tapestry/tapestry-framework/src/java/org/apache/tapestry/describe/HTMLDescriptionReceiver.java

// Copyright 2005 The Apache Software Foundation
//
// 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 org.apache.tapestry.describe;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

import org.apache.hivemind.util.Defense;
import org.apache.tapestry.IMarkupWriter;

/**
 * Implementation of {@link org.apache.tapestry.describe.DescriptionReceiver}
 * that produces HTML output using a {@link org.apache.tapestry.IMarkupWriter}.
 * <p>
 * TODO: Make {@link #describeAlternate(Object)} exclusive with the other
 * methods {@link #title(String)}, {@link #property(String, Object)}, etc.
 * </p>
 * 
 * @author Howard M. Lewis Ship
 * @since 4.0
 */
public class HTMLDescriptionReceiver implements RootDescriptionReciever
{

    // Emitted for null values.

    static final String NULL_VALUE = "<NULL>";

    private final IMarkupWriter _writer;

    private boolean _emitDefault = true;

    private String _title;

    private String _section;

    private DescribableStrategy _strategy;

    private HTMLDescriptionReceiverStyles _styles;

    private boolean _even = true;

    public HTMLDescriptionReceiver(IMarkupWriter writer,
            DescribableStrategy adapter)
    {
        this(writer, adapter, new HTMLDescriptionReceiverStyles());
    }

    public HTMLDescriptionReceiver(IMarkupWriter writer,
            DescribableStrategy strategy, HTMLDescriptionReceiverStyles styles)
    {
        Defense.notNull(writer, "writer");
        Defense.notNull(strategy, "strategy");
        Defense.notNull(styles, "styles");

        _writer = writer;
        _strategy = strategy;
        _styles = styles;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.tapestry.describe.RootDescriptionReciever#describe(java.lang.Object)
     */
    public void describe(Object object)
    {
        if (object == null)
        {
            _writer.print(NULL_VALUE);
            return;
        }

        _strategy.describeObject(object, this);

        finishUp(object);
    }

    public void describeAlternate(Object alternate)
    {
        _strategy.describeObject(alternate, this);
    }

    public void finishUp()
    {
        // When false, a <table> was started, which must be closed.

        if (!_emitDefault) _writer.end("table");

        _writer.println();

        _emitDefault = true;
        _title = null;
        _section = null;
        _even = true;
    }

    void finishUp(Object object)
    {
        if (_emitDefault)
        {
            String value = _title != null ? _title : object.toString();

            _writer.print(value);
        }

        finishUp();
    }

    public void title(String title)
    {
        Defense.notNull(title, "title");

        if (_title != null)
            throw new IllegalStateException(DescribeMessages.setTitleOnce());

        _title = title;
    }

    public void section(String section)
    {
        Defense.notNull(section, "section");

        if (_title == null)
            throw new IllegalStateException(DescribeMessages
                    .mustSetTitleBeforeSection());

        _section = section;
    }

    private void assertTitleSet()
    {
        if (_title == null)
            throw new IllegalStateException(DescribeMessages
                    .mustSetTitleBeforeProperty());
    }

    /**
     * Invoked to ensure that the section portion has been output, before any
     * properties within the section are output.
     */

    private void emitSection()
    {
        if (_emitDefault)
        {
            _emitDefault = false;

            _writer.begin("div");
            _writer.attribute("class", _styles.getHeaderClass());
            _writer.print(_title);
            _writer.end();
            _writer.println();

            _writer.begin("table");
            _writer.attribute("class", _styles.getTableClass());
            _writer.println();

            _even = true;
        }

        if (_section != null)
        {
            _writer.begin("tr");
            _writer.attribute("class", _styles.getSubheaderClass());
            _writer.begin("th");
            _writer.attribute("colspan", 2);
            _writer.print(_section);
            _writer.end("tr");
            _writer.println();

            _section = null;

            _even = true;
        }

    }

    private void pair(String key, String value)
    {
        assertTitleSet();
        emitSection();

        _writer.begin("tr");
        writeRowClass();

        _writer.begin("th");
        _writer.print(key);
        _writer.end();
        _writer.begin("td");
        _writer.print(value);
        _writer.end("tr");
        _writer.println();

    }

    private void writeRowClass()
    {
        _writer.attribute("class", _even ? "even" : "odd");
        _even = !_even;
    }

    public void property(String key, Object value)
    {
        Defense.notNull(key, "key");

        assertTitleSet();
        emitSection();

        _writer.begin("tr");
        writeRowClass();

        _writer.begin("th");
        _writer.print(key);
        _writer.end();
        _writer.begin("td");

        describeNested(value);

        _writer.end("tr");
        _writer.println();
    }

    private void describeNested(Object value)
    {
        if (value == null)
        {
            _writer.print(NULL_VALUE);
            return;
        }

        new HTMLDescriptionReceiver(_writer, _strategy, _styles).describe(value);
    }

    public void property(String key, boolean value)
    {
        Defense.notNull(key, "key");

        // toString is JDK 1.4 and above, so we'll provide our own.

        pair(key, value ? "true" : "false");
    }

    public void property(String key, byte value)
    {
        Defense.notNull(key, "key");

        pair(key, Byte.toString(value));
    }

    public void property(String key, short value)
    {
        Defense.notNull(key, "key");

        pair(key, Short.toString(value));
    }

    public void property(String key, int value)
    {
        Defense.notNull(key, "key");

        pair(key, Integer.toString(value));
    }

    public void property(String key, long value)
    {
        Defense.notNull(key, "key");

        pair(key, Long.toString(value));
    }

    public void property(String key, float value)
    {
        Defense.notNull(key, "key");

        pair(key, Float.toString(value));
    }

    public void property(String key, double value)
    {
        Defense.notNull(key, "key");

        pair(key, Double.toString(value));
    }

    public void property(String key, char value)
    {
        Defense.notNull(key, "key");

        pair(key, Character.toString(value));
    }

    public void array(String key, Object[] values)
    {
        Defense.notNull(key, "key");

        assertTitleSet();

        if (values == null || values.length == 0) return;

        emitSection();
        
        for(int i = 0; i < values.length; i++)
        {
            _writer.begin("tr");
            writeRowClass();

            _writer.begin("th");

            if (i == 0) _writer.print(key);

            _writer.end();

            _writer.begin("td");

            describeNested(values[i]);

            _writer.end("tr");
            _writer.println();
        }

    }

    public void collection(String key, Collection values)
    {
        Defense.notNull(key, "key");
        
        assertTitleSet();
        
        if (values == null || values.isEmpty()) return;
        
        emitSection();
        
        Iterator i = new ArrayList(values).iterator();
        boolean first = true;
        
        while(i.hasNext())
        {
            _writer.begin("tr");
            writeRowClass();
            
            _writer.begin("th");

            if (first) 
                _writer.print(key);
            
            _writer.end();
            _writer.begin("td");
            
            describeNested(i.next());
            
            _writer.end("tr");
            _writer.println();
            
            first = false;
        }
    }
}