package org.apache.maven.plugins.shade.resource;

/*
 * 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.
 */

import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.jar.JarEntry;
import java.util.jar.JarOutputStream;

import org.apache.commons.io.IOUtils;
import org.apache.maven.plugins.shade.relocation.Relocator;

/**
 * Resources transformer that relocates classes in META-INF/services and appends entries in META-INF/services resources
 * into a single resource. For example, if there are several META-INF/services/org.apache.maven.project.ProjectBuilder
 * resources spread across many JARs the individual entries will all be concatenated into a single
 * META-INF/services/org.apache.maven.project.ProjectBuilder resource packaged into the resultant JAR produced by the
 * shading process.
 */
public class ServicesResourceTransformer
        extends AbstractCompatibilityTransformer
{
    private static final String SERVICES_PATH = "META-INF/services";

    private final Map<String, ArrayList<String>> serviceEntries = new HashMap<>();

    private long time = Long.MIN_VALUE;

    public boolean canTransformResource( String resource )
    {
        return resource.startsWith( SERVICES_PATH );
    }

    public void processResource( String resource, InputStream is, final List<Relocator> relocators, long time )
            throws IOException
    {
        resource = resource.substring( SERVICES_PATH.length() + 1 );
        for ( Relocator relocator : relocators )
        {
            if ( relocator.canRelocateClass( resource ) )
            {
                resource = relocator.relocateClass( resource );
                break;
            }
        }
        resource = SERVICES_PATH + '/' + resource;

        ArrayList<String> out = serviceEntries.computeIfAbsent( resource, k -> new ArrayList<>() );

        Scanner scanner = new Scanner( is, StandardCharsets.UTF_8.name() );
        while ( scanner.hasNextLine() )
        {
            String relContent = scanner.nextLine();
            for ( Relocator relocator : relocators )
            {
                if ( relocator.canRelocateClass( relContent ) )
                {
                    relContent = relocator.applyToSourceContent( relContent );
                }
            }
            out.add( relContent );
        }

        if ( time > this.time )
        {
            this.time = time;
        }
    }

    public boolean hasTransformedResource()
    {
        return !serviceEntries.isEmpty();
    }

    public void modifyOutputStream( JarOutputStream jos )
            throws IOException
    {
        for ( Map.Entry<String, ArrayList<String>> entry : serviceEntries.entrySet() )
        {
            String key = entry.getKey();
            ArrayList<String> data = entry.getValue();

            JarEntry jarEntry = new JarEntry( key );
            jarEntry.setTime( time );
            jos.putNextEntry( jarEntry );

            IOUtils.writeLines( data, "\n", jos, StandardCharsets.UTF_8 );
            jos.flush();
            data.clear();
        }
    }
}
