biskuteri-cafe-JKomasto2/RudimentaryHTMLParser.java

import cafe.biskuteri.hinoki.Tree;
import java.io.StringReader;
import java.io.Reader;
import java.io.IOException;

class
RudimentaryHTMLParser {

    public static Tree<String>
    depthlessRead(String html)
    throws IOException
    {
        return pass2(pass1(html));
    }

//     -    -%-     -

    private static Tree<String>
    pass1(String html)
    throws IOException
    {
        Reader r = new StringReader(html);
        Tree<String> docu = new Tree<String>();
        StringBuilder text = new StringBuilder();
        StringBuilder htmlEscape = new StringBuilder();
        boolean quoted = false;
        int c; while ((c = r.read()) != -1)
        {
            if (c == '&' || htmlEscape.length() > 0)
            {
                htmlEscape.append((char)c);
                if (c == ';')
                {
                    String s = empty(htmlEscape);
                    if (quoted) text.append('\\');
                    /*
                    * If we're quoted (i.e. within unescaped
                    * quotes), we're in a tag, add escaping
                    * backslash for pass2 to work with.
                    * Only necessary for the quotes, but,
                    * might as well uniformly use.
                    */
                    if (s.equals("&lt;")) text.append('<');
                    if (s.equals("&gt;")) text.append('>');
                    if (s.equals("&amp;")) text.append('&');
                    if (s.equals("&quot;")) text.append('"');
                    if (s.equals("&apos;")) text.append('\'');
                }
                continue;
            }
            if (c == '"')
            {
                text.append((char)c);
                quoted = !quoted;
                continue;
            }
            if (!quoted)
            {
                if (c == '<')
                {
                    if (text.length() > 0)
                    {
                        Tree<String> node = new Tree<>();
                        node.key = "text";
                        node.value = empty(text);
                        docu.add(node);
                    }
                    continue;
                }
                if (c == '>')
                {
                    Tree<String> node = new Tree<>();
                    node.key = "tag";
                    node.value = empty(text);
                    docu.add(node);
                    continue;
                }
            }
            text.append((char)c);
            continue;
        }
        if (text.length() > 0)
        {
            Tree<String> node = new Tree<>();
            node.key = "text";
            node.value = empty(text);
            docu.add(node);
        }
        return docu;
    }

    private static Tree<String>
    pass2(Tree<String> docu)
    throws IOException
    {
        for (Tree<String> node: docu.children)
        {
            if (node.key.equals("text")) continue;
            assert node.key.equals("tag");

            Reader r = new StringReader(node.value);
            Tree<String> part = new Tree<String>();
            boolean escaped = false, quoted = false;
            StringBuilder field = new StringBuilder();
            int c; while ((c = r.read()) != -1)
            {
                if (escaped) {
                    field.append((char)c);
                    escaped = false;
                    continue;
                }
                if (c == '\\') {
                    escaped = true;
                    continue;
                }
                if (c == '"') {
                    quoted = !quoted;
                    continue;
                }
                if (quoted) {
                    field.append((char)c);
                    continue;
                }
                if (c == '=') {
                    part.key = empty(field);
                    continue;
                }
                if (c == ' ') {
                    if (field.length() > 0) {
                        boolean v = part.key != null;
                        if (v) part.value = empty(field);
                        else part.key = empty(field);
                        node.add(part);
                        part = new Tree<String>();
                    }
                    continue;
                }
                field.append((char)c);
            }
            if (field.length() > 0) {
                boolean v = part.key != null;
                if (v) part.value = empty(field);
                else part.key = empty(field);
                node.add(part);
            }
            node.value = null;
        }
        return docu;
    }

    private static String
    empty(StringBuilder b)
    {
        String s = b.toString();
        b.delete(0, b.length());
        return s;
    }

//    ---%-@-%---

    public static void
    main(String... args)
    {
        final String EX2 =
            "<p>2000s energy<br /><a href=\"http://www.pspad.com/en/screenshot.htm\" rel=\"nofollow noopener noreferrer\" target=\"_blank\"><span class=\"invisible\">http://www.</span><span class=\"\">pspad.com/en/screenshot.htm</span><span class=\"invisible\"></span></a></p>";
    }

}