/*
 * Copyright 2009 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.uibinder.elementparsers;

import com.google.gwt.core.ext.UnableToCompleteException;
import com.google.gwt.core.ext.typeinfo.JClassType;
import com.google.gwt.core.ext.typeinfo.JEnumType;
import com.google.gwt.dom.client.Style.Unit;
import com.google.gwt.uibinder.rebind.UiBinderWriter;
import com.google.gwt.uibinder.rebind.XMLElement;
import com.google.gwt.user.client.ui.TabLayoutPanel;

/**
 * Parses {@link TabLayoutPanel} widgets.
 */
public class TabLayoutPanelParser implements ElementParser {

  private static class Children {
    XMLElement body;
    XMLElement header;
    XMLElement customHeader;
  }

  private static final String CUSTOM = "customHeader";
  private static final String HEADER = "header";
  private static final String TAB = "tab";

  public void parse(XMLElement panelElem, String fieldName, JClassType type,
      UiBinderWriter writer) throws UnableToCompleteException {
    // TabLayoutPanel requires tabBar size and unit ctor args.

    String size = panelElem.consumeRequiredDoubleAttribute("barHeight");
    if ("".equals(size)) {
      writer.die(panelElem, "barHeight attribute is required");
    }

    JEnumType unitEnumType = writer.getOracle().findType(
        Unit.class.getCanonicalName()).isEnum();
    String unit = panelElem.consumeAttributeWithDefault("barUnit",
        String.format("%s.%s", unitEnumType.getQualifiedSourceName(), "PX"),
        unitEnumType);

    writer.setFieldInitializerAsConstructor(fieldName,
        writer.getOracle().findType(TabLayoutPanel.class.getName()), size, unit);

    // Parse children.
    for (XMLElement tabElem : panelElem.consumeChildElements()) {
      // Get the tab element.
      if (!isElementType(panelElem, tabElem, TAB)) {
        writer.die(tabElem, "Only <%s:%s> children are allowed.",
            panelElem.getPrefix(), TAB);
      }

      // Find all the children of the <tab>.
      Children children = findChildren(tabElem, writer);

      // Parse the child widget.
      if (children.body == null) {
        writer.die(tabElem, "Must have a child widget");
      }
      if (!writer.isWidgetElement(children.body)) {
        writer.die(children.body, "Must be a widget");
      }
      String childFieldName = writer.parseElementToField(children.body);

      // Parse the header.
      if (children.header != null) {
        HtmlInterpreter htmlInt = HtmlInterpreter.newInterpreterForUiObject(
            writer, fieldName);
        String html = children.header.consumeInnerHtml(htmlInt);
        writer.addStatement("%s.add(%s, \"%s\", true);", fieldName,
            childFieldName, html);
      } else if (children.customHeader != null) {
        XMLElement headerElement =
          children.customHeader.consumeSingleChildElement();

        if (!writer.isWidgetElement(headerElement)) {
          writer.die(headerElement, "Is not a widget");
        }

        String headerField = writer.parseElementToField(headerElement);
        writer.addStatement("%s.add(%s, %s);", fieldName, childFieldName,
            headerField);
      } else {
        // Neither a header or customHeader.
        writer.die(tabElem, "Requires either a <%1$s:%2$s> or <%1$s:%3$s>",
            tabElem.getPrefix(), HEADER, CUSTOM);
      }
    }
  }

  private Children findChildren(final XMLElement elem,
      final UiBinderWriter writer) throws UnableToCompleteException {
    final Children children = new Children();

    elem.consumeChildElements(new XMLElement.Interpreter<Boolean>() {
      public Boolean interpretElement(XMLElement child)
          throws UnableToCompleteException {

        if (hasTag(child, HEADER)) {
          assertFirstHeader();
          children.header = child;
          return true;
        }

        if (hasTag(child, CUSTOM)) {
          assertFirstHeader();
          children.customHeader = child;
          return true;
        }

        // Must be the body, then
        if (null != children.body) {
          writer.die(children.body, "May have only one body element");
        }

        children.body = child;
        return true;
      }

      void assertFirstHeader() throws UnableToCompleteException {
        if ((null != children.header) && (null != children.customHeader)) {
          writer.die(elem, "May have only one %1$s:header "
              + "or %1$s:customHeader", elem.getPrefix());
        }
      }

      private boolean hasTag(XMLElement child, final String attribute) {
        return rightNamespace(child) && child.getLocalName().equals(attribute);
      }

      private boolean rightNamespace(XMLElement child) {
        return child.getNamespaceUri().equals(elem.getNamespaceUri());
      }
    });

    return children;
  }

  private boolean isElementType(XMLElement parent, XMLElement child, String type) {
    return parent.getNamespaceUri().equals(child.getNamespaceUri())
        && type.equals(child.getLocalName());
  }
}