/*
 * The MIT License
 *
 * Copyright (c) 2011, Oracle Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package hudson;

import javax.tools.Diagnostic;
import org.kohsuke.MetaInfServices;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.TypeElement;
import javax.lang.model.util.ElementScanner6;
import javax.tools.FileObject;
import javax.tools.StandardLocation;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Set;

/**
 *
 * Discovers the type of {@link Plugin} and generates "META-INF/services/hudson.Plugin".
 * It's used for manifest creation (Plugin-Class section) and  the plugin loading.
 * Custom {@link Plugin} implementation is required for the -plugin initialization, for example XStream aliases, etc
 */
@SupportedSourceVersion(SourceVersion.RELEASE_6)
@SupportedAnnotationTypes("*")
@MetaInfServices(Processor.class)
@SuppressWarnings({"Since15"})
public class PluginMarker extends AbstractProcessor {

    protected static final String HUDSON_PLUGIN_QUAFIFIER = "hudson.Plugin";
    protected static final String META_INF_SERVICES_LOCATION = "META-INF/services/hudson.Plugin";

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
            ElementScanner6<Void,Void> scanner = new ElementScanner6<Void, Void>() {
                @Override
                public Void visitType(TypeElement e, Void aVoid) {
                    if(!e.getModifiers().contains(Modifier.ABSTRACT)) {
                        Element sc = processingEnv.getTypeUtils().asElement(e.getSuperclass());
                        if (sc!=null && ((TypeElement)sc).getQualifiedName().contentEquals(HUDSON_PLUGIN_QUAFIFIER)) {
                            try {
                                write(e);
                            } catch (IOException x) {
                                StringWriter sw = new StringWriter();
                                x.printStackTrace(new PrintWriter(sw));
                                processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,sw.toString(),e);
                            }
                        }
                    }

                    return super.visitType(e, aVoid);
                }
            };

            for( Element e : roundEnv.getRootElements() )
                scanner.scan(e,null);

            return false;
    }

    /**
     * Writes plugin class name to the defined location.
     *
     * @param typeElement detected element.
     * @throws IOException exception.
     */
    private void write(TypeElement typeElement) throws IOException {
        FileObject f = processingEnv.getFiler().createResource(StandardLocation.CLASS_OUTPUT,
                "", META_INF_SERVICES_LOCATION);
        Writer w = new OutputStreamWriter(f.openOutputStream(),"UTF-8");
        try {
            w.write(typeElement.getQualifiedName().toString());
        } finally {
            w.close();
        }
    }
}