");
+var ctx = document.querySelector("canvas").getContext("2d");
 ctx.fillStyle = 'black';
 ctx.fillRect(0, 0, 300, 300);
 
diff --git a/Base/home/anon/www/img-canvas.html b/Base/home/anon/www/img-canvas.html
index 5a4f0fde80..a21add25ac 100644
--- a/Base/home/anon/www/img-canvas.html
+++ b/Base/home/anon/www/img-canvas.html
@@ -9,10 +9,10 @@
     </style>
     <script>
         document.addEventListener("DOMContentLoaded", function() {
-            img = document.querySelectorAll("img")[0];
+            img = document.querySelector("img");
 
             img.addEventListener("load", function() {
-                var ctx = document.querySelectorAll("canvas")[0].getContext("2d");
+                var ctx = document.querySelector("canvas").getContext("2d");
                 ctx.fillStyle = '#666';
                 ctx.fillRect(0, 0, 400, 400);
                 ctx.scale(2, 2);
diff --git a/Base/home/anon/www/location.html b/Base/home/anon/www/location.html
index d7e08fe5d4..5633fa3df9 100644
--- a/Base/home/anon/www/location.html
+++ b/Base/home/anon/www/location.html
@@ -12,7 +12,7 @@
     <div id="set_href">Click me to set location.href!</div>
     <div id="reload">Click me to call location.reload()!</div>
     <script>
-        var pre = document.querySelectorAll("pre")[0];
+        var pre = document.querySelector("pre");
         pre.innerHTML += "href: " + location.href + '\n';
         pre.innerHTML += "protocol: " + location.protocol + '\n';
         pre.innerHTML += "host: " + location.host + '\n';
diff --git a/Libraries/LibWeb/Bindings/DocumentWrapper.cpp b/Libraries/LibWeb/Bindings/DocumentWrapper.cpp
index 13381d82a7..a74fa06b01 100644
--- a/Libraries/LibWeb/Bindings/DocumentWrapper.cpp
+++ b/Libraries/LibWeb/Bindings/DocumentWrapper.cpp
@@ -41,6 +41,7 @@ DocumentWrapper::DocumentWrapper(Document& document)
     : NodeWrapper(document)
 {
     put_native_function("getElementById", get_element_by_id, 1);
+    put_native_function("querySelector", query_selector, 1);
     put_native_function("querySelectorAll", query_selector_all, 1);
 }
 
@@ -86,6 +87,23 @@ JS::Value DocumentWrapper::get_element_by_id(JS::Interpreter& interpreter)
     return wrap(interpreter.heap(), const_cast<Element&>(*element));
 }
 
+JS::Value DocumentWrapper::query_selector(JS::Interpreter& interpreter)
+{
+    auto* document = document_from(interpreter);
+    if (!document)
+        return {};
+    if (!interpreter.argument_count())
+        return interpreter.throw_exception<JS::TypeError>("querySelector() needs one argument");
+    auto selector = interpreter.argument(0).to_string(interpreter);
+    if (interpreter.exception())
+        return {};
+    // FIXME: Throw if selector is invalid
+    auto element = document->query_selector(selector);
+    if (!element)
+        return JS::js_null();
+    return wrap(interpreter.heap(), *element);
+}
+
 JS::Value DocumentWrapper::query_selector_all(JS::Interpreter& interpreter)
 {
     auto* document = document_from(interpreter);
@@ -96,6 +114,7 @@ JS::Value DocumentWrapper::query_selector_all(JS::Interpreter& interpreter)
     auto selector = interpreter.argument(0).to_string(interpreter);
     if (interpreter.exception())
         return {};
+    // FIXME: Throw if selector is invalid
     auto elements = document->query_selector_all(selector);
     // FIXME: This should be a static NodeList, not a plain JS::Array.
     auto* node_list = JS::Array::create(interpreter.global_object());
diff --git a/Libraries/LibWeb/Bindings/DocumentWrapper.h b/Libraries/LibWeb/Bindings/DocumentWrapper.h
index 86f2270ae9..9cf4c765b3 100644
--- a/Libraries/LibWeb/Bindings/DocumentWrapper.h
+++ b/Libraries/LibWeb/Bindings/DocumentWrapper.h
@@ -43,6 +43,7 @@ private:
     virtual const char* class_name() const override { return "DocumentWrapper"; }
 
     static JS::Value get_element_by_id(JS::Interpreter&);
+    static JS::Value query_selector(JS::Interpreter&);
     static JS::Value query_selector_all(JS::Interpreter&);
 };
 
diff --git a/Libraries/LibWeb/DOM/Document.cpp b/Libraries/LibWeb/DOM/Document.cpp
index dec30f6e80..c01cb1c1ba 100644
--- a/Libraries/LibWeb/DOM/Document.cpp
+++ b/Libraries/LibWeb/DOM/Document.cpp
@@ -321,6 +321,26 @@ Vector<const Element*> Document::get_elements_by_name(const String& name) const
     return elements;
 }
 
+RefPtr<Element> Document::query_selector(const StringView& selector_text)
+{
+    auto selector = parse_selector(selector_text);
+    if (!selector.has_value())
+        return {};
+
+    dump_selector(selector.value());
+
+    RefPtr<Element> result;
+    for_each_in_subtree_of_type<Element>([&](auto& element) {
+        if (SelectorEngine::matches(selector.value(), element)) {
+            result = element;
+            return IterationDecision::Break;
+        }
+        return IterationDecision::Continue;
+    });
+
+    return result;
+}
+
 NonnullRefPtrVector<Element> Document::query_selector_all(const StringView& selector_text)
 {
     auto selector = parse_selector(selector_text);
diff --git a/Libraries/LibWeb/DOM/Document.h b/Libraries/LibWeb/DOM/Document.h
index dc9c88bb56..8829171c7a 100644
--- a/Libraries/LibWeb/DOM/Document.h
+++ b/Libraries/LibWeb/DOM/Document.h
@@ -116,6 +116,7 @@ public:
     void schedule_style_update();
 
     Vector<const Element*> get_elements_by_name(const String&) const;
+    RefPtr<Element> query_selector(const StringView&);
     NonnullRefPtrVector<Element> query_selector_all(const StringView&);
 
     const String& source() const { return m_source; }