LibHTML: Start working on a very simplified HTML parser.

LibHTML/Parser.cpp

@@ -1,32 +1,120 @@
 #include <LibHTML/Element.h>
 #include <LibHTML/Parser.h>
 #include <LibHTML/Text.h>
+#include <ctype.h>
 
 static Retained<Element> create_element(const String& tag_name)
 {
     return adopt(*new Element(tag_name));
 }
 
-Retained<Document> parse(const String& html)
+static bool is_self_closing_tag(const String& tag_name)
 {
-    auto doc = adopt(*new Document);
-
-    auto head = create_element("head");
-    auto title = create_element("title");
-    auto title_text = adopt(*new Text("Page Title"));
-    title->append_child(title_text);
-    head->append_child(title);
-
-    doc->append_child(head);
-
-    auto body = create_element("body");
-    auto h1 = create_element("h1");
-    auto h1_text = adopt(*new Text("Hello World!"));
-
-    h1->append_child(h1_text);
-    body->append_child(h1);
-    doc->append_child(body);
-
-    return doc;
+    return tag_name == "area"
+        || tag_name == "base"
+        || tag_name == "br"
+        || tag_name == "col"
+        || tag_name == "embed"
+        || tag_name == "hr"
+        || tag_name == "img"
+        || tag_name == "input"
+        || tag_name == "link"
+        || tag_name == "meta"
+        || tag_name == "param"
+        || tag_name == "source"
+        || tag_name == "track"
+        || tag_name == "wbr";
 }
 
+Retained<Document> parse(const String& html)
+{
+    Vector<Retained<ParentNode>> node_stack;
+
+    auto doc = adopt(*new Document);
+    node_stack.append(doc);
+
+    enum class State {
+        Free,
+        BeforeTagName,
+        InTagName,
+        InAttributeList,
+        InAttributeName,
+        InAttributeValueNoQuote,
+        InAttributeValueSingleQuote,
+        InAttributeValueDoubleQuote,
+    };
+
+    auto state = State::Free;
+
+    Vector<char, 256> buffer;
+
+    bool is_slash_tag = false;
+
+    auto move_to_state = [&](State new_state) {
+        if (new_state == State::BeforeTagName)
+            is_slash_tag = false;
+        if (state == State::Free && !buffer.is_empty()) {
+            auto text_node = adopt(*new Text(String::copy(buffer)));
+            node_stack.last()->append_child(text_node);
+        }
+        state = new_state;
+        buffer.clear();
+    };
+
+    auto close_tag = [&] {
+        if (node_stack.size() > 1)
+            node_stack.take_last();
+    };
+
+    auto open_tag = [&] {
+        auto new_element = create_element(String::copy(buffer));
+        node_stack.append(new_element);
+        if (node_stack.size() != 1)
+            node_stack[node_stack.size() - 2]->append_child(new_element);
+
+        if (is_self_closing_tag(new_element->tag_name()))
+            close_tag();
+    };
+
+    for (int i = 0; i < html.length(); ++i) {
+        char ch = html[i];
+        switch (state) {
+        case State::Free:
+            if (ch == '<') {
+                move_to_state(State::BeforeTagName);
+                break;
+            }
+            buffer.append(ch);
+            break;
+        case State::BeforeTagName:
+            if (ch == '/') {
+                is_slash_tag = true;
+                break;
+            }
+            if (ch == '>') {
+                move_to_state(State::Free);
+                break;
+            }
+            if (!isascii(ch))
+                break;
+            move_to_state(State::InTagName);
+            [[fallthrough]];
+        case State::InTagName:
+            if (ch == ' ') {
+                move_to_state(State::InAttributeList);
+                break;
+            }
+            if (ch == '>') {
+                if (is_slash_tag)
+                    close_tag();
+                else
+                    open_tag();
+                move_to_state(State::Free);
+                break;
+            }
+            buffer.append(ch);
+            break;
+        }
+    }
+    return doc;
+}

LibHTML/test.cpp

@@ -1,10 +1,18 @@
+#include <LibCore/CFile.h>
 #include <LibHTML/Dump.h>
 #include <LibHTML/Element.h>
 #include <LibHTML/Parser.h>
+#include <stdio.h>
 
-int main()
+int main(int argc, char** argv)
 {
-    String html = "<html><head><title>my page</title></head><body><h1>Hi there</h1><p>Hello World!</p></body></html>";
+    CFile f(argc == 1 ? "/home/anon/small.html" : argv[1]);
+    if (!f.open(CIODevice::ReadOnly)) {
+        fprintf(stderr, "Error: %s\n", f.error_string());
+        return 1;
+    }
+    String html = String::copy(f.read_all());
     auto doc = parse(html);
     dump_tree(doc);
+    return 0;
 }