/**
 *   ownCloud Android client application
 *
 *   @author Bartek Przybylski
 *   @author David A. Velasco
 *   Copyright (C) 2011  Bartek Przybylski
 *   Copyright (C) 2015 ownCloud Inc.
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License version 2,
 *   as published by the Free Software Foundation.
 *
 *   This program 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 General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package com.owncloud.android.syncadapter;

import android.accounts.Account;
import android.accounts.AccountsException;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.AbstractThreadedSyncAdapter;
import android.content.ContentProviderClient;
import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.content.SyncResult;
import android.os.Bundle;
import android.support.annotation.PluralsRes;
import android.support.v4.app.NotificationCompat;

import com.owncloud.android.R;
import com.owncloud.android.authentication.AuthenticatorActivity;
import com.owncloud.android.datamodel.FileDataStorageManager;
import com.owncloud.android.datamodel.OCFile;
import com.owncloud.android.lib.common.operations.RemoteOperationResult;
import com.owncloud.android.lib.common.operations.RemoteOperationResult.ResultCode;
import com.owncloud.android.lib.common.utils.Log_OC;
import com.owncloud.android.operations.RefreshFolderOperation;
import com.owncloud.android.operations.UpdateOCVersionOperation;
import com.owncloud.android.ui.activity.ErrorsWhileCopyingHandlerActivity;
import com.owncloud.android.ui.notifications.NotificationUtils;
import com.owncloud.android.utils.DataHolderUtil;
import com.owncloud.android.utils.ThemeUtils;

import org.apache.jackrabbit.webdav.DavException;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Implementation of {@link AbstractThreadedSyncAdapter} responsible for synchronizing 
 * ownCloud files.
 * 
 * Performs a full synchronization of the account received in {@link #onPerformSync(Account, Bundle,
 * String, ContentProviderClient, SyncResult)}.
 */
public class FileSyncAdapter extends AbstractOwnCloudSyncAdapter {

    private final static String TAG = FileSyncAdapter.class.getSimpleName();

    /** Maximum number of failed folder synchronizations that are supported before finishing
     * the synchronization operation */
    private static final int MAX_FAILED_RESULTS = 3; 
    
    
    public static final String EVENT_FULL_SYNC_START = FileSyncAdapter.class.getName() +
            ".EVENT_FULL_SYNC_START";
    public static final String EVENT_FULL_SYNC_END = FileSyncAdapter.class.getName() +
            ".EVENT_FULL_SYNC_END";
    public static final String EVENT_FULL_SYNC_FOLDER_CONTENTS_SYNCED =
            FileSyncAdapter.class.getName() + ".EVENT_FULL_SYNC_FOLDER_CONTENTS_SYNCED";

    public static final String EXTRA_ACCOUNT_NAME = FileSyncAdapter.class.getName() +
            ".EXTRA_ACCOUNT_NAME";
    public static final String EXTRA_FOLDER_PATH = FileSyncAdapter.class.getName() +
            ".EXTRA_FOLDER_PATH";
    public static final String EXTRA_RESULT = FileSyncAdapter.class.getName() + ".EXTRA_RESULT";

    /** Time stamp for the current synchronization process, used to distinguish fresh data */
    private long mCurrentSyncTime;
    
    /** Flag made 'true' when a request to cancel the synchronization is received */
    private boolean mCancellation;

    /** Counter for failed operations in the synchronization process */
    private int mFailedResultsCounter;
    
    /** Result of the last failed operation */
    private RemoteOperationResult mLastFailedResult;
    
    /** Counter of conflicts found between local and remote files */
    private int mConflictsFound;
    
    /** Counter of failed operations in synchronization of kept-in-sync files */
    private int mFailsInFavouritesFound;
    
    /** Map of remote and local paths to files that where locally stored in a location out
     * of the ownCloud folder and couldn't be copied automatically into it */
    private Map<String, String> mForgottenLocalFiles;

    /** {@link SyncResult} instance to return to the system when the synchronization finish */
    private SyncResult mSyncResult;

    /** 'True' means that the server supports the share API */
    private boolean mIsShareSupported;
    
    
    /**
     * Creates a {@link FileSyncAdapter}
     *
     * {@inheritDoc}
     */
    public FileSyncAdapter(Context context, boolean autoInitialize) {
        super(context, autoInitialize);
    }

    
    /**
     * Creates a {@link FileSyncAdapter}
     *
     * {@inheritDoc}
     */
    public FileSyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
        super(context, autoInitialize, allowParallelSyncs);
    }

    
    /**
     * {@inheritDoc}
     */
    @Override
    public synchronized void onPerformSync(Account account, Bundle extras,
            String authority, ContentProviderClient providerClient,
            SyncResult syncResult) {

        mCancellation = false;
        /* When 'true' the process was requested by the user through the user interface;
       when 'false', it was requested automatically by the system */
        boolean mIsManualSync = extras.getBoolean(ContentResolver.SYNC_EXTRAS_MANUAL, false);
        mFailedResultsCounter = 0;
        mLastFailedResult = null;
        mConflictsFound = 0;
        mFailsInFavouritesFound = 0;
        mForgottenLocalFiles = new HashMap<String, String>();
        mSyncResult = syncResult;
        mSyncResult.fullSyncRequested = false;
        mSyncResult.delayUntil = (System.currentTimeMillis()/1000) + 3*60*60; // avoid too many automatic synchronizations

        this.setAccount(account);
        this.setContentProviderClient(providerClient);
        this.setStorageManager(new FileDataStorageManager(account, providerClient));
        
        try {
            this.initClientForCurrentAccount();
        } catch (IOException | AccountsException e) {
            /// the account is unknown for the Synchronization Manager, unreachable this context,
            // or can not be authenticated; don't try this again
            mSyncResult.tooManyRetries = true;
            notifyFailedSynchronization();
            return;
        }

        Log_OC.d(TAG, "Synchronization of ownCloud account " + account.name + " starting");
        sendLocalBroadcast(EVENT_FULL_SYNC_START, null, null);  // message to signal the start
                                                                // of the synchronization to the UI
        
        try {
            updateOCVersion();
            mCurrentSyncTime = System.currentTimeMillis();
            if (!mCancellation) {
                synchronizeFolder(getStorageManager().getFileByPath(OCFile.ROOT_PATH));
                
            } else {
                Log_OC.d(TAG, "Leaving synchronization before synchronizing the root folder " +
                        "because cancellation request");
            }
            
            
        } finally {
            // it's important making this although very unexpected errors occur;
            // that's the reason for the finally
            
            if (mFailedResultsCounter > 0 && mIsManualSync) {
                /// don't let the system synchronization manager retries MANUAL synchronizations
                //      (be careful: "MANUAL" currently includes the synchronization requested when
                //      a new account is created and when the user changes the current account)
                mSyncResult.tooManyRetries = true;
                
                /// notify the user about the failure of MANUAL synchronization
                notifyFailedSynchronization();
            }
            if (mConflictsFound > 0 || mFailsInFavouritesFound > 0) {
                notifyFailsInFavourites();
            }
            if (mForgottenLocalFiles.size() > 0) {
                notifyForgottenLocalFiles();
            }
            sendLocalBroadcast(EVENT_FULL_SYNC_END, null, mLastFailedResult);   // message to signal
                                                                                // the end to the UI
        }
        
    }
    
    /**
     * Called by system SyncManager when a synchronization is required to be cancelled.
     * 
     * Sets the mCancellation flag to 'true'. THe synchronization will be stopped later, 
     * before a new folder is fetched. Data of the last folder synchronized will be still 
     * locally saved. 
     * 
     * See {@link #onPerformSync(Account, Bundle, String, ContentProviderClient, SyncResult)}
     * and {@link #synchronizeFolder(OCFile)}.
     */
    @Override
    public void onSyncCanceled() {
        Log_OC.d(TAG, "Synchronization of " + getAccount().name + " has been requested to cancel");
        mCancellation = true;
        super.onSyncCanceled();
    }
    
    
    /**
     * Updates the locally stored version value of the ownCloud server
     */
    private void updateOCVersion() {
        UpdateOCVersionOperation update = new UpdateOCVersionOperation(getAccount(), getContext());
        RemoteOperationResult result = update.execute(getClient());
        if (!result.isSuccess()) {
            mLastFailedResult = result; 
        } else {
            mIsShareSupported = update.getOCVersion().isSharedSupported();
        }
    }
    
    
    /**
     *  Synchronizes the list of files contained in a folder identified with its remote path.
     *  
     *  Fetches the list and properties of the files contained in the given folder, including their 
     *  properties, and updates the local database with them.
     *  
     *  Enters in the child folders to synchronize their contents also, following a recursive
     *  depth first strategy. 
     * 
     *  @param folder                   Folder to synchronize.
     */
    private void synchronizeFolder(OCFile folder) {
        
        if (mFailedResultsCounter > MAX_FAILED_RESULTS || isFinisher(mLastFailedResult)) {
            return;
        }
        
        // folder synchronization
        RefreshFolderOperation synchFolderOp = new RefreshFolderOperation( folder,
                                                                                   mCurrentSyncTime,
                                                                                   true,
                                                                                   mIsShareSupported,
                                                                                   false,
                                                                                   getStorageManager(),
                                                                                   getAccount(),
                                                                                   getContext()
                                                                                  );
        RemoteOperationResult result = synchFolderOp.execute(getClient());
        
        
        // synchronized folder -> notice to UI - ALWAYS, although !result.isSuccess
        sendLocalBroadcast(EVENT_FULL_SYNC_FOLDER_CONTENTS_SYNCED, folder.getRemotePath(), result);
        
        // check the result of synchronizing the folder
        if (result.isSuccess() || result.getCode() == ResultCode.SYNC_CONFLICT) {
            
            if (result.getCode() == ResultCode.SYNC_CONFLICT) {
                mConflictsFound += synchFolderOp.getConflictsFound();
                mFailsInFavouritesFound += synchFolderOp.getFailsInKeptInSyncFound();
            }
            if (synchFolderOp.getForgottenLocalFiles().size() > 0) {
                mForgottenLocalFiles.putAll(synchFolderOp.getForgottenLocalFiles());
            }
            if (result.isSuccess()) {
                // synchronize children folders 
                List<OCFile> children = synchFolderOp.getChildren();
                // beware of the 'hidden' recursion here!
                syncChildren(children);
            }
            
        } else if (result.getCode() != ResultCode.FILE_NOT_FOUND) {
            // in failures, the statistics for the global result are updated
            if (RemoteOperationResult.ResultCode.UNAUTHORIZED.equals(result.getCode())) {
                mSyncResult.stats.numAuthExceptions++;
                
            } else if (result.getException() instanceof DavException) {
                mSyncResult.stats.numParseExceptions++;
                
            } else if (result.getException() instanceof IOException) { 
                mSyncResult.stats.numIoExceptions++;
            }
            mFailedResultsCounter++;
            mLastFailedResult = result;

        } // else, ResultCode.FILE_NOT_FOUND is ignored, remote folder was
          // removed from other thread or other client during the synchronization,
          // before this thread fetched its contents
            
    }

    /**
     * Checks if a failed result should terminate the synchronization process immediately,
     * according to OUR OWN POLICY
     * 
     * @param   failedResult        Remote operation result to check.
     * @return                      'True' if the result should immediately finish the
     *                              synchronization
     */
    private boolean isFinisher(RemoteOperationResult failedResult) {
        if  (failedResult != null) {
            RemoteOperationResult.ResultCode code = failedResult.getCode();
            return (code.equals(RemoteOperationResult.ResultCode.SSL_ERROR) ||
                    code.equals(RemoteOperationResult.ResultCode.SSL_RECOVERABLE_PEER_UNVERIFIED) ||
                    code.equals(RemoteOperationResult.ResultCode.BAD_OC_VERSION) ||
                    code.equals(RemoteOperationResult.ResultCode.INSTANCE_NOT_CONFIGURED));
        }
        return false;
    }

    /**
     * Triggers the synchronization of any folder contained in the list of received files.
     *
     * No consideration of etag here because it MUST walk down anyway, in case that kept-in-sync files
     * have local changes.
     * 
     * @param files         Files to recursively synchronize.
     */
    private void syncChildren(List<OCFile> files) {
        int i;
        OCFile newFile;
        for (i=0; i < files.size() && !mCancellation; i++) {
            newFile = files.get(i);
            if (newFile.isFolder()) {
                synchronizeFolder(newFile);
            }
        }
       
        if (mCancellation && i <files.size()) {
            Log_OC.d(TAG,
                    "Leaving synchronization before synchronizing " + files.get(i).getRemotePath() +
                            " due to cancellation request");
        }
    }

    
    /**
     * Sends a message to any application component interested in the progress of the
     * synchronization.
     * 
     * @param event             Event in the process of synchronization to be notified.   
     * @param dirRemotePath     Remote path of the folder target of the event occurred.
     * @param result            Result of an individual {@ SynchronizeFolderOperation},
     *                          if completed; may be null.
     */
    private void sendLocalBroadcast(String event, String dirRemotePath,
                                    RemoteOperationResult result) {
        Log_OC.d(TAG, "Send broadcast " + event);
        Intent intent = new Intent(event);
        intent.putExtra(FileSyncAdapter.EXTRA_ACCOUNT_NAME, getAccount().name);
        if (dirRemotePath != null) {
            intent.putExtra(FileSyncAdapter.EXTRA_FOLDER_PATH, dirRemotePath);
        }

        if (result != null) {
            DataHolderUtil dataHolderUtil = DataHolderUtil.getInstance();
            String dataHolderItemId = dataHolderUtil.nextItemId();
            dataHolderUtil.save(dataHolderUtil.nextItemId(), result);
            intent.putExtra(FileSyncAdapter.EXTRA_RESULT, dataHolderItemId);
        }

        intent.setPackage(getContext().getPackageName());
        getContext().sendStickyBroadcast(intent);
        //LocalBroadcastManager.getInstance(getContext()).sendBroadcast(intent);
    }

    
    
    /**
     * Notifies the user about a failed synchronization through the status notification bar 
     */
    private void notifyFailedSynchronization() {
        NotificationCompat.Builder notificationBuilder = createNotificationBuilder();
        boolean needsToUpdateCredentials = (
                mLastFailedResult != null &&
                ResultCode.UNAUTHORIZED.equals(mLastFailedResult.getCode())
        );
        if (needsToUpdateCredentials) {
            // let the user update credentials with one click
            Intent updateAccountCredentials = new Intent(getContext(), AuthenticatorActivity.class);
            updateAccountCredentials.putExtra(AuthenticatorActivity.EXTRA_ACCOUNT, getAccount());
            updateAccountCredentials.putExtra(AuthenticatorActivity.EXTRA_ACTION,
                    AuthenticatorActivity.ACTION_UPDATE_EXPIRED_TOKEN);
            updateAccountCredentials.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            updateAccountCredentials.addFlags(Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
            updateAccountCredentials.addFlags(Intent.FLAG_FROM_BACKGROUND);
            notificationBuilder
                .setTicker(i18n(R.string.sync_fail_ticker_unauthorized))
                .setContentTitle(i18n(R.string.sync_fail_ticker_unauthorized))
                .setContentIntent(PendingIntent.getActivity(
                    getContext(), (int)System.currentTimeMillis(), updateAccountCredentials,
                        PendingIntent.FLAG_ONE_SHOT
                ))
                .setContentText(i18n(R.string.sync_fail_content_unauthorized, getAccount().name));
        } else {
            notificationBuilder
                .setTicker(i18n(R.string.sync_fail_ticker))
                .setContentTitle(i18n(R.string.sync_fail_ticker))
                .setContentText(i18n(R.string.sync_fail_content, getAccount().name));
        }
        
        showNotification(R.string.sync_fail_ticker, notificationBuilder);
    }


    /**
     * Notifies the user about conflicts and strange fails when trying to synchronize the contents
     * of kept-in-sync files.
     * 
     * By now, we won't consider a failed synchronization.
     */
    private void notifyFailsInFavourites() {
        if (mFailedResultsCounter > 0) {
            NotificationCompat.Builder notificationBuilder = createNotificationBuilder();
            notificationBuilder.setTicker(i18n(R.string.sync_fail_in_favourites_ticker));
                
            // TODO put something smart in the contentIntent below
            notificationBuilder
                .setContentIntent(PendingIntent.getActivity(
                    getContext(), (int) System.currentTimeMillis(), new Intent(), 0
                ))
                .setContentTitle(i18n(R.string.sync_fail_in_favourites_ticker))
                .setContentText(getQuantityString(
                    R.plurals.sync_fail_in_favourites_content,
                    mFailedResultsCounter,
                    mFailedResultsCounter + mConflictsFound, mConflictsFound
                    )
                );
            
            showNotification(R.string.sync_fail_in_favourites_ticker, notificationBuilder);
        } else {
            NotificationCompat.Builder notificationBuilder = createNotificationBuilder();
            notificationBuilder.setTicker(i18n(R.string.sync_conflicts_in_favourites_ticker));
          
            // TODO put something smart in the contentIntent below
            notificationBuilder
                .setContentIntent(PendingIntent.getActivity(
                    getContext(), (int) System.currentTimeMillis(), new Intent(), 0
                ))
                .setContentTitle(i18n(R.string.sync_conflicts_in_favourites_ticker))
                .setContentText(i18n(R.string.sync_conflicts_in_favourites_ticker, mConflictsFound));
            
            showNotification(R.string.sync_conflicts_in_favourites_ticker, notificationBuilder);
        } 
    }
    
    /**
     * Notifies the user about local copies of files out of the ownCloud local directory that
     * were 'forgotten' because copying them inside the ownCloud local directory was not possible.
     * 
     * We don't want links to files out of the ownCloud local directory (foreign files) anymore.
     * It's easy to have synchronization problems if a local file is linked to more than one
     * remote file.
     * 
     * We won't consider a synchronization as failed when foreign files can not be copied to
     * the ownCloud local directory.
     */
    private void notifyForgottenLocalFiles() {
        NotificationCompat.Builder notificationBuilder = createNotificationBuilder();
        notificationBuilder.setTicker(i18n(R.string.sync_foreign_files_forgotten_ticker));
      
        /// includes a pending intent in the notification showing a more detailed explanation
        Intent explanationIntent = new Intent(getContext(), ErrorsWhileCopyingHandlerActivity.class);
        explanationIntent.putExtra(ErrorsWhileCopyingHandlerActivity.EXTRA_ACCOUNT, getAccount());
        ArrayList<String> remotePaths = new ArrayList<String>();
        ArrayList<String> localPaths = new ArrayList<String>();
        remotePaths.addAll(mForgottenLocalFiles.keySet());
        localPaths.addAll(mForgottenLocalFiles.values());
        explanationIntent.putExtra(ErrorsWhileCopyingHandlerActivity.EXTRA_LOCAL_PATHS, localPaths);
        explanationIntent.putExtra(ErrorsWhileCopyingHandlerActivity.EXTRA_REMOTE_PATHS, remotePaths);  
        explanationIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        
        notificationBuilder
            .setContentIntent(PendingIntent.getActivity(
                getContext(), (int) System.currentTimeMillis(), explanationIntent, 0
            ))
            .setContentTitle(i18n(R.string.sync_foreign_files_forgotten_ticker))
            .setContentText(getQuantityString(
                    R.plurals.sync_foreign_files_forgotten_content,
                    mForgottenLocalFiles.size(),
                    mForgottenLocalFiles.size(),
                    i18n(R.string.app_name))
            );
        
        showNotification(R.string.sync_foreign_files_forgotten_ticker, notificationBuilder);
    }
    
    /**
     * Creates a notification builder with some commonly used settings
     * 
     * @return notification builder
     */
    private NotificationCompat.Builder createNotificationBuilder() {
        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(getContext());
        notificationBuilder.setSmallIcon(R.drawable.notification_icon).setAutoCancel(true);
        notificationBuilder.setColor(ThemeUtils.primaryColor());
        return notificationBuilder;
    }
    
    /**
     * Builds and shows the notification
     * 
     * @param id
     * @param builder
     */
    private void showNotification(int id, NotificationCompat.Builder builder) {
        NotificationManager notificationManager = ((NotificationManager) getContext().
                getSystemService(Context.NOTIFICATION_SERVICE));

        if ((android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O)) {
            builder.setChannelId(NotificationUtils.NOTIFICATION_CHANNEL_FILE_SYNC);
        }

        notificationManager.notify(id, builder.build());
    }
    /**
     * Shorthand translation
     * 
     * @param key
     * @param args
     * @return
     */
    private String i18n(int key, Object... args) {
        return getContext().getString(key, args);
    }

    /**
     * Shorthand plurals translation.
     *
     * @param id         The desired plurals identifier.
     * @param quantity   The number used to get the correct string for the current language's plural rules.
     * @param formatArgs The format arguments that will be used for substitution.
     * @return formatted, plurals respecting string
     */
    private String getQuantityString(@PluralsRes int id, int quantity, Object... formatArgs) {
        return getContext().getResources().getQuantityString(id, quantity, formatArgs);
    }
}