    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005// http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.internal.webresources;
    014
    015import com.github.sommeri.less4j.Less4jException;
    016import com.github.sommeri.less4j.LessCompiler;
    017import com.github.sommeri.less4j.LessSource;
    018import com.github.sommeri.less4j.core.DefaultLessCompiler;
    019import org.apache.tapestry5.ContentType;
    020import org.apache.tapestry5.internal.services.assets.BytestreamCache;
    021import org.apache.tapestry5.ioc.Resource;
    022import org.apache.tapestry5.services.assets.ResourceDependencies;
    023import org.apache.tapestry5.services.assets.ResourceTransformer;
    024
    025import java.io.IOException;
    026import java.io.InputStream;
    027import java.io.UnsupportedEncodingException;
    028
    029/**
    030 * Direct wrapper around the LessCompiler, so that Less source files may use {@code @import}, which isn't
    031 * supported by the normal WRO4J processor.
    032 */
    033public class LessResourceTransformer implements ResourceTransformer
    034{
    035    private static final ContentType CSS = new ContentType("text/css");
    036
    037    private final LessCompiler compiler = new DefaultLessCompiler();
    038
    039    @Override
    040    public ContentType getTransformedContentType()
    041    {
    042        return CSS;
    043    }
    044
    045
    046    @Override
    047    public InputStream transform(Resource source, ResourceDependencies dependencies) throws IOException
    048    {
    049        BytestreamCache compiled = invokeLessCompiler(source, dependencies);
    050
    051        return compiled.openStream();
    052    }
    053
    054    private BytestreamCache invokeLessCompiler(Resource source, ResourceDependencies dependencies) throws IOException
    055    {
    056        try
    057        {
    058            LessSource lessSource = new ResourceLessSource(source, dependencies);
    059
    060            LessCompiler.CompilationResult compilationResult = compile(compiler, lessSource);
    061
    062            // Currently, ignoring any warnings.
    063
    064            return new BytestreamCache(compilationResult.getCss().getBytes("utf-8"));
    065
    066        } catch (Less4jException ex)
    067        {
    068            throw new IOException(ex);
    069        } catch (UnsupportedEncodingException ex)
    070        {
    071            throw new IOException(ex);
    072        }
    073    }
    074
    075    /**
    076     * Invoked from {@link #transform(org.apache.tapestry5.ioc.Resource, org.apache.tapestry5.services.assets.ResourceDependencies)}
    077     * to perform the actual work of compiling a {@link org.apache.tapestry5.ioc.Resource} which has been wrapped as a
    078     * {@link com.github.sommeri.less4j.LessSource}.
    079     */
    080    protected LessCompiler.CompilationResult compile(LessCompiler compiler, LessSource lessSource) throws Less4jException
    081    {
    082        return compiler.compile(lessSource);
    083    }
    084}