package hudson;

import hudson.util.IOException2;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.taskdefs.Expand;
import org.apache.tools.ant.types.FileSet;
import org.kohsuke.stapler.StaplerRequest;
import org.kohsuke.stapler.StaplerResponse;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.jar.Manifest;
import java.util.logging.Logger;

/**
 * Represents a Hudson plug-in and associated control information
 * for Hudson to control {@link Plugin}.
 *
 * <p>
 * A plug-in is packaged into a jar file whose extension is <tt>".hpi"</tt>,
 * A plugin needs to have a special manifest entry to identify what it is.
 *
 * <p>
 * At the runtime, a plugin has two distinct state axis.
 * <ol>
 *  <li>Enabled/Disabled. If enabled, Hudson is going to use it
 *      next time Hudson runs. Otherwise the next run will ignore it.
 *  <li>Activated/Deactivated. If activated, that means Hudson is using
 *      the plugin in this session. Otherwise it's not.
 * </ol>
 * <p>
 * For example, an activated but disabled plugin is still running but the next
 * time it won't.
 *
 * @author Kohsuke Kawaguchi
 */
public final class PluginWrapper {
    /**
     * Plugin manifest.
     * Contains description of the plugin.
     */
    private final Manifest manifest;

    /**
     * Loaded plugin instance.
     * Null if disabled.
     */
    public final Plugin plugin;

    /**
     * {@link ClassLoader} for loading classes from this plugin.
     * Null if disabled.
     */
    public final ClassLoader classLoader;

    /**
     * Base URL for loading static resources from this plugin.
     * Null if disabled. The static resources are mapped under
     * <tt>hudson/plugin/SHORTNAME/</tt>.
     */
    public final URL baseResourceURL;

    /**
     * Used to control enable/disable setting of the plugin.
     * If this file exists, plugin will be disabled.
     */
    private final File disableFile;

    /**
     * Short name of the plugin. The "abc" portion of "abc.hpl".
     */
    private final String shortName;

    /**
     * @param archive
     *      A .hpi archive file jar file, or a .hpl linked plugin.
     *
     * @throws IOException
     *      if an installation of this plugin failed. The caller should
     *      proceed to work with other plugins.
     */
    public PluginWrapper(PluginManager owner, File archive) throws IOException {
        LOGGER.info("Loading plugin: "+archive);

        this.shortName = getShortName(archive);

        boolean isLinked = archive.getName().endsWith(".hpl");

        File expandDir = null;  // if .hpi, this is the directory where war is expanded

        if(isLinked) {
            // resolve the .hpl file to the location of the manifest file
            String firstLine = new BufferedReader(new FileReader(archive)).readLine();
            if(firstLine.startsWith("Manifest-Version:")) {
                // this is the manifest already
            } else {
                // in direction
                archive = resolve(archive, firstLine);
            }
            // then parse manifest
            FileInputStream in = new FileInputStream(archive);
            try {
                manifest = new Manifest(in);
            } catch(IOException e) {
                throw new IOException2("Failed to load "+archive,e);
            } finally {
                in.close();
            }
        } else {
            expandDir = new File(archive.getParentFile(), shortName);
            explode(archive,expandDir);

            File manifestFile = new File(expandDir,"META-INF/MANIFEST.MF");
            if(!manifestFile.exists()) {
                throw new IOException("Plugin installation failed. No manifest at "+manifestFile);
            }
            FileInputStream fin = new FileInputStream(manifestFile);
            try {
                manifest = new Manifest(fin);
            } finally {
                fin.close();
            }
        }

        // TODO: define a mechanism to hide classes
        // String export = manifest.getMainAttributes().getValue("Export");

        List<URL> paths = new ArrayList<URL>();
        if(isLinked) {
            parseClassPath(archive, paths, "Libraries", ",");
            parseClassPath(archive, paths, "Class-Path", " +"); // backward compatibility

            this.baseResourceURL = resolve(archive,
                manifest.getMainAttributes().getValue("Resource-Path")).toURL();
        } else {
            File classes = new File(expandDir,"WEB-INF/classes");
            if(classes.exists())
                paths.add(classes.toURL());
            File lib = new File(expandDir,"WEB-INF/lib");
            File[] libs = lib.listFiles(JAR_FILTER);
            if(libs!=null) {
                for (File jar : libs)
                    paths.add(jar.toURL());
            }

            this.baseResourceURL = expandDir.toURL();
        }
        this.classLoader = new URLClassLoader(paths.toArray(new URL[0]), getClass().getClassLoader());

        disableFile = new File(archive.getPath()+".disabled");
        if(disableFile.exists()) {
            LOGGER.info("Plugin is disabled");
            this.plugin = null;
            return;
        }

        String className = manifest.getMainAttributes().getValue("Plugin-Class");
        if(className ==null) {
            throw new IOException("Plugin installation failed. No 'Plugin-Class' entry in the manifest of "+archive);
        }

        // override the context classloader so that XStream activity in plugin.start()
        // will be able to resolve classes in this plugin
        ClassLoader old = Thread.currentThread().getContextClassLoader();
        Thread.currentThread().setContextClassLoader(classLoader);
        try {
            try {
                Class clazz = classLoader.loadClass(className);
                Object plugin = clazz.newInstance();
                if(!(plugin instanceof Plugin)) {
                    throw new IOException(className+" doesn't extend from hudson.Plugin");
                }
                this.plugin = (Plugin)plugin;
                this.plugin.wrapper = this;
            } catch (ClassNotFoundException e) {
                IOException ioe = new IOException("Unable to load " + className + " from " + archive);
                ioe.initCause(e);
                throw ioe;
            } catch (IllegalAccessException e) {
                IOException ioe = new IOException("Unable to create instance of " + className + " from " + archive);
                ioe.initCause(e);
                throw ioe;
            } catch (InstantiationException e) {
                IOException ioe = new IOException("Unable to create instance of " + className + " from " + archive);
                ioe.initCause(e);
                throw ioe;
            }

            // initialize plugin
            try {
                plugin.setServletContext(owner.context);
                plugin.start();
            } catch(Throwable t) {
                // gracefully handle any error in plugin.
                IOException ioe = new IOException("Failed to initialize");
                ioe.initCause(t);
                throw ioe;
            }
        } finally {
            Thread.currentThread().setContextClassLoader(old);
        }
    }

    private void parseClassPath(File archive, List<URL> paths, String attributeName, String separator) throws IOException {
        String classPath = manifest.getMainAttributes().getValue(attributeName);
        if(classPath==null) return; // attribute not found
        for (String s : classPath.split(separator)) {
            File file = resolve(archive, s);
            if(file.getName().contains("*")) {
                // handle wildcard
                FileSet fs = new FileSet();
                File dir = file.getParentFile();
                fs.setDir(dir);
                fs.setIncludes(file.getName());
                for( String included : fs.getDirectoryScanner(new Project()).getIncludedFiles() ) {
                    paths.add(new File(dir,included).toURL());
                }
            } else {
                if(!file.exists())
                    throw new IOException("No such file: "+file);
                paths.add(file.toURL());
            }
        }
    }

    private static File resolve(File base, String relative) {
        File rel = new File(relative);
        if(rel.isAbsolute())
            return rel;
        else
            return new File(base.getParentFile(),relative);
    }

    /**
     * Returns the URL of the index page jelly script.
     */
    public URL getIndexPage() {
        return classLoader.getResource("index.jelly");
    }

    /**
     * Returns the short name suitable for URL.
     */
    public String getShortName() {
        return shortName;
    }

    @Override
    public String toString() {
        return "Plugin:" + getShortName();
    }

    /**
     * Returns a one-line descriptive name of this plugin.
     */
    public String getLongName() {
        String name = manifest.getMainAttributes().getValue("Long-PluginName");
        if(name!=null)      return name;
        return shortName;
    }

    /**
     * Gets the "abc" portion from "abc.ext".
     */
    private static String getShortName(File archive) {
        String n = archive.getName();
        int idx = n.lastIndexOf('.');
        if(idx>=0)
            n = n.substring(0,idx);
        return n;
    }

    /**
     * Terminates the plugin.
     */
    void stop() {
        LOGGER.info("Stopping "+shortName);
        try {
            plugin.stop();
        } catch(Throwable t) {
            System.err.println("Failed to shut down "+shortName);
            System.err.println(t);
        }
    }

    /**
     * Enables this plugin next time Hudson runs.
     */
    public void enable() throws IOException {
        if(!disableFile.delete())
            throw new IOException("Failed to delete "+disableFile);
    }

    /**
     * Disables this plugin next time Hudson runs.
     */
    public void disable() throws IOException {
        // creates an empty file
        OutputStream os = new FileOutputStream(disableFile);
        os.close();
    }

    /**
     * Returns true if this plugin is enabled for this session.
     */
    public boolean isActive() {
        return plugin!=null;
    }

    /**
     * If true, the plugin is going to be activated next time
     * Hudson runs.
     */
    public boolean isEnabled() {
        return !disableFile.exists();
    }

    /**
     * Explodes the plugin into a directory, if necessary.
     */
    private void explode(File archive, File destDir) throws IOException {
        if(!destDir.exists())
            destDir.mkdirs();

        // timestamp check
        File explodeTime = new File(destDir,".timestamp");
        if(explodeTime.exists() && explodeTime.lastModified()>archive.lastModified())
            return; // no need to expand

        LOGGER.info("Extracting "+archive);

        // delete the contents so that old files won't interfere with new files
        Util.deleteContentsRecursive(destDir);

        try {
            Expand e = new Expand();
            e.setProject(new Project());
            e.setTaskType("unzip");
            e.setSrc(archive);
            e.setDest(destDir);
            e.execute();
        } catch (BuildException x) {
            IOException ioe = new IOException("Failed to expand " + archive);
            ioe.initCause(x);
            throw ioe;
        }

        Util.touch(explodeTime);
    }


//
//
// Action methods
//
//
    public void doMakeEnabled(StaplerRequest req, StaplerResponse rsp) throws IOException {
        enable();
        rsp.setStatus(200);
    }
    public void doMakeDisabled(StaplerRequest req, StaplerResponse rsp) throws IOException {
        disable();
        rsp.setStatus(200);
    }


    private static final Logger LOGGER = Logger.getLogger(PluginWrapper.class.getName());

    /**
     * Filter for jar files.
     */
    private static final FilenameFilter JAR_FILTER = new FilenameFilter() {
        public boolean accept(File dir,String name) {
            return name.endsWith(".jar");
        }
    };
}