/*
 * Copyright 2014, 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 com.android.managedprovisioning.task;

import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.content.pm.ComponentInfo;
import android.content.pm.IPackageDeleteObserver;
import android.content.pm.IPackageManager;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.content.res.Resources;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.util.Xml;

import com.android.internal.util.FastXmlSerializer;
import com.android.managedprovisioning.ProvisionLogger;
import com.android.managedprovisioning.R;
import com.android.managedprovisioning.Utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlSerializer;

/**
 * Deletes all system apps with a launcher that are not in the required set of packages.
 * Furthermore deletes all disallowed apps.
 *
 * Note: If an app is mistakenly listed as both required and disallowed, it will be treated as
 * required.
 *
 * This task may be run when a profile (both for managed device and managed profile) is created.
 * In that case the newProfile flag should be true.
 *
 * It should also be run after a system update with newProfile false, if
 * {@link #shouldDeleteNonRequiredApps} returns true. Note that only newly installed system apps
 * will be deleted.
 */
public class DeleteNonRequiredAppsTask {
    private final Callback mCallback;
    private final Context mContext;
    private final String mMdmPackageName;
    private final IPackageManager mIpm;
    private final PackageManager mPm;
    private final List<String> mRequiredAppsList;
    private final List<String> mDisallowedAppsList;
    private final List<String> mVendorRequiredAppsList;
    private final List<String> mVendorDisallowedAppsList;
    private final int mUserId;
    private final boolean mNewProfile; // If we are provisioning a new managed profile/device.
    private final boolean mLeaveAllSystemAppsEnabled;

    private static final String TAG_SYSTEM_APPS = "system-apps";
    private static final String TAG_PACKAGE_LIST_ITEM = "item";
    private static final String ATTR_VALUE = "value";

    public static final int DEVICE_OWNER = 0;
    public static final int PROFILE_OWNER = 1;

    /**
     * Provisioning type should be either {@link #DEVICE_OWNER} or {@link #PROFILE_OWNER}.
     **/
    public DeleteNonRequiredAppsTask(Context context, String mdmPackageName, int provisioningType,
            boolean newProfile, int userId, boolean leaveAllSystemAppsEnabled, Callback callback) {

        mCallback = callback;
        mContext = context;
        mMdmPackageName = mdmPackageName;
        mUserId = userId;
        mNewProfile = newProfile;
        mLeaveAllSystemAppsEnabled = leaveAllSystemAppsEnabled;
        mIpm = IPackageManager.Stub.asInterface(ServiceManager.getService("package"));
        mPm = context.getPackageManager();

        int requiredAppsListArray;
        int vendorRequiredAppsListArray;
        int disallowedAppsListArray;
        int vendorDisallowedAppsListArray;
        if (provisioningType == DEVICE_OWNER) {
            requiredAppsListArray = R.array.required_apps_managed_device;
            disallowedAppsListArray = R.array.disallowed_apps_managed_device;
            vendorRequiredAppsListArray = R.array.vendor_required_apps_managed_device;
            vendorDisallowedAppsListArray = R.array.vendor_disallowed_apps_managed_device;
        } else if (provisioningType == PROFILE_OWNER) {
            requiredAppsListArray = R.array.required_apps_managed_profile;
            disallowedAppsListArray = R.array.disallowed_apps_managed_profile;
            vendorRequiredAppsListArray = R.array.vendor_required_apps_managed_profile;
            vendorDisallowedAppsListArray = R.array.vendor_disallowed_apps_managed_profile;
        } else {
            throw new IllegalArgumentException("Provisioning type " + provisioningType +
                    " not supported.");
        }

        Resources resources = mContext.getResources();
        mRequiredAppsList = Arrays.asList(resources.getStringArray(requiredAppsListArray));
        mDisallowedAppsList = Arrays.asList(resources.getStringArray(disallowedAppsListArray));
        mVendorRequiredAppsList = Arrays.asList(
                resources.getStringArray(vendorRequiredAppsListArray));
        mVendorDisallowedAppsList = Arrays.asList(
                resources.getStringArray(vendorDisallowedAppsListArray));
    }

    public void run() {
        if (mLeaveAllSystemAppsEnabled) {
            ProvisionLogger.logd("Not deleting non-required apps.");
            mCallback.onSuccess();
            return;
        }
        ProvisionLogger.logd("Deleting non required apps.");

        File systemAppsFile = getSystemAppsFile(mContext, mUserId);
        systemAppsFile.getParentFile().mkdirs(); // Creating the folder if it does not exist

        Set<String> currentApps = Utils.getCurrentSystemApps(mUserId);
        Set<String> previousApps;
        if (mNewProfile) {
            // Provisioning case.
            previousApps = new HashSet<String>();
        } else {
            // OTA case.
            if (!systemAppsFile.exists()) {
                ProvisionLogger.loge("Could not find the system apps file " +
                        systemAppsFile.getAbsolutePath());
                mCallback.onError();
                return;
            }
            previousApps = readSystemApps(systemAppsFile);
        }

        writeSystemApps(currentApps, systemAppsFile);
        Set<String> newApps = currentApps;
        newApps.removeAll(previousApps);

        // Newly installed system apps are uninstalled when they are not required and are either
        // disallowed or have a launcher icon.
        Set<String> packagesToDelete = newApps;
        packagesToDelete.removeAll(getRequiredApps());
        Set<String> packagesToRetain = getCurrentAppsWithLauncher();
        packagesToRetain.addAll(getDisallowedApps());
        packagesToDelete.retainAll(packagesToRetain);

        if (packagesToDelete.isEmpty()) {
            mCallback.onSuccess();
            return;
        }
        removeNonInstalledPackages(packagesToDelete);

        PackageDeleteObserver packageDeleteObserver =
                new PackageDeleteObserver(packagesToDelete.size());
        for (String packageName : packagesToDelete) {
            try {
                mIpm.deletePackageAsUser(packageName, packageDeleteObserver, mUserId,
                        PackageManager.DELETE_SYSTEM_APP);
            } catch (RemoteException neverThrown) {
                // Never thrown, as we are making local calls.
                ProvisionLogger.loge("This should not happen.", neverThrown);
            }
        }
    }

    /**
     * Remove all packages from the set that are not installed.
     */
    private void removeNonInstalledPackages(Set<String> packages) {
        Set<String> toBeRemoved = new HashSet<String>();
        for (String packageName : packages) {
            try {
                PackageInfo info = mIpm.getPackageInfo(packageName, 0 /* default flags */, mUserId);
                if (info == null) {
                    toBeRemoved.add(packageName);
                }
            } catch (RemoteException neverThrown) {
                // Never thrown, as we are making local calls.
                ProvisionLogger.loge("This should not happen.", neverThrown);
            }
        }
        packages.removeAll(toBeRemoved);
    }

    /**
     * Returns if this task should be run on OTA.
     * This is indicated by the presence of the system apps file.
     */
    public static boolean shouldDeleteNonRequiredApps(Context context, int userId) {
        return getSystemAppsFile(context, userId).exists();
    }

    static File getSystemAppsFile(Context context, int userId) {
        return new File(context.getFilesDir() + File.separator + "system_apps"
                + File.separator + "user" + userId + ".xml");
    }

    private Set<String> getCurrentAppsWithLauncher() {
        Intent launcherIntent = new Intent(Intent.ACTION_MAIN);
        launcherIntent.addCategory(Intent.CATEGORY_LAUNCHER);
        List<ResolveInfo> resolveInfos = mPm.queryIntentActivitiesAsUser(launcherIntent,
                PackageManager.GET_UNINSTALLED_PACKAGES, mUserId);
        Set<String> apps = new HashSet<String>();
        for (ResolveInfo resolveInfo : resolveInfos) {
            apps.add(resolveInfo.activityInfo.packageName);
        }
        return apps;
    }

    private void writeSystemApps(Set<String> packageNames, File systemAppsFile) {
        try {
            FileOutputStream stream = new FileOutputStream(systemAppsFile, false);
            XmlSerializer serializer = new FastXmlSerializer();
            serializer.setOutput(stream, "utf-8");
            serializer.startDocument(null, true);
            serializer.startTag(null, TAG_SYSTEM_APPS);
            for (String packageName : packageNames) {
                serializer.startTag(null, TAG_PACKAGE_LIST_ITEM);
                serializer.attribute(null, ATTR_VALUE, packageName);
                serializer.endTag(null, TAG_PACKAGE_LIST_ITEM);
            }
            serializer.endTag(null, TAG_SYSTEM_APPS);
            serializer.endDocument();
            stream.close();
        } catch (IOException e) {
            ProvisionLogger.loge("IOException trying to write the system apps", e);
        }
    }

    private Set<String> readSystemApps(File systemAppsFile) {
        Set<String> result = new HashSet<String>();
        if (!systemAppsFile.exists()) {
            return result;
        }
        try {
            FileInputStream stream = new FileInputStream(systemAppsFile);

            XmlPullParser parser = Xml.newPullParser();
            parser.setInput(stream, null);

            int type = parser.next();
            int outerDepth = parser.getDepth();
            while ((type=parser.next()) != XmlPullParser.END_DOCUMENT
                   && (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {
                if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
                    continue;
                }
                String tag = parser.getName();
                if (tag.equals(TAG_PACKAGE_LIST_ITEM)) {
                    result.add(parser.getAttributeValue(null, ATTR_VALUE));
                } else {
                    ProvisionLogger.loge("Unknown tag: " + tag);
                }
            }
            stream.close();
        } catch (IOException e) {
            ProvisionLogger.loge("IOException trying to read the system apps", e);
        } catch (XmlPullParserException e) {
            ProvisionLogger.loge("XmlPullParserException trying to read the system apps", e);
        }
        return result;
    }

    protected Set<String> getRequiredApps() {
        HashSet<String> requiredApps = new HashSet<String>();
        requiredApps.addAll(mRequiredAppsList);
        requiredApps.addAll(mVendorRequiredAppsList);
        requiredApps.add(mMdmPackageName);
        return requiredApps;
    }

    private Set<String> getDisallowedApps() {
        HashSet<String> disallowedApps = new HashSet<String>();
        disallowedApps.addAll(mDisallowedAppsList);
        disallowedApps.addAll(mVendorDisallowedAppsList);
        return disallowedApps;
    }

    /**
     * Runs the next task when all packages have been deleted or shuts down the activity if package
     * deletion fails.
     */
    class PackageDeleteObserver extends IPackageDeleteObserver.Stub {
        private final AtomicInteger mPackageCount = new AtomicInteger(0);

        public PackageDeleteObserver(int packageCount) {
            this.mPackageCount.set(packageCount);
        }

        @Override
        public void packageDeleted(String packageName, int returnCode) {
            if (returnCode != PackageManager.DELETE_SUCCEEDED) {
                ProvisionLogger.logw(
                        "Could not finish the provisioning: package deletion failed");
                mCallback.onError();
                return;
            }
            int currentPackageCount = mPackageCount.decrementAndGet();
            if (currentPackageCount == 0) {
                ProvisionLogger.logi("All non-required system apps with launcher icon, "
                        + "and all disallowed apps have been uninstalled.");
                mCallback.onSuccess();
            }
        }
    }

    public abstract static class Callback {
        public abstract void onSuccess();
        public abstract void onError();
    }
}