/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.taglibs.standard.tag.common.fmt;

import java.io.IOException;
import java.util.TimeZone;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.jstl.core.Config;
import javax.servlet.jsp.tagext.BodyTagSupport;
import javax.servlet.jsp.tagext.Tag;

/**
 * Support for tag handlers for &lt;timeZone&gt;, the time zone tag in
 * JSTL 1.0.
 *
 * @author Jan Luehe
 */

public abstract class TimeZoneSupport extends BodyTagSupport {


    //*********************************************************************
    // Protected state

    protected Object value;                      // 'value' attribute


    //*********************************************************************
    // Private state

    private TimeZone timeZone;


    //*********************************************************************
    // Constructor and initialization

    public TimeZoneSupport() {
        super();
        init();
    }

    private void init() {
        value = null;
    }


    //*********************************************************************
    // Collaboration with subtags

    public TimeZone getTimeZone() {
        return timeZone;
    }


    //*********************************************************************
    // Tag logic

    @Override
    public int doStartTag() throws JspException {

        if (value == null) {
            timeZone = TimeZone.getTimeZone("GMT");
        } else if (value instanceof String) {
            if (((String) value).trim().equals("")) {
                timeZone = TimeZone.getTimeZone("GMT");
            } else {
                timeZone = TimeZone.getTimeZone((String) value);
            }
        } else {
            timeZone = (TimeZone) value;
        }

        return EVAL_BODY_BUFFERED;
    }

    @Override
    public int doEndTag() throws JspException {
        try {
            pageContext.getOut().print(bodyContent.getString());
        } catch (IOException ioe) {
            throw new JspTagException(ioe.toString(), ioe);
        }

        return EVAL_PAGE;
    }

    // Releases any resources we may have (or inherit)

    @Override
    public void release() {
        init();
    }


    //*********************************************************************
    // Package-scoped utility methods

    /*
     * Determines and returns the time zone to be used by the given action.
     *
     * <p> If the given action is nested inside a &lt;timeZone&gt; action,
     * the time zone is taken from the enclosing &lt;timeZone&gt; action.
     *
     * <p> Otherwise, the time zone configuration setting
     * <tt>javax.servlet.jsp.jstl.core.Config.FMT_TIME_ZONE</tt>
     * is used.
     *
     * @param pageContext the page containing the action for which the
     * time zone needs to be determined
     * @param fromTag the action for which the time zone needs to be
     * determined
     *
     * @return the time zone, or <tt>null</tt> if the given action is not 
     * nested inside a &lt;timeZone&gt; action and no time zone configuration
     * setting exists
     */

    static TimeZone getTimeZone(PageContext pc, Tag fromTag) {
        TimeZone tz = null;

        Tag t = findAncestorWithClass(fromTag, TimeZoneSupport.class);
        if (t != null) {
            // use time zone from parent <timeZone> tag
            TimeZoneSupport parent = (TimeZoneSupport) t;
            tz = parent.getTimeZone();
        } else {
            // get time zone from configuration setting
            Object obj = Config.find(pc, Config.FMT_TIME_ZONE);
            if (obj != null) {
                if (obj instanceof TimeZone) {
                    tz = (TimeZone) obj;
                } else {
                    tz = TimeZone.getTimeZone((String) obj);
                }
            }
        }

        return tz;
    }
}
