package org.apache.maven.tools.plugin.generator;

/*
 * 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.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.StringWriter;
import java.io.Writer;

import org.apache.maven.project.MavenProject;
import org.apache.velocity.VelocityContext;
import org.codehaus.plexus.logging.AbstractLogEnabled;
import org.codehaus.plexus.logging.Logger;
import org.codehaus.plexus.logging.console.ConsoleLogger;
import org.codehaus.plexus.util.StringUtils;
import org.codehaus.plexus.util.io.CachingOutputStream;
import org.codehaus.plexus.velocity.VelocityComponent;

import static java.nio.charset.StandardCharsets.UTF_8;

/**
 * Generates an <code>HelpMojo</code> class from <code>help-class-source.vm</code> template.
 * The generated mojo reads help content from <code>META-INF/maven/${groupId}/${artifactId}/plugin-help.xml</code>
 * resource, which is generated by this {@link PluginDescriptorFilesGenerator}.
 *
 * @author <a href="mailto:vincent.siveton@gmail.com">Vincent Siveton</a>
 * @since 2.4
 */
public class PluginHelpGenerator
    extends AbstractLogEnabled
{
    /**
     * Default generated class name
     */
    private static final String HELP_MOJO_CLASS_NAME = "HelpMojo";

    private String helpPackageName;
    private String goalPrefix;
    private MavenProject mavenProject;
    private VelocityComponent velocityComponent;

    /**
     * Default constructor
     */
    public PluginHelpGenerator()
    {
        this.enableLogging( new ConsoleLogger( Logger.LEVEL_INFO, "PluginHelpGenerator" ) );
    }

    // ----------------------------------------------------------------------
    // Public methods
    // ----------------------------------------------------------------------

    public void execute( File destinationDirectory )
        throws GeneratorException
    {
        String helpImplementation = getImplementation();

        try
        {
            String sourcePath = helpImplementation.replace( '.', File.separatorChar ) + ".java";

            File helpClass = new File( destinationDirectory, sourcePath );
            helpClass.getParentFile().mkdirs();

            String helpClassSources =
                getHelpClassSources( getPluginHelpPath( mavenProject ) );

            try ( Writer w = new OutputStreamWriter( new CachingOutputStream( helpClass ), UTF_8 ) )
            {
                w.write( helpClassSources );
            }
        }
        catch ( IOException e )
        {
            throw new GeneratorException( e.getMessage(), e );
        }
    }

    public PluginHelpGenerator setHelpPackageName( String helpPackageName )
    {
        this.helpPackageName = helpPackageName;
        return this;
    }

    public PluginHelpGenerator setVelocityComponent( VelocityComponent velocityComponent )
    {
        this.velocityComponent = velocityComponent;
        return this;
    }

    public PluginHelpGenerator setGoalPrefix( String goalPrefix )
    {
        this.goalPrefix = goalPrefix;
        return this;
    }

    public PluginHelpGenerator setMavenProject( MavenProject mavenProject )
    {
        this.mavenProject = mavenProject;
        return this;
    }

    // ----------------------------------------------------------------------
    // Private methods
    // ----------------------------------------------------------------------

    private String getHelpClassSources( String pluginHelpPath )
        throws IOException
    {
        VelocityContext context = new VelocityContext();
        boolean useAnnotations = mavenProject.getArtifactMap().containsKey(
            "org.apache.maven.plugin-tools:maven-plugin-annotations" );

        context.put( "helpPackageName", helpPackageName );
        context.put( "pluginHelpPath", pluginHelpPath );
        context.put( "artifactId", mavenProject.getArtifactId() );
        // TODO: evaluate prefix from deserialized plugin
        context.put( "goalPrefix", goalPrefix );
        context.put( "useAnnotations", useAnnotations );

        StringWriter stringWriter = new StringWriter();

        // plugin-tools sources are UTF-8 (and even ASCII in this case))
        try ( InputStream is = //
                 Thread.currentThread().getContextClassLoader().getResourceAsStream( "help-class-source.vm" ); //
             InputStreamReader isReader = new InputStreamReader( is, UTF_8 ) )
        {
            //isReader =
            velocityComponent.getEngine().evaluate( context, stringWriter, "", isReader );
        }
        // Apply OS lineSeparator instead of template's lineSeparator to have consistent separators for
        // all source files.
        return stringWriter.toString().replaceAll( "(\r\n|\n|\r)", System.lineSeparator() );
    }

    /**
     * @return The implementation.
     */
    private String getImplementation( )
    {
        return StringUtils.isEmpty( helpPackageName )
            ? HELP_MOJO_CLASS_NAME
            : helpPackageName + '.' + HELP_MOJO_CLASS_NAME;
    }

    static String getPluginHelpPath( MavenProject mavenProject )
    {
        return mavenProject.getGroupId() + "/" + mavenProject.getArtifactId() + "/plugin-help.xml";
    }
}