package nokogiri;

import static nokogiri.internals.NokogiriHelpers.getLocalPart;
import static nokogiri.internals.NokogiriHelpers.getNokogiriClass;
import static nokogiri.internals.NokogiriHelpers.getPrefix;
import static nokogiri.internals.NokogiriHelpers.nonEmptyStringOrNil;

import org.cyberneko.dtd.DTDConfiguration;
import org.jruby.Ruby;
import org.jruby.RubyClass;
import org.jruby.RubyObject;
import org.jruby.anno.JRubyClass;
import org.jruby.anno.JRubyMethod;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

/**
 * DTD element content model. This converts the nice tree of content
 * model declarations returned by NekoDTD into the convoluted binary
 * tree used by libxml.
 *
 * @author Patrick Mahoney <pat@polycrystal.org>
 */
@JRubyClass(name = "Nokogiri::XML::ElementContent")
public class XmlElementContent extends RubyObject
{
  protected String element_name = null;

  protected String name;
  protected Type type;
  protected Occur occur;
  protected IRubyObject left;
  protected IRubyObject right;

  /** values hardcoded from nokogiri/xml/element_content.rb; this
   * makes me uneasy, but it works */
  public enum Type {
    PCDATA(1),
    ELEMENT(2),
    SEQ(3),
    OR(4);

    private final int value;
    Type(int value)
    {
      this.value = value;
    }
    public IRubyObject value(Ruby runtime)
    {
      return runtime.newFixnum(value);
    }
  }

  public enum Occur {
    ONCE(1),
    OPT(2),
    MULT(3),
    PLUS(4);

    private final int value;
    Occur(int value)
    {
      this.value = value;
    }
    public IRubyObject value(Ruby runtime)
    {
      return runtime.newFixnum(value);
    }
  }

  public
  XmlElementContent(Ruby runtime, RubyClass klass,
                    XmlDocument document, Node node)
  {
    this(runtime, klass, document, new NodeIter(node));
    element_name = ((Element)node).getAttribute("ename");

    /*
     * This is a bit of a hack to match libxml behavior.
     *
     * If the tree contains but a single group with a single
     * element, we can simply return the bare element without the
     * surrounding group.
     *
     * TODO: is SEQ/ONCE with a single child the only case for
     * reduction?
     *
     * - pmahoney
     */
    if (!this.left.isNil()) {
      XmlElementContent left = (XmlElementContent) this.left;
      if (type == Type.SEQ &&
          occur == Occur.ONCE &&
          left.type == Type.ELEMENT &&
          right.isNil()) {
        this.name = left.name;
        this.type = left.type;
        this.occur = left.occur;
        this.left = this.right; // both nil
      }
    }
  }

  public
  XmlElementContent(Ruby runtime, XmlDocument document, Node node)
  {
    this(runtime, getNokogiriClass(runtime, "Nokogiri::XML::ElementContent"), document, node);
  }

  public
  XmlElementContent(Ruby runtime, RubyClass klass,
                    XmlDocument doc, NodeIter iter)
  {
    super(runtime, klass);

    setInstanceVariable("@document", doc);

    name = null;
    type = Type.SEQ;
    occur = Occur.ONCE;
    left = runtime.getNil();
    right = runtime.getNil();

    apply(runtime, klass, doc, iter);
  }

  protected
  XmlElementContent(Ruby runtime, RubyClass klass,
                    Type type, XmlDocument doc, NodeIter iter,
                    XmlElementContent left)
  {
    super(runtime, klass);

    setInstanceVariable("@document", doc);

    name = null;
    this.type = type;
    occur = Occur.ONCE;
    this.left = left;
    right = runtime.getNil();

    switch (type) {
      case SEQ:
      case OR:
        applyGroup(runtime, klass, doc, iter);
      default:
        // noop
    }
  }

  /**
   * Applies the current node in <code>iter</code> to this content
   * model.  When finished, <code>iter</code> will point to the last
   * processed node.
   */
  protected void
  apply(Ruby runtime, RubyClass klass,
        XmlDocument doc,
        NodeIter iter)
  {
    if (iter.isNull()) { return; }

    Element elem = (Element) iter.current();

    if (isGroup(elem) && iter.hasChildren()) {
      iter.firstChild();
      applyGroup(runtime, klass, doc, iter);
      iter.parent();
    } else if (isElement(elem)) {
      name = elem.getAttribute("name");
      type = Type.ELEMENT;
    }

    iter.nextSibling();
    if (iter.isNull()) { return; }
    if (isOccurrence(iter.current())) {
      setOccur(((Element)iter.current()).getAttribute("type"));
      iter.nextSibling();
    }
  }

  protected void
  applyGroup(Ruby runtime, RubyClass klass,
             XmlDocument doc, NodeIter iter)
  {
    // LEFT branch

    if (iter.isNull()) { return; }

    if (left.isNil()) {
      left = new XmlElementContent(runtime, klass, doc, iter);

      if (iter.isNull()) { return; }

      if (isSeparator(iter.current())) {
        setType(((Element)iter.current()).getAttribute("type"));
        iter.nextSibling(); // skip separator
      }
    }

    // RIGHT branch

    if (iter.isNull()) { return; }

    right = new XmlElementContent(runtime, klass, doc, iter);

    if (iter.isNull()) { return; }
    if (isSeparator(iter.current())) {
      iter.nextSibling();  // skip separator
    }
    if (iter.isNull()) { return; }

    // binary tree can only hold two children.  If we have more,
    // the right child is another tree with the same sequence
    // "type".  The "left" of the new tree is what we've
    // currently consumed as our "right" branch of this tree.
    right = new XmlElementContent(runtime, klass, type, doc, iter,
                                  (XmlElementContent) right);
  }

  /**
   * Set the type based on the separator node type string.
   */
  protected void
  setType(String type)
  {
    if ("|".equals(type)) { this.type = Type.OR; }
    else if (",".equals(type)) { this.type = Type.SEQ; }
  }

  protected void
  setOccur(String type)
  {
    if ("*".equals(type)) { this.occur = Occur.MULT; }
    else if ("+".equals(type)) { this.occur = Occur.PLUS; }
  }

  public static boolean
  isGroup(Node node)
  {
    return XmlDtd.nameEquals(node, DTDConfiguration.E_GROUP);
  }

  // content model element, not Element node type
  public static boolean
  isElement(Node node)
  {
    return XmlDtd.nameEquals(node, DTDConfiguration.E_ELEMENT);
  }

  public static boolean
  isSeparator(Node node)
  {
    return XmlDtd.nameEquals(node, DTDConfiguration.E_SEPARATOR);
  }

  public static boolean
  isOccurrence(Node node)
  {
    return XmlDtd.nameEquals(node, DTDConfiguration.E_OCCURRENCE);
  }

  /**
   * Return the name of the element to which this content model
   * applies.  Only works for the root of the tree.
   */
  public IRubyObject
  element_name(ThreadContext context)
  {
    return nonEmptyStringOrNil(context.getRuntime(), element_name);
  }

  @JRubyMethod
  public IRubyObject
  prefix(ThreadContext context)
  {
    return nonEmptyStringOrNil(context.getRuntime(), getPrefix(name));
  }

  @JRubyMethod
  public IRubyObject
  name(ThreadContext context)
  {
    return nonEmptyStringOrNil(context.getRuntime(), getLocalPart(name));
  }

  @JRubyMethod
  public IRubyObject
  type(ThreadContext context)
  {
    return type.value(context.getRuntime());
  }

  @JRubyMethod
  public IRubyObject
  occur(ThreadContext context)
  {
    return occur.value(context.getRuntime());
  }

  @JRubyMethod
  public IRubyObject
  c1(ThreadContext context)
  {
    return left;
  }

  @JRubyMethod
  public IRubyObject
  c2(ThreadContext context)
  {
    return right;
  }

  /**
   * Iterator for a tree of Nodes.  Has a current position that
   * points to a given node. Calling nextSibling() on the last
   * sibling results in a current position of null.  This position
   * is not fatal and can be escaped by calling parent() (which
   * moves to the parent of previous sibling).  The null position is
   * used to indicate the end of a list.
   */
  protected static class NodeIter
  {
    protected Node pre;
    protected Node cur;

    /**
     * The first time, we fake a previous sibling element.  Thus,
     * initially, current() is null, and the first call should be
     * nextSibling().
     */
    public
    NodeIter(Node node)
    {
      pre = null;
      cur = node.getFirstChild(); // skip root contentModel node
    }

    public Node
    current()
    {
      return cur;
    }

    public boolean
    isNull()
    {
      return (cur == null);
    }

    public boolean
    hasChildren()
    {
      return (cur != null && cur.hasChildNodes());
    }

    /**
     * Descend to the first child.
     */
    public Node
    firstChild()
    {
      if (cur == null) { throw new RuntimeException("no children"); }
      Node ch = cur.getFirstChild();
      if (ch == null) { throw new RuntimeException("no children"); }

      cur = ch;
      return cur;
    }

    /**
     * Move to the next sibling
     */
    public Node
    nextSibling()
    {
      if (cur == null) {
        throw new RuntimeException("no next sibling");
      } else {
        Node ns = cur.getNextSibling();
        if (ns == null) {
          pre = cur;
          cur = null;
        } else {
          cur = ns;
        }
        return cur;
      }
    }

    /**
     * Move to the parent.
     */
    public Node
    parent()
    {
      if (cur == null) { cur = pre; }

      Node p = cur.getParentNode();
      if (p == null) { throw new RuntimeException("no parent"); }

      cur = p;
      return cur;
    }
  }
}