/*******************************************************************************
 *
 * Copyright (c) 2004-2010 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *
 *
 *******************************************************************************/ 

package hudson.init;

import org.jvnet.hudson.reactor.Task;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.logging.Logger;

import hudson.PluginManager;
import hudson.util.Service;

/**
 * Strategy pattern of the various key decision making during the Hudson
 * initialization.
 *
 * <p> Because the act of initializing plugins is a part of the Hudson
 * initialization, this extension point cannot be implemented in a plugin. You
 * need to place your jar inside {@code WEB-INF/lib} instead.
 *
 * <p> Register your implementation at META-INF/services.
 *
 * @author Kohsuke Kawaguchi
 */
public class InitStrategy {

    /**
     * Returns the list of *.hpi and *.hpl to expand and load.
     *
     * <p> Normally we look at {@code $HUDSON_HOME/plugins/*.hpi} and *.hpl.
     *
     * @return never null but can be empty. The list can contain different
     * versions of the same plugin, and when that happens, Hudson will ignore
     * all but the first one in the list.
     */
    public List<File> listPluginArchives(PluginManager pm) throws IOException {
        File[] hpi = pm.rootDir.listFiles(new FilterByExtension(".hpi")); // plugin jar file
        File[] hpl = pm.rootDir.listFiles(new FilterByExtension(".hpl")); // linked plugin. for debugging.
        if (hpi == null || hpl == null) {
            throw new IOException("Hudson is unable to create " + pm.rootDir + "\nPerhaps its security privilege is insufficient");
        }

        List<File> r = new ArrayList<File>();

        // the ordering makes sure that during the debugging we get proper precedence among duplicates.
        // for example, while doing "mvn hpi:run" on a plugin that's bundled with Hudson, we want to the
        // *.hpl file to override the bundled hpi file.
        getBundledPluginsFromProperty(r);
        r.addAll(Arrays.asList(hpl));
        r.addAll(Arrays.asList(hpi));

        return r;
    }

    /**
     * Lists up additional bundled plugins from the system property.
     *
     * For use in the "mvn hudson-dev:run". TODO: maven-hpi-plugin should inject
     * its own InitStrategy instead of having this in the core.
     */
    protected void getBundledPluginsFromProperty(List<File> r) {
        String hplProperty = System.getProperty("hudson.bundled.plugins");
        if (hplProperty != null) {
            for (String hplLocation : hplProperty.split(",")) {
                File hpl = new File(hplLocation.trim());
                if (hpl.exists()) {
                    r.add(hpl);
                } else {
                    LOGGER.warning("bundled plugin " + hplLocation + " does not exist");
                }
            }
        }
    }

    /**
     * Selectively skip some of the initialization tasks.
     *
     * @return true to skip the execution.
     */
    public boolean skipInitTask(Task task) {
        return false;
    }

    /**
     * Obtains the instance to be used.
     */
    public static InitStrategy get(ClassLoader cl) throws IOException {
        List<InitStrategy> r = Service.loadInstances(cl, InitStrategy.class);
        if (r.isEmpty()) {
            return new InitStrategy();      // default
        }
        InitStrategy s = r.get(0);
        LOGGER.fine("Using " + s + " as InitStrategy");
        return s;
    }
    private static final Logger LOGGER = Logger.getLogger(InitStrategy.class.getName());

    private static class FilterByExtension implements FilenameFilter {

        private final String extension;

        public FilterByExtension(String extension) {
            this.extension = extension;
        }

        public boolean accept(File dir, String name) {
            return name.endsWith(extension); // plugin jar file
                    // result in duplicate plugin loading during testing || name.endsWith(".hpl");       // linked plugin. for debugging.
        }
    }
}