// Copyright (C) 2001-2003 Jon A. Maxwell (JAM)
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

package net.sourceforge.jnlp.cache;

import java.io.*;
import java.net.*;
import java.util.*;

import net.sourceforge.jnlp.*;
import net.sourceforge.jnlp.runtime.*;
import net.sourceforge.jnlp.util.*;

/**
 * Information about a single resource to download.
 * This class tracks the downloading of various resources of a
 * JNLP file to local files.  It can be used to download icons,
 * jnlp and extension files, jars, and jardiff files using the
 * version based protocol or any file using the basic download
 * protocol.<p>
 *
 * Resources can be put into download groups by specifying a part
 * name for the resource.  The resource tracker can also be
 * configured to prefetch resources, which are downloaded in the
 * order added to the media tracker.<p>
 *
 * @author <a href="mailto:jmaxwell@users.sourceforge.net">Jon A. Maxwell (JAM)</a> - initial author
 * @version $Revision: 1.9 $
 */
public class Resource {

    // todo: fix resources to handle different versions

    // todo: IIRC, any resource is checked for being up-to-date
    // only once, regardless of UpdatePolicy.  verify and fix.

    /** status bits */
    public static final int UNINITIALIZED = 0;
    public static final int CONNECT = 1;
    public static final int CONNECTING = 2;
    public static final int CONNECTED = 4;
    public static final int DOWNLOAD = 8;
    public static final int DOWNLOADING = 16;
    public static final int DOWNLOADED = 32;
    public static final int ERROR = 64;
    public static final int STARTED = 128; // enqueued or being worked on

    /** list of weak references of resources currently in use */
    private static WeakList<Resource> resources = new WeakList<Resource>();

    /** weak list of trackers monitoring this resource */
    private WeakList<ResourceTracker> trackers = new WeakList<ResourceTracker>();

    /** the remote location of the resource */
    URL location;

    /** the location to use when downloading */
    private URL downloadLocation;

    /** the local file downloaded to */
    File localFile;

    /** the requested version */
    Version requestVersion;

    /** the version downloaded from server */
    Version downloadVersion;

    /** amount in bytes transferred */
    long transferred = 0;

    /** total size of the resource, or -1 if unknown */
    long size = -1;

    /** the status of the resource */
    int status = UNINITIALIZED;

    /** Update policy for this resource */
    UpdatePolicy updatePolicy;

    /**
     * Create a resource.
     */
    private Resource(URL location, Version requestVersion, UpdatePolicy updatePolicy) {
        this.location = location;
        this.downloadLocation = location;
        this.requestVersion = requestVersion;
        this.updatePolicy = updatePolicy;
    }

    /**
     * Return a shared Resource object representing the given
     * location and version.
     */
    public static Resource getResource(URL location, Version requestVersion, UpdatePolicy updatePolicy) {
        synchronized (resources) {
            Resource resource = new Resource(location, requestVersion, updatePolicy);

            int index = resources.indexOf(resource);
            if (index >= 0) { // return existing object
                Resource result = resources.get(index);
                if (result != null)
                    return result;
            }

            resources.add(resource);
            resources.trimToSize();

            return resource;
        }
    }

    /**
     * Returns the remote location of the resource.
     */
    public URL getLocation() {
        return location;
    }

    /**
     * Returns the URL to use for downloading the resource. This can be
     * different from the original location since it may use a different
     * file name to support versioning and compression
     * @return the url to use when downloading
     */
    public URL getDownloadLocation() {
        return downloadLocation;
    }

    /**
     * Set the url to use for downloading the resource
     * @param location
     */
    public void setDownloadLocation(URL location) {
        downloadLocation = location;
    }

    /**
     * Returns the tracker that first created or monitored the
     * resource, or null if no trackers are monitoring the resource.
     */
    ResourceTracker getTracker() {
        synchronized (trackers) {
            List<ResourceTracker> t = trackers.hardList();
            if (t.size() > 0)
                return t.get(0);

            return null;
        }
    }

    /**
     * Returns true if any of the specified flags are set.
     */
    public boolean isSet(int flag) {
        if (flag == UNINITIALIZED)
            return status == UNINITIALIZED;
        else
            return (status & flag) != 0;
    }

    /**
     * Returns the update policy for this resource
     *
     * @return The update policy
     */
    public UpdatePolicy getUpdatePolicy() {
        return this.updatePolicy;
    }

    /**
     * Returns a human-readable status string.
     */
    private String getStatusString(int flag) {
        StringBuffer result = new StringBuffer();

        if (flag == 0)
            result.append("<> ");
        if ((flag & CONNECT) != 0)
            result.append("CONNECT ");
        if ((flag & CONNECTING) != 0)
            result.append("CONNECTING ");
        if ((flag & CONNECTED) != 0)
            result.append("CONNECTED ");
        if ((flag & DOWNLOAD) != 0)
            result.append("DOWNLOAD ");
        if ((flag & DOWNLOADING) != 0)
            result.append("DOWNLOADING ");
        if ((flag & DOWNLOADED) != 0)
            result.append("DOWNLOADED ");
        if ((flag & ERROR) != 0)
            result.append("ERROR ");
        if ((flag & STARTED) != 0)
            result.append("STARTED ");

        return result.deleteCharAt(result.length() - 1).toString();
    }

    /**
     * Changes the status by clearing the flags in the first
     * parameter and setting the flags in the second.  This method
     * is synchronized on this resource.
     */
    public void changeStatus(int clear, int add) {
        int orig = 0;

        synchronized (this) {
            orig = status;

            this.status &= ~clear;
            this.status |= add;
        }

        if (JNLPRuntime.isDebug())
            if (status != orig) {
                System.out.print("Status: " + getStatusString(status));
                if ((status & ~orig) != 0)
                    System.out.print(" +(" + getStatusString(status & ~orig) + ")");
                if ((~status & orig) != 0)
                    System.out.print(" -(" + getStatusString(~status & orig) + ")");
                System.out.println(" @ " + location.getPath());
            }
    }

    /**
     * Removes the tracker to the list of trackers monitoring this
     * resource.
     */
    public void removeTracker(ResourceTracker tracker) {
        synchronized (trackers) {
            trackers.remove(tracker);
            trackers.trimToSize();
        }
    }

    /**
     * Adds the tracker to the list of trackers monitoring this
     * resource.
     */
    public void addTracker(ResourceTracker tracker) {
        synchronized (trackers) {
            // prevent GC between contains and add
            List<ResourceTracker> t = trackers.hardList();
            if (!t.contains(tracker))
                trackers.add(tracker);

            trackers.trimToSize();
        }
    }

    /**
     * Instructs the trackers monitoring this resource to fire a
     * download event.
     */
    protected void fireDownloadEvent() {
        List<ResourceTracker> send;

        synchronized (trackers) {
            send = trackers.hardList();
        }

        for (int i = 0; i < send.size(); i++) {
            ResourceTracker rt = send.get(i);
            rt.fireDownloadEvent(this);
        }
    }

    public boolean equals(Object other) {
        if (other instanceof Resource) {
            // this prevents the URL handler from looking up the IP
            // address and doing name resolution; much faster so less
            // time spent in synchronized addResource determining if
            // Resource is already in a tracker, and better for offline
            // mode on some OS.
            return CacheUtil.urlEquals(location, ((Resource) other).location);
        }
        return false;
    }

    public String toString() {
        return "location=" + location.toString() + " state=" + getStatusString(status);
    }

}