/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed 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.
 */

package android.webkit;

import android.content.Context;
import android.util.Log;


/**
 * The CookieSyncManager is used to synchronize the browser cookie store
 * between RAM and permanent storage. To get the best performance, browser cookies are
 * saved in RAM. A separate thread saves the cookies between, driven by a timer.
 * <p>
 *
 * To use the CookieSyncManager, the host application has to call the following
 * when the application starts:
 * <p>
 *
 * <pre class="prettyprint">CookieSyncManager.createInstance(context)</pre><p>
 *
 * To set up for sync, the host application has to call<p>
 * <pre class="prettyprint">CookieSyncManager.getInstance().startSync()</pre><p>
 *
 * in Activity.onResume(), and call
 * <p>
 *
 * <pre class="prettyprint">
 * CookieSyncManager.getInstance().stopSync()
 * </pre><p>
 *
 * in Activity.onPause().<p>
 *
 * To get instant sync instead of waiting for the timer to trigger, the host can
 * call
 * <p>
 * <pre class="prettyprint">CookieSyncManager.getInstance().sync()</pre><p>
 *
 * The sync interval is 5 minutes, so you will want to force syncs
 * manually anyway, for instance in {@link
 * WebViewClient#onPageFinished}. Note that even sync() happens
 * asynchronously, so don't do it just as your activity is shutting
 * down.
 */
public final class CookieSyncManager extends WebSyncManager {

    private static CookieSyncManager sRef;

    private static boolean sGetInstanceAllowed = false;

    private CookieSyncManager() {
        super("CookieSyncManager");
    }

    /**
     * Singleton access to a {@link CookieSyncManager}. An
     * IllegalStateException will be thrown if
     * {@link CookieSyncManager#createInstance(Context)} is not called before.
     * 
     * @return CookieSyncManager
     */
    public static synchronized CookieSyncManager getInstance() {
        checkInstanceIsAllowed();
        if (sRef == null) {
            sRef = new CookieSyncManager();
        }
        return sRef;
    }

    /**
     * Create a singleton CookieSyncManager within a context
     * @param context
     * @return CookieSyncManager
     */
    public static synchronized CookieSyncManager createInstance(Context context) {
        if (context == null) {
            throw new IllegalArgumentException("Invalid context argument");
        }

        setGetInstanceIsAllowed();
        return getInstance();
    }

    protected void syncFromRamToFlash() {
        if (DebugFlags.COOKIE_SYNC_MANAGER) {
            Log.v(LOGTAG, "CookieSyncManager::syncFromRamToFlash STARTS");
        }

        CookieManager manager = CookieManager.getInstance();

        if (!manager.acceptCookie()) {
            return;
        }

        manager.flushCookieStore();

        if (DebugFlags.COOKIE_SYNC_MANAGER) {
            Log.v(LOGTAG, "CookieSyncManager::syncFromRamToFlash DONE");
        }
    }

    static void setGetInstanceIsAllowed() {
        sGetInstanceAllowed = true;
    }

    private static void checkInstanceIsAllowed() {
        // Prior to Android KK, calling createInstance() or constructing a WebView is
        // a hard pre-condition for calling getInstance(). We retain that contract to aid
        // developers targeting a range of SDK levels.
        if (!sGetInstanceAllowed) {
            throw new IllegalStateException(
                    "CookieSyncManager::createInstance() needs to be called "
                            + "before CookieSyncManager::getInstance()");
        }
    }
}