package eu.siacs.conversations.services;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.os.IBinder;
import androidx.core.app.NotificationCompat;
import android.util.Log;

import com.google.common.base.Strings;

import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.zip.GZIPOutputStream;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import eu.siacs.conversations.Config;
import eu.siacs.conversations.R;
import eu.siacs.conversations.crypto.axolotl.SQLiteAxolotlStore;
import eu.siacs.conversations.entities.Account;
import eu.siacs.conversations.entities.Conversation;
import eu.siacs.conversations.entities.Message;
import eu.siacs.conversations.persistance.DatabaseBackend;
import eu.siacs.conversations.persistance.FileBackend;
import eu.siacs.conversations.utils.BackupFileHeader;
import eu.siacs.conversations.utils.Compatibility;

public class ExportBackupService extends Service {

    public static final String KEYTYPE = "AES";
    public static final String CIPHERMODE = "AES/GCM/NoPadding";
    public static final String PROVIDER = "BC";

    public static final String MIME_TYPE = "application/vnd.conversations.backup";

    private static final int NOTIFICATION_ID = 19;
    private static final int PAGE_SIZE = 20;
    private static final AtomicBoolean RUNNING = new AtomicBoolean(false);
    private DatabaseBackend mDatabaseBackend;
    private List<Account> mAccounts;
    private NotificationManager notificationManager;

    private static List<Intent> getPossibleFileOpenIntents(final Context context, final String path) {

        //http://www.openintents.org/action/android-intent-action-view/file-directory
        //do not use 'vnd.android.document/directory' since this will trigger system file manager
        final Intent openIntent = new Intent(Intent.ACTION_VIEW);
        openIntent.addCategory(Intent.CATEGORY_DEFAULT);
        if (Compatibility.runsAndTargetsTwentyFour(context)) {
            openIntent.setType("resource/folder");
        } else {
            openIntent.setDataAndType(Uri.parse("file://" + path), "resource/folder");
        }
        openIntent.putExtra("org.openintents.extra.ABSOLUTE_PATH", path);

        final Intent amazeIntent = new Intent(Intent.ACTION_VIEW);
        amazeIntent.setDataAndType(Uri.parse("com.amaze.filemanager:" + path), "resource/folder");

        //will open a file manager at root and user can navigate themselves
        final Intent systemFallBack = new Intent(Intent.ACTION_VIEW);
        systemFallBack.addCategory(Intent.CATEGORY_DEFAULT);
        systemFallBack.setData(Uri.parse("content://com.android.externalstorage.documents/root/primary"));

        return Arrays.asList(openIntent, amazeIntent, systemFallBack);
    }

    private static void accountExport(final SQLiteDatabase db, final String uuid, final PrintWriter writer) {
        final StringBuilder builder = new StringBuilder();
        final Cursor accountCursor = db.query(Account.TABLENAME, null, Account.UUID + "=?", new String[]{uuid}, null, null, null);
        while (accountCursor != null && accountCursor.moveToNext()) {
            builder.append("INSERT INTO ").append(Account.TABLENAME).append("(");
            for (int i = 0; i < accountCursor.getColumnCount(); ++i) {
                if (i != 0) {
                    builder.append(',');
                }
                builder.append(accountCursor.getColumnName(i));
            }
            builder.append(") VALUES(");
            for (int i = 0; i < accountCursor.getColumnCount(); ++i) {
                if (i != 0) {
                    builder.append(',');
                }
                final String value = accountCursor.getString(i);
                if (value == null || Account.ROSTERVERSION.equals(accountCursor.getColumnName(i))) {
                    builder.append("NULL");
                } else if (value.matches("\\d+")) {
                    int intValue = Integer.parseInt(value);
                    if (Account.OPTIONS.equals(accountCursor.getColumnName(i))) {
                        intValue |= 1 << Account.OPTION_DISABLED;
                    }
                    builder.append(intValue);
                } else {
                    DatabaseUtils.appendEscapedSQLString(builder, value);
                }
            }
            builder.append(")");
            builder.append(';');
            builder.append('\n');
        }
        if (accountCursor != null) {
            accountCursor.close();
        }
        writer.append(builder.toString());
    }

    private static void simpleExport(SQLiteDatabase db, String table, String column, String uuid, PrintWriter writer) {
        final Cursor cursor = db.query(table, null, column + "=?", new String[]{uuid}, null, null, null);
        while (cursor != null && cursor.moveToNext()) {
            writer.write(cursorToString(table, cursor, PAGE_SIZE));
        }
        if (cursor != null) {
            cursor.close();
        }
    }

    public static byte[] getKey(final String password, final byte[] salt) throws InvalidKeySpecException {
        final SecretKeyFactory factory;
        try {
            factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException(e);
        }
        return factory.generateSecret(new PBEKeySpec(password.toCharArray(), salt, 1024, 128)).getEncoded();
    }

    private static String cursorToString(final String table, final Cursor cursor, final int max) {
        return cursorToString(table, cursor, max, false);
    }

    private static String cursorToString(final String table, final Cursor cursor, int max, boolean ignore) {
        final boolean identities = SQLiteAxolotlStore.IDENTITIES_TABLENAME.equals(table);
        StringBuilder builder = new StringBuilder();
        builder.append("INSERT ");
        if (ignore) {
            builder.append("OR IGNORE ");
        }
        builder.append("INTO ").append(table).append("(");
        int skipColumn = -1;
        for (int i = 0; i < cursor.getColumnCount(); ++i) {
            final String name = cursor.getColumnName(i);
            if (identities && SQLiteAxolotlStore.TRUSTED.equals(name)) {
                skipColumn = i;
                continue;
            }
            if (i != 0) {
                builder.append(',');
            }
            builder.append(name);
        }
        builder.append(") VALUES");
        for (int i = 0; i < max; ++i) {
            if (i != 0) {
                builder.append(',');
            }
            appendValues(cursor, builder, skipColumn);
            if (i < max - 1 && !cursor.moveToNext()) {
                break;
            }
        }
        builder.append(';');
        builder.append('\n');
        return builder.toString();
    }

    private static void appendValues(final Cursor cursor, final StringBuilder builder, final int skipColumn) {
        builder.append("(");
        for (int i = 0; i < cursor.getColumnCount(); ++i) {
            if (i == skipColumn) {
                continue;
            }
            if (i != 0) {
                builder.append(',');
            }
            final String value = cursor.getString(i);
            if (value == null) {
                builder.append("NULL");
            } else if (value.matches("[0-9]+")) {
                builder.append(value);
            } else {
                DatabaseUtils.appendEscapedSQLString(builder, value);
            }
        }
        builder.append(")");

    }

    @Override
    public void onCreate() {
        mDatabaseBackend = DatabaseBackend.getInstance(getBaseContext());
        mAccounts = mDatabaseBackend.getAccounts();
        notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (RUNNING.compareAndSet(false, true)) {
            new Thread(() -> {
                boolean success;
                List<File> files;
                try {
                    files = export();
                    success = true;
                } catch (final Exception e) {
                    Log.d(Config.LOGTAG, "unable to create backup", e);
                    success = false;
                    files = Collections.emptyList();
                }
                stopForeground(true);
                RUNNING.set(false);
                if (success) {
                    notifySuccess(files);
                }
                stopSelf();
            }).start();
            return START_STICKY;
        } else {
            Log.d(Config.LOGTAG, "ExportBackupService. ignoring start command because already running");
        }
        return START_NOT_STICKY;
    }

    private void messageExport(SQLiteDatabase db, String uuid, PrintWriter writer, Progress progress) {
        Cursor cursor = db.rawQuery("select messages.* from messages join conversations on conversations.uuid=messages.conversationUuid where conversations.accountUuid=?", new String[]{uuid});
        int size = cursor != null ? cursor.getCount() : 0;
        Log.d(Config.LOGTAG, "exporting " + size + " messages for account " + uuid);
        int i = 0;
        int p = 0;
        while (cursor != null && cursor.moveToNext()) {
            writer.write(cursorToString(Message.TABLENAME, cursor, PAGE_SIZE, false));
            if (i + PAGE_SIZE > size) {
                i = size;
            } else {
                i += PAGE_SIZE;
            }
            final int percentage = i * 100 / size;
            if (p < percentage) {
                p = percentage;
                notificationManager.notify(NOTIFICATION_ID, progress.build(p));
            }
        }
        if (cursor != null) {
            cursor.close();
        }
    }

    private List<File> export() throws Exception {
        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(getBaseContext(), "backup");
        mBuilder.setContentTitle(getString(R.string.notification_create_backup_title))
                .setSmallIcon(R.drawable.ic_archive_white_24dp)
                .setProgress(1, 0, false);
        startForeground(NOTIFICATION_ID, mBuilder.build());
        int count = 0;
        final int max = this.mAccounts.size();
        final SecureRandom secureRandom = new SecureRandom();
        final List<File> files = new ArrayList<>();
        Log.d(Config.LOGTAG, "starting backup for " + max + " accounts");
        for (final Account account : this.mAccounts) {
            final String password = account.getPassword();
            if (Strings.nullToEmpty(password).trim().isEmpty()) {
                Log.d(Config.LOGTAG, String.format("skipping backup for %s because password is empty. unable to encrypt", account.getJid().asBareJid()));
                continue;
            }
            Log.d(Config.LOGTAG, String.format("exporting data for account %s (%s)", account.getJid().asBareJid(), account.getUuid()));
            final byte[] IV = new byte[12];
            final byte[] salt = new byte[16];
            secureRandom.nextBytes(IV);
            secureRandom.nextBytes(salt);
            final BackupFileHeader backupFileHeader = new BackupFileHeader(getString(R.string.app_name), account.getJid(), System.currentTimeMillis(), IV, salt);
            final Progress progress = new Progress(mBuilder, max, count);
            final File file = new File(FileBackend.getBackupDirectory(this) + account.getJid().asBareJid().toEscapedString() + ".ceb");
            files.add(file);
            final File directory = file.getParentFile();
            if (directory != null && directory.mkdirs()) {
                Log.d(Config.LOGTAG, "created backup directory " + directory.getAbsolutePath());
            }
            final FileOutputStream fileOutputStream = new FileOutputStream(file);
            final DataOutputStream dataOutputStream = new DataOutputStream(fileOutputStream);
            backupFileHeader.write(dataOutputStream);
            dataOutputStream.flush();

            final Cipher cipher = Compatibility.twentyEight() ? Cipher.getInstance(CIPHERMODE) : Cipher.getInstance(CIPHERMODE, PROVIDER);
            final byte[] key = getKey(password, salt);
            SecretKeySpec keySpec = new SecretKeySpec(key, KEYTYPE);
            IvParameterSpec ivSpec = new IvParameterSpec(IV);
            cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
            CipherOutputStream cipherOutputStream = new CipherOutputStream(fileOutputStream, cipher);

            GZIPOutputStream gzipOutputStream = new GZIPOutputStream(cipherOutputStream);
            PrintWriter writer = new PrintWriter(gzipOutputStream);
            SQLiteDatabase db = this.mDatabaseBackend.getReadableDatabase();
            final String uuid = account.getUuid();
            accountExport(db, uuid, writer);
            simpleExport(db, Conversation.TABLENAME, Conversation.ACCOUNT, uuid, writer);
            messageExport(db, uuid, writer, progress);
            for (String table : Arrays.asList(SQLiteAxolotlStore.PREKEY_TABLENAME, SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME, SQLiteAxolotlStore.SESSION_TABLENAME, SQLiteAxolotlStore.IDENTITIES_TABLENAME)) {
                simpleExport(db, table, SQLiteAxolotlStore.ACCOUNT, uuid, writer);
            }
            writer.flush();
            writer.close();
            mediaScannerScanFile(file);
            Log.d(Config.LOGTAG, "written backup to " + file.getAbsoluteFile());
            count++;
        }
        return files;
    }

    private void mediaScannerScanFile(final File file) {
        final Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
        intent.setData(Uri.fromFile(file));
        sendBroadcast(intent);
    }

    private void notifySuccess(final List<File> files) {
        final String path = FileBackend.getBackupDirectory(this);

        PendingIntent openFolderIntent = null;

        for (Intent intent : getPossibleFileOpenIntents(this, path)) {
            if (intent.resolveActivityInfo(getPackageManager(), 0) != null) {
                openFolderIntent = PendingIntent.getActivity(this, 189, intent, PendingIntent.FLAG_UPDATE_CURRENT);
                break;
            }
        }

        PendingIntent shareFilesIntent = null;
        if (files.size() > 0) {
            final Intent intent = new Intent(Intent.ACTION_SEND_MULTIPLE);
            ArrayList<Uri> uris = new ArrayList<>();
            for (File file : files) {
                uris.add(FileBackend.getUriForFile(this, file));
            }
            intent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, uris);
            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
            intent.setType(MIME_TYPE);
            final Intent chooser = Intent.createChooser(intent, getString(R.string.share_backup_files));
            shareFilesIntent = PendingIntent.getActivity(this, 190, chooser, PendingIntent.FLAG_UPDATE_CURRENT);
        }

        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(getBaseContext(), "backup");
        mBuilder.setContentTitle(getString(R.string.notification_backup_created_title))
                .setContentText(getString(R.string.notification_backup_created_subtitle, path))
                .setStyle(new NotificationCompat.BigTextStyle().bigText(getString(R.string.notification_backup_created_subtitle, FileBackend.getBackupDirectory(this))))
                .setAutoCancel(true)
                .setContentIntent(openFolderIntent)
                .setSmallIcon(R.drawable.ic_archive_white_24dp);

        if (shareFilesIntent != null) {
            mBuilder.addAction(R.drawable.ic_share_white_24dp, getString(R.string.share_backup_files), shareFilesIntent);
        }

        notificationManager.notify(NOTIFICATION_ID, mBuilder.build());
    }

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

    private static class Progress {
        private final NotificationCompat.Builder builder;
        private final int max;
        private final int count;

        private Progress(NotificationCompat.Builder builder, int max, int count) {
            this.builder = builder;
            this.max = max;
            this.count = count;
        }

        private Notification build(int percentage) {
            builder.setProgress(max * 100, count * 100 + percentage, false);
            return builder.build();
        }
    }
}