//  Copyright 2004 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.valid;

import org.apache.tapestry.AbstractComponent;
import org.apache.tapestry.ApplicationRuntimeException;
import org.apache.tapestry.BindingException;
import org.apache.tapestry.IForm;
import org.apache.tapestry.IMarkupWriter;
import org.apache.tapestry.IRequestCycle;
import org.apache.tapestry.Tapestry;
import org.apache.tapestry.form.Form;
import org.apache.tapestry.form.IFormComponent;

/**
 *  Used to label an {@link IFormComponent}.  Because such fields
 *  know their displayName (user-presentable name), there's no reason
 *  to hard code the label in a page's HTML template (this also helps
 *  with localization).
 *
 *  [<a href="../../../../../ComponentReference/FieldLabel.html">Component Reference</a>]

 *
 *  @author Howard Lewis Lewis Ship
 *  @version $Id$
 * 
 **/

public abstract class FieldLabel extends AbstractComponent
{
    /**
    *  Gets the {@link IFormComponent}
    *  and {@link IValidationDelegate delegate},
    *  then renders the label obtained from the field.  Does nothing
    *  when rewinding.
    *
    **/

    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
        if (cycle.isRewinding())
            return;

        IFormComponent field = getField();
        String displayName = getDisplayName();

        if (displayName == null)
        {
            if (field == null)
                throw Tapestry.createRequiredParameterException(this, "field");

            displayName = field.getDisplayName();

            if (displayName == null)
            {
                String msg = Tapestry.format("FieldLabel.no-display-name", field.getExtendedId());

                throw new BindingException(msg, this, null, getBinding("field"), null);
            }
        }

        IForm form = Form.get(cycle);

        if (form == null)
        {
            String msg = Tapestry.getMessage("FieldLabel.must-be-contained-by-form");

            throw new ApplicationRuntimeException(msg, this, null, null);
        }

        IValidationDelegate delegate = form.getDelegate();

        if (delegate == null)
        {
            String msg =
                Tapestry.format("FieldLabel.no-delegate", getExtendedId(), form.getExtendedId());

            throw new ApplicationRuntimeException(msg, this, null, null);
        }

        delegate.writeLabelPrefix(field, writer, cycle);

        if (getRaw()) {
            writer.printRaw(displayName);
        } else {
            writer.print(displayName);
        }

        delegate.writeLabelSuffix(field, writer, cycle);
    }

    public abstract String getDisplayName();

    public abstract IFormComponent getField();

    public abstract boolean getRaw();
}