LibWeb: Start building the tree building part of the new HTML parser

This patch adds a new HTMLDocumentParser class. It keeps a tokenizer
object internally and feeds itself with one token at a time from it.

The names and idioms in this class are expressed as closely to the
actual HTML parsing spec as possible, to make development as easy
and bug free as possible. :^)

This is going to become pretty large, but it's pretty cool!

Libraries/LibWeb/Parser/HTMLDocumentParser.cpp

@@ -0,0 +1,263 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/DOM/DocumentType.h>
+#include <LibWeb/DOM/ElementFactory.h>
+#include <LibWeb/DOM/HTMLFormElement.h>
+#include <LibWeb/DOM/HTMLHeadElement.h>
+#include <LibWeb/Parser/HTMLDocumentParser.h>
+#include <LibWeb/Parser/HTMLToken.h>
+
+namespace Web {
+
+HTMLDocumentParser::HTMLDocumentParser(const StringView& input)
+    : m_tokenizer(input)
+{
+}
+
+HTMLDocumentParser::~HTMLDocumentParser()
+{
+}
+
+void HTMLDocumentParser::run()
+{
+    m_document = adopt(*new Document);
+
+    for (;;) {
+        auto optional_token = m_tokenizer.next_token();
+        if (!optional_token.has_value())
+            return;
+        auto& token = optional_token.value();
+
+        dbg() << "[" << insertion_mode_name() << "] " << token.to_string();
+
+        if (token.type() == HTMLToken::Type::EndOfFile)
+            return;
+
+        switch (m_insertion_mode) {
+        case InsertionMode::Initial:
+            handle_initial(token);
+            break;
+        case InsertionMode::BeforeHTML:
+            handle_before_html(token);
+            break;
+        case InsertionMode::BeforeHead:
+            handle_before_head(token);
+            break;
+        case InsertionMode::InHead:
+            handle_in_head(token);
+            break;
+        case InsertionMode::InHeadNoscript:
+            handle_in_head_noscript(token);
+            break;
+        case InsertionMode::AfterHead:
+            handle_after_head(token);
+            break;
+        case InsertionMode::InBody:
+            handle_in_body(token);
+            break;
+        case InsertionMode::Text:
+            handle_text(token);
+            break;
+        default:
+            ASSERT_NOT_REACHED();
+        }
+    }
+}
+
+void HTMLDocumentParser::handle_initial(HTMLToken& token)
+{
+    if (token.type() == HTMLToken::Type::DOCTYPE) {
+        auto doctype = adopt(*new DocumentType(document()));
+        doctype->set_name(token.m_doctype.name.to_string());
+        document().append_child(move(doctype));
+        m_insertion_mode = InsertionMode::BeforeHTML;
+        return;
+    }
+    ASSERT_NOT_REACHED();
+}
+
+void HTMLDocumentParser::handle_before_html(HTMLToken& token)
+{
+    if (token.is_start_tag() && token.tag_name() == "html") {
+        auto element = create_element_for(token);
+        document().append_child(element);
+        m_stack_of_open_elements.append(element);
+        m_insertion_mode = InsertionMode::BeforeHead;
+        return;
+    }
+    ASSERT_NOT_REACHED();
+}
+
+NonnullRefPtr<Node> HTMLDocumentParser::current_node()
+{
+    return m_stack_of_open_elements.last();
+}
+
+RefPtr<Node> HTMLDocumentParser::find_appropriate_place_for_inserting_node()
+{
+    auto target = current_node();
+    if (m_foster_parenting) {
+        ASSERT_NOT_REACHED();
+    }
+    return target;
+}
+
+NonnullRefPtr<Element> HTMLDocumentParser::create_element_for(HTMLToken& token)
+{
+    auto element = create_element(document(), token.tag_name());
+    for (auto& attribute : token.m_tag.attributes) {
+        element->set_attribute(attribute.name_builder.to_string(), attribute.value_builder.to_string());
+    }
+    return element;
+}
+
+RefPtr<Element> HTMLDocumentParser::insert_html_element(HTMLToken& token)
+{
+    auto adjusted_insertion_location = find_appropriate_place_for_inserting_node();
+    auto element = create_element_for(token);
+    // FIXME: Check if it's possible to insert `element` at `adjusted_insertion_location`
+    adjusted_insertion_location->append_child(element);
+    m_stack_of_open_elements.append(element);
+    return element;
+}
+
+void HTMLDocumentParser::handle_before_head(HTMLToken& token)
+{
+    if (token.is_start_tag() && token.tag_name() == "head") {
+        auto element = insert_html_element(token);
+        m_head_element = to<HTMLHeadElement>(element);
+        m_insertion_mode = InsertionMode::InHead;
+        return;
+    }
+    ASSERT_NOT_REACHED();
+}
+
+void HTMLDocumentParser::handle_in_head(HTMLToken& token)
+{
+    if (token.is_start_tag() && token.tag_name() == "meta") {
+        auto element = insert_html_element(token);
+        m_stack_of_open_elements.take_last();
+        if (token.is_self_closing()) {
+            ASSERT_NOT_REACHED();
+        }
+        return;
+    }
+    if (token.is_end_tag() && token.tag_name() == "head") {
+        m_stack_of_open_elements.take_last();
+        m_insertion_mode = InsertionMode::AfterHead;
+        return;
+    }
+    ASSERT_NOT_REACHED();
+}
+
+void HTMLDocumentParser::handle_in_head_noscript(HTMLToken&)
+{
+    ASSERT_NOT_REACHED();
+}
+
+void HTMLDocumentParser::handle_after_head(HTMLToken& token)
+{
+    if (token.is_character()) {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (token.is_comment()) {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (token.is_doctype()) {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (token.is_start_tag() && token.tag_name() == "html") {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (token.is_start_tag() && token.tag_name() == "body") {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (token.is_start_tag() && token.tag_name() == "frameset") {
+        ASSERT_NOT_REACHED();
+    }
+
+    {
+        Vector<String> names = { "base", "basefont", "bgsound", "link", "meta", "noframes", "script", "style", "template", "title" };
+        if (token.is_end_tag() && names.contains_slow(token.tag_name())) {
+            ASSERT_NOT_REACHED();
+        }
+    }
+
+    if (token.is_end_tag() && token.tag_name() == "template") {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (token.is_end_tag() && (token.tag_name() == "body" || token.tag_name() == "html" || token.tag_name() == "br")) {
+        goto AnythingElse;
+    }
+
+    if ((token.is_start_tag() && token.tag_name() == "head") || token.is_end_tag()) {
+        ASSERT_NOT_REACHED();
+    }
+
+AnythingElse:
+    HTMLToken fake_body_token;
+    fake_body_token.m_type = HTMLToken::Type::StartTag;
+    fake_body_token.m_tag.tag_name.append("body");
+    insert_html_element(fake_body_token);
+    m_insertion_mode = InsertionMode::InBody;
+}
+
+void HTMLDocumentParser::handle_in_body(HTMLToken&)
+{
+    ASSERT_NOT_REACHED();
+}
+
+void HTMLDocumentParser::handle_text(HTMLToken&)
+{
+    ASSERT_NOT_REACHED();
+}
+
+const char* HTMLDocumentParser::insertion_mode_name() const
+{
+    switch (m_insertion_mode) {
+#define __ENUMERATE_INSERTION_MODE(mode) \
+    case InsertionMode::mode:            \
+        return #mode;
+        ENUMERATE_INSERTION_MODES
+#undef __ENUMERATE_INSERTION_MODE
+    }
+    ASSERT_NOT_REACHED();
+}
+
+Document& HTMLDocumentParser::document()
+{
+    return *m_document;
+}
+
+}