/*
 * Copyright (C) 2010 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.contacts.vcard;

import android.app.Service;
import android.content.Intent;
import android.media.MediaScannerConnection;
import android.media.MediaScannerConnection.MediaScannerConnectionClient;
import android.net.Uri;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import android.util.SparseArray;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.RejectedExecutionException;

/**
 * The class responsible for handling vCard import/export requests.
 *
 * This Service creates one ImportRequest/ExportRequest object (as Runnable) per request and push
 * it to {@link ExecutorService} with single thread executor. The executor handles each request
 * one by one, and notifies users when needed.
 */
// TODO: Using IntentService looks simpler than using Service + ServiceConnection though this
// works fine enough. Investigate the feasibility.
public class VCardService extends Service {
    private final static String LOG_TAG = "VCardService";

    /* package */ final static boolean DEBUG = false;

    /**
     * Specifies the type of operation. Used when constructing a notification, canceling
     * some operation, etc.
     */
    /* package */ static final int TYPE_IMPORT = 1;
    /* package */ static final int TYPE_EXPORT = 2;

    /* package */ static final String CACHE_FILE_PREFIX = "import_tmp_";

    /* package */ static final String X_VCARD_MIME_TYPE = "text/x-vcard";

    private class CustomMediaScannerConnectionClient implements MediaScannerConnectionClient {
        final MediaScannerConnection mConnection;
        final String mPath;

        public CustomMediaScannerConnectionClient(String path) {
            mConnection = new MediaScannerConnection(VCardService.this, this);
            mPath = path;
        }

        public void start() {
            mConnection.connect();
        }

        @Override
        public void onMediaScannerConnected() {
            if (DEBUG) { Log.d(LOG_TAG, "Connected to MediaScanner. Start scanning."); }
            mConnection.scanFile(mPath, null);
        }

        @Override
        public void onScanCompleted(String path, Uri uri) {
            if (DEBUG) { Log.d(LOG_TAG, "scan completed: " + path); }
            mConnection.disconnect();
            removeConnectionClient(this);
        }
    }

    // Should be single thread, as we don't want to simultaneously handle import and export
    // requests.
    private final ExecutorService mExecutorService = Executors.newSingleThreadExecutor();

    private int mCurrentJobId;

    // Stores all unfinished import/export jobs which will be executed by mExecutorService.
    // Key is jobId.
    private final SparseArray<ProcessorBase> mRunningJobMap = new SparseArray<ProcessorBase>();
    // Stores ScannerConnectionClient objects until they finish scanning requested files.
    // Uses List class for simplicity. It's not costly as we won't have multiple objects in
    // almost all cases.
    private final List<CustomMediaScannerConnectionClient> mRemainingScannerConnections =
            new ArrayList<CustomMediaScannerConnectionClient>();

    private MyBinder mBinder;

    private String mCallingActivity;

    // File names currently reserved by some export job.
    private final Set<String> mReservedDestination = new HashSet<String>();
    /* ** end of vCard exporter params ** */

    public class MyBinder extends Binder {
        public VCardService getService() {
            return VCardService.this;
        }
    }

   @Override
    public void onCreate() {
        super.onCreate();
        mBinder = new MyBinder();
        if (DEBUG) Log.d(LOG_TAG, "vCard Service is being created.");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int id) {
        if (intent != null && intent.getExtras() != null) {
            mCallingActivity = intent.getExtras().getString(
                    VCardCommonArguments.ARG_CALLING_ACTIVITY);
        } else {
            mCallingActivity = null;
        }
        return START_STICKY;
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    @Override
    public void onDestroy() {
        if (DEBUG) Log.d(LOG_TAG, "VCardService is being destroyed.");
        cancelAllRequestsAndShutdown();
        clearCache();
        super.onDestroy();
    }

    public synchronized void handleImportRequest(List<ImportRequest> requests,
            VCardImportExportListener listener) {
        if (DEBUG) {
            final ArrayList<String> uris = new ArrayList<String>();
            final ArrayList<String> displayNames = new ArrayList<String>();
            for (ImportRequest request : requests) {
                uris.add(request.uri.toString());
                displayNames.add(request.displayName);
            }
            Log.d(LOG_TAG,
                    String.format("received multiple import request (uri: %s, displayName: %s)",
                            uris.toString(), displayNames.toString()));
        }
        final int size = requests.size();
        for (int i = 0; i < size; i++) {
            ImportRequest request = requests.get(i);

            if (tryExecute(new ImportProcessor(this, listener, request, mCurrentJobId))) {
                if (listener != null) {
                    listener.onImportProcessed(request, mCurrentJobId, i);
                }
                mCurrentJobId++;
            } else {
                if (listener != null) {
                    listener.onImportFailed(request);
                }
                // A rejection means executor doesn't run any more. Exit.
                break;
            }
        }
    }

    public synchronized void handleExportRequest(ExportRequest request,
            VCardImportExportListener listener) {
        if (tryExecute(new ExportProcessor(this, request, mCurrentJobId, mCallingActivity))) {
            final String path = request.destUri.getEncodedPath();
            if (DEBUG) Log.d(LOG_TAG, "Reserve the path " + path);
            if (!mReservedDestination.add(path)) {
                Log.w(LOG_TAG,
                        String.format("The path %s is already reserved. Reject export request",
                                path));
                if (listener != null) {
                    listener.onExportFailed(request);
                }
                return;
            }

            if (listener != null) {
                listener.onExportProcessed(request, mCurrentJobId);
            }
            mCurrentJobId++;
        } else {
            if (listener != null) {
                listener.onExportFailed(request);
            }
        }
    }

    /**
     * Tries to call {@link ExecutorService#execute(Runnable)} toward a given processor.
     * @return true when successful.
     */
    private synchronized boolean tryExecute(ProcessorBase processor) {
        try {
            if (DEBUG) {
                Log.d(LOG_TAG, "Executor service status: shutdown: " + mExecutorService.isShutdown()
                        + ", terminated: " + mExecutorService.isTerminated());
            }
            mExecutorService.execute(processor);
            mRunningJobMap.put(mCurrentJobId, processor);
            return true;
        } catch (RejectedExecutionException e) {
            Log.w(LOG_TAG, "Failed to excetute a job.", e);
            return false;
        }
    }

    public synchronized void handleCancelRequest(CancelRequest request,
            VCardImportExportListener listener) {
        final int jobId = request.jobId;
        if (DEBUG) Log.d(LOG_TAG, String.format("Received cancel request. (id: %d)", jobId));

        final ProcessorBase processor = mRunningJobMap.get(jobId);
        mRunningJobMap.remove(jobId);

        if (processor != null) {
            processor.cancel(true);
            final int type = processor.getType();
            if (listener != null) {
                listener.onCancelRequest(request, type);
            }
            if (type == TYPE_EXPORT) {
                final String path =
                        ((ExportProcessor)processor).getRequest().destUri.getEncodedPath();
                Log.i(LOG_TAG,
                        String.format("Cancel reservation for the path %s if appropriate", path));
                if (!mReservedDestination.remove(path)) {
                    Log.w(LOG_TAG, "Not reserved.");
                }
            }
        } else {
            Log.w(LOG_TAG, String.format("Tried to remove unknown job (id: %d)", jobId));
        }
        stopServiceIfAppropriate();
    }

    /**
     * Checks job list and call {@link #stopSelf()} when there's no job and no scanner connection
     * is remaining.
     * A new job (import/export) cannot be submitted any more after this call.
     */
    private synchronized void stopServiceIfAppropriate() {
        if (mRunningJobMap.size() > 0) {
            final int size = mRunningJobMap.size();

            // Check if there are processors which aren't finished yet. If we still have ones to
            // process, we cannot stop the service yet. Also clean up already finished processors
            // here.

            // Job-ids to be removed. At first all elements in the array are invalid and will
            // be filled with real job-ids from the array's top. When we find a not-yet-finished
            // processor, then we start removing those finished jobs. In that case latter half of
            // this array will be invalid.
            final int[] toBeRemoved = new int[size];
            for (int i = 0; i < size; i++) {
                final int jobId = mRunningJobMap.keyAt(i);
                final ProcessorBase processor = mRunningJobMap.valueAt(i);
                if (!processor.isDone()) {
                    Log.i(LOG_TAG, String.format("Found unfinished job (id: %d)", jobId));

                    // Remove processors which are already "done", all of which should be before
                    // processors which aren't done yet.
                    for (int j = 0; j < i; j++) {
                        mRunningJobMap.remove(toBeRemoved[j]);
                    }
                    return;
                }

                // Remember the finished processor.
                toBeRemoved[i] = jobId;
            }

            // We're sure we can remove all. Instead of removing one by one, just call clear().
            mRunningJobMap.clear();
        }

        if (!mRemainingScannerConnections.isEmpty()) {
            Log.i(LOG_TAG, "MediaScanner update is in progress.");
            return;
        }

        Log.i(LOG_TAG, "No unfinished job. Stop this service.");
        mExecutorService.shutdown();
        stopSelf();
    }

    /* package */ synchronized void updateMediaScanner(String path) {
        if (DEBUG) {
            Log.d(LOG_TAG, "MediaScanner is being updated: " + path);
        }

        if (mExecutorService.isShutdown()) {
            Log.w(LOG_TAG, "MediaScanner update is requested after executor's being shut down. " +
                    "Ignoring the update request");
            return;
        }
        final CustomMediaScannerConnectionClient client =
                new CustomMediaScannerConnectionClient(path);
        mRemainingScannerConnections.add(client);
        client.start();
    }

    private synchronized void removeConnectionClient(
            CustomMediaScannerConnectionClient client) {
        if (DEBUG) {
            Log.d(LOG_TAG, "Removing custom MediaScannerConnectionClient.");
        }
        mRemainingScannerConnections.remove(client);
        stopServiceIfAppropriate();
    }

    /* package */ synchronized void handleFinishImportNotification(
            int jobId, boolean successful) {
        if (DEBUG) {
            Log.d(LOG_TAG, String.format("Received vCard import finish notification (id: %d). "
                    + "Result: %b", jobId, (successful ? "success" : "failure")));
        }
        mRunningJobMap.remove(jobId);
        stopServiceIfAppropriate();
    }

    /* package */ synchronized void handleFinishExportNotification(
            int jobId, boolean successful) {
        if (DEBUG) {
            Log.d(LOG_TAG, String.format("Received vCard export finish notification (id: %d). "
                    + "Result: %b", jobId, (successful ? "success" : "failure")));
        }
        final ProcessorBase job = mRunningJobMap.get(jobId);
        mRunningJobMap.remove(jobId);
        if (job == null) {
            Log.w(LOG_TAG, String.format("Tried to remove unknown job (id: %d)", jobId));
        } else if (!(job instanceof ExportProcessor)) {
            Log.w(LOG_TAG,
                    String.format("Removed job (id: %s) isn't ExportProcessor", jobId));
        } else {
            final String path = ((ExportProcessor)job).getRequest().destUri.getEncodedPath();
            if (DEBUG) Log.d(LOG_TAG, "Remove reserved path " + path);
            mReservedDestination.remove(path);
        }

        stopServiceIfAppropriate();
    }

    /**
     * Cancels all the import/export requests and calls {@link ExecutorService#shutdown()}, which
     * means this Service becomes no longer ready for import/export requests.
     *
     * Mainly called from onDestroy().
     */
    private synchronized void cancelAllRequestsAndShutdown() {
        for (int i = 0; i < mRunningJobMap.size(); i++) {
            mRunningJobMap.valueAt(i).cancel(true);
        }
        mRunningJobMap.clear();
        mExecutorService.shutdown();
    }

    /**
     * Removes import caches stored locally.
     */
    private void clearCache() {
        for (final String fileName : fileList()) {
            if (fileName.startsWith(CACHE_FILE_PREFIX)) {
                // We don't want to keep all the caches so we remove cache files old enough.
                Log.i(LOG_TAG, "Remove a temporary file: " + fileName);
                deleteFile(fileName);
            }
        }
    }
}